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Earthworks - Design and

Preparation of Contract

Documents

Summary: This Amendment deletes the specific formula for earthworks quantitiesmeasurement, clarifies the relationship between earthworks quantitiesmeasurement pre-tender and post-contract, and corrects the references to thelatest contract documents consequent on the publication of the Manual ofContract Documents for Highway Works dated December 1991.

THE HIGHWAYS AGENCY HA 44/91

THE SCOTTISH OFFICE DEVELOPMENT DEPARTMENT

Incorporating Amendment No. 1

dated April 1995

THE WELSH OFFICE

Y SWYDDFA GYMREIG

THE DEPARTMENT OF

THE ENVIRONMENT FOR NORTHERN IRELAND

Volume 4 Section 1Part 1 HA 44/91 Amendment No.1 (April 1995)

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AMENDMENT NO.1 (APRIL 1995)

Replacement, Additional and Deleted Pages

Page No. Date

Front sheet

Contents page April 1995 Replace Chapter 1 pages 1-4 incl. April 1995

Add Chapter 1 pages 5, 6 April 1995

Replace Chapter 3 pages 7, 8 April 1995

Delete Chapter 3 pages 9, 10 April 1995

Replace Chapter 14 pages 1, 2 April 1995

Delete Annex B pages i, ii April 1995

The replacement sheets supersede those dated June 1991. All superseded and deleted pages should be archived asappropriate.

Summary

1. As noted in the amended Chapter 1, paragraph 1.13, the `Designer' has been retained throughout forconsistency within the amended document. The equivalent current term is the Design Organisation (DO).

2. "Paragraph(s)" (with an upper case `P') has been used throughout this amendment for consistency with theoriginal document. At a future revision "paragraph" (with a lower case `p') will be used throughout.

Implementation

The amended Advice Note should be used forthwith for all schemes currently under preparation, unless, in the opinionof the Overseeing Organisation, this would result in significant additional expense or delay progress. DesignOrganisations should verify the use of this Advice Note with the Overseeing Organisation.

DESIGN MANUAL FOR ROADS AND BRIDGES


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VOLUME 4 GEOTECHNICS ANDDRAINAGE

SECTION 1 EARTHWORKS

PART 1

HA 44/91

DESIGN AND PREPARATION OFCONTRACT DOCUMENTS

Contents

Chapter

1. Introduction

2. Ground Investigation

3. Specification and Method of Measurementfor Highway Works

4. Use of Materials and Construction

5. Information on Some Specific Materials

6. Slope Stability Analysis

7. Cuttings

8. Embankments

9. Ground Conditions Requiring SpecialTreatments

10. Subgrade and Capping

11. Soil Structures

12. Landscaping and Planting

13. Use of Computers in Design

14. References

15. Enquiries

Annex A

Volume 4 Section 1 Chapter 1Part 1 HA 44/91 Introduction

1. INTRODUCTION

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General

1.1 The guidance given in this DepartmentalAdvice Note covers two areas. The first area isspecifically directed to preparing contract documentsunder the Manual of Contract Documents for HighwaWorks (MCHW) dated December 1991, and itsamendments. See Paragraphs 1.4 to 1.16 below. T1/1 below shows where advice on each SHW SeriesClause and relevant Appendix is given in this AdviceNote. The second area covers general advice on deand assessment of earthworks.

1.2 The following Departmental Standard andAdvice Note have been reviewed and are nowsuperseded by this Advice Note:-

i. HD 6/80 Specification for DynamicCompaction;

ii. HA 11/80 Dynamic Compaction ofEarthworks.

Scope

1.3 The guidance given on design of earthworksand preparation of that part of contract documentatiofor highway construction relating to earthworks, isapplicable to all Department of Transport Trunk Roaincluding Motorway projects. This Advice Note mayalso be considered as good practice on other scheminvolving major earthworks.

Definitions and Abbreviations

1.4 The following definitions and abbreviations aused and shall apply in this Advice Note.

1.5 Ground Investigation (GI) is the examinationof a site required to provide geotechnical data whichrepresentative of the ground conditions and relevantthe scheme considered. It forms part of the overall SInvestigation (SI).

1.6 Specification for Road and Bridge Works(SRBW) is the Department of Transport Specificationfor Road and Bridge Works published in 1976 and isnow superseded.

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1.7 Specification for Highway Works (SHW) is theDepartment of Transport Specification for HighwayWorks published as Volume 1 of the Manual ofContract Documents for Highway Works (MCHW1).

1.8 Notes for Guidance (NG) are the Notes forGuidance on the Specification for Highway Works(NGSHW) published as Volume 2 of the Manual ofContract Documents for Highway Works (MCHW 2).

1.9 Method of Measurement is the Department ofTransport Method of Measurement for Highway Works(MMHW) published as Section 1 of Volume 4 of theManual of Contract Documents for Highway Works(MCHW 4.1) (Bills of Quantities for Highway Works).

1.10 This Advice Note was published in June 1991on the basis that the, then current, HighwayConstruction Details (HCD) are the Department ofTransport Highway Construction Details (ThirdEdition) published in 1987. However, the current HCDpublished as Volurme 3 of the Manual of ContractDocuments for Highway Works (MCHW 3) should beused. These do not differ significantly on earthworksand drainage matters.

1.11 Regional Geotechnical Engineer (GE) is theRegional Office (Transport) Geotechnical Engineerwith delegated responsibility for the geotechnicalaspects of the scheme.

1.12 Geotechnical Liaison Engineer (GLE) is theDesigner's nominee responsible for geotechnical mattrelating to the scheme.

1.13 The Designer is the Consulting Engineer orAgent Authority responsible for the earthworks designThe 'Designer' is now termed the 'Design Organisation(DO) but, pending a future complete revision of thisAdvice Note, the former term is retained pro tem forconsistency within the amended document.

1.14 The Engineer is the Engineer as defined in theConditions of Contract.

1.15 The Project Manager is appointed by theRegional Office Director (Transport) to be responsiblefor the day-to-day management of the scheme on behof Dtp.

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Chapter 1 Volume 4 Section 1Introduction Part 1 HA 44/91

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1.16 In this Advice Note it has been assumed thathe Conditions of Contract (CoC) are the Institution oCivil Engineers (ICE) Conditions of Contract for use connection with Works of Civil EngineeringConstruction, Fifth Edition, as amended by the ModeContract Document (MCD) for Highway WorksContracts issued by the Department of Transport asVolume 0 of the MCHW (MCHW 0.1) for use with theDecember 1991 edition of the SHW. The actual CoCwill be those promulgated by the SD series ofDepartmental standards and the relevant MCD statetherein.

Stages of Earthworks Design

General

1.17 The use of the Department's Standards, AdvNotes, Specifications etc are all part of the Certificatiprocedures. For these to work satisfactorily there neto be good liaison between the Project Manager,Designer, GE and GLE. It must be noted that theProject Manager has a clear responsibility for thetechnical aspects and the management of the schemwhilst the GE is responsible for receipt of Certificatioand may be required to be involved in the geotechnicaspects. The GE must keep the Project Manager fulinformed of all geotechnical matters which might affethe cost and progress of the scheme. Equally, theProject Manager must inform the GE of anygeotechnical work required to progress the scheme.

Project Stages

1.18 The stages of a highway scheme, and theappropriate geotechnical works, are given as a guideTable 1/2. The geotechnical complexity of any schemmay mean some latitude is required if unnecessarystudy and abortive costs are to be avoided. On certaschemes, alternative lines may each require a siteinvestigation to properly determine the choice of rout

1.19 For some schemes, at the Main GroundInvestigation stage, it may be that either the bridgetypes or actual locations may not be fully confirmed sthat the Main Ground Investigation may need to be sinto two parts. The first GI will give sufficientinformation to enable the general geology to beidentified for the highway design with nominal bridgesites located. The second stage would complete theMain Investigation with further boreholes located in tproposed bridge foundation areas (BD 2, DMRB 1.1)so that the design of the structures can be confirmeda submission made for technical approval.

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deals only with design and preparation of contract

ice remeasuring for final account, the earthworks balaon tabulation should be based on the actual classificaeds of soils made by the Engineer or by the Contracto

appropriate and construed in accordance with theContract. This will generally depend on the contenAppendix 6/1.

en 1.22 Volumes 1 to 4 of the MCHW dated Decemal 1991, published by HMSO, were promulgated by Sly SD 2 and SD 3 (MCHW 0.2.1, MCHW 0.2.2 andct MCHW 0.2.3), the August 1993 amendments were

promulgated by SD 6 (MCHW 0.2.5).

unless, in the opinion of the Overseeing Organisat in this would result in significant additional expense e delay progress. Design Organisations should verif

use of this Advice Note with the Overseeingin Organisation.

Guide to Manual

1.20 At scheme preparation and contract preparationstages, the Designer should classify the materials inorder to enable him to make the appreciation ofearthworks balance to which reference is made atParagraphs 3.45, 3.46 and 4.33 to 4.38 below. To assiwith this classification, reference should be made toMCHW 1, Series 600 and MCHW 2 Series NG600 andto Table 1/1 below. It is emphasised that the actualclassification of soils in the Contract should now followthe guidance in Paragraph 2.22 of SA3 (MCHW 0.3.3)which superseded paragraph 3.5 of this document.

1.21 It should be remembered that this Advice Note

documents for earthworks. In an actual contract when

Implementation

1.23 The amended Advice Note should be usedforthwith for all schemes currently under preparation,

FOR USE OUTSIDE THE AGENCY

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TABLE 1/1

SPECIFICATION CLAUSE RELEVANT APPENDIX CHAPTERIN HA 44/91

Clause Title

601 Classification, Definitions and Uses of Earthworks Materials 6/1, 6/2, 6/3, 6/9 3, 4, 5602 General Requirements 6/1, 6/2, 6/3, 6/7, 6/8 3, 4603 Forming of Cuttings and Cutting Slopes 6/3, 6/10 7604 Excavation for Foundations 7605 Special Requirements for Class 3 Material 6/1, 6/4 5606 Watercourses 6/3 12607 Explosives and Blasting Used for Excavation 6/3 7608 Construction of Fills 6/1, 6/3, 6/9,6/12,6/13 4, 5, 8, 609 Geotextiles used to Separate Earthworks Materials 6/5 5610 Fill to Structures 6/6 11611 Fill above Structural Concrete Foundations 6/6 4612 Compaction of Fills 6/3, 6/9 4613 Sub-formation and Capping 6/7 10614 Cement Stabilisation to Form Capping 10615 Lime Stabilisation to Form Capping 6/7 10616 Preparation and Surface Treatment of Formation 6/7 10617 Use of Sub-formation or Formation by Construction Plant 10618 Topsoiling, Grass Seeding and Turfing 6/8 12619 Earthwork Environmental Bunds 6/9 4, 8, 12620 Landscape Areas 6/9 4, 8, 12621 Strengthened Embankments 6/9 5, 8, 11,622 Earthworks for Reinforced Earth and Anchored Earth Structures 6/1, 6/3, 6/9 11623 Earthworks for Corrugated Steel Buried Structures 11624 Ground Anchorages 6/10 11625 Crib Walling 6/10 11626 Gabions 6/10 11

Chapter 1 Volume 4 Section 1Introduction Part 1 HA 44/91


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TABLE 1/1 (Continued)

SPECIFICATION CLAUSE RELEVANT APPENDIX CHAPTERIN HA 44/91

Clause Title

627 Swallow Holes & other Naturally Occurring Cavities 6/11 9628 Disused Mine Workings 6/11 9629 Instrumentation and Monitoring 6/12 4630 Ground Improvement 6/13 9631 Earthworks Materials Tests 4632 Determination of Moisture Condition Value (MCV)

of Earthworks Materials 4633 Determination of Undrained Shear Strength of

Remoulded Cohesive Material 4634 Determination of Saturation Moisture Content

(SMC) of Chalk 5635 10% Fines Value and Other Tests of Particle

Soundness 4636 Determination of Effective Angle of Internal

Friction (M’) and Effective Cohesion (c’) ofEarthworks Materials 4

637 Determination of Resistivity to AssessCorrosivity of Soil, Rock or Earthworks Materials 11

638 Determination of Redox Potential to AssessCorrosivity of Earthworks Materials for ReinforcedEarth and Anchored Earth Structures 11

639 Determination of Coefficient of Friction andAdhesion between Fill and Reinforcing Elementsor Anchor Elements for Reinforced Earth andAnchored Earth Structures 11

640 Determination of Permeability of EarthworksMaterials 4, 10

641 Determination of Available Lime Content of Limefor Lime Stabilised Capping 10

642 Determination of the Constrained Soil Modulus (M*)of Earthworks Materials 11

Table 6/1 Acceptable Earthworks Materials: Classification and Compaction Requirements 6/1 3, 4

Table 6/2 Grading Requirements for Acceptable EarthworksMaterials 6/1 2, 3, 4

Table 6/3 Limits of Material Properties of Fill for Use withMetal Components in Reinforced Earth and Anchored EarthStructures for Class 6H, 6I, 6J, 7C and 7D Materials. 11

Table 6/4 Method Compaction for Earthworks Materials:Plant and Methods 6/3 4

Table 6/5 Grass Seed Mixture per 50kg 6/8 12

NOTES:1. See also MCHW 2, Series NG000, Table NG0/1, page 7, List of sub-clauses which refer to

Contract-specific requirements described in Numbered Appendices 6/1 to 6/13 inclusive.



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TABLE 1/2

Stages of a highway scheme and associatedgeotechnical work

Geotechnical Work Scheme Stage Scheme Report Stage

Admission to Road Programme

Pre Public Consultation

Consultation & Route Announcement

Pre Public Inquiry

Publication of Draft Orders ObjectionsPeriod & Inquiry

Pre Contract Tender (Post ordermaking)

Works Commitment Stage, Construction StagePost-Construction

Maintenance Period

(a) Procedural Statement-1 Preliminary Report

(b) Preliminary SourcesStudy(Desk Study) andpreliminary investigation ifrequired.

(c) Procedural Statement-2

(d) Main Investigation Order Publication

(e) Geotechnical Certificate 1 Factual ReportConsultation & Route Interpretative ReportAnnouncement

Report

(f) Supplementary Procedural Earthworks DesignStatement-2 (if required) Report

(g) Supplementary Investigation Notes to Resident(if required) Engineer

(h) Supplementary GeotechnicalCertificate 1 (if required)

(i) Geotechnical Certificate 2

GeotechnicalFeedbackReport

Volume 4 Section 1 Chapter 2Part 1 HA 44/91 Ground Investigation

2. GROUND INVESTIGATION

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Ground Investigation

2.1 Advice on carrying out GI is given in AdviceNote HA 34/87 `Ground Investigation Procedure' whishould be referred to for further details. Using thePreliminary Source Study (PSS) as a basis, the GrouInvestigation will need to be planned in considerabledetail to ensure that samples of sufficient size, type anumber are obtained from each soil or rock type. This necessary to enable the requisite tests to be carrieout. Tests will need to be selected bearing in mind thinformation that is required for the design ofembankment foundations, the design of slopes, for thselection of appropriate acceptance criteria for fill andto assess the subgrade properties. It is essential thalatter subject is not left until the preparation of contradocumentation but is considered at the early stages oGI and is developed throughout the design process.The GI should also provide sufficient information forTenderers in order to price the Contract and for theContractor to decide on types of construction plant anprogramming. Long-term monitoring of ground waterdata should form part of each investigation. Furtheradvice is given in Chapter 4.

2.2 Designers should be aware that tests required bSHW may not necessarily be standard tests describeBritish Standards or other references used as a standThe most obvious example of this are the gradings seout in Table 6/2 of the SHW where sieve sizes greatethan 75mm have been quoted. The BS 1377 tests fodetermination of the particle size distribution of a soilsample does not cater for this. The Designer will,therefore, have to ensure that tests he specifies in thembody the extra requirements of the SHW.

2.3 Consideration should also be given to materialswhose characteristics can alter on exposure or duringremoulding. For instance, there is considerableevidence available to suggest that pyritic shales exhiincreased acidity and sulphate content on exposure owhen placed in embankments. Testing at the GI stamay not indicate this and in these cases the Standar1377 test for sulphate content is not appropriate, andspecialist advice should be sought. Stabilization ofmaterials may be an option for capping layers and sothe GI should include adequate sampling and testingfor sulphates, organics and Atterberg Limits.


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2.6 The properties of engineering soils and rocconsiderably not only from one geology to anothewithin the same geology and it should not be asswithout full supporting evidence, that the behavio

materials in apparently identical

2.4 In the engineering discipline, the definitions anddistinctions between the terms `soil' and `rock' areusually based on measures of particle size and eitherhardness, durability, inertness, or any combination ofthese. The accepted values for these criteria aregoverned by the intended use of the material. Furthermore the use of `soil' or `rock' can haveimplications for administering and costing projects. The result has been a number of definitions for eachspecific field of work. In the `Specification and Methoof Measurement for Ground Investigation', soil and rocare defined, in paragraph 2.2, in terms of either the tyof excavation tool, or drill bit required, or size ofboulder encountered, in a ground investigation. Thepurpose in defining material in this way is to form abasis for payment for the ground investigation and foradministering the contract. This definition is not usedin other applications such as classifying fill materials. The SHW, appropriately, prefers to use `material' and`classes of material' so avoiding any confusion of termWhere the word `rock' is used, in Clauses 603.5, 603.and 604.1, it refers to insitu rock or to argillaceous rocand is defined for use in selected fills. There is no suterm as `rock in excavation' in the SHW and forexcavation purposes `Hard Material', as defined in theMMHW (see Paragraph 3.18), should be assessed frothe investigation drilling, rate and type of recovery,insitu tests, trial pits and exposures. As far as thisAdvice Note is concerned, rock, soil, or just materialare used as general engineering terms and no strictcontractual definition should be inferred. This reflectsthe differing terminology found in earthworks design,assessment, and documentation, all of which aresubjects covered by this Note. (See also Chapter 3 orock and paragraphs 4.51 and 4.52).

2.5 The extent of `Topsoil', as defined in SHW Table6/1, should be determined from the GI and tests. (Sealso Chapter 12).

Sampling and Testing



Chapter 2 Volume 4 Section 1Ground Investigation Part 1 HA 44/91

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geological environments will be the same. Consequently representative and thorough samplingtechniques and accurate testing, both insitu and in thlaboratory, are required. `Site Investigation PracticeAssessing BS 5930' includes many useful reference

2.7 Difficulties arise because no two soil or rocksamples will give exactly the same test results althouthey may well perform in a similar manner from anengineering point of view. Classification systems haevolved to sort materials into groups which all behavin a similar manner under particular conditions. Thelimits that are applied in sorting materials into thedifferent groups or classifications may be somewhatarbitrary. However, the system does provide a unifieapproach to assessing the characteristics of a massmaterial rather than attempting to assess thecharacteristics of innumerable individual samples.

2.8 The classification set out in SHW Table 6/1 hasbeen developed to suit the requirements of handlingearthworks materials to construct embankments usindefined compaction methods or procedures to produdefined or pre-determined end product. The limits umay or may not be the same as those used for otherclassification systems. For example, there is a conflwith the British Soils Classification Systems (BSCS) BS 5930. Following the theme set in Paragraph 2.2above, soil descriptions provided in groundinvestigation documents to BS 5930 may not accordwith descriptions resulting from classifications inaccordance with SHW Table 6/1. Designers shouldensure that where descriptions and classifications ofmaterials are given the system used is clearly descri

2.9 One of the objects of an investigation is to provsoil and rock test results to investigate the engineeriproperties of the materials which can be used in thedesign. There are a number of factors which must bconsidered to produce as representative results as ispossible.

2.10 Borehole and trial pit location. The location ofboreholes and trial pits is crucial. All the informationfrom the PSS must be used as a guide to identify tholocations which will provide the maximum amount ofinformation about the surface and sub-surface geoloCritical areas identified in the PSS, such as soft grouand areas associated with large structures, such asbridge foundations, will require particular attention.



2.11 Sample Location. Sample locations should bechosen to include those materials on which the de

e depends. Carefully planned sampling of this sort: linking geological knowledge with the requirement. design is the main factor in determining sample

any expected variations in the properties of a mategh

2.12 Sample disturbance. Methods of sampling shve be chosen to produce samples which are only diste by the amount allowable in the required testing an

suit the extent to which the results are expected torepresentative of the in-situ conditions.

d 2.13 Sample size. At normal rates of sampling anof sample many represent a mass of soil in a cuttin

ratio of typically 1:100,000 by weight. However,ultimately the size of sample will depend on the am

the geology.

g 2.14 Testing errors. Research has shown thatce a considerable errors can be introduced at the tested stage even under controlled laboratory conditions

is well described by Sherwood in TRRL Report Lict 339.in

2.15 It should be appreciated that the samplingprocedure will have an effect on the reliance that caplaced on the soil properties being measured - se

2/1.

2.16 The number of tests carried out must be suffbed. to draw conclusions from; 20-30 test results from

ide will obviously depend on the uniformity of the mateg in each area and how critical the results are to the

design. The types of test will depend on the matee property to be measured. The criteria to be used

determining the limits of the material property foracceptability depend on a number of factors given

2.17 The choice of material property and limits to bse applied depend on:-

gy. i. the material type;nd,

ii. ease of application of test during the earthwcontract - speed of result required;

location. Locations should also be chosen that include

of material required for testing and the complexity of

particular material would normally be required. This

below.


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J

TABLE 2/1

Applications of the various qualities of soil samples derivedfrom different sampling procedures

QUALITY CLASS TYPICAL SAMPLING PROPERTIES EXAMINED APPLICATIONPROCEDURE

1 Piston thin walled sampler Remoulded properties Laboratory data on insitu soils.with water balance Fabric Classification

Water ContentDensity and porosityCompressibilityEffective strength parametersPermeabilityCoefficient of consolidation

2 Pressed or driven thin or Remoulded properties Laboratory data on insitu insensitivethick walled sampler with Fabric soils.water balance Water Content Classification

Density and porosityCompressibilityEffective strength parametersTotal strength parameters

3 3A 100% Fabric examination & laboratory datarecovery. Pressed or driven thin or Remoulded properties on remoulded soils.Continuous thick walled samplers. Water Fabric Classification

balance in highly permeablesoils.3B 90%

recoveryConsecutive

4 Bulk and jar samples Remoulded properties Laboratory data on remoulded soils.Sequence of strata.Classification

5 Washings. Disturbed None Approximate sequence of strata onlysamples from percussionboring in non-cohesive soils

(after Rowe (1972))


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Chapter 2 Volume 4 Section 1Ground Investigation Part 1 HA 44/91

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iii. reproducibility of test results;

iv. the amount of acceptable material available,earthworks balance;

v. the adaptability required - a wet period mayreduce the quantity of acceptable on-site material andresult in increased importation of off-site material.

vi. Engineering requirements:-

Stability of fill material.

Trafficability and compaction (CBR).

Control of settlements.

2.18 The criteria available for determining acceptabilifor the above are:-

i. upper and lower limit moisture content -applicable to all soils;

ii. optimum mc (determined from compaction test) +x% and -y%, limits mainly applicable to non-cohesivesoils;

iii. LL. PL. and PI. Upper limits applicable tocohesive soils;

iv undrained shear strength (in-situ or remoulded)lower and sometimes upper limit applied to cohesivesoils;

v. moisture content as a factor of PL, for applicationto most cohesive materials; one factor times PL for anupper limit and another factor times PL for a lowerlimit; vi. Moisture Condition Value which can be found fora wide range of cohesive soils and certain granularsoils.

2.19 Note that the choice of criteria will have a bearinon the investigation eg trial pits may be required forin-situ vane tests, large samples are required forremoulded shear strengths and the Moisture Conditiotest.

2.20 The choice of criteria should not be made until thresults of a number of different classification tests havbeen analyzed. The limits for acceptability willprobably be chosen in the light of the amount ofacceptable material required and the test resultsobtained. Both these processes are very much aidedplotting and tabulating the results. The choice of limit



and consequential volume of acceptable material can

carrying out simple statistical analysis. Thepresentation of data in this form will assist in assessin

and unacceptable material should this become neceat any stage of the project.

show erratic variations from what might be expected

computers. There is considerable benefit to be gaine

the GI, to store the relevant data for retrieval and

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termed `prediction'. This process can be aided by

the effects of varying limits on volumes of acceptable

2.21 Consideration should be given to test data that

they may indicate possible problem areas.

2.22 Large quantities of data can best be handled by

by using computers at an early stage, preferably during

analysis later.

Planning the Earthworks Design

2.23 The design of a highway scheme develops withtime, but the initial feasibility stage is often critical inestablishing the probable horizontal and verticalalignment. As the scheme develops and moreinformation becomes available from the investigationsof the site the line may be varied to a lesser or greaterdegree. The line of the highway is still, however,broadly fixed and the materials that are available for theearthworks can be deduced. In arriving at the finalearthworks design a number of factors should becarefully considered in order to produce a safe andeconomic scheme.

2.24 The approximate quantities of material requiredfor the fill areas, including pavement construction,should be matched by the quantities of acceptablematerial likely to arise from the excavations. Dueallowance should be made, except for measurementpurposes, for bulking or shrinking and compaction. Itmay be possible to change the road line slightly eitherto avoid undesirable materials and areas or to increasethe available quantity of a particular class of material(see Paragraphs 4.1 to 4.32). A perfect earthworksbalance will, however, rarely be obtained in practice.

2.25 The basic physical properties of the insitumaterials are fundamental to the initial earthworksdesign and will determine the shape of the cuttings andembankments. The designer may use interpretativeinformation to assist in his design. The relative locationof each cut and fill area, the approximate quantities ineach and the distribution of the various materials withinor below these earthworks all affect the design. Thereare also external factors which will effect theearthworks, such as land-take restrictions in urban




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areas, the visual intrusion of the earthworks into thesurrounding rural countryside, limitations on the accesalong the site caused by railways, roads, rivers etc. Athese must be considered in the light of how they willaffect excavating the material from the cuttings andplacing it in the desired sequence into theembankments, and they will be more fully discussedlater in this document. It is prudent at the PSS stage(Desk Study) to examine similar soils in any nearbyproject for initial assessment of the earthworks designThe local authority's view on the use of a particular sois also likely to be of value.


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Volume 4 Section 1 Chapter 3Part 1 HA 44/91 Specification and Method of Measurement for Highway Works

3. SPECIFICATION AND METHOD OFMEASUREMENT FOR HIGHWAY WORKS

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General

3.1 The information given in this Chaptercomplements the SHW 600 Series Notes for Guidanand provides assistance on completing the associatenumbered Appendices. The object of the Specificatiis to provide the Contractor with sufficient detail that may provide materials and work in such a manner ththe end product is that required by the DTp. The 60Series Specification is a mixture of ènd product' and`method' specifications. The Notes for Guidance areassist the Designer in preparing the Specification anthis Advice Note provides technical details andbackground to assist in this preparation.

3.2 The Method of Measurement (MoM) includes thItem Coverages which are incorporated in the Contraby the provisions of the Preamble to the Bill ofQuantities. The MoM sets out the basis on whichpayment is made and the ground rules for preparingBills of Quantities. It is essential that amendments toexisting Specification clauses or new clauses arefollowed up with appropriate amendments to the MoThe Method of Measurement for Highway Works(MMHW) defines the coverage of items in Bills ofQuantities and their Method of Measurement for useconstruction DTp highways.

Additional information for the Notes for Guidance

3.3 The following guide indicates where advice maybe obtained for a particular note in the Notes forGuidance.

NG600.1 Design of earthworks; refer toParagraphs 2.6 and 2.22 and Chapters 7 a8. Selection of limits for soil properties andpreparation of Appendix 6/1; refer to Chapt4.

NG600.4 Examples of Appendices are givein Annex A.

NG601.7 Limits for acceptability; refer toChapter 4.



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the

M. 3.4 Table 1/1 Advice Note Guide shows where aon each SHW Clause may be found within this Adv

Note and also cross refers with the relevant in Specification Appendix.

for testing for the purposes of classification anddetermining acceptability. The SHW Clause 602.1

little more helpful in directing the reader to Appendix

amongst other things, `Special Requirements fornd determining acceptability, who classifies and whe

and whether trial pitting is required'. It is thereforeer recommended that generally the Contractor should

given responsibility for classification and determining

n including the appropriate sampling and testing forcompliance. In some circumstances, however, it is

take this responsibility.

NG605.3 and 4 Designation of Class 3material, compaction of chalk and times ofthe year when chalk earthworks may not becarried out; refer to Paragraphs 5.8 to 5.20.

NG613.3 Advice on subgrade assessment anappropriate capping materials is given inChapter 10.

NG618.2 and 4 See advice given in Chapter12.

NG621.2 Properties of Geotextiles andGeomeshes are given in Paragraphs 5.72 to5.89.

NG640.1 Permeability tests for earthworksmaterials are described in Chapter 4 and 9.

Advice on the Specification

Testing for Classification and Acceptability

3.5 The SRBW did not set down who was responsible

6/1 which in turn indicates that the Designer is to state,

acceptability based on the Designers limits and criteria

possible that the Engineer may be more appropriate to



Chapter 3 Volume 4 Section 1Specification and Method of Measurement for Highway Works Part 1 HA 44/91

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3.6 If the Contractor is given the responsibility fordetermining the acceptability of all the materials usedon site, he will need to carry out the required samplinand testing to prove to himself and to the Engineer ththe correct materials are being used. Therefore theEngineer must specify what tests the Contractor shacarry out and give a frequency of testing for each testogether with any other relevant information. Providithe contract makes it absolutely clear what and howmuch testing the Contractor is expected to carry out,then payment is allowed under Clause 36 of the CoCFor this reason sampling and testing has not beenincluded in MMHW item coverage and no separateBoQ items are included for them. Suggestedfrequencies of testing are given in Paragraphs 3.8 to3.12 but the Designer would be well advised to ensuthat his estimate of the quantity of testing given inAppendix 6/1 is generous. Whatever sampling andtesting is carried out by the Contractor, this does notaffect the Engineer's own tests, although the frequenof sampling and testing by the Engineer's staff shouldnot be as high as the Contractor's. Whoever is maderesponsible for the sampling and testing, all the relevinformation should be included in Appendix 6/1.

3.7 If in Appendix 6/1 the Engineer undertakes theresponsibility for classification and determiningacceptability, then this should not detract from theContractor's overall responsibility to provide acceptamaterial as defined in the Contract.

3.8 If testing is the responsibility of the Engineer thethe Contract should include details of all the apparatuand equipment required to equip the Engineer's sitelaboratory, as well as the usual services. If testing isContractor's responsibility, then in addition to theEngineer's laboratory, a list of tests together with thesource reference for each test (BS, ASTM, SHW etcwhich the Contractor is expected to carry out must bincluded in Appendix 6/1. Details about the submissof test results to the Engineer must also be set out. already the Department's policy that all permanenttesting laboratories should be accredited by the NatioMeasurement Accreditation Service (NAMAS) as parof their Quality Control policies: accreditation of sitelaboratories will follow at a later date. No mentionshould be made as to where the Contractor should cout his testing ie his own site laboratory, independentesting laboratories etc, this should be left for him toorganise.



3.9 In order for the Contractor to be able to includtesting in his rates, the frequency of each test sho

g also be stated.at

3.10 The tests fall into two categories:-llt i. tests involving taking representative samplesng materials and carrying out the test either on the sit

in a site or other laboratory;

. ii. insitu tests, such as plate bearing tests, andfor controlling method compaction.

3.11 Compliance sampling and testing should becarried out at excavation for on-site materials unl

re material is likely to change between excavation adeposition, in which case further sampling and tesshould be carried out at deposition. Imported mashould be sampled and tested for compliance at

cy deposition and preferably at source. Appendix 6should state the locations of all compliance sampand testing. The onus is placed on the Contract

ant maintaining the acceptability of material.

of the contract, uniformity of material and how critithe results are to the design, and so the frequency testing given in Table 3/1 is given only as a guide.

ble3.13 For the purposes of measurement, the MMHW

n topsoil Class 5A, chalk Class 3, other acceptables materials or unacceptable material Classes U1 a

the 3.14 For measurement purposes, the MMHW rematerial at deposition and compaction to be classias acceptable, Class 1C, 3 and 6B, although Clas

) and 6B should only be measured separately whee are specifically stated in the Contract to be placedion particular location. For practical purposes on siteIt is Engineer will need to subdivide existing Classes

to ensure that the correct acceptability criteria andnal compaction method is applied to the material andt where zoning is required the correct Class of mate

placed in that zone. Measurement will then follow appropriate. Figure 3/1 of this Advice Note shows

arry classification requirements for measurement purt during the various earthworks operations.

3.12 The scale of testing depends very much on the s

requires material in excavation to be classified as




J

TABLE 3/1

Suggested frequency for classification and acceptability testing

Material Class Requirement Suggested Frequency Per Source

1 Grading/Uniformity Coeff Twice a weekGeneral GranularFill mc/MCV 1-2 tests per 1000m of material 3

up to a max 5 per daySMC of Chalk Twice a week

2 Grading Twice a weekGeneral CohesiveFill mc/MCV/PL/Shear strength 1-2 tests per 1000m of material 3

up to max of 5 per daySMC Twice a weekBulk Density (PFA) 1-2 tests per 1000m of material3

up to max of 5 per day.

3 mc 1-2 tests per 1000m of material3

General Chalk up to max 5 per dayFill

SMC Daily

4 Grading/mc/MCV DailyLandscape Fill

5 Grading DailyTopsoil

6 Grading/Uniformity Coeff 1 test per 400 tonnes of materialSelectedGranular Fill PI/LL Daily

10% Fines Value/SMC Weeklyomc/mc/MCV 1 test per 400 tonnes of materialOrganic Matter/ As required or weeklyTotal Sulphate ContentpH/Chloride Ion Content As required or weeklyResistivity As requiredUndrained Shear Parameters As required

7 Grading/mc/MCV 1 test per 400 tonnes of materialSelectedCohesive Fill SMC Twice a week

PI/LL As required or dailyOrganic Matter/ As required or weeklyTotal Sulphate ContentpH/Chloride Ion Content As required or weeklyResistivity As requiredUndrained and Drained parameters As requiredPermeability As requiredCoeff of Friction/Adhesion As required

8 mc/MCV DailyMiscellaneousFill

9 Pulverisation 1 test per lane width per 200m lengthStabilisedMaterials mc/MCV 1 test per lane width per 200m length

Bearing Ratio 1 test per lane width per 200m length


une 1991 PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED 3/3


EXCAVATIONAT EXCAVATION CLASSIFY AS :

TOPSOILCLASS 5A

CHALKCLASS 3

ACCEPTABLEEXCLUDING

CLASS 3 & 5AFROZEN

UNACCEPTABLEU1

UNACCEPTABLEU2

IMPORT

TOPSOILCLASS 5B

STATED CLASSES (2)

TOPSOILINGDEPOSIT

RENDER ACCEPTABLE (1)

DEPOSITIONCLASSIFY AS : (3)

1. Acceptable2. Acceptable Class 1C3. Acceptable Class 34. Acceptable Class 6B

COMPACTIONCLASSIFY AS : (3)

1. Acceptable2. Acceptable Class 1C3. Acceptable Class 34. Acceptable Class 6B

DISPOSECLASSIFY AS :

1. Acceptable excluding Class 5A2. Unacceptable Class U13. Unacceptable Class U2

If the Contractor opts to render unacceptable material acceptable for use in the Works, then he willbe paid as though he had disposed and then imported the class of material he rendered acceptable.If the contract requires material to be so treated then payment will be at rates in the BoQ.

For Import, only Stated Classes have to be classified (Group I, Feature 2)

Deposition and Compaction of Class 1C and 6B materials shall be measured separately only whereClass 1C or 6B material as such is specifically stated by the Contract to be required to be placedand compacted in a particular location.

(1)

(2)

(3)

Figure 6/1 Classification during earthworks operations.

NOTES :


PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED June 19913/4


l

Advice on the Method of Measurement

3.15 Part I of the MMHW provides definitions for`Hard Material' and Èxisting Ground Level' and PartIV, Section 6: Earthworks defines Èarthworks Outlin`Sub-soil level', `Surcharge' and further amplifiesÈxisting Ground Level'.

3.16 It is required that the Bill of Quantities is dividedinto parts. Earthworks as described in this Advice Nwill fall within both the Roadworks and Structures paof the Bill.

3.17 The earthworks items fall under the MMHWheadings of:-ExcavationExcavation in Hard MaterialDeposition of FillDisposal of MaterialImported FillCompaction of Fill

3.18 The MMHW defines `Hard Material' as follows.

i. Material which requires the use of blasting,breakers or splitters for its removal but excludingindividual masses less than 0.20 cubic metres.

ii. Those strata or deposits so designated in theContract.

3.19 Hard Material is paid for as an èxtra over' itemwhich means that an increased rate is paid over normexcavation rates. The Designer must make anassessment of where and how much hard material woccur in excavations and indicate this in the contractdrawings (see Paragraphs 3.39 and 3.40). He will alneed to assess whether the hard material, on excavawill be acceptable. Many hard materials may besuitable for use as one of the selected granularmaterials. The Designer will have to assess whetherdesignate any hard material for use as selected fills awhether to make allowance for rendering unacceptabmaterial into acceptable material or leave both decisto the Contractor. Whichever approach is adoptedshould be made clear in the contract documents.

3.20 It is recommended that no more classification this required for measurement purposes is set out in thContract. For excavation purposes this will be:-


June 1991 PAPER COPIES OF THIS ELECTR

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1. Acceptable Topsoil Class 5A2. Acceptable Chalk Class 33. Acceptable Material excluding Classes 3 and 5A4. Unacceptable U15. Unacceptable U2

3.21 These are the MMHW Group II Features. Theassociated Group III Features are:-

1. Cutting and other excavation2. Structural foundations4. New watercourses5. Enlarged watercourses6. Intercepting ditches7. Clearing abandoned watercourses8. Removal of surcharge

3.22 Feature 2 will usually apply only to the StructuresBill. Feature 2 is further subdivided by Group IVFeatures:-

1. 0 metres to 3 metres in depth2. 0 metres to 6 metres in depth and so on in steps of

3 metres.

3.23 For deposition purposes the drawings must showthe locations of selected materials (see Paragraphs 3.39and 3.40). However, measurement will fall under thefollowing MMHW Group II Features except that thedeposition of Class 1C and 6B materials should beseparately measured only when Class 1C or 6B materiaas such is specially stated by the Contract as required tobe placed in a particular location.

1. Acceptable material2. Acceptable material Class 1C3. Acceptable material Class 34. Acceptable material Class 6B

3.24 These will have to be sub-divided into thefollowing MMHW Group III Features whereappropriate.

1. Embankments and other areas of fill2. Strengthened embankments3. Reinforced earth structures4. Anchored earth structures5. Landscape areas6. Environmental bunds7. Fill to structures8. Fill above structural concrete foundations9. Fill on sub-base material, roadbase and capping10. Fill on bridges (under footways, verges and central

reserves)


ONIC DOCUMENT ARE UNCONTROLLED 3/5


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3.25 It is worth noting the acceptable materialexcavated for structural foundation may not be suitafor backfilling. It is generally accepted that all thismaterial is billed as being deposited as àcceptablematerial' in Group III Features 1 or 5.

3.26 The drawings must make clear the dividing linebetween `fill to structures' and `fill above structuralconcrete foundations'.

3.27 Unless selected materials can unquestionably bwon from the site it is recommended that they aretreated as imported materials. For imported materiathe MMHW allows the following Group I Features.

1. Imported acceptable material2. Other stated classes of imported acceptable fill3. Imported topsoil Class 5B

Imported topsoil Class 5B shall not be identified by aGroup II Features.

3.28 Figure 3/1 shows the classes which fall into theMMHW categories. It can be seen that for import onStated Classes require classification; importedacceptable material does not require classification. imported materials must however, be specified asGroup I Features 1, 2 or 3. It is recommended thatGroup I Feature 2 be used when Class 6, 7 and 8materials and material to SHW Clause 512 are to beimported. Where Class 1, 2 and 3 materials are to bimported, either Group I Feature 1 or Group I Featurmay be used, depending on whether it is necessary distinguish between the classes or not. Furtherdiscussion on the classes of materials is given inChapter 4.

3.29 However, for the purpose of assessing whichmaterials may be considered for import the followinginformation may be useful:-

3.30 If PFA is required as general fill then Class 2Emust be stated.

3.31 Where chalk does not fall into the categories ofClass 3 or unacceptable it may be included in Classe1A, 1B, 1C, 2A, 4, 6A, 6B, 6E, 6F, 6H, 6I, 6J, 6P, 7Aand 8.

3.32 Except in exceptional circumstances, Class 4material should not be imported. Limits should be seso that sufficient site arising material is available. Ifthere is a shortfall then Classes 1, 2 or 3 material shbe specified and used.


PAPER COPIES OF THIS ELECTR3/6

3.33 Class 5A cannot be imported.ble

3.34 Class 6E, 7E and 7F materials for stabilisationnot intended for import as a design option. Where

possible stabilisation should be allowed for as an op

3.35 Where there is an obvious excess of acceptabsite material the Designer should make every effort to

e of designs using lesser quality but acceptable maAn example would be to design a slightly more cos

ls structure which could tolerate acceptable site arisimaterial rather than expensive imported granular

the Designer should not indicate their location but hemust be able to justify his design and may have to

up his decision in the event of a dispute. It can be se

ny acceptable material into the various classes in theexcavation but nevertheless he should be satisfied th

ly 3.36 Sufficient detail must be given on the drawingthe Contractor to assess how much of each class o

All material is required and to determine where it is toplaced. The Designer will need to determine quanof each class for his own purposes. The drawingsneed to show where each class of material is to bplaced, but the quantities shown will only be those

e required by the MMHW (see Paragraphs 3.23 to 3e 2to 3.37 Compaction follows the same measuremen

as Deposition: only Classes 1C, 3 and 6B arespecifically stated, the remainder being included in

term àcceptable material'. As stated in Section 6, Pa

where they are specifically required in the Contracbe placed at a particular location.

requirements of SHW Clauses 602.15 and 16. Hoitems need to be included in the BoQ for any

Contractor elects to render unacceptable material s acceptable material (SHW Clause 602.7) then he

be paid as though the material concerned was dispof and a similar quantity imported. If the Engineer

Clause 602.17, the necessary requirements shall t out in SHW Appendix 6/1 and paid for by an item i

BoQ.

in the Contract.

reduce the quantity of imported selected fills by means

backfill material. Where selected materials arise on site

that there is no necessity for the Designer to break dow

the materials available meet the design requirements.

43 of the MMHW, Class 1C and 6B are only measured

3.38 In his prices, the Contractor is to include the

requirements under SHW Clause 602.17. If the

wishes to carry out a similar operation then, under SHW


ONIC DOCUMENT ARE UNCONTROLLED June 1991


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Preparation of Contract Drawings and EarthworksQuantities

3.39 For a scheme which requires the excavation ofcuttings and construction of embankments the followinformation will need to be shown.

i. Areas where topsoiling is required and thespecified thickness and whether the slope is greater10 to the horizontal or at 10 or less.

ii. Areas as above for grass seeding, turfing orhydraulic mulch grass seeding.

iii. Areas where any previous pavement is to beperforated or broken up and left insitu.

iv. Areas where any previous road pavement is to removed and to be measured as `hard material'.

v. Areas where any special treatment is required sas:-

- benching;

- special embankment foundations - dig out andstarter layers, backfill, selected fills etc;

- lengths of strengthened or reinforced embankmshoulders;

- surcharge;

- cut/fill transition zones.

vi. Earthworks limits and batter slopes required.

vii. Landscape areas and extent of amenity bunds.

viii. Noise measuring stations.

ix. Extent of earthworks to structures.

x. Extent of earthworks to side roads andinterchanges.

xi. Extent of earthworks to main carriageway.

xii. Quantities of excavation, deposition and hardmaterial, with a clear statement as to what is, onecessary, what is not designated as hard matefor payment purposes.



ing

than

be

uch

ent

r ifrial

xiii. Details of special treatments (see (v)).

xiv. Exploratory holes in plan and section showinggroundwater strikes, standpipe/observation welllevels, extent of hard material, defined as eitherstrata or within limits defined by levels, shearstrength, MCV and Atterberg Limit testparameters.

3.40 It is suggested that the above information shoube shown on the drawings in the following format:

A. 1:25000 scale drawing showing geological planwith route superimposed.

B. 1:2500 scale plan drawings and 1:2500 horizon1:250 vertical scale longitudinal sections, showingexploratory holes, items (xiv) above formation level osections, centre line on plans and simplified geologyexploratory hole locations. Larger scales such as1:1250 horizontally and 1:125 vertically will benecessary for clarity where there is a preponderanceinformation.

C. 1:2500 horizontal, 1:250 vertical scalelongitudinal sections showing the earthworks anddetailing quantities of excavation and deposition; item(xii) above.

D. 1:500 scale plan drawings showing items (i), (ii)(iii), (iv), (v), (vi), (vii), (viii), (x), (xi) above. Morethan one volume of drawings will be required toaccommodate all these items.

E. 1:500 scale plan drawings showing item (ix)above.

F. 1:100 or 1:500 plan drawings showing standardand special details; item (xiii) above.

Interpretative information should not be included in thcontract documentation.

3.41 The earthworks to structures drawings (E) shouindicate the extent of filling to each structure and fillabove structural concrete foundations in order that thquantity and location of each class of material may bdetermined. The actual quantities should be includeon the earthworks drawings' longitudinal sections (Calong with all the other quantities.




earlygner, if

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alance,orkstitiesll best 600,

rksll inactionbease ofsition,

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3.42 It is convenient to divide the earthworks intosections corresponding with the following:-

Cuttings if large volumes involved, eachFills cutting or embankment may be subdividedStructuresInterchangesSide roadsLandscape areasAccommodation worksOthers including watercourses and drainage lagoons

3.43 These sections should reflect the separatetreatment of earthworks in the various Bills under theheadings of Roadworks and Structures as describedParagraphs 3.16 and 3.17. Thus the structuralearthworks associated with a bridge spanning a cuttiwill be kept separate from the cutting earthworksquantities. The following information in terms ofearthworks quantities should be provided whereappropriate for each section:-

Excavate Topsoil (Class 5A)Excavate Acceptable Material Class 3Excavate Acceptable Material other than Class 3 and5AExtra Over Excavation for Excavation in Hard MateriExcavate Unacceptable Material Class U1Excavate Unacceptable Material Class U2Deposit Acceptable Material Other than Class 3Deposit Acceptable Material Class 1C*Deposit Acceptable Material Class 3Deposit Acceptable Material Class 6B*

* See MCHW 4.1 Chapter IV Series 600 paragraph 31.

3.44 This information can conveniently be displayedthe Drawings using a table of quantities for eachearthwork. For billing purposes, quantities will need be entered on the earthworks schedules which includtotals for the whole Contract for each group ofmaterials. Proformas for completion are given inMCHW 4.2, Chapter IV, Series 600, pages 6 and 7.

3.45 Where there are major obstacles to the freepassage of earthmoving machinery through the site (rivers, railways, canals, major roads) then theearthworks need to balance between them byminimising import and/or export of material, using theprinciple of making the most economic use of materiavailable on site; this results in sub-divisions of thequantities of embankments and cuttings which exten



over these haulage barriers. This aspect needs consideration by the Department and by the Desi

into a series of discrete schemes. It should beremembered that what constitutes an 'obstacle' i

subjective and depends on the amount of money wit is economic to expend to overcome it. Althoughresponsibility for such decisions remains with theDepartment and the Designer up till contract awar

should also be remembered that the Contractor the. assumes ultimate responsibility in most cases a

earthworks will be hauled past an 'obstruction',there is an express restriction in the Contract to

in contrary (usually in Appendix 1/13).

ng 3.46 After an initial assessment of cut and fill bthe Designer should then ensure that the earthw

quantities balance arithmetically in the bill of quanwithin each contract within the scheme. This wi

be done by use of MCHW 4.2, Chapter IV, Series

Schedules" (sic) and "Typical Roadworks EarthwoSchedule", in that order. Where there is a shortfa

material for structures, the deposition and compof acceptable materials from elsewhere on site shall

al measured with the relevant structure(s). In the csurplus material arising from structures the depocompaction or disposal, as appropriate, shall bemeasured with roadworks. See also Paragraphs

4.38 concerning earthworks balance.

yet appointed, when the proposed works are being s

usually make the final decision as to whether soil for

pages 7 and 6, "Typical Structures Earthworks




or
material from structures deposition, compaction disposal, as appropriate, shall be measured withroadworks.


Volume 4 Section 1 Chapter 4Part 1 HA 44/91 Use of Materials and Construction

4. USE OF MATERIALS AND CONSTRUCTION

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Assessing Acceptability Criteria

4.1 The main objective of acceptability assessmentto enable the scheme to be constructed to a satisfactstandard of design and longevity for the minimum coThis requires the maximum use of on-site or locallyavailable materials, and setting specifications forimported materials which are adequate for performanbut not unnecessarily restrictive thereby incurringincreased cost. The change in name from `suitabilityàcceptability' is intended to emphasize this desire tomaximise the use of on-site materials, and also todemonstrate that although some material is not suitafor general or selected fills, it may be acceptable forother uses eg landscaping.

4.2 Clause 601.1 SHW defines acceptable materialthat which meets the requirements of Table 6/1 SHWand Appendix 6/1 SHW, and both Table and Appendhave been arranged so as to allow the Designer to butilise the available materials on each individualscheme. Table 6/1 SHW divides both on-site andimported materials into 9 principal classes, which arefurther sub-divided for compaction purposes or becauof particular properties or applications. It also lists thcriteria and relevant tests whereby a material may beidentified as belonging to a particular class, togetherwith the limiting values for some of those criteria whicdefine whether the material is acceptable or not. Appendix 6/1 SHW is the means whereby the Designcan state values for those acceptability limits notalready given in Table 6/1 SHW for the remainingcriteria tests. This Appendix gives the Designerflexibility by allowing him to vary the acceptabilitylimits of any fill material that would be acceptable insome circumstances and locations and not in otherswhich may prevail on a site. Figure 4/1 sets out arecommended sequence for the use of Table 6/1 SHand Appendix 6/1 SHW in the classification ofmaterials and the setting of the acceptability limits foreach property mentioned.

4.3 It is vital that site investigations should bethorough and carried out sufficiently in advance of thdesign stage to enable a proper appraisal to be madethe materials that will be encountered. The groundinvestigation should give comprehensive informationregarding the insitu ground conditions, particularlyconcerning those conditions governing acceptability



isoryst.

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ble

as

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W

e of

criteria as mentioned in Table 6/1 SHW. From theexploratory hole logs, sample descriptions, trial pit logexposures, and the results of those tests for whichacceptability limits are already specified in the Table,judgement can be made regarding which of thesub-divisions each material or stratum falls within, anwhether it can be regarded as acceptable or not. TheDesigner now assesses which of the acceptabilitycriteria he wishes to use for each material, eg MCV omoisture content, since all of them may not beapplicable at the same time, and after consideration ofthe insitu properties of he materials, establishesdesirable limits for those criteria he has chosen. Inarriving at these criteria he must take into account thetype of material ie cohesive or granular, and whetherthe tests are applicable to it, and also that the criteriawill be used during construction to check complianceand acceptability and the tests should be relativelysimple and robust. Table 4/1 gives a suggested list obasic tests which should help the Designer to assessclassification and acceptability of the materials. Additional tests may be required for specific andselected materials such as Saturated Moisture Contefor chalk or 10% Fines.

4.4 It should be noted that material classificationsmade during the GI to the British Soil ClassificationSystem (BS 5930) must be reviewed against therequirements of SHW Tables 6/1 and 6/2 since they anot always compatible.

4.5 An important aspect of classification for the SHWand of soils in general is the Particle Size Distribution(PSD). Poor sampling techniques particularly withgranular soils can mask the true profile, andparticularly, percussive boring techniques are unlikelyto provide samples of sufficient quality and size foraccurate PSDs (see Chpater 2). A knowledge of thesoils to be expected will enable the Designer to assesthat the test results are those which might be expectefor a particular soil type. As a guide engineeringproperties are mainly determined by the finest 25% omaterial in a soil sample. The coarser 75% doeshowever contribute to the soil compressibility potentiaSoil permeability, its ability to transmit water, is largeldetermined by the finest 10% to 15% of material. It cbe seen, therefore, that a knowledge of the geologicamake-up of the soils and careful interpretation of the data is essential if a decision on the proper use ofmaterials is to be made.



Chapter 4 Volume 4 Section 1Use of Materials and Construction Part 1 HA 44/91

4/2

STRUCTURAL CAPPING LANDSCAPING OTHERBULK

FILL FILL

GROUND INVESTIGATIONSAMPLES

CLASSIFICATION TESTS INTABLE 6/1 SHW ON

SAMPLES AS REQUIRED

PRELIMINARY DESIGNATION ASTABLE 6/1 MATERIAL CLASSES

AND SET PRELIMINARY LIMITINGVALUES FOR ACCEPTABILITY

PRELIMINARY EARTHWORKSDESIGN

ASSESS PROVISIONAL EXCAVATIONQUANTITIES OF EACH CLASS

AVAILABLE AGAINST FILL QUANTITIESAND LOCATIONS

DECIDE ON FINAL LIMITINGVALUES FOR APPENDIX 6/1

TESTS AND FINALMATERIAL CLASSIFICATION

CONFIRM QUANTITIES OFEACH MATERIAL CLASS IN

EACH FILL LOCATION

Figure 4/1 Earthworks classification assessment


PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED June 1991


ts to

TABLE 4/1

Classification and acceptability tests

TEST APPLICABLE PURPOSE REFERENCEMATERIAL TYPE

Moisture content All Classification BS 1377/BS 812

Atterburg Limits Cohesive Classification BS 1377

Particle Size Distribution Classification

MCV Cohesive and/or some Acceptability Clause 632 SHW

Maximum Density and Mainly Granular Acceptability BS 1377/BS 812Optimum Moisture CompatibilityContent

CBR All except coarse Trafficability BS 1377

Triaxial (quick) Cohesive Acceptability BS 1377

Chemical Tests All Acceptability BS 1377

Relationship Testing+ All Acceptability -

All Acceptability BS 1377*

Granular Trafficability TRRL LR 1034

Granular Stabilisation BS 1924

Stabilisation

Classification BS 1377

Trafficability

TRRL RR 130TRRL RR 90BS 1377

* BS 1377 Part 2 should be expanded to include all sieve sizes quoted in Table 6/2 SHW. See 2.2.

+ Testing soils at various moisture contents to study the change in soil properties.

NOTE: Further reference should be made to Paragraph 4.8 regarding a combination of a number of these tesdetermine acceptability limits.




may be

In MCV,studieds foundonship

t a

nt

r

uts

nd

he

t

al,

4.6 The preliminary earthworks design can now becompleted with appropriate side slopes. Theapproximate quantities of the required fill volumes foreach embankment or other fill area can then be asseagainst the available excavated materials for all thevarious requirements such as general fill, selected filland capping materials. The Designer may vary thelimiting values for acceptability in order to maximisethe use of the materials available. For instance a wecohesive material may not be acceptable for use in ashallow embankment, but may be acceptable if placewithin the lower areas of a larger embankment. Therefore a further sub-division of Class 2A would bemade in Appendix 6/1 SHW to allow for this and therestrictions under which the wetter material could beplaced would also be defined. However, care shouldtaken in the assessment of available quantities since material could quality for more than one classification

Assessing Acceptability Limits

4.7 When establishing the limiting values of theacceptability criteria the Designer should consider anumber of factors which could influence his choice ofvalues and therefore his choice of fill:-

i. Earthworks balance, haul distances and ease oftransportation within the site.

ii. Availability of imported material from localborrow pits and ease of transportation to the site.

iii. Ability of the material to withstand site andconstruction traffic. Information regarding the effect oearthmoving plant on soil conditions can be found inTRRL LR 1034, SR 522 and RR 130.

iv. Ability of material to compact to a satisfactorydensity (grading and natural moisture content).

v. Moisture content and susceptibility to moisture.

vi. Frost susceptibility and rate of water supplythrough underlying soil.

vii. Possibility of improvement by groundwaterlowering, drying.

viii. Chemical nature of material and affect on adjacematerial, structures, pipes etc.



ix. Availability of material for landscaping,environmental bunds etc.

ssed x. Location of material within the fill area. Itpossible to use poorer material in the core of anembankment.

4.8 A suitable method of arriving at the desirablet limits for acceptability is by relationship testing.

relationship testing, material properties such asd CBR, undrained shear strength and density are

at varying moisture contents and the relationshipare used as a basis for various decisions. Relatitests are used to:-

be i. provide information on soil characteristics aa range of moisture contents,.

f

ii. indicate susceptibility to a reduction in strengthdue to wetting and increased strength due to drying,

iii. help determine wet and dry acceptability limits fothe optimum use of available materials,

iv. enable acceptability assessments to be carried oby different methods and approaches, and correlationto be made between them,

v. aid site control testing where sometimes onlylimited data, ie moisture content or MCV, areimmediately available.

vi. help the Contractor assess plant requirements aassess haul distances.

4.9 Typically two or three relationship test packagesare required for each material type. If the material isvariable then relationships should be determined on ttwo èxtremes' and on the àverage' material. It isrecommended that the emphasis on the spread of tespoints should be to the `wet' side of optimum todemonstrate the more critical behaviour of the materiie CBR 2%, MCV 6 and shear strength 30kN/m . 2

Additional test points should always be included if theinitial spread is inadequate.




e rried

on

onde to

, B, Cainednd

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t pende

fromaluesass to ther

ert limits

andr

hen the

ed in bulke.

oftable

lead to a

that iners each

s urfacedprial

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4.10 A recommended test package is shown in Tabl4/2.

4.11 The use of relationship testing allows the Desigto relate various properties to each other by means othe varying moisture contents. For cohesive soils, afconsidering various matters such as trafficability(TRRL RR 130), stability and settlement, the Designemust decide upon a minimum shear strength or MCVThe upper limit is usually dependent upon the ability the likely compaction plant to compact a very stiff orhard clay, but a flexible approach is recommended toavoid having to dispose of dry material from site whiccould be used as a satisfactory fill material. Therelationship curves then allow these design values torelated to other properties, such as CBR and MCV, aenable a decision to be made on the most appropriamethod of assessment and site control testing. Forgranular soils the dry density/moisture contentrelationship is probably the most relevant with themoisture content range which achieves 95% of thestandard maximum density to BS 1377: Part 4 (2.5kgrammer method) being a reasonable yardstick to avolater significant settlements within the fill.

4.12 The values that the Designer will enter for theacceptable limits in Appendix 6/1 SHW should reflecthe results obtained from the comprehensive testingcarried out on the ground investigation samples. Nofixed figures can be given for the majority of thesevalues, which will obviously vary for different soilswithin the same material class, but the followingcomments should be considered by the Designer whpreparing Appendix 6/1 SHW.

4.13 Class 1 - General Granular Fill - Classes 1A an1B both contain moisture content and MCVacceptability properties. Moisture content is usuallyrecommended as the best option for specifying agranular material by means of the dry density/moistucontent relationship from the material samplecompaction curves and a permitted moisture contentrange may be deduced which achieves 95% of thestandard maximum density to BS 1377: Part 4 (2.5kgrammer method). Typically an acceptable range coube a lower limit of 1% to 2% below optimum moisturecontent and an upper limit of 1% to 2% above optimumoisture content. This does not totally preclude theMCV being related to those moisture contents and uas the limiting acceptability values if it is demonstrateby relationship testing, to be a responsive test on theparticular granular materials encountered. However is strongly recommended that either moisture conten


June 1991 PAPER COPIES OF THIS ELECTRON

MCV be used but not both. Either test can be caout on site for compliance testing and they are both

ner relatively slow compared to MCV. Further advicef the suitability and use of the Moisture Conditionter Apparatus with granular materials may be found

TRRL RR 90. In Scotland reference should be mar SDD SH 7/83.. of 4.14 Class 2 - General Cohesive Fill - Classes 2A

and D all contain moisture content, MCV and undrshear strength acceptability properties. The grou

h investigation samples should provide relationshipcurves for each material as described before. Typ

be acceptable strength limits for such cohesive matnd could be a lower limit of 30-50kN/m and an uppee limit of 150-200kN/m . The lower limit would de

on factors such as trafficability or stability, and thupper limit on the ability of the material to becompacted successfully using the relevant methodTable 6/4 SHW. From these figures, equivalent vmay be established for the other properties such

id moisture content or MCV and a decision made amost appropriate method of defining acceptability fo

Similarly lower MCVs of between 7 and 9 and uppMCVs of between 13 and 15 could be the starting

from which the equivalent moisture content, CBRshear strength figures are deduced. The Designe

should exercise his judgement and experience indeciding which properties he uses.

en 4.15 If Class 2A material is composed of chalk tSMC should not exceed 26%. This is more fully

d4.16 Class 2E, (PFA cohesive material) is discussParagraphs 5.58 to 5.66, but typical values for thedensity limits could be in the 1.3-1.65Mg/m rang

re4.17 The Specification considers separate classesacceptable material; however the mixing of accepgranular and acceptable cohesive materials can combined material which is unacceptable for the

ld purpose intended. It is recommended, therefore,variable materials, such as mixed sands and clays

m glacial tills, should be constructed in separate layacross the full width of the embankment ensuring

ed layer contains acceptable material. The upper sd, of impermeable layers should be cambered to she

water transversely. If it is unavoidable that the toit layers of an embankment are constructed of mate

simple although moisture content determination is

2

2

that material and construction compliance testing.

discussed in Paragraphs 5.8 to 5.20.

3


IC DOCUMENT ARE UNCONTROLLED 4/5


TABLE 4/2

Relationship testing - sample test package

TEST COMMENT

MCV/Moisture Content Calibration (5 points) As Clause 632 SHW. The changes in moisture content

Dry Density/Moisture Content BS 1377: Part 4, 2.5kg rammer method; 4.5kg rammer

CBR/Moisture Content BS 1377: Part 4 (Determination of CBR) on compaction

Shear Strength/Moisture Content Hand vane and/or penetrometer tests may be adequate

Atterberg Limits Natural Moisture For each test package. All tests to BS 1377Content/Particle Size Distribution

should be carried out by wetting and drying from thenatural state

method may also effect of greater compactive effort andvibrating hammer method for appropriate granularmaterials

sample from above. Normally unsoaked but may besoaked under appropriate surcharge for special studies. Normal surcharge is usually 10kN/m². CBR test oncompaction sample from dry density test if CBR mouldis used

on the MCV and CBR samples. Remoulded triaxialsamples may also be used at each moisture content forundrained testing. Vane and triaxial tests may notprovide collaborative data and site specific correlationsbetween these tests should be checked




se anh

ents. um

n P

size of

. Forld

f 5

rt

uphere is

at the MCV.

c -

hem the 4 osignVs

ese at

d toses

ant

susceptible to erosion then protection from wateringress should be provided.

4.18 Class 3 - General Chalk Fill - The designation ochalk fill as Class 3 material is discussed in Paragrap5.8 to 5.20. However the limiting values for SMCwould have a lower limit of 26% an upper limit ofapproximately 38%. The predicted moisture contentchalk fill is 0.85 x SMC in summer conditions and soupper limit for moisture content would beapproximately 33%. Chalk however is a notoriouslyvariable material and these figures should be treatedwith caution.

4.19 Class 4 - Landscape Fill - The fill for landscapeareas can usually be drawn from a far greater spectrof materials than other acceptable fills. It is notnormally intended that the material should be able tosupport foundations, safety or noise fencing, vehicleparking etc, and the limiting values of acceptability fothis class should reflect this. The basic requirement that the material should be able to be transported anplaced, be stable in its design profile, and be able toreceive sufficient compaction to avoid subsequentexcessive internal settlement.

4.20 It is recommended that for cohesive material thMCV test is used, with values of 6 or more, whereasgranular material the maximum moisture content coube in the range of 1.4 to 1.6 times the optimum valuegive 90% of maximum dry density to BS 1377: Part 4(2.5kg rammer method). The Designer can widen ornarrow these ranges of values depending on availabof better material or for any particular material he mawish to use solely as landscape fill. The gradingrequirements would be similarly variable.

4.21 Class 6 - Selected Granular Fill - Class 6D, H, IN and P all contain moisture content and MCVacceptability properties. As discussed for Class 1granular materials, moisture content limits are moresatisfactory than MCV, and should be set at the rangmoisture contents which achieve 95% of standardmaximum density to BS 1377: Part 4 (2.5kg rammermethod) for Classes 6D, H, I and J, and to BS 1377:Part 4 (vibrating hammer method) for Classes N and

4.22 Classes 6I, J, N and P all refer to structuralbackfills and the properties listed in Table 6/1 SHWwill have been tested and defined as stated. Thesevalues will have been used in the design of the relevstructures, and the Designer should investigate what



percentage variation in these properties would cauunacceptable change in the Factors of Safety of eac

f Appendix 6/1 SHW for properties such as M' and c', thehs coefficient of friction and the adhesion for fill/elem

Further information is given in Technical Memorand(Bridges) BE 3/78 (Amended 1987) Reinforced Earth

of Retaining Walls and Bridge Abutments for an Embankments, and BD 30/87 Backfilled Retaining

Walls and Bridge Abutments.

4.23 Where permeability figures for Classes 6N aare required, the actual permeability of the material

hydraulic gradient permeability test method. Theum precise test depends upon the maximum particle

the material, and full details of the procedures andequipment are given in BS 1377: Part 5 and Part 6testing in the triaxial cell, vertical permeability shou

r be measured. If imported material is to be used, ais minimum value for the coefficient of permeability od x 10-5m/sec is recommended.

4.24 Class 6F2. The 10% Fines minimum value fomaterials found on-site should be set 10% below tha

e taken during the ground investigation and rounded for although a minimum of 50kN is recommended. Wld imported fill is to be used a minimum value of 50kN to recommended.

4.25 Class 6K, 6M and 6Q. It is recommended thility moisture content be specified in preference to they However if it is necessary to quote values for MCV

then they should be the equivalent figures for themoisture content values, ie the MCVs at optimum m

, J,4.26 Class 7 - Selected Cohesive Fill - Class 7A. Tcompaction requirement should be established froground investigation samples using BS 1377: Part

e of (2.5kg rammer method). The limiting values of c,M

and c', M' should be set by the Designer to correspond tthose values which would significantly affect the deof the structure, and the recommended limiting MC

P. or moisture content values set to correspond to th

material is chalk, the SMC values are recommendebe 20% and 26%, which includes part of chalk Clas

A and B of TRRL LR 806.

structure. It is these limits which should be included in

should be measured using a constant head or constant

value measured from samples of acceptable material

2%, and at optimum mc + 1%.

the limiting levels of the specified compaction. If the




t the

be

, the

eing/1stto

ertiesnd. A

ndoyers

o

her

al

s

f

sf

4.27 Class 7B. PFA is more fully discussed inParagraphs 5.58 to 5.66, but limiting values of bulkdensity should be in range 1.3-1.65Mg/m . As stated3

for Class 7A, the limiting values of c, M and c', M' andcoefficient of friction and adhesion (fill/element) shoube established by the Designer. A reasonablepermeability figure would be between 1x10-8m/sec a1x10-6m/sec, although figures for the actual materiashould be obtained from the supplier.

4.28 Classes 7C and D. The values of c', M' and thecoefficient of friction and adhesion (fill/element) shoube established by the Designer from the structuraldesign. The upper limits of moisture content for Clas7C can be based on these values of c' and M', and thelower limit on the equivalent MCV of 13 to 14. Thelimiting values for moisture content or MCV for Class7D should be those which equate to the 95% ofmaximum dry density to BS 1377: Part 4 (2.5kgrammer method).

4.29 Class 7E. This material should be subjected totests to determine what range of moisture contents, therefore MCV, in its untreated state would give 95%maximum standard dry density to BS 1377: Part 4(2.5kg rammer method) in its treated condition. Thiswill obviously be affected by the percentage of addelime, and it may be advisable to carry out a series oftests to allow for different percentages of lime conten

4.30 Class 8 - Miscellaneous Fill - Since this materiacomposed of either Class 1, Class 2 or Class 3 themoisture content or MCV limiting values should beestablished in the same way as each respective matclass. It is noted that the MCV test is not generallyrecommended for use with granular material althougmay be used with a few specific granular materials, sParagraph 4.13. Compaction requirements have beleft unspecified in Table 6/1 SHW, but should matchthe requirements for the relevant material class,although circumstances on site may dictate the use alternative methods and plant.

4.31 Class 9 - Stabilised Materials - In general, forClass 9A the limiting values of moisture content coulbe based on achieving 95% of maximum dry densityusing 2.5kg rammer method of BS 1924; for Class 9the limiting values of moisture content are to be baseon achieving the end product specification; for Class9B and 9D the limiting values are based on achievin95% of maximum dry density to BS 1377: Part 4 (2.5rammer method). The minimum bearing ratio isrecommended to be 15% to be achieved at the end appropriate curing periods for Classes 9A, 9B, 9C, a9D. In any event the specified minimum bearing ratimust be achieved before subsequent construction la



are placed and compacted. The maximum MCVrequirement for Class 9D material should be set aminimum moisture content which would normally

allow 95% of maximum dry density to BS 1377: Part 4ld (2.5kg rammer method); the minimum MCV should

based on achieving a bearing ratio of 15%, takingnd account of lime content and curing period.l

4.32 When preparing Appendix 6/1 for the scheme

SHW, but only list the classes of material that held intends to use, and for these classes, only list thos

properties required for acceptability testing includs those for which limits are already given in Table 6

SHW. Therefore Appendix 6/1 will give a complete liof acceptability criteria and limits for each material be used in that scheme. If different or alternativematerials are later specified the full details of prop

should also be given in this form. Those criteria amaterial classes not required should not be included

Advice Note.and of

d

t.

l is

erial

h itee

en

of

d

Cd

esgkg

of

Designer should use the same format as Table 6/1

sample Appendix 6/1 is included in Annex A to this

Earthworks Balance

4.33 On an ideal scheme the quantity of fill requiredshould match the quantity of acceptable excavatedmaterial, and whenever possible schemes should be sarranged that there is a near balance between cut andfill. However in arriving at the final earthworks figuresand deciding upon the classes of fill for eachembankment as shown on the earthworks' drawings, tfollowing factors should be considered and allowed fowhere appropriate.

4.34 The distribution of the different classes of materiin the cuttings; the availability of those materials for fillin the embankments and the sequence in which theywill become available and be required.

4.35 The various restrictions which could apply to theexcavation, haul and deposition of fill material, such athe presence across the site of an obstruction (egrailway, river, wet ground, main road or motorway); theability of the insitu material to withstand the passage othe earthworks plant hauling the fill without therequirement of an expensive haul road; possiblerestrictions in land availability which could requiresteeper side slopes to some embankments and cuttingand which in turn could necessitate a particular type omaterial being specified for that fill material.




ifiedofction and is inecifiedoduce

aterial.

77:nsityd 4

one arehould2. made

liesethods

ethode

d by it mayf SHW so that

insituteheth any

er

e

n

o

4.36 Where imported materials are required, locallyavailable materials should be investigated in the firstinstance. The highway maintaining authority must beconsulted regarding possible access roads to the siteand their distribution along the site could be critical insome cases. Department of Transport Circular 3/87contains information regarding Planning Authoritiesand borrow pits etc.

4.37 Landscape areas within the construction site casometimes be used as a convenient reservoir foracceptable material. They can be increased ordecreased as construction proceeds by providing onlocations for placing excess fill, or by reducing theextent and nature of the landscaping if the amount oacceptable fill material is less than anticipated. Therefore the contouring of a landscape area shouldbe too rigidly specified to allow the site engineers solatitude in the amounts of material put into it, but ofcourse the basic function of the area must always beprimary importance which is usually to protect orpreserve an existing feature. Off-site landscape areaare normally shown in contract documents as part ofsite to ensure all provisions apply to them. Theyusually require planning permission and thereforeshould be considered permanent features duringconstruction and should not be used to temporarilystockpile material.

4.38 When considering all these factors, the temptatto anticipate how the Contractor will programme theearthworks and select fill material must be strictlyavoided. What may seem to be an obvious sequencwork to the Designer when preparing the earthworkdocuments may not be so attractive to a Contractor,who could well be subject to financial and commerciarestraints and pressures which the Designer could nopossibly foresee. The Designer should thereforeconcentrate on the finished earthworks and let theContractor decide how to achieve it within his overallprogramme.

Compaction

4.39 Soil compaction is the process whereby soilparticles are constrained to pack more closely togeththrough a reduction in air voids leading to reducedinternal settlement, higher strength and stability of thcompacted material.

4.40 Two basic types of compaction specification cabe applied.



4.41 Method. The method of compaction is specin terms of plant, method of operation, thickness layer and number of passes. This type of compa

, specification is detailed in Table 6/4 of the SHWthe type specified for most of the material classesTable 6/1 of the SHW. The compactive effort sp

in Table 6/4 for Methods 1 and 2 is designed to pra maximum air-voids content of 10% assuming a

n average field moisture content for the relevant m

4.42 Method 3 should give approx 95% of BS 13-site Part 4 (2.5kg rammer method), maximum dry de

assuming a conservative moisture content; Methof should produce a maximum 10% air voids at high

moisture content (chalk); Method 5 is based on not continental experience which gives satisfactoryme performance when this compactive effort is used

coarse granular material; Method 6 should produc of maximum 5% air voids at a lower limit of moistu

content for sub-base compaction, and Method 7 ss produce a maximum 5% air voids at a MCV of 1

the However this does not preclude provision being for some insitu density testing to ensure that thecompactive effort is sufficient. Where a material across a boundary between two of the different mof compaction described in Table 6/4, then the m

which requires the higher compactive effort should b

ion4.43 End Product. The state of compaction to beachieved is specified, leaving the choice of metho

e of which it is achieved to the Contractor. Even so,be advisable in some instances in Appendix 6/3 oto restrict the thickness of each compacted layer

l effective control can be maintained on site. Thist control will necessitate the determination of the

bulk density and moisture content for the compledepth of the compacted layer or, failing this, for t

lower 150mm of the compacted layer, together wiother material property defined in Table 6/1 of SHW.

conservative moisture content which is dry of the

specified.

4.44 Vibrating rollers are now extensively used and inurban areas excessive vibration may cause damage tadjacent buildings. In contracts where this is thoughtlikely TRRL RR 53 should be referred to for advice.




d

inult tohardl maymeious

d

of

t

ks

to

esy

ch

Instrumentation

4.45 The use of instrumentation as a means ofgathering geotechnical information for highway-relatearthworks may be divided into two main areas ofoperation.

i. Monitoring of construction. This is the mostfrequent application for instrumentation and is usedwhere uncontrolled filling, excavation or otheroperation would invalidate design assumptions orreduce factors of safety to potentially dangerous leve

ii. Performance evaluation. The object here is toprovide data on the performance of the earthworks ostructure. This is used to assess compliance with deassumptions and to predict long term behaviour.

4.46 There are a great number of applications forinstrumentation and many different types of instrumebut the most common measurements within thehighway context are included in the following.

i. Vertical and horizontal movement. Measuremeof movement is commonly carried out by the use ofsettlement pins or gauges, profile gauges,extensometers, strain meters, inclinometers,photogrammetric methods etc.

ii. Measurement of pore water pressures, by variotypes of piezometer such as open standpipe,Casagrande, electrical, pneumatic etc.

iii. Earth pressures by various cell types.

iv. Load measurement, by load cells, strain-gaugedload cells, vibrating wire load cells etc.

4.47 Instrumentation can be expensive, so whenconsidering its use on a highway scheme thegeotechnical problems must be properly defined toestablish the extent of the required data. The type aquantity of instrumentation proposed can then bejustified and the frequency of readings properly set. The physical location of the instruments is obviouslyvital, and areas of uncertainty must first be establishin the design process. A decision can then be madeto which of these areas is critical and what informatiois required. It should be remembered that simplesolutions are often the best, for example a row of pealong the toe of an embankment can provide a reliabindication of impending slope failure at low cost.


PAPER COPIES OF THIS ELECTR4/10

ed

ls.

rsign

nt

nt

us

nd 4.51 See also Chapter 3 on measurement of harmaterials. Rock assessment can be based on thedifficulty of excavation and handling the materialscuttings. Some soft rocks may be extremely diffic

ed excavate when in massive forms in cuttings and as rocks in thin bands interlayered with soft materian be excavated easily. Whilst the GI will provide so

pointers the best assessment will come from prevgs experience of a comparable material in a similarle geotechnical and design situation.

4.48 It is essential that provision is made for propercalibration of the instrumentation before installation anfor checks to be made on read-out units, probes etcduring the course of construction. Adequate referencepoints should be located outside the area of influence the construction. Sufficient time must be allowed fordatum readings to be taken prior to commencement ofconstruction.

4.49 Damage to instrumentation is almost inevitableand back-up instrumentation may be required in areaswhere it may be vital to keep a constant flow ofinformation. However in areas where instrumentationis vital to the control of construction, an AdditionalSpecification Clause should be included in the contracstating that, if the instrumentation is damaged and thedata is affected or is discontinued, then no further worin that area shall be allowed until the instrumentation ireplaced or repaired, and is again operatingsatisfactorily. When locating piezometer read-outcabinets, inclinometer ducts etc, potential vandalismmust be considered, and appropriate measures taken either physically protect instrument housings or locatethem in an inconspicuous position. Whilst access to thinstruments may be simple during construction, accesin the long-term, after a road or motorway is open, mabe much more difficult, and thought should be given tothis problem.

4.50 At the time of recording, the instrumentationreadings must be related to values which the Designerhas specified will correspond to two levels ofawareness; a trigger value to alert and allow correctivemeasures to be taken, and a critical value beyond whithe construction is at risk. It is essential that theEngineer designates one or more individuals toco-ordinate the reading and analysis of the results.

Rock Assessment and Fill


ONIC DOCUMENT ARE UNCONTROLLED June 1991


gs

PF)

hing

4.52 Rock fill is a term which will not be found inSHW or MMHW, but, for all intents and purposes,SHW Classes 1C, 6B and 6C are rock fill. Suchmaterials need to be hard and durable. The gradindiffer for each of these classes but soundness isdetermined by the soak Ten-Per-Cent Fines Test (Twhere a fines value of 50kN needs to be achieved. Other classes of material may be produced by crusrock and it should be noted that a number of otherclasses also require a TPF value to be met.



Volume 4 Section 1 Chapter 5Part 1 HA 44/91 Information on some Specific Materials

5. INFORMATION ON SOME SPECIFICMATERIALS

hh

enahe

s se

H

nds beering

d

g

.

General

5.1 Some general information is given below for awide range of soils and rocks, to help Designers withtheir classification and assessment of materials. Insome cases, for example chalk and PFA materials, tuse and treatment of a particular material is describesome detail. More specific information on assessingmaterial types, their classification and acceptability igiven in Chapter 4.

Argillaceous Rock

5.2 Argillaceous rocks have been defined by the Sprincipally to prohibit their use in most of the SHWClass 6 `Selected Granular Materials' and is not usethe strict geological sense. The definition includesshales, mudstones, slates and unburnt colliery shale(Minestone). These materials have a tendency to brdown during weathering and are unlikely to have thelong-term durability required for Class 6 materials: they also exhibit properties which can make themchemically aggressive to structures. Shales may alsexhibit the same problems as those described forunburnt colliery shale in Paragraphs 5.27 to 5.30 anParagraph 12.14.

Soft Rocks

5.3 The term `soft' applied to rocks is not particularmeaningful except in so far that it tends to describethose materials which are likely to break down durinexcavation, placing, compaction or most importantlyservice. Rocks under this heading are likely to besedimentary deposits. But some metamorphic rockssuch as schists, and some igneous rocks are also vesusceptible to weathering. This does not preclude srocks from being used. Nearly all materials will fit inthe SHW classification system, and soft rocks,especially those of a basically granular nature, may used as one of the selected granular fills; the class omaterial and the design parameters depending on thdegree of degradation of the material.



Sherwood Sandstone (includes Bunter Sandstone)

5.4 Sherwood Sandstone consists mainly of softisrock composed of cemented particles of sand whicbreak down during compaction and beneath

he construction traffic. It is uniformly graded and whd in freshly excavated has been used successfully as

capping layer on embankments. When trafficked tpercentage passing the 75 micron sieve can increa

from approximately 10% to 20%, making it frost

W

d in

eak

5.5 Mercian Mudstone is largely comprised ofargillaceous rocks and outcrops widely in the midla

o and West of England. Their bearing capacity candifficult to assess due to a variable depth of weathand interbedding with sandstones. They are often

highly fissured and the resultant percolation of water

ly

in

,ry

oftto

befe

susceptible. It is not recommended for use as cappingin cutting unless good drainage can be assured. Although very weather susceptible, degrading to alower permeability and CBR, it has successfully beenused as a fill to structures. Close control of both theupper and lower moisture content limits is advisable toensure good compaction.

Mercian Mudstone (includes Keuper Marl)

leads to softening around the fissures. Near the groundsurface the whole mass may be softened by weatheringThe classification of `Keuper Marl' into four weatheringzones, together with typical index properties, effectivestress parameters and other properties can be found inCIRIA Report 47. Details of allowable bearingcapacities can also be found in BS 8004:1986;Foundations; Section 2. The 1976 Rankine Lecture`The Triassic Rocks' by A C Meigh, is also a valuablesource of information on the geology of MercianMudstone.

5.6 Mercian Mudstone generally contains sulphates,and tests should be carried out as part of the groundinvestigation to discover their concentration. They maybe sufficiently high to require protection measures toadjacent steel or concrete.



Chapter 5 Volume 4 Section 1Information on some Specific Materials Part 1 HA 44/91

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5.7 In places, rocksalt within the Keuper Marl hasbeen mined. CIRIA/PSA publication `Constructionover abandoned mine workings' discusses methods dealing with problems associated with mined areas. Man-made or natural disturbances of the groundwateregime can dissolve the salt beds resulting in subsid(Howell and Jenkins, 1976).

Chalk

Description

5.8 Chalk is usually a soft, white, porous, jointedlimestone of greatly varying strength. However in thelower layers of the Lower Chalk there is a transitionzone from the underlying clays which consists of agreyish or buff coloured chalk marl. The marl can befound either in separate layers, or homogeneouslydistributed in varying proportions with the chalk. Insome cases the marl can form up to 40% of such amixture. The upper layers of Lower Chalk, togetherwith the Middle and Upper Chalk, are much purer. Some relatively thin layers of very hard chalk aresometimes found at intervals throughout the Chalk ain the Middle and Upper Chalk, bands of flint nodulesare also found.

Moisture Content

5.9 Chalks have a natural moisture content varyingfrom 8% to 36%. During earthworks operations theexcavation and compaction processes break down thnatural structure of the chalk releasing some of thiswater and generating fine material. If the amount offines and released water, added to any free water foin the joints, is high enough, then the result is atemporarily unstable fill material which may remainunstable for a period varying from days to weeks,depending on the rate of drying. Therefore anyclassification of chalk for acceptability as a fill materimust be based on a prediction of moisture content andegree of crushing. It has been found that stableconditions are likely at moisture contents below 23%and these stable conditions can be maintained abovethis moisture content by reducing the degree ofcrushing, ie by reducing the compaction, and selectioof appropriate earthworks plant.


5.10 On sites where chalk is present, the GroundInvestigation should include trial pits or large diameteshafts to obtain suitable samples of the chalk, both fo



classification purposes and to inspect the structurethe chalk. Closed circuit television cameras may a

of be lowered down the shafts for an insitu inspectithe degree of fissuring and flint content. Where t

r are deposits of other materials overlaying the chaence interface between them can be sharply undulatin

solution features can allow extensive infilling of the

nd

e

und

ald

,

n

rr

overlaying deposits into the chalk. Consequently,additional boreholes may be required at criticallocations such as structural foundations.

Chalk Classification

5.11 The classification test for chalk requires themeasurement of the saturated moisture content (SMCas described in Clause 634 SHW and the ChalkCrushing Value (CCV) as described in BS 1377: Part 4Using the results from these tests, the chalk samples cbe classified from A to D by employing the ChalkClassification Chart in Figure 5/1 which is based on thchart from TRRL Laboratory Report LR 806. Thepercentages of each class of chalk likely to be presentwithin each cut area and also for the whole scheme cathen be estimated. The earthworks classification of thmaterial in Appendix 6/1 of SHW will depend on thesepercentages. It should be noted that the chalkclassification must not be quoted in the Contract, beingfor the Designer's use only. The recommendedearthworks classification procedure for chalk, and othematerials which may be mixed with it, is given in a flowdiagram in Figure 5/2. Whilst this procedure should beapplied individually to each cutting containing chalk, itis possible that a small cutting may be included with alarger adjacent cutting for the purposes of earthworksclassification. However, the chalk must be looked at aa whole and the chalk classification described aboveshould be viewed as an aid to assessing the chalk marather than a mechanical exercise which is complete initself. There are areas of greatly disturbed chalk, oftencontaining solution features, where the quality does noalways improve with depth, and in these areas a simplchalk classification may be inappropriate because of thvariability. In such cases, unless there is anoverwhelming requirement for the chalk to be used asfill, it should be classified as acceptable for landscapinarea only (Class 4) or as unacceptable because of thedifficulty of specifying suitable overall compactionmethods.

Chalk Compaction

5.12 The Designer should bear in mind whenconsidering the use of cut material that Chalk Classesand C may occasionally produce unstable conditions




Ju

36

34

32

30

28

26

24

22

2.6 3.0 3.4 4.2

23.5

27.8

30.4

CHALKCLASS D

CHALKCLASS C

CHALKCLASS B

CHALKCLASS A

SA

TU

RA

TIO

N M

OIS

TU

RE

CO

NT

EN

T (

PE

RC

EN

T)

CHALK CRUSHING VALUE

Figure 5/1 Chalk Classification Chart


ne 1991 PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED 5/3


5

CLASSIFYAS SURPLUS

IS CHALK REQUIREDFOR FILL?

NO

YES

GROUND INVESTIGATION

CLASSIFICATIONOF CHALK TO

FIGURE 5/1

IS CHALK GREATERTHAN 30% OF TOTAL

EXCAVATIONNO YES

IS % SOFT CHALK (CLASSESC & D) MORE THAN 30% OF

TOTAL CHALK EXCAVATION?

NO

CLASSIFY ASCLASS 1 OR 2

MATERIAL

CLASSIFY ALL CHALKAS CLASS 3 MATERIAL*

IS CHALK PREDOMINANTLYHARD? (CLASSES A & B)

YES

NOKEEP TO COMPACTIONMETHOD 4 IN TABLE 6/4

YES

NO

YES

IS SMC LESS THAN OR EQUAL TO 20%

CHANGE TO COMPACTIONMETHOD 2 IN TABLE 6/4(USING APPENDIX 6/1)

CHANGE TO COMPACTIONMETHOD 1 IN TABLE 6/1(USING APPENDIX 6/1)

Chalk having a 10% Fines valueof 50kN or more should beclassified as Class 1C material

*

Figure 5/2 Flow diagram for use in classifying chalk




ss A

laxed. thatation

l is

ambered causectinglong

, and

ent

ned

le from

tl.

g

t

even when the specified type of compaction plant isused. It may be better to leave the compaction methunchanged and remove occasional unstable materialwhen it is found or allow for delays to recover stabilityrather than reduce the compactive effort and risklong-term settlement in the under-compacted materiaThe flow diagram also indicates which compactionmethod from Specification Table 6/4 should apply. Method 4 compaction should be used for chalkdesignated Class 3 material which is wholly or mostlycomposed of Chalk Classes other than A or B. If theClass 3 Chalk is predominantly A or B the compactiogroup should be amended to Method 1 if the SMC isgreater than 20%, or Method 2 if the SMC is less thaor equal to 20%. The Resident Engineer therefore mreduce the compaction requirement if it is found toconsistently cause instability on site.

Information for Appendix 6/4 5.13 If Class 3 material is designated in Appendix 6/1further information should be given in Appendix 6/4, othe following. 5.14 The time period, when no Class 3 earthworks stake place (Clause 605.1(i)) ie Winter. This is intendto be the period when the rainfall exceeds theevaporation rate, over monthly or weekly periods. Amethod does exist for calculating the evaporation ratbut the formula is very complex and is not reallysuitable. A practical approach to the prediction of themost likely period is to use the rainfall and theevaporation figures from the Meteorological Officelong-term statistical records. Analyses of records forthe last 25 years are available for any area in the UnKingdom and may be obtained from the MeteorologicOffice Advisory Service at Bracknell. If the appropriarainfall or evaporation figures are not available, then winter period of 1st November to 31 March should bespecified.

5.15 Minimum height of excavation (Clause 605.1(iii)). If possible this height should be extended to 5mand worked as a quarry face. However it would bepreferable to work a 6m high cutting in two layers of3m each rather than a 5m layer followed by a 1m layand so the depth of chalk in the cuttings must beconsidered before amending the minimum excavationheight. If the chalk is surplus and will be taken off-sitthen the plant restriction and minimum height may beignored.



5.16 If the majority of chalk is estimated to be Claod or B the restriction of haulage vehicles to a 15m3

maximum capacity (Clause 605.1 (v)) may be reIf there is any doubt it would be preferable to leavedecision to the Engineer on site after close observ

l. of the behaviour of the material.

5.17 Layering of Class 3 Chalk with other materianot recommended unless absolutely unavoidable(Clause 605.1 (vii)). However if chalk is placed onless permeable material, that material must be ca

n to shed water transversely. Failure to do so couldfree water released during the placing and compa

n processes to pond inside the chalk with possible ay term instability setting in. Therefore if composite

embankments are envisaged the surface of anyrelatively impermeable material must be cambered

Appendix 6/4. For the same reason Class 3 material

;n

halled

e

itedaltea

5.20 Materials which cannot be separated from thchalk and are therefore included with it, such as fli

er, bands or any other material which may affect theContractor's method of working, should be mentioin the Contract. Where infilling occurs of solution

e, features by overlying material, the infilling materiashould be excavated separately and kept separat

a suitable requirement to this effect included in

must extend the full width of the embankment and musnot be contained within bunds of impermeable materia

5.18 Period of waiting (Clause 605.1 (viii) and (ix)). Ifrequired, a pre-contract trial may be carried out on thechalk to investigate its readiness to become unstableand then stable again. If the time for the hardeningprocess is delayed beyond 4 weeks the period inAppendix 6/4 should be lengthened accordingly:similarly if the chalk hardens quickly the period may bereduced. Chalk which has been contaminated withsandy material sometimes requires a much longer timeto harden.

5.19 Rolling to seal material at the end of each workinday (Clause 605.1 (x)). If the chalk is estimated to bevery hard or very soft, this rolling may be omitted. Also if the chalk has become unstable, rolling mayaggravate the situation by preventing the chalk fromhardening, and should also be omitted by the ResidenEngineer.

Included and Infilling Materials




entritish

rface spoilcrued

ed fillable

in

l

e

r.

h a

the chalk, allowance being made for this in theContract; the excavated material is usually classified unacceptable. Treatment of infilled solution featuresusing granular infill and concrete plug or similarmethods should be included in a detailed specificatioespecially where extensive treatments have to be carout.

Coal Measures

General

5.21 Coal is the most important lithology within theCoal Measures, although the bulk of the beds aresandstones, siltstones and mudstones with seat earthand sometimes limestones and other rock types. Durmining operations quantities of these rocks,unavoidably extracted with the coal or in driving theaccess tunnels, are brought to the surface with the coThe separated non-coal material is known as Minesto(Paragraphs 5.27 to 5.30) and is usually tipped ontospoil heaps. Many of the problems associated with thshales and mudstones of the Coal Measures also appto Minestone.


5.22 The Coal Industry Nationalisation Act 1946vested, with a few exceptions, the freehold interest ofall coal and mines of coal including shafts and outletsthe National Coal Board later renamed British Coal. Iis therefore necessary that British Coal be consultedbefore any ground investigation is carried out on landbeneath which there are coal seams and again whenlocation, depth and thickness of the seams, are knowand the road design is being considered. The OpencExecutive of British Coal should be consulted forinformation on worked, prospected and proposed siteFurther information on ground investigation procedurefor land, where coal seams, opencast sites and mineshafts are known or suspected, is given in DepartmenAdvice Note HA 34/87.

Disused Mine Workings

5.23 If disused mine shafts and adits or other workinghave been located and identified there is the chance they may well cause surface instability in underminedareas. Methods of dealing with the various problemsassociated with mine workings are discussed in theCIRIA/PSA publication `Construction over



abandoned mine workings', and also in `The Treatmas of Disused Mine Shafts and Adits' published by B

Coal, Mining Department.

nried

s,ing

al. ne

ely

int

thenast

s. s

tal

s mudstones and siltstones and is brought to the suthat during the mining of coal, to be placed in colliery

tips. Large amounts of this waste material have acover the years and are potential sources of importmaterial. Minestone can, however, have consider

ranges of hardness and durability depending on the

Slope Stability

5.24 Care should be taken when designing cut slopes Coal Measures rocks. The mudstones and siltstoneswhich are found in the Measures may containweathered layers which have softened and are potentiaslip planes. Indeed, there may be existing slip planesalready within these soft clay layers and cutting slopefailures have occurred because of them. Groundinvestigations in these materials should be verycarefully conducted so that these potential shear zonesare identified.

Soil Aggressivity

5.25 The dark colours of some mudstones may indicata high proportion of disseminated pyrite which mayoxidise in time and form sulphuric acid (H2SO4). Hawkins and Pinches reported that samples ofmudstone retested after 17 months showed a fivefoldincrease in SO3 content. Therefore, when thesemudstones are present, care should be taken that theeffects of such an increase in SO3 content andconsequent increase in soil aggressivity are allowed fo

5.26 One additional problem is that when H2SO4 isleached from these materials and comes into contactwith carbonate rocks, gypsum is produced. Within adrainage system this can cause blockages and beneatroad pavement it can cause heave. The reactionbetween the acid and carbonate rocks also producescarbon dioxide (CO2) which can cause asphyxiation inconfined spaces.

Minestone

General

5.27 Minestone is the generic term for unburnt collieryshale which is a mixture of rock debris from the CoalMeasures. The debris mainly contains shales,

strata worked and the method of mining.




e

es 6

ed

r

ss

n

Colliery Spoil Tips

5.28 The material in older tips often have a high carbcontent whereas newer tips tend to contain moresandstone waste and coarser discards. The older tipare nearly always loose and open textured allowing ato penetrate the tip. If the coal in the tip is ignited, forany reason, a burning section can consequently besustained and extended. These older burnt tips cancontain anhydride salts which expand on exposure tomoisture. Newer tips are compacted, significantlyreducing the opportunity for sustained fires.

Minestone in Fill

5.29 Minestone, if compacted to the SHW, will notspontaneously combust as oxygen will be excluded. Many examples exist of hot burnt minestone beingsatisfactorily compacted to form stable embankmentsMinestone can therefore make very good all-weathergeneral fill provided it is of sufficient quality. Someshales may be prone to softening and swelling ifexposed to moisture and weathering when stockpiledIt is the Department's policy that the Designer shouldidentify possible sources of this material for importedfill and ensure that Tenderers are aware of them. However, Tenderers must be left to choose their souron a commercial basis, and it is unlikely that a hauldistance to site of more than 20km will be economic. The designation of sources of fill does not inferacceptability and testing must still be conducted. Further information on available sources may beobtained from British Coal Minestone Services,Philadelphia, Houghton le Spring, Tyne and Wear, DH4TG.

5.30 In the unburnt state, minestone is not one of thepermitted materials for the selected fills defined inClasses 6 and 7 of Table 6/1 SHW: the use ofMinestone as a fill to bridge abutments and retainingwalls is also prohibited in BD 30/87. Furtherinformation is given in Tech Memo H4/74, `The use oColliery Shale as Filling Material in Embankments'. See also Paragraph 12.14.

Sands and Gravels

5.31 Sands and gravels originate from the weatherinand disintegration of a wide variety of rocks. Commonly the geological processes of transport anddeposition are by water but many deposits are formedby wind action (producing perfectly rounded sandgrains) and some by ice action and others under theaction of gravity. The majority of sand-size grains areof quartz which is the mineral most resistant to



on

sir

.

.

ces

4

f

g

weathering whereas gravel-size fragments and stonescan consist of a wide variety of rock types. However,gravels in the Midlands and South of England areusually flint, quartzite or limestone. In the North ofEngland and in Scotland, mixed gravels occursometimes containing pieces of soft material, such as,clay lumps, shale or soft sandstone, which are a sourcof weakness.

5.32 Many deposits consist of a mixture of both sandand gravel size particles (as defined in BS 5930 but sealso Paragraph 4.4) and some of the Class 1 and Clasgranular materials in Table 6/1 of SHW can bedescribed as `sand and gravel' whereas other areessentially `gravel' or `sand' only. Table 6/2 of theSHW gives the particle size limits of these classes. Grain shape can affect engineering properties egangular sands have a higher shear strength than roundsands because of enhanced granular interlock.

5.33 Acceptability of sands and gravels may be statedin terms of moisture content, although for some sandsMCV is also practical. Assessing moisture contentsmay be difficult especially as the material becomescoarser and the percentage exceeding 20mm sizebecomes critical. Sands and gravels are free-drainingand will become àcceptable' within a short period afteexcavation, however the presence of fines may inhibitdrainage. If initially too wet, sands and gravels exhibitfrictional behaviour when sheared even under rapidloading conditions. Settlement under load is almostimmediate.

Heavy Clays

5.34 Heavy clay is a term used to denote soils of highplasticity; they are usually encountered in anover-consolidated state and comprise such geologies aLondon Clay, Oxford Clay, Gault Clay, etc. The excesnegative pore pressures of these clays developed onexcavation are only slightly reduced with time whenplaced within the embankment. On the surface of acutting or embankment slope, with a steady supply ofwater from various sources, excess negative porepressures dissipate locally with a subsequent loss ofshear strength and reduction in the factor of safety. Failures have occurred as a result of this mechanism,over varying time scales following construction; theseusually take the form of shallow slips with a typicaldepth of failure plane ranging from 1.0m to 1.5m asdescribed in TRRL RR 199 (see Paragraphs 7.2 to 7.6and Paragraphs 8.2 to 8.4). Instability usually occurs oslopes steeper than or equal to a slope angle of 1 in 3,although a few failures have been recorded at 1 in 4.




o

nt to

f the ofblems

est of

ofie

m

logy

r

a

g

y

d

ays

e

to

5.35 The permeability of clays is generally much lowthan sands and gravels but is still significant in the lterm and can lead to settlement as a result ofconsolidation.

Silts and Fine Sands

5.36 These soils are predominantly those identifiedClass 2D of Table 6/1 SHW and require Method 3compaction (Table 6/4, SHW). In their properties anengineering behaviour they tend to intermediatebetween typical `granular' and typical `cohesive'materials. The silt particles differ from the sandparticles in size and are sometimes similar bothphysically and chemically. However, the surfacetension of the inter-particle water confers a degree ocohesion on the soil.

5.37 Silts and fine sands are liable to liquefaction incircumstances where the effective stress, and, for thmaterials, the shear strength, is reduced to zero. Thproblem can be encountered during cutting excavatand during embankment construction where they arused as fill or where they form `soft ground' beneathembankment. Liquefaction occurs:-

i. in class 2D earthworks. When the surfacebecomes saturated and then trafficked or subjectedother forms of loading. Where Class 2D forms theslope of an earthwork, slides, landslips or mud-flowscan occur;

ii. under drains, leading to washing out of fines anthe formation of cavities (`piping');

iii. under conditions of rapid increase in pore watepressure (including earthquakes);

iv. when water flows through the soil under a largehydraulic gradient near the surface of the earthwork(cuttings mainly).

5.38 Silts and fine sands are amongst the materialsmost susceptible to frost heave and must not beincluded within the top 450mm of the Works unlesstesting indicates otherwise. (See Clause 602.19 SHThe permeability of these materials permits readyaccess of water and the pore spaces are too small taccommodate the growth of ice crystals withoutdisruption of the structure (unlike the coarse sands gravels).



erng

as embankments is by moisture content it is importaspecify the grading fraction on which it is taken.

d5.40 In cutting slopes, the stability of undisturbedfissured clay is conditioned by the orientation andfrequency of the fissures rather than the strength ointact clay. Glacial Till frequently contains lenseswater bearing sand which can cause drainage pro

f and soften the clay at the interface with the sand.

in this material improves further to the North or Wese England and Wales, reflecting its variation inis properties. The effect of fissures on the stabilityons excavated slopes in Glacial Tills is described by

McGown (1985). the

5.42 Other reference sources include the Symposiu

Birmingham and the Quaternary Engineering Geoto Conference, Edinburgh.

d

s

W).

o

nd

Glacial Till

5.39 Glacial Till is a widespread drift deposit consistinof mixtures of materials ranging in particle size fromclay to boulder and showing considerable variations ingradings. The amount of fines in a till will determinethe till's behaviour, and a high silt content makes it verweather susceptible. If control for suitability to form

5.41 As shown in TRRL RR 199, the stability of slopes

on the Engineering Behaviour of Glacial Materials,

Alluvium, and Estuarine and Marine Sediments

5.43 Alluvium is a material which has been transporteand laid down in the bed or flood-plain of a stream orriver. It can comprise most types of soil from gravel atone extreme to clay at the other. However, it is moretypically fine sands, silts and clays often in alternatinglayers of a seasonal nature as in the case of varved cl(glacial lake deposits).

5.44 The silts and clays are `normally consolidated'rather than over-consolidated and are frequently softand compressible. The water table is often close to thsurface. Hence there is usually a `soft ground' problemwhen embankments are constructed across alluvialareas. Some of the measures for dealing with theseproblems are described in Chapter 9 of this AdviceNote. Ground water lowering may also be necessary facilitate cutting excavation and to improve otherwiseunacceptable material.




s

bogs

5.45 Estuarine sediments occur in the estuaries of larivers and are often characterized by the presence ofand clay with a small amount of sand and gravel, andbanks of shells. Similar `soft ground' problems canoccur to those cited above.

5.46 Shallow water marine sediments are again variadepending on the geology, onshore and offshore, anthe vicinity of other sources of material. Materials vaconsiderably from gravel to clay and sometimes occuwith shells.

Organic Materials and Peat

5.47 These materials are included in Class U1unacceptable material (Clause 601.2 (ii), (a) and (b)SHW) unless designated by the Engineer as landscafill Class 4, in Appendix 6/1. When peat and relateddeposits occur at or below formation level orembankment foundation level, they can lead toembankment instability during and after constructionand to long-term settlements causing damage topavement structures.

5.48 Peat accumulates in wet, flat or hollow areas whthe rate of addition of vegetable matter exceeds the rof decay. Fen peats form on low ground whereas bopeats form on high ground. Bog peat is normally moacidic than fen peat. Organic soils range from peatyclay through clayey peat to peat, and start to behavepeat once the organic content (by weight) exceeds a27%. Peat can be light brown and fibrous or a darkbrown or black amorphous jelly-like material.

5.49 The principal engineering characteristics of peaare its exceptionally high water content and theimportance of secondary consolidation. Secondaryconsolidation under load is prolonged (taking manyyears) and is dominant over primary consolidationwhich is complete after a relatively short time (weeksrather than years). Settlement on site may be difficupredict because the coefficient of secondarycompression can vary with time (Hobbs, 1986). Fibrous peats on site have a higher permeability thanthe small specimens tested in the laboratory. Largescale and prolonged site trials may be necessary toassess the parameters for secondary compression ahence predict the likely settlement over a period ofyears (eg 30 years). The shear strength (stability) ofpeat depends on time as well as effective stress becathe void ratio continuously decreases under themaintained load. Stability and rate of loading are les



rge critical for fibrous peat than they are for amorphou silt peat. A change in regional drainage can increase

drainage leading to lowering of the surface of peat without any loading.

ble embankments can be reduced either by:-dry i. treatment of the ground; orrii. reducing the load applied to the ground.

pe

enategre

likebout

t

lt to

nd

use

s

5.50 Settlement of peaty ground beneath roads or

5.51 Of the treatment methods described in Chapter 9,dynamic compaction is unsuitable for peat. Vertical(sand) drains will probably not be effective unless thepeat is a thin layer interbedded with other materialsbecause such drains only accelerate primaryconsolidation which involves dissipation of excesspore-water pressure. Secondary compression consistsof a process of void reduction involving only a smalldecrease in pore pressure.

5.52 When the base of the peat deposit is less than 5mbelow ground level, complete excavation andreplacement may be the economic solution providedacceptable fill (eg Class 6A for deposition below water)is available. When the base of the deposit is more than5m below ground level preloading (surcharge of theembankment) may provide a solution, but specialistadvice should be sought. Preloading can improve theproperties of the peat with the aim of accelerating andanticipating the settlement to be caused by the serviceload, over the required period of years.

5.53 Methods of reducing or distributing the loadapplied to peaty ground include:-

i. changing embankment geometry eg widening itsbase;

ii. providing a sort of `raft foundation' eg by meansof geogrids at or near the base of the embankment or atformation level;

iii. staged construction of embankment;

iv. use of light-weight fill;

v. piled foundations taken down to firm ground.

5.54 Peat may occur in cutting and will require very flatslopes or containment. Drainage is an important designcriterion here as flows and slides can occur; also openditches are likely to collapse.




s

do

t

l

Waste Materials and Industrial By-Products

5.55 The better known materials, Minestone and PFare dealt with in Paragraphs 5.27 to 5.30 and Paragr5.58 to 5.66 respectively. Toxic and domestic wasteare discussed in Paragraphs 5.67 to 5.71. Wastematerials should be used in road construction whereis environmentally desirable and economic.

5.56 Further information may be obtained from TRRLaboratory Report 647, `The Use of Waste andLow-Grade Materials in Road Construction', and alsofrom BRE Paper 19/74, À Survey on the Locations,Disposal and Prospective Uses of the Major IndustriBy-Products and Waste Materials'.

5.57 Crushed lean mix concrete is acceptable in thoclasses where crushed concrete is allowed, providedmeets the other requirements for that class of mater

Pulverised Fuel Ash (PFA)

5.58 PFA is an industrial by-product and for thepurposes of SHW Table 6/1 is designated as Classeand 7B material, or Classes 7G and 9C if cementstabilization is required (see Chapter 10). The sulphcontent of PFA is likely to be such that SHW Clause601 is relevant. The dimension restriction on depthbelow sub-formation and formation in SHW Clause 6has been introduced for the following reasons:-

i. because of the grain shape and size the upperlayers of PFA are difficult to compact;

ii. freshly placed PFA behaves in a manner similara pure silt and, if not protected, may liquify followingwet conditions;

iii. capping and sub-base materials tend to berelatively permeable and a layer of general fill overPFA is considered desirable to provide some protect

5.59 The dimension may be marked on the drawingsbut it is recommended that SHW Appendix 6/3 is moappropriate. A figure of 600mm is consideredacceptable, and any reduction needs to be carefullyconsidered.



Aaphss

this

L

al

se it

ial.

s 2E

ate

01

to

ion.

re

5.60 Erosion can be a particular problem where PFAembankments are exposed to the weather.

5.61 PFA properties vary, not only from source tosource, but also within a single source. These variationwill affect the ability to achieve the requiredcompaction which may be particularly critical wherePFA is being placed adjacent to structures and wherethe density achieved may affect the design criteria. SHW Clause 601 enables the Engineer to keep a recorof the sources, and places the onus on the Contractor tprovide the requisite data including the natural moisturecontent, and the optimum moisture content andmaximum dry density of each consignment. Wherefield densities are being taken the top 100mm of PFAshould be removed before testing.

5.62 The Classes of PFA found in SHW Table 6/1 varydepending on whether the material is conditioned, orfrom lagoons or stockpiles.

5.63 Conditioned PFA is specified in SHW Class 7Bfor use as fill to structures and reinforced earths. It isobtained directly from the coal burning process andsufficient water added to bring it to a state suitable forcompaction. The optimum moisture content is typically25%, but may be as high as 35%.

5.64 SHW Class 2E includes lagoon PFA which ismaterial which has been transported in slurry form andstored in lagoons and may be used as a general lightweight fill.

5.65 SHW Class 2E also includes stockpiled PFAwhich can be either (i) or (ii) above which has beenstockpiled. After a period of storage this material tendsto approach its optimum moisture content. It may alsobe used as a general lightweight fill.

5.66 As shown in Table 6/1 SHW, for Class 2Ematerial the acceptability criteria need only be sufficiento provide the required compaction; for general fillpurposes it is sufficient to rely on the end productspecification and bulk density limits need not be stated.If the weight of the embankment is critical to the design(see Chapter 9) then density limits may be stated alongwith the end product. These limits may typically bebetween 1.3Mg/m3 and 1.65Mg/m3. Class 7B materiaas above should rely on the end product specification. For conditioned PFA bulk density limits are alsotypically 1.3Mg/m3 to 1.65Mg/m3. For both classes ofmaterial it is advisable to check on sources and likelyavailability with the appropriate generating authoritywho will also provide typical test results for the varioussources.




ted

d

my

e

en

y

Domestic and Toxic Wastes

5.67 Toxic wastes are classified in Clause 601 SHWunacceptable material Class U2 and usually consist either industrial and chemical wastes, or domesticwastes. When toxic or other hazardous waste materis to be removed, the regulations covering excavatiotransportation and deposition into a registered tip areclosely governed. The local Environmental HealthOfficer (EHO) must be contacted and consultedregarding the treatment of any toxic waste materiallocated within or affected by the scheme.

5.68 Similarly domestic waste or refuse can produceinflammable or toxic gas and leachate, and surfacewater drainage from the road which passes throughdomestic tips must be sealed systems to avoidcontamination of the underlying aquifer. To avoidcontaminated water reaching the road drainage fromtip, or to prevent gas migration into the road structurethe road, whether at ground level, in cutting or onshallow embankment, must be sealed off from thedomestic waste material by a continuous impermeabmembrane. On higher embankments, fill of suitablepermeability and thickness can be placed to preventupward migration of the leachates and gases, possibremoving the need for a membrane. The EHO mustconsulted about roads through domestic waste tips athe appropriate specification clauses agreed regardinoperations within the area, and precautions to be takfor toxic and noxious gases which may be present suas methane, hydrogen sulphide etc.

5.69 In some instances it may be possible to leave thdomestic waste in place and treat it by dynamiccompaction to produce a dense foundation for the roThe overseeing department should be consulted fordetails of other similar schemes which may have beecarried out successfully.

5.70 Where domestic waste is exposed on a cuttingslope it should be protected by an impermeable claycover and/or membrane to ensure that leachates aredirected away from carriageway drainage systems. deep cuttings, as a result of sealing the slope, the heof water may be sufficient to cause failure of the roaor the slope so subsurface drainage must be provideintercept contaminated water for transport to atreatment works. The Local Water Authority will neeto be consulted on the precautions taken. Gasescontained within the slope by the sealing of the face within chambers and ducts for services and drains,should be vented. In some cases where the road is from leachates and the gas produced does not affec



asof

ialn,

the,

le

ly bendgench

e

ad.

n

Inaddd to

d

or

awayt the

vegetation on the slope, then no sealing may berequired. Monitoring of the amounts and types of gasproduced, before, during and after construction isadvised.

5.71 References covering construction and safety onmarginal, derelict and contaminated land, are includedin Cairney (1987), Building on Marginal and DerelictLand, ICE (1987) and Fleming (1991).

Geotextiles and Related Products

General

5.72 Geotextiles, geogrids, geomeshes and other relaproducts comprise a family which may be called`geosynthetics'. They are usually made from suchsynthetic polymers as polypropylene, polyester,polyethylene and polyamide which have a high degreeof inertness to biological and chemical degradation, ana high mechanical strength.

Types of Geosynthetics

5.73 Woven geotextiles are composed of twoperpendicular sets of parallel yarns interlacedsystematically to form a single planar structure. Themanner in which the two sets of yarns are interlaceddetermines the weave pattern and it is possible toproduce an almost unlimited variety of fabricconstructions. Woven geotextiles are used in a widevariety of applications.

5.74 Non-woven geotextiles are formed from fibresarranged in either an oriented or random pattern to fora planar structure. The fibres may be bonded either bchemical bonding using a cementing medium; bythermal bonding, where heat is used to partially melt thfibres so they adhere together; or by mechanicalbonding using small barbed needles, set into a board,which are punched through the loose fibre web and thwithdrawn leaving the fibres entangled. Non-wovengeotextiles are also used in a wide variety ofapplications.

5.75 Composite geotextiles combine multiple layers ofthe woven and non-woven material, bonded together ba stitching or a needle punching process.

5.76 Geowebs are very coarse woven fabrics madefrom strips and are used for erosion control, bankprotection and soil reinforcement.




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5.77 Geonets consist of two sets of coarse parallelextruded strands intersecting at a constant angle. Thwidth of strand varies from 1 to 5mm and the size ofopening varies from a few millimetres to severalcentimetres. They are typically used in soilreinforcement and in fabricating gabions.

5.78 Geogrids can be made by a variety of methods of which involves drawing a perforated plate ofpolymer in perpendicular directions. They may beuniaxial or biaxial in character and are normally madeof polyethylene or polypropylene. They can be usedsoil reinforcement, retaining walls, foundations andsub-bases.

5.79 Geomembranes are sheets of synthetic materiawhich act as impermeable barriers.

Functions of Geosynthetics

5.80 Whilst there is an enormous number ofapplications for an equally large number of types ofgeosynthetic, the applications can be grouped into fomain functions.

i. separation;ii. reinforcement and retention;iii. drainage and filtration;iv. impermeable barrier.

Separation

5.81 Geotextiles may be used to separate two differematerials which would otherwise have a tendency tomix under working conditions. There is also an addefunction whereby the geotextile, being permeable,allows the passage of water across it to reduce thebuild-up of undesirable pore water pressures in eithethe adjacent materials. Clause 609 SHW defines somof the minimum physical properties that the geotextilemust possess. If different values of these, or other,properties are required then they should be inserted Appendix 6/5. The NG Sample Appendix 6/5 givesdetails of the information to be included. The amounof lapping of the geotextile is specified as 300mmminimum, but the Designer should consider themaximum possible amount of differential settlementand deformation that could occur in the soil close to tgeotextile. If the differential settlement is more than200mm the minimum lap stated in Appendix 6/5 shoube increased accordingly. In normal circumstances,



geotextile should not be physically jointed but ae material to slide and not `bridge' over low areas

could become overstressed and tear.

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Guide 5, will allow isochronous curves to be prodenabling allowable loads to be determined for dif

ur design lives. The reinforcement should also hacoefficient of interface friction with the adjacent soil

of friction should be determined using a method simto the testing requirements of Clause 639 SHW. It

necessary, to ensure that the soils provided duringconstruction have the same characteristics as thos

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Reinforcement and Retention

5.82 Geosynthetics are widely used as soilreinforcement in embankments and in fill materialbehind retaining walls or similar structures, and mostthe types included in Paragraphs 5.73 to 5.79 aresuitable for this use. Embankments can be reinforcefor a variety of reasons and in a variety of ways. Thebasic requirement for the reinforcement is that it musbe able to sustain the allowable load over the specifieperiod of time without its strain exceeding apredetermined limit. If the reinforcement achieves thallowable load at large strains then the soil structurewill probably have already failed and therefore themaximum allowable strain should be determined by tlimitations of the structure. A series of creep testscarried out in accordance with TRRL Application

sufficient magnitude to prevent failure. This coefficie

assumed for design purposes.

5.83 The technical literature published by themanufacturers usually provides detailed informationregarding the physical properties of their products, buDesigner is advised to acquire evidence that theparticular product which the Contractor proposes to usatisfies the design requirements for the reinforcemeand the details of the required evidence should beincluded in the reinforcement specification. It shouldbe noted that the properties of geotextiles (accordingBS 6906) and related materials in isolation may bedifferent to the properties when placed in soil, and camust be exercised that the appropriate materialproperties are chosen.

5.84 The Department's Technical Memorandum BE3/78 (revised 1987) Reinforced and Anchored EarthRetaining Walls and Bridge Abutments forEmbankments provides design criteria and constructrequirements for reinforced and anchored earthretaining walls.




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Drainage and Filtration

5.85 Geotextiles and related products are alsocommonly used as drains and filters. Such applicatioinclude the following.

i. For use in narrow filter drains to wrap freedraining granular fill, containing a perforated pipe(Drain Type 9, HCD). An alternative option is to wrathe pipe directly in a geotextile and fill around andabove it (Drain Type 8, HCD).

ii. To form a horizontal drainage blanket underembankments. Here the geotextile can also act as aseparator between the embankment and its foundati

iii. To form fin drains which are usually of compositconstruction with geotextile filters sandwiching aplastic core which allows the water to flow between tgeotextile layers to a carrier pipe (Drain Type 6 and 7HCD). Some of these cores are designed to havesufficient capacity so as not to require a carrier pipe(Drain Type 5, HCD).

5.86 In all the above applications the function of thegeotextile is to retain the soil particles whilst allowingthe water to pass through; the size and number of thopenings in the geotextile are therefore critical. Thefilter fabric must be chosen bearing in mind the gradiand particle size of the material surrounding the drainwell as the estimated ground water flow.



Impermeable Barrier

5.87 This function applies to geomembranes whichns commonly used to contain or exclude liquids and gThey are frequently used in areas of contaminated lan

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or for construction below the water table level.

Material Durability and Degradation

5.88 A further aspect of the choice of material is thepossibility of degradation by environmental agents. Each of the polymers has varying durability andresistance to degradation, and an indication of thedegree of resistance of the main four polymers to thevarious agents is given in Table 5/1. However, verylittle in the way of degradation testing and long-termdurability assessment has been carried out and therefoadvice in this area is limited.

5.89 A case has been reported where geonet gabionbaskets caught fire after installation and continuedburning even on the buried faces until all structuralintegrity was lost resulting in total collapse of the fillingmaterial. Cutting of the geonet by vandals can also leato loss of structural integrity. Therefore it isrecommended that these gabions are not used inexposed positions or critical locations where such acollapse could have serious consequences. Fires on thslopes of reinforced earth embankments are unlikely toaffect the geosynthetic if adequate topsoil cover hasbeen provided.

TABLE 5/1

The degree of resistance to degradation

AGENT POLYESTER POLYETHYLENE POLYPROPYLENE POLYAMIDE

Acid 2 1 1 1Alkali 3 1 1 2Dry Heat 2 3 3 3Moist Heat 3 3 3 2Abrasion 1 2 2 1Fungus 4 1 2 2Oxidising Agent 2 4 2 3U V Light 1 4 2 2

1 - Excellent 2 - Good 3 - Fair 4 - Poor

Taken from 'Reinforced Earth' by T S Ingold; Thomas Telford 1982



Volume 4 Section 1 Chapter 6Part 1 HA 44/91 Slope Stability Analysis

6. SLOPE STABILITY ANALYSIS

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General

6.1 The stability of soil and rock is a complex subjeand it should be emphasised that failure to understanthe engineering significance of the geological strata agroundwater is invariably a more important factor inslope failures than the method of stability analysisemployed.

Soil and Soft Rock Slopes and Their Analysis

6.2 Considerations of the stability of cuttings,embankments or natural slopes must always start bydefining the topography and geological aspects of thproblem. Once the topography, geology andgroundwater conditions are known the Designer will able to make a preliminary assessment of possible sside slopes based on previous experience in similarstrata, and also make a comparison with what is stabor not within the scheme area. However soils of thesame geological horizon can vary locally and thedetailed ground investigation must check very carefufor any discontinuities or weaker horizons which mayaffect the stability of the slope. In particular,consideration needs to be given to the dip of any natstrata and direction of any discontinuities in relation tthe proposed slope, and the possibility of anypre-existing shear surfaces. The effect of exposure soil and rock strata to weathering processes must alsbe taken into account. All these considerations willaffect the value of shear strength parameters used inanalysis.

6.3 The Designer should develop an understandingand appreciation of the factors that affect slope stabiby using analysis methods that can be done by handbefore progressing to methods requiring a computer.Sophisticated computer programs and analysistechniques should only be used when the Designerunderstands the processes involved and is confidentit is the correct method for a particular situation. Search programs which locate the most critical slipsurfaces can be valuable but the Designer must beaware of their limitations. Parametric studies arevaluable to demonstrate likely variations in thecalculated factor of safety due to a range of inputparameters. Unless the soil parameters and waterpressures have been accurately determined,sophisticated methods of analysis are not justified.



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6.4 In determining acceptable factors of safety forslopes the designer must carefully consider theconsequences of failure (ie risk to life or property), thereliability (and conservatism) of the parameters used inthe analysis and the accuracy of the method of analysis(Most methods are subject to error from effects such asthree dimensions, horizontal stresses, progressivefailure etc). The most reliable factor of safety is likelyto be that based on parameters derived from backanalysis (by the same method) of a failed slope in thesame soil strata.

6.5 In low permeability materials such as clays, thestability assessment must consider stability both in theshort-term, during and immediately after construction,and in the long-term, when pore water pressureequilibrium has been achieved. Which condition provethe more critical is likely to depend largely on whetherthe ground is subjected to a net increase or decrease inloading by the construction. For an increase in loadingsuch as the construction of an embankment on afoundation of soft soil, the critical condition is likely tooccur in the short-term. For unloading, as in the case oa cutting in stiff clay, long-term conditions are likely toprove the more critical.

6.6 Effective stress methods of analyses should beused for determining stability in more permeable(granular) soils and for assessing the long-term stabilityin cohesive soils. Effective stress analyses can also beused to assess the short-term stability in cohesive soilsprovided that adequate information is available on thepore water pressure regime. However, the prediction opore water pressures during construction in cohesivematerials is difficult and for preliminary assessments ofstability, consideration should be given to the use ofsimpler total stress methods based on the undrainedstrength of the soil. An inherent assumption of suchanalyses is that no drainage occurs during theconstruction period. Measurements of undrainedstrength are often unrepresentative because of problemof rates of testing, confinement conditions anddiscontinuities in the soil and are likely to depend onthe test method. Total stress methods are thereforelikely to be most reliable in situations involving softhomogeneous soils.



Chapter 6 Volume 4 Section 1Slope Stability Analysis Part 1 HA 44/91

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6.7 There are various methods of stability analysiswhich may be used to estimate the factor of safety oslope, most of which use variations of the `method oslices'. The methods differ mainly in the manner inwhich interslice forces are considered and the shapefailure surface investigated. For circular shaped failusurfaces, the Swedish solution gives very conservatifactors of safety when pore water pressures are presThe Bishop Simplified Solution can overestimate orunderestimate the factor of safety for certain deep slsurfaces, but generally gives fairly accurate results. simple method of Greenwood and the simplifiedmethod of Morrison and Greenwood may be used focircular shaped failure surfaces and slip surfaces ofarbitrary shape. Suitable methods for slip surfaces oarbitrary shape include Janbu Simplified Method, witcorrection factors as necessary; Janbu RigorousMethod; Morgenstern and Price, although considerabexperience and judgement is required to use this mereliably; and Spencer's Method which was originallydevised for circular failure surfaces but has beenadapted for non-circular failure surfaces. The infiniteslope analysis is best used for extensive planar slipswhere the slip surface is approximately parallel to theground surface and the influence of the toe and headportions of the slide is negligible. References to theabove methods are given in Chapter 14.

6.8 Stability charts can be helpful but their use isrestricted to uniform non-layered soils and slopes ofregular geometry. Use of charts might restrict theDesigner's understanding of the mechanics of slopestability analysis. Charts such as those of Bishop anMorgenstern (Geotechnique, Vol 10, No 1, 1960) arecommonly used.

6.9 More sophisticated methods such as `Sarma' aavailable but these require computer assistance andconsiderable geotechnical expertise to apply.

6.10 Simple three part wedge analyses, based on acand passive wedges with a middle sliding section, aroften most appropriate for embankment stability whethe risk of a near horizontal weaker stratum is to beinvestigated. Such a calculation uses a differentdefinition of the factor of safety and is likely to result a somewhat different assessment of stability. Othermore sophisticated wedge type solutions are availab

6.11 When geomesh reinforcement or ground anchoare included in a slope an initial appraisal of theirpotential benefit may be obtained by including thereinforcement forces in the Swedish and Greenwoodsimple (Greenwood 1990) methods of analysis. Embedment lengths and strain compatibility betweenreinforcement and soil must be carefully considered.



6.12 More rigorous methods of analysis of reinforcf a soil slopes are available, but care is needed in thef of materials and design assumptions in this relativ

new and developing field. ofre 6.13 A survey of slope condition of motorway

ve earthworks by Perry (TRRL RR 199) provides aent. valuable source of empirical information for new

construction and maintenance. The survey discovip considerable lengths of shallow failures on the sloThe both cuttings and embankments.

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Rock Slopes and Their Analysis

6.14 Rock masses contain numerous planar featureswhich can reduce the bulk strength of the rockconsiderably. These features such as bedding planes,faults and joints are collectively known asdiscontinuities and the rock mass is divided into blockswhose shape and size are dictated by dip (inclination),azimuth (direction of the dip) and the frequency of thesdiscontinuities.

6.15 When designing rock cuttings the steepest sideslope compatible with stability is generally chosen toreduce the quantity of rock to be excavated andtherefore the cost. The stability of rock side slopes isgoverned by the bulk strength of the rock mass, theexcavation technique and the design chosen. The mosstable design will be that which matches the rockdiscontinuities, thereby reducing any subsequentremedial and maintenance works on the slope. This isusually achieved by preventing discontinuities`daylighting' on the slope (plane failure) whereverpossible by making the dip of the slope less than the dof the discontinuities into the cutting, or preventing theline of intersection of two discontinuities fromemerging above formation level and daylighting ontothe slope (wedge failure). Toppling failure can occurwhere near vertical columns of rock, which lean into acutting or excavation, fail along near horizontaldiscontinuities or by failure of the rock columns as theyflex. The Designer will obviously require themaximum information which can be obtainedeconomically from both sub-surface exploration andsurface geological mapping before attempting to assesthe potential stability of the excavated faces.



Volume 4 Section 1 Chapter 6Part 1 HA 44/91 Slope Stability Analysis

6.16 Further information and guidance on rock slopestability, methods of assessment and preventativemeasures is given in Hoek and Bray (1981), TRRL LR1039, Matheson (1989), Hudson (1989) and acomprehensive description of available rock supportsystems is given in Hoek and Wood (1988).



Volume 4 Section 1 Chapter 7Part 1 HA 44/91 Cuttings

7. CUTTINGS

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General

7.1 Cuttings are excavated in the existing ground antherefore the nature and condition of the natural stratshould be thoroughly investigated. The ground wateregime represents the most critical aspect of cuttingdesign, and attempts must be made during the GrounInvestigation to determine water levels, seasonalvariations and soil permeability. Cutting slope designmust be considered in both the short-term, during orshortly after construction, and long-term, many yearsafter construction. Drainage should be considered foboth surface and ground water during these periods.

Stability

7.2 Cutting instability may occur soon afterexcavation if there are any undetected discontinuitiesfissures or existing shear surfaces, in the soil structuor if seepage is allowed to occur from semi-permeabstrata such as silts.

7.3 TRRL Report RR 199 lists the slope angles, for wide range of geologies, at which slopes remain stabthese are based only on engineering considerations account must be taken of land take costs, environmeimpact and possible uses of the slope.

7.4 In the long-term, over-consolidated clay soils arprone to softening as the pore pressures, which areinitially reduced due to the removal of overburden loareturn to equilibrium. This can result in shallowfailures as mentioned in Paragraph 5.34. Assuming reduction of the slope angle to allow for the weakenematerial is not feasible, the designer has the followinoptions in order to retain steep slopes in cuttings:-

i. to install relatively shallow trenches, filled withstone (slope drains or rock ribs) normal to the slope,and from top to bottom, to remove water; this solutionis economic (TRRL RR 30) and may be perfectlyadequate (TRRL RR 199).

ii. to install deeper trenches than in (i) above, filledwith stone (counterfort drains) normal to the slope, anfrom top to bottom, which buttress the slope as well adraining the soil to considerable depth; this solution ihowever, expensive;



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iii. in some circumstances it may be more economicto allow some slope failures and accept highermaintenance costs;

iv. use soil nails or soil anchors with geotextiles toretain the soil in order to prevent failures.

7.5 Slope design should be based on equilibrium waterlevels with permanent drainage requirements kept to aminimum, consistent with reasonable side slopes, toreduce maintenance commitments.

7.6 Where the cutting is excavated in side-long groundwhere there is a possibility of relic landslips orslickensided ground, care should be taken to:-

i. ensure adequate drainage (see Paragraphs 7.7 to7.11 below);

ii. check exposed strata;

iii. watch for signs of fresh instability.

Groundwater

7.7 If stability cannot be achieved without slopedrainage, consideration may be given to the use ofinterceptor drains, deep counterfort drains, shallowbatter or blanket drains.

7.8 The filter materials used in slope drains must bedesigned for the maximum flows likely but bearing inmind the risk of loss of ground if the filter is too coarse. Because natural sand and gravel are often very variablewith water flows concentrated in the coarser gravellayers, it may be expedient to use a coarse graveldrainage material surrounded by a filter fabric toprevent silting and loss of ground. In the same way it isextremely difficult to predict water flows in fissuredclays. It should also be recognised that the groundwatelevel at the GI stage may not be the longer term levelfor cutting design; the level may be affected by a spellof dry weather or water extractions.

7.9 It is for the Designer to ensure that the permanentdrainage is adequate for the stability of the completedcutting. If, however, temporary drainage is required forstability during excavation, or until the permanentdrainage can be brought into play, then the Appendixshould make this clear and the MMHW



Chapter 7 Volume 4 Section 1Cuttings Part 1 HA 44/91

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amended to suit. The Contractor must be made awathat he is responsible for maintaining any temporarydrainage required and he should not assume that andrainage which is part of the design will necessarily adequate for dewatering earthworks for the purposerendering soil acceptable.

7.10 Where the natural ground slopes towards the tof a cutting or any erodible soil, a lined interceptordrain or lined ditch may be required to prevent erosior instability occurring. During design and subsequeexcavation, care is needed to identify any existing fiedrains and intercept their flow before it reaches thecutting face.

7.11 Placing of drainage ditches relative to the top obottom of a slope may influence the stability of theslope by creating soft areas and can be associated wthe formation of failure planes.

Foundations

7.12 When considering structural foundations incuttings, the Designer must have an understanding how the soil will behave during excavation,construction and beneath the completed structure. Factors to be borne in mind must include the probabeffects on the foundation material of frost heave durconstruction and after. Changes will occur in theground water regime from both temporary drainageschemes during construction and permanent drainagConsequently, the ground water levels as well as theflow directions will vary.

7.13 The material itself may suffer changes due to tremoval of surcharge by the excavation of the cuttinby exposure to the weather during construction(moisture susceptibility) and by the application ofworking loads. Over-consolidated clays can softenwhen exposed to water with corresponding loss ofbearing capacity, swelling etc.



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Explosives and blasting

General

7.14 The term èxplosives' includes both highexplosives and also slow-burning materials such aspropellants. Hence devices incorporating a cartridgeresembling a shot-gun cartridge for boulder or rocksplitting are also covered by SHW Clause 607.

7.15 The use of blasting for excavation should only beallowed in SHW Appendix 6/3 where it is considered tobe necessary. Where it is considered not likely to causedamage or nuisance, the contractor should be permittedin Appendix 6/3 to use it as an alternative method ofexcavation.

7.16 To avoid intrusion, permitted hours for blastingentered in Appendix 6/3 should not extend outsidenormal working hours except where the site is remotefrom any inhabited area.

7.17 For further advice, TRRL Report RR 53 should beconsulted. Among other subjects this Report coversblasting trials, establishment of vibrational limits(damage criteria), vibrational measurement proceduresand equipment, and establishment of site scaling laws.

7.18 At the pre-construction consultation stage acondition survey of neighbouring properties at riskshould be carried out as described in BS 5607: 1978Clause 4.2. Photographs should be included in thesurvey. Departmental Advice Note HA 34/87 `GroundInvestigation Procedure' stresses the need for conditionsurveys `before, during and after the execution of themain Works'. At the same time notice should be givenregarding the need for temporary and permanentprotection and for monitoring as the work proceeds. Itshould be noted that the permission of the ProjectManager must be obtained before any condition surveyare carried out.

Plaster Shooting

7.19 Plaster shooting is defined in BS 5607:1978 as`blasting by placing a quantity of explosive against arock, boulder or other object without confining theexplosive in a shot hole'. While this procedure may beacceptable in rock quarries it is too dangerous for useon construction sites and has been prohibited in Clause607.



Volume 4 Section 1 Chapter 7Part 1 HA 44/91 Cuttings

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Pre-Split Blasting

7.20 This is dealt with in SHW Clause 603 but issubject to the requirements of Clause 607.

7.21 Pre-split blasting is employed to reduce theharmful effects of bulk blasting on the final rock faceIt involves the drilling of closely spaced holes along design slope, charging the holes relatively lightly andfiring the charges to form a fracture plane along theslope, before firing the bulk blast. The time intervalbetween the two firings must be at least 50 millisecsThe adverse effects of bulk blasting for the rockexcavation on the design slope are therefore almosteliminated by the pre-split fracture plane so thatdisturbance of the rock in the final slope is minimal. Whilst pre-splitting can initially be expensive, its cosmay be offset by the subsequent lack of remedial anlong term maintenance works to the rock slope and designer should consider the whole-life costs of thecutting to see if pre-splitting is economically desirablFor further details and guidance, including referencethe important matter of drilling accuracy, TRRLReports LR 1094 and SR 817 should be consulted inaddition to NG 603.

7.22 Flattening the rock slope may be a cheaper opto pre-split blasting, from the maintenance point ofview, in some cases such as when land take is not aproblem and the rock weathers quickly on exposure

Blasting Trials and Trial Explosions

7.23 Pre-contract blasting trials are required by Clau607 and are fully covered by TRRL Report RR 53. These should preferably be carried out at the groundinvestigation stage and, if comprehensive, will reducthe extent of the trial explosions conducted by theContractor at the Main Works stage. Trial explosionshould start with small charges and increase to charsimilar to the working charges but only if themeasurements show that it is safe and environmentacceptable to do so.

Safety Matters

7.24 In addition to BS 5607:1988, manufacturers sapublications such as Èxplosives - Safe Practice andStorage' published by Nobel Explosives Co Ltd shoualso be consulted. BS 5607 lays down rules for safeblasting on construction sites where a public highwain use, as in a road improvement or



he

7.25 Factors affecting vibration levels when explos are used include:-

i. size of charge;

ii. pattern of charges;

d iii. confinement of charge;he

iv. geology and nature of ground eg dip, depth a. type of rock, and presence of fault planes.

to7.26 The safe level of peak particle velocity (ppv) is

governed by the type and state of repair of the staffected and very importantly by the frequency of the

ion vibration of the structure. Peak particle velocitiesexcess of 50mm/sec (up to say 100mm/sec) may

and acceptable for some structures. However, llimits may be necessary in other cases. This sub

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maintenance scheme. Clause 3.12 of BS 5607 define`danger area'. The temporary works required to retainprojectiles are also described in BS 5607. Suitablematting for use in pre-split blasting to contain air blastand reduce fly rock is described in TRRL Report LR1094 page 36.

Vibrational Limits

vibrations in relation to the natural frequency of

dealt with in TRRL Report RR 53 and reference shouldbe made to Figure 2 on Page 4 of this publication whicgives ppv's for residential structures; these can be muless than 50mm/sec depending on the frequency ofvibration.

7.27 The upper limit of 0.2mm vibrational amplitudegiven in Clause 607 SHW is considered to be more inline with case history data than the limit of 0.1mmquoted in the Fifth Edition of the Specification. Amplitude criteria should only be considered where thepredominant frequency of the motions is usually low(<5Hz).

7.28 The delay between explosions necessary to avoisuperposition of vibrations from successive delaysshould be determined during trial blasting.

7.29 Good public relations attitudes and an educationprogramme by the blasting Contractor are essential. Human reactions to vibration can be limiting factor andcomplaints can arise at ppv levels as low as 2mm/sec.ISO Standard 2631 (1978) and BS 6472:1984 bothprovide valuable guidance on



Chapter 7 Volume 4 Section 1Cuttings Part 1 HA 44/91

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acceptable levels of human exposure to vibration. Human response should be considered whendetermining a criterion for ppv but should not beregarded as paramount provided the Contractor keepthe public well-informed.

Peak Overpressures, and Damage to Windows andGlazed Areas

7.30 An accepted maximum safe value for air-blast orpeak overpressure is 0.7kN/m2 but this value is unliketo be reached where the ground vibration ppv is keptbelow 50mm/sec. Windows may rattle with a peakoverpressure of 0.3kN/m2 (see Nobel Explosives CoLtd Booklet) and this will cause alarm to the publicunless they are kept well-informed.

Instrumentation and Measurements

7.31 TRRL Report RR 53 describes the procedures aequipment necessary for effective vibration studies. Ishould be noted that instruments exist which canmeasure both the peak overpressure associated withair-blast and ground vibration in three orthogonalplanes. In deciding whether the Engineer or theContractor should make arrangements for theinstallation of instruments for the monitoring ofproperty off the construction site, (Appendix 6/3 to theSpecification), the nature and condition of the propertyshould be taken into account and an assessment madthe sensitivity of the situation regarding the occupiers such property. Similar considerations apply to thereading of the instruments and the reporting of theresults.



Volume 4 Section 1 Chapter 8Part 1 HA 44/91 Embankments

8. EMBANKMENTS

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General

8.1 Embankments have the basic function ofproviding a stable foundation for the road, and theremust be sufficiently strong to carry the imposed loadand remain stable in terms of settlement and slopefailure. Assumptions have to be made at the designstage as to the nature of the material that will form tembankment, which is usually material from adjacencuttings unless an imported material is specified. Thdesign aspects to be considered are:-

i. possible failure of the embankment slopes;

ii. possible failure of the underlying strata;

iii. both (i) and (ii) together;

iv. settlement of the embankment fill;

v. consolidation of the underlying strata.

Advice on the construction of embankments adjacenpiled foundations is given in BA 25/88, PiledFoundations.

Stability

8.2 Embankment fill material is usually selected onthe basis of minimum strength criteria and does notgenerally have problems of instability during orimmediately after construction provided compactionadequate.

8.3 Granular embankments are usually stable withsettlement occurring immediately; however some rofill embankments may show appreciable settlementswith time. Clay embankments may be subject to alonger settling period whilst the moisture contentreaches equilibrium for the new overburden load. Tmay take several years to occur and may be counteby expansion of clays which have been excavated adepth. As explained in Paragraph 5.34, the stifferover-consolidated clays are particularly prone tomoisture content increase and subsequent loss ofstrength when placed at the top, base and in the sloof embankments. Experience has shown thatover-consolidated clay soils tend to become unstablfew years after construction on embankment slopessteeper than or equal to 1 in 3 (1 vertical to 3 horizounits), although failures can occur at 1 in 4 but they



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infrequent at the present time. TRRL Report RR 199includes tables which suggest the most suitable slopeangle for an extensive range of materials in slopes ofvarying height. Slope angles steeper than those givenwill lead to failures in the long-term. It should be bornein mind that, in addition, the economics of land take,the environmental impact of a scheme and the expecteuse of the slope may all have an affect on the choice oslope angle.

8.4 Embankments slopes of 1 in 2 are often requiredand therefore if over-consolidated clays are used eithethe risk of shallow slope failure must be accepted as amaintenance liability or the over-consolidated claysexcluded from the slopes of the embankment. Alternatively the slopes may be strengthened asdescribed in Paragraphs 8.9 to 8.13, or buttressed withgranular material. The use of tamping rollers on theseclays during construction much reduces the risk ofpremature failure by breaking down aggregates of clayand by disrupting polished surfaces left by smoothwheeled rollers (Whyte and Vakalis, 1988).

Drainage

8.5 Surface water from carriageways should becollected by channels discharging into toe ditches toreduce the risk of surface water entering the pavemenlayers and the subgrade. The use of surface channelspreferred with water being led away to ditches at the toof embankments or other available out-falls. Drainagechannel blocks may be used down embankment slopeto take surface water from gullies or surface channels toe ditches or outfalls.

8.6 Over the edge drainage is permitted providing themethod has not led to problems in the past or when usin particular situations (see Advice Note HA 39/89). The effect of wetting material in the embankmentshoulders should be considered in the design.

8.7 In over-consolidated clay embankments extendedsub-base layers have in the past been used to disposeany water which finds its way into the lower pavementlayers. This may contribute to softening and instabilityof the side slopes. The recommended method ofinterception of sub-surface water is by means of findrains (Types 5, 6 and 7, HCD) or narrow filter drains(Types 8 and 9, HCD). Drains and any services inembankment shoulders should be avoided, but ifnecessary they should be carefully installed as they



Chapter 8 Volume 4 Section 1Embankments Part 1 HA 44/91

always carry a risk of creating potential tension cracksallowing subsequent ingress of water.

8.8 When the highway passes from cut toembankment on a downgrade there is sometimes apossibility of groundwater collecting at the interface. Interceptor drains may be installed across the highwayat the end of the cutting to collect this water if theground investigation indicates a problem area.

Strengthening Slopes

8.9 As mentioned in Paragraph 5.34 and Paragraphs8.2 to 8.4, embankments constructed ofover-consolidated clay may develop shallow slips in thelong-term. To counteract this development inembankments, and to retain steep slopes, the Designerhas some options available other than reducing theslope angle.

8.10 Reinforcement of the embankment slopes bysubstituting the outer layers of clay fill by materials thatare not susceptible to long-term softening such as agranular material. This option usually depends on theavailability of the material on-site or suitability of anyclose by and economic off-site sources.

8.11 Reinforcement of the outer layers of theembankment during construction, using polymericreinforcement such as geotextiles or geogrids.

8.12 Options (i), (ii), (iii) and (iv) of Paragraph 7.4.

8.13 The advantages of (ii) Polymeric Reinforcementare that it can be installed during construction of theembankment, it does not require the importing of analternative material or the simultaneous placing of twodifferent types of material adjacent to each other, it isrelatively inexpensive, and by varying the verticalspacing and length of embedment of the reinforcementlayers, the embankment slopes may be steepenedbeyond 1 in 2 if required. Further advice is availablefrom the Department.



Volume 4 Section 1 Chapter 9Part 1 HA 44/91 Ground Conditions Requiring Special Treatments

9. GROUND CONDITIONS REQUIRING SPECIALTREATMENTS

houldter have

endevedt

inguld beions.

khis

ils

ent

,

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Weak Materials Beneath Embankments

9.1 Embankments impose considerable shear forceson the basal deposits of the embankment fill and theupper layers of the foundation soils. These areas mube carefully investigated for any weak layers whichcould cause instability.

9.2 Where soft compressible soils are present, thestability and settlements require careful considerationdescribed in the following sections. Stability problemsalso arise in some stiffer materials. These materialswere subjected to a more severe climate in thegeological past and many have developed low strengpre-existing shear surfaces when located in slopingground. These surfaces can be difficult to detect androad construction may reactivate the slope movemen

9.3 Restrictions on the rate of either the constructionor any staged loading or both may be necessary formany embankments. All embankments should becarefully observed during construction for signs ofexcessive deformation. Areas particularly at risk mayneed to be fully instrumented with readings of porewater pressure, settlement and deformation takenregularly as construction proceeds. A line of toe pegsobserved regularly for line and level can provide avaluable warning of any problems and these should binstalled on all major embankments. Details and rateof controlled filling are to be set out in SHW Appendix6/3 and instrumentation details in SHW Appendix 6/12

9.4 Where basal drainage blankets (starter layers) arequired by the design their function and permeabilitymust be checked to ensure that water drains freely anthey do not act as a reservoir of water which couldsoften adjacent clayey soils. Horizontal permeability drainage layers may be measured by means of the`Permeability Box', (see HA 41/90: A permeameter foroad drainage layers). In some circumstances theDesigner may find his requirements for a basal drainablanket are met by Class 1C material which can be acheap and effective alternative to the more difficult toproduce Class 6B material.

9.5 Cut/fill transition areas are a common source ofsub-grade problems and should also be given specialattention. The material immediately below topsoil mabe weathered and produce a poor formation and weasub-grade. Therefore it may be prudent to excavate t



st

as

th

ts.

es

.

re

d

of

r 9.8 Where possible, embankment construction sonly commence when any ponds or areas of wa

ge been drained. Where this is not possible a selfcompacting granular material may be placed by

tipping into the water until sufficient height is achito continue with normal construction methods. Sof

carefully checked as instability can occur. If varywater levels are possible, the embankment sho

y designed to withstand the likely drawdown condit

material and replace it with a selected material over asuitable area. The appropriate drawing showing detaof the treatment should always be included in thecontract.

9.6 Soft alluvial deposits always require specialattention. Removal of the soft deposits and replacemwith acceptable fill material may be economical forlimited depths particularly if the area can be readilydewatered. If left in place the soft deposits must haveor develop, sufficient strength to maintain stabilityduring construction, usually staged, and considerationmust be given to the likely settlements both in theshort-term and in the long-term, under the embankmeloading. Embankments on compressible foundationsshould be built early in the contract so that sufficienttime is allowed for complete primary consolidationbefore pavement construction. Pre-loading, with orwithout surcharging, allows some or all of theconsolidation and dissipation of pore pressures to takplace before the road pavement is constructed. Whethis method is employed, calculations must be made optimize the amount of pre-loading with regard tostability. Consideration must also be given toimproving drainage using vertical drains andmonitoring progress using instrumentation. TheContract Period must be adjusted to include this perioof pre-loading, or advance works, carried out prior tothe main works contract.

9.7 Analysis will usually be required in order todetermine the likely behaviour of weak material as afoundation including finite element analysis for speciacases.

Open Water

deposits immediately beneath the embankment must



Chapter 9 Volume 4 Section 1Ground Conditions Requiring Special Treatments Part 1 HA 44/91

' or or

age

aleneath

r

n

n

h

s

f

Ground Treatment

9.9 Various techniques are available for improving tstrength of foundation soils and some are mentioned this Chapter. Cohesive soils containing pre-existingshear surfaces, may need to be excavated below thecritical toe area of the proposed embankment andreplaced with acceptable material. The re-use of theclay after reworking has been found to be satisfactoryalthough it is prone to softening following the release high insitu stresses. Foundation excavations shouldhave battered sides and be backfilled as soon as posafter excavation. Groundwater must not be allowed tenter or stand in the open excavations. Lowering of twater table by deep trench drains may provide someimprovement in the factor of safety. If solifluction isknown or suspected, it would be wise to destroy theshear planes and provide deep drainage facilities.

9.10 Alternatively, and possibly more economically,the base of the embankment may be reinforced with oof a variety of methods using geosynthetics. Thiswould give adequate factors of safety with the shearematerial still present. Such methods would includegeogrids or geotextiles laid transversely across the baand turned back at each end to form an anchorarrangement: embankment stability is then provided bthe tensile strength of the geosynthetic. Also geogridmay be used to form geocells and vertical webfoundations filled with selected material.

9.11 Other ground improvement techniques includedeep compaction by vibration to achieve settlement oloose non-cohesive granular soils or fill materials aboor below the water table, up to depths of 25m. Columof coarse granular material can be formed in either soclays, silts or compressible fills by vibro-displacemenand vibro-replacement to reduce their compressibilityand improve shearing resistance. In somecircumstances it may be possible to alter theengineering properties of the ground by grout injectioand a number of grouts and techniques are availabledeal with specific problems. More details of thesetreatments can be found in BS 8004:1986, FoundatioSection 6.

9.12 Many of these techniques require specialistcontractors and further detailed information can beobtained from the technical literature. Whichevertechnique is adopted the Designer should ensure thasolution does not in itself create a new failure surface



hein

of

sibleohe

ne

d

se

ys 9.15 Groundwater lowering may be either àctive

`passive'. Active techniques include well-pointingdeep trench drain systems which temporarily or

are those which are designed to reduce the drainf path and thereby decrease pore water pressuresve generated by increased loadings. Typically verticns wick drains, sand drains and drainage blankets bft embankments can fulfil this role.

t

n, to

ns,

t his.

9.13 Ground improvement details should be providedin SHW Appendix 6/13. Earthworks details forexcavation and replacement etc should be detailed onthe drawings and in SHW Appendix 6/3. The Designeshould be aware of the Specification for GroundTreatment and Notes for Guidance published by ICE i1987.

9.14 The rate of consolidation of soft compressiblesoils may be increased, if necessary, by the installatioof vertical drains to reduce the drainage path, soassisting the outward migration of the water. Installation of such drains can cause smearing of thefaces of the vertical bores thus reducing theireffectiveness. A drainage blanket is usually includedand consideration may be given to the use of geomeslayers to improve stability and spread the effects ofirregular settlement. Lightweight fills (ie PFA, seeParagraphs 5.58 to 5.66) or ultra lightweight fills (ieExpanded Polystyrene Foam to BS 3837) may beconsidered to reduce the settlement and instabilityproblems. Further advice may be obtained from theDepartment.

Groundwater Lowering

permanently lower the water level. Passive technique

Voided Ground

9.16 If the highway passes either over or close tounderground voids, where there is a danger ofsubsidence affecting the road, it is common practicewherever possible to fill these voids as a preventativemeasure.

9.17 Underground voids are either man-made or ofnatural origin. Natural cavities are usually the result othe flow of water through soluble rocks. If they stillform part of an underground watercourse they maypresent special difficulties, since any measures to fill




ogridsipated

tound

df

nd

f

en

d

the cavities could interfere with the ground water flowand could cause problems upstream or downstream.Therefore the consequences of such a filling should thoroughly investigated beforehand. In some casescavities are disguised by being covered with detritussuch as is sometimes found in swallow holes in chalkand magnesian limestone, and are only discoveredduring construction. It is therefore sensible to allow fthis when the scheme passes through these materiaand a detailed specification of the treatment requiredsuch natural voids included in the Specification. Onesuggested method of dealing with swallow holes is tofill them with a granular material, sealed over by a laof clay or other relatively impermeable material suchlean-mix concrete.

9.18 Man-made cavities are usually the result ofmining, whether for building stone, coal or otherminerals. The procedure for locating these mines isgiven in Departmental Advice Note HA 34/87, GrounInvestigation Procedure. Guidance on measures torender openings into coal mines safe is given in aBritish Coal publication `The Treatment of DisusedMine Shafts and Adits'. Further advice on measuresrender such openings safe is given in DepartmentalAdvice Note HA 34/87, Ground InvestigationProcedure. British Coal must be consulted andinformed, at all stages, about any operation which wiaffect their workings. The treatment of other mineralmines may be dealt with in a similar manner, andfurther advice may be obtained from CIRIA SpecialPublication 32, Construction over Abandoned MineWorkings as well as Departmental Standard BD 10/8The Design of Highway Structures in Areas of MiningSubsidence.

9.19 A method for the stabilisation of ground affectedby shallow mine workings is the use of grout injectionThis is a noisy and dirty operation, and care should btaken in specifying the equipment to be used especiain urban areas. Air flushed drilling rigs should be fittewith a suitable dust extractor to prevent the emissiondust or other airborne particles. All drilling rigs andassociated pneumatic equipment should be fitted witmufflers or silencers of a type recommended by themanufacturer, and all compressors should be `soundreduced' models fitted with properly lined and sealedacoustic covers which must be kept closed when themachines are in use. Suitable provision should also made to eliminate any dust problems caused by windaction on stockpiles of grouting materials, particularlyPFA.



9.20 Embankment bases may be reinforced by ge over ground where differential settlement is anticbe above filled voids, or the embankment may be

surcharged to accelerate any such movement. , Instrumentation, as discussed in Paragraphs 4.45

4.50, should also be considered to monitor the groprofile during and after construction.

orls, for

yer as

d

to

ll

2,

. ellyd of

h

be

Dynamic Compaction

9.21 Clause 617 in Appendix A of DepartmentalStandard HD 6/80 is superseded by Clause 630 of the7th Edition of the Specification for Highway Works. The Method of Measurement for the 7th Editionsupersedes Appendix B of Departmental Standard HD6/80. The advice given below supersedes that given inDepartmental Advice Note HA 11/80 and is intended toassist in the compilation of the data to be inserted inAppendix 6/13.

9.22 Dynamic Compaction (DC) is the process bywhich a rapid increase in the density of soil or othermaterial is achieved by dropping a free-falling heavymass (pounder) a number of times from pre-determineheights at pre-determined spacings onto the surface othe ground or fill. This rapid densification is producedby the expulsion of air, reduced spacing andrearrangement of the particles by mechanical means aresults in settlement of the ground surface. However,this is different from the Menard system of `dynamicconsolidation' which employs the improvement of theproperties of saturated soft fine-grained soils by meansof the expulsion of water. Whereas DC has been usedextensively in Continental countries for the treatment osoil on roads and other civil engineering sites,experience in Great Britain is more limited. TheEngineer is, therefore, often obliged to follow theadvice provided by the specialist firms which carry outthis process which, in many cases, will result in anend-product specification being followed rather than amethod specification. In other cases the choice betwemethod and end-product specification will depend onthe type of material to be compacted, the conditions onsite and the experience of either the Engineer or theContractor or both with the materials and methods useand the quantity of testing required for end-productspecification.



Chapter 9 Volume 4 Section 1Ground Conditions Requiring Special Treatments Part 1 HA 44/91

ehe

esHW,d limits

arried

n ahichfted by

nd sore

l

adeimum time

nd the

be

of

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of

two

s

9.23 DC is intended for the improvement of thefoundation soils beneath earthworks, pavements andstructures. Its use within earthworks would beexceptional. The process is not suitable for use on asoil types. In general, it is unsuitable for application peat, soft heavy clays and probably soft medium clayand silty clays. At present it is advisable to restrict ituse to granular material such as silty sands, sands agravels, uncompacted man-made fill and refuse. Consideration should be given to its possible effects the underlying layer of soil as well as the layer beingtreated. If the former is a soft clay, dynamiccompaction of the material above it could havedetrimental effects at the lower level, causingindentations which serve as reservoirs for ground wawhich is unable to drain away. Limited experience inthis country does indicate that the process is particulsuitable for the treatment of deep deposits of domesand industrial refuse where the alternative would beremoval and replacement. In areas where open-casmineral workings have been filled with uncompactedsoil, surcharging has been found to be as effective aDC. In saturated low permeability ground with a highwater table, particular care should be taken to prevenan excessive rise in pore water pressure and anyliquefaction of the ground caused by over-tamping:piezometers should be installed before the treatmentcommences. From investigations carried out by theBuilding Research Establishment at sites wheredynamic compaction has been used to compact loosfills, the depth of effectiveness Z in metres is given aconservative approximation by:-

Z = 0.4 T (W.H)where W = mass of pounder (Tonnes)

H = drop height (m)

9.24 Limited feedback suggests that where construcis delayed after Dynamic Compaction, furthersettlement may be expected, due to the dissipation opore water pressures built up during the initialtreatment: possibly as much as 50mm of settlementcould occur over the 25 years after treatment.

9.25 Vibration caused by the falling mass will betransmitted throughout the ground and air and couldconceivably cause damage to property off the site, acould flying debris. The close proximity of houses orother buildings may preclude the use of DynamicCompaction and this must be considered at the earlydesign stage.

9.26 Vibration may be minimised by decreasing theheight of free fall while increasing the number of blow



of the pounder. Consideration should be given to thconstruction of isolating trenches so as to inhibit t

ground vibrations from reaching adjacent property.llto 9.27 The safe vibrational limits at adjacent structurs are those specified for blasting in Clause 607 of S

s and the advice given in Paragraphs 7.14 to 7.31 annd TRRL RR 53 applies. If there is any risk of these

being exceeded, an instrumented trial should be con out.

9.28 The primary aim of the process is to achieve, irelatively short period, settlements of the ground wwould normally occur some time after completion o

ter the works. where a high embankment is construcconventional methods on ground that has been

arly dynamically treated, it is important to differentiatetic between any settlement within the embankment a

settlement within the treated ground. Failure to dot may give rise to unresolvable argument as to whe

responsibility lies. It is therefore important to instals suitable gauges which will indicate the degree of

settlement within the two components of the work.t

9.29 The total and differential settlements to beexpected should be indicated in preliminary tests mby the specialist contractor. In specifying the maxacceptable value, it is essential to bear in mind theinterval between completion of the embankment a

e construction of the pavement. Higher values ofs a acceptable total and differential settlement would

expected as this time interval increases.

9.30 While it is very difficult to specify values for thetotal and differential settlements at different stages

the works, since each site is unique, the following

tion settlement, in the treated ground, which can be toin the time between completion of the embankment

f trimming the formation:-

i. mean differential settlement between all pairsadjacent gauge locations not to exceed

ii. maximum differential settlement between anys adjacent gauge locations not to exceed

80mm or 1 in 125,

iii. mean total settlement not to exceed80mm

figures may give some guidance on the amount of

40mm or 1 in 250,




n

cl

andtsr

9.31 Settlements of the treated ground taken at laterstages can be expected to exceed these figures by aproportion dependent on the time that has elapsed. Ithe long-term, settlement of treated refuse, which issubject to decay, may be difficult to predict to anyaccuracy.

9.32 The extent and magnitude of the densificationachieved can be verified by appropriate strength testsincluding:-

i. plate bearing tests at the surface or in a trial pit;

ii. dynamic probing, static probing (including electricone penetrometer) and self-boring pressuremeter alfrom the surface;

iii. pressuremeter tests, vane tests or penetrationresistance tests in boreholes drilled for the purpose.

9.33 In selecting a suitable test, the type of materialbeing processed, the accessibility of the site to plant vehicles, and the presence of stones and larger objecin the material must be considered. In fills of rubble orefuse which contain large obstructions, only platebearing or àd hoc' load tests at the surface would befeasible. The equipment and procedure for all thesetests is set out in Section 8 of `Specification andMethod of Measurement for Ground InvestigationContracts. First Edition. 1987'.

9.34 Further information on a specification and testmethods is given in ICE publication `Specification andNotes for Guidance on Ground Treatment'.



Volume 4 Section 1 Chapter 10Part 1 HA 44/91 Subgrade and Capping

10. SUBGRADE AND CAPPING

bility its

gd

of

ss

e

R

s

nd

ust

Pavement Design

10.1 For the purposes of this Advice Note `pavemencovers all material from surfacing down to the uppersurface of the sub-base: sub-base covers materialbetween the bottom of the pavement and formation. Capping, and materials below sub-formation andformation, are earthworks materials (see Figure 10/1The acceptability limits for earthworks materials areselected on the basis of how the material is to be usand its ability to be handled, compacted and traffickeEach earthworks layer provides a platform upon whithe next may be placed and compacted. In the samway the sub-formation is used as a platform on whicplace and compact the capping and the formation isused as a platform for the sub-base. The pavementdesigned on the basis that the sub-base can beconstructed to a particular standard and that its integcan be maintained. This requires construction on aformation of a certain quality, achieved by ensuring tthe whole of an embankment, or at least the upper zis constructed of good quality materials. If the materin the upper layer is zoned then, in effect, a capping been applied. In cuttings, where the subgrade may be suitable as a platform for the sub-base, then acapping must be used.

10.2 The capping performs two functions.

i. In the short-term it acts as a working platform foconstruction of the sub-base, and provides protectiofor weak subgrades.

ii. Acts as a structural layer, in the long term.

10.3 Pavement design is covered by DepartmentalStandard HD 14/87 and Departmental Advice Note H35/87 `Structural Design of New Road Pavements'. background to the design procedure is contained inTRRL Report LR 1132. As a reliance has been placon the formation to provide a sufficient platform onwhich to place and compact the sub-base, the sub-bthickness, with one exception, does not vary for a givdesign. Table 10/1 shows how the normal sub-basethickness of 150mm must be increased to 225mm foflexible and flexible composite pavements onformations with a CBR percentage less than or equa15 but greater than 5.



in

t'

).

edd.

cheh to

is

rity

hatone,ialhasnot

rn

AThe

ed

aseen

r 10.8 The CBR is an index of bearing ratio used toindirectly measure soil strength and stiffness. Its a

l to to measure these depends upon the soil type andstate; see Hight and Stevens Àn Analysis of the

10.4 It is the combination of subgrade strength, cappinthickness and capping material which gives the requirestrength characteristics at formation. The cappingmaterials and stabilisation processes described in theSHW are deemed to provide similar strengthcharacteristics at formation. The only variables are,therefore, the thickness of capping, and strength andstiffness of subgrade. Appendix A of DepartmentalStandard HD 14/87 relates these variables in a series steps shown in Table 10/1.

10.5 The designer needs, therefore, to be able to assethe CBR of the subgrade. In the design, a CBR ofgreater than 15% is required at formation forconstruction of rigid and rigid composite pavementsand a CBR of greater than 5% is required at formationfor flexible and flexible composite pavements. If thesubgrade soil cannot achieve this then a capping will brequired of sufficient thickness, depending on the CBRof the subgrade, to provide the necessary strength andstiffness at formation.

10.6 The materials permitted for capping have beenchosen to meet the requirements for a formation of CBof greater than 15%.

10.7 A further consideration is frost susceptibility. Nomaterial within 450mm of the designed final roadsurface shall be frost susceptible, as tested inaccordance with Clause 602.19 SHW, whether used apavement sub-base, capping, fill material inembankments or insitu material in cuttings. If the totalconstruction depth as designed is less than 450mm, athe insitu material below is frost susceptible, then thecapping or, when there is no capping, the sub-base mbe thickened to give a total minimum constructiondepth of 450mm irrespective of CBR or other strengthconsiderations. Frost susceptibility requirements forconstruction layers are defined in SHW Clauses 602and 705.

Subgrade Assessment

California Bearing Ratio Test in Saturated Clays'. TheCBR has been correlated with pavement performancethe development of empirical design methods.



Chapter 10 Volume 4 Section 1Subgrade and Capping Part 1 HA 44/91

1

Surfacing andRoadbase

Materials orHigh Strength

Concrete Slab orComposite

Construction

Sub-base

Formation

Sub-Formation

Capping

Pavement

Sub-Base

Earthworks outlinefor measurementpurposes

Earthworks

Pav

emen

t Fou

ndat

ion

Figure 10/1 Composition below road surface

Subgrade

Subgrade

TABLE 10/1

Capping thickness for different subgrade strengthsand stiffnesses

CBR (%) CAPPING THICKNESS (mm)

CBR # 2 600 2 < CBR # 5 350 5 < CBR # 15 150 for rigid and rigid

15 < CBR No capping

composite. No capping for flexible and flexible composite but sub-base increased to 225




tet or

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ly

.

eder

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.

ent

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or

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10.9 Although not wholly satisfactory the CBR iscurrently used as a measure of subgrade strength anstiffness. BS 1377: Part 4 describes how CBR ismeasured in the laboratory. Field measurements mabe carried out insitu but lower values are possible forsoils coarser than fine sands due to the soil not beingconfined in a mould (see p191 of `The Design andPerformance of Road Pavements' by Croney). Otherindirect methods of arriving at a CBR may be used,such as the insitu plate bearing test. See Wood andBoud `Foundation Design Principles'. It is essential tlaboratory CBRs reproduce as closely as possible themoisture content and the state of compaction likely toapply to the subgrade.

10.10 The CBR of a soil under particular conditionswill vary with changes in moisture content. Themoisture content will depend on the position of grounwater table, stress history, overburden or surchargeload, availability of free water etc. In addition, the CBwill be different for a soil in its remoulded state and wdepend upon the degree of remoulding. In practicemost subgrade soils may be assumed to be remouldedue to earthmoving and compaction, trimming,preparation and compaction of formation orsub-formation. The moisture content of soils suitablefor placing in embankments will invariably be differenfrom that when preparing the formation orsub-formation for sub-base or capping and will almoscertainly be different to the long term èquilibrium'moisture content attained under the completedpavement. The CBR of the material will vary with timas well and the èquilibrium' CBR is not necessarily tlowest value of CBR achieved under certain conditionIt would not be inconsistent for construction CBRs tolower than long-term CBRs. The Designer shouldensure that the CBR during construction is checkedagainst his design values for construction and thelong-term CBRs.

10.11 The long-term or equilibrium moisture contenwill depend on a number of factors including:-

i. soil type and properties;ii. groundwater table;iii. drainage;iv. weather;v. state of pavement maintenance;vi. state of stress and stress history;vii. construction history.



y

10.12 The construction history embraces amongsd other things whether the material became very w

very dry or alternated from wet to dry. There arey procedures available (LR 1132) for estimating th

equilibrium moisture content and, therefore, theequilibrium subgrade strength of cohesive soils.

However, these can produce conservatively low vof CBR for saturated cohesive soils.

hat

d

Rill

d

t

t

ehes.

be

t

Capping Design

10.13 It is for the Designer to assess how muchinvestigation and testing is required to produce hisdesign. However, this should be tailored to the soil typand the road's use. Reference to Table 10/2, based oTable C1 of LR 1132, indicates that sands and sandygravels present no problems as formations, whilst siltsand cohesive soils will require consideration. Generalwith these latter soils it is not until the CBR falls toaround 2% that difficulties occur with placing,trafficking, compaction and embankment slope stability

10.14 The estimation of the equilibrium CBR forclays is critical. Drainage conditions are discussed inParagraphs 10.25 to 10.27; however, it may be assumfor the purposes of using Table 10/2 that the `high wattable' condition is relevant. Silts are deemed to have aCBR of 2% or less and will therefore have the fullthickness of capping given in Table 10/1. The Designeshould assume that the SHW is complied with and,therefore, àverage construction conditions' will pertainThe Designer must give his reasons if other thanaverage conditions are assumed. The thinnest pavemproposed in HD 14/87 consists of a 150mm thickconcrete surface slab. Including a 150mm thicksub-base and 350mm thick capping gives the least deto subgrade of 650mm, for CBRs greater than 2 and lethan or equal to 5 per cent. The thickest pavementgiven in HD 14/87 is a 450mm thick flexible compositepavement with an indeterminate life. A sub-basethickness of 150mm and a capping thickness of 350mwill give a depth to subgrade of 950mm for CBRsgreater than 2 and less than or equal to 5 per cent. Interpolating between the depths given in Table 10/2 fthe critical clay subgrades gives equilibrium CBRs forall but the heaviest clays of greater than 2 and less thaor equal to 5 per cent and confirms the assumption of 350mm thick capping. The heaviest clays are lessaffected by the thickness of construction and with apredicted equilibrium CBR of 2 per cent or less requirea thicker capping of 600mm thickness. Table 10/2 matherefore be rewritten in the form given in Table 10/3.



W WATER TABLE

UCTION CONDITIONS:

AVERAGE GOOD

Thin Thick Thin

TABLE 13/2

ORMATIONORMATION OF 1200mmF 300mm

>8

2

2

2

2

2

22.5

2.5

2.5

2.5

3 3 3

4 4 4

4.5

5 6 6

6

6

7

8

3.5

2

2

2 2 2 2

PROBABILITY OF MATERIAL SATURATING

Thick

Chapter 10

Volum

e 4 Section 1

Subgrade and C

appingP

art 1 HA

44/91

PA

PE

R C

OP

IES

OF

TH

IS E

LEC

TR

ON

IC D

OC

UM

EN

T A

RE

UN

CO

NT

RO

LLED

June 199110/4

TYPE OF SOIL HIGH WATER TABLE LO

CONSTRUCTION CONDITIONS:

POOR AVERAGE GOOD

Thin ThickPL

AS

TIC

ITY

IND

EX

HEAVY CLAY

SILTY CLAY

SANDY CLAY

SILT*

SAND (POORLYGRADED)

SAND (WELLGRADED)

SANDY GRAVEL(WELL GRADED)

Equilibrium suction - index CBR values

Thin Thick Thin Thick

CONSTR

POOR

Thin Thick

(Based on Table C1 of LR1132)

NOTES: 1) A HIGH WATER TABLE IS 300mm BELOW FORMATION OR SUBF2) A LOW WATER TABLE IS 1000mm BELOW FORMATION OR SUBF3) A THICK LAYERED CONSTRUCTION IS A DEPTH TO SUBGRADE4) A THIN LAYERED CONSTRUCTION IS A DEPTH TO SUBGRADE O

70

60

50

40

30

20

10

1.5

2.5

3.5

4

20

40

60

2

1.5

1.5

1.5

1.5

1.52

2

2

2

2

2

2

2

2

2

2

2 2

2

2

2.5

2.5

2.5

2.5

2.5

2.5

2.5 2.5

3

3

3 3

3

3

4

4 44.55

5

6

7

73.5

3.5 3.5

42.5

2

2.5

3.5

1 1 1 1 1 12 2

* ESTIMATED ASSUMING SOME

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Volum

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Chapter 10

Part 1 H

A 44/91

Subgrade and C

apping

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June 1991P

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D10/5

TABLE 10/3

subgrade strengths and stiffnesses, and cappingesses for typical construction conditions.

PI PREDICTED

706050

40302010

2 600mm capping 2 2 ________________________________________________ 2 to 3 350mm capping 3 to 4 4 to 5 4 to 5

Equilibriumthickn

TYPE OF SOIL

Heavy Clay

Silty Clay

Sandy Clay


crete

ition

ist ces,

e atis not

dottant

rmr

e an 5% a

ueshouldalue

osmentthe

s of

ly be

ne

10.15 Further investigation will be required usingTable 10/2 if average construction conditions and `hiwater tables' are not appropriate.

10.16 There are, therefore, three distinct assessmeof the subgrade to be made.

i. Suitability, where appropriate, for construction.

ii. Prediction of CBR during construction - this willhave some relationship with soil acceptability.

iii. Prediction of the long-term CBR at equilibriummc.

10.17 The GI should normally be designed to obtathe full range of natural moisture contents of eachrelevant soil type. The relation between laboratoryCBR and moisture content for at least six to ten poinshould then be determined for each soil type to provia basis for suitability for construction throughknowledge of the natural moisture content. Thisrelationship also allows the CBR during constructionbe estimated, bearing in mind the SHW requirementsfor protection of the subgrade, and that CBR isdependent on soil type and dry density. The CBRduring construction may also be estimated using theplasticity characteristics as shown in LR 1132. Laboratory CBRs should be determined in accordancwith BS 1377. Cohesive samples should be compacas closely as possible to the density expected in theroad, but to not less than 5% air voids to avoid spurioeffects from pore water pressures. The staticcompaction method should be used for most soil typthe dynamic compaction method should only be usedfor sandy soils. The total annular surcharge weightshould be calculated to equate to the pavementoverburden pressure and the CBR calculated on the2.5mm plunger penetration for cohesive soils.

10.18 Where possible insitu CBRs should be takenthe GI and compared to the relation between laboratCBR and mc for the same soil type to ensure acorrelation. In some circumstances insitu CBRs cangive different values than laboratory CBRs. If there isignificant difference then corrections will have to bemade when using the lab CBR/mc relation.

10.19 The assessment of the long-term CBR atequilibrium mc may be found by using one of thefollowing predictive methods depending on the desigassumptions made in the case of (i) (ii) and (iii), or thavailability of a comparable site for (iv).


PAPER COPIES OF THIS ELECTRON10/6

i. Estimation or calculation (Blood and Lord, andgh LR 889)

ii. Using LR 1132

nts iv. Prediction by testing (see Paragraph 10.20)

(see also Paragraphs 4.8 to 4.32).

10.20 Prediction by testing at the GI stage wouldtake the form of locating an existing pavement, con

soil type in question. This may take the form of anexisting road, farm track, farm yard etc. As far as

n obtained and it should be at least 3 years old. Theprocedure is then to excavate through the construcand obtain insitu CBRs and moisture contents. Th

s will give good guidance, depending on circumstande as to the equilibrium CBR and mc to be expected.

Because of edge drying effects tests should be madleast 2m from an unpaved or drained edge. If this

to possible tests should be carried out in the periodNovember - April.

10.21 Soaked laboratory CBRs do not mirror theequilibrium situation or the stress history, but they

give an indication of worst conditions and will detece the presence of sulphates in the soil; this is imported for soil that are to be stabilised.

us 10.22 If both the long-term CBR and the short-te(during construction) CBR are greater than 15% fo

s; rigid and rigid composite pavements, or greater thfor flexible and flexible composite pavements, thencapping is not required. If conditions duringconstruction are likely to result in a lower CBR valthan in the long-term, then the construction CBR

be used for design. However, normally, the CBR v

at usually the lower value of CBR.ry

10.23 In the absence of better methods of assesusing strength measurements it is suggested that

s a CBR for cohesive soils for both long and short termconditions is assessed using the plasticity propertiethe soil. For the long-term condition Table C1 of LR

10/3. `High water table' conditions should generalused for design (see Paragraph 10.27).

iii. Using Table 10/3

All these methods will require soil classification, PI etc,

slab or similar semi-impermeable construction over the

possible the history of the construction should be

for design will be the equilibrium value as this is

1132 may be used or the simplified form given in Table


IC DOCUMENT ARE UNCONTROLLED June 1991


tiontheir

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ds

In

Capping Materials

10.24 Capping materials described in SHW aredesigned to provide a stiffness and strength equivaleto a CBR of at least 15% at their top surface whenplaced and compacted to the thickness commensurawith the subgrade CBR given in Table 10/1. SHWTable 6/1 Class 6F1 and 6F2 are selected granularmaterials of fine and coarse grading respectively. Omaterials which may be stabilised insitu to form acapping are described below in Paragraphs 10.28 to10.67 on Lime Stabilisation and Paragraphs 10.68 to10.80 on Cement Stabilisation. The Designer shouldallow the widest possible choice of capping materialsbe used and should only restrict the choice if there asound engineering reasons.

Drainage

10.25 It is strongly recommended that surface wateis never collected by systems which might allow wateto flow into the subgrade. It is preferable that surfaceand sub-surface water drains are kept separate. Aminimum of 2E% crossfall should normally be provideat all locations. A narrow filter drain or fin drain shoualways be provided on the low side of pavementsimmediately adjacent to the pavement layers to colleand dispose of water seeping into the pavement. Thpipe for such a system should always be set slightlylower than the sub-formation of a 600mm capping toenable it to act as a sump for percolation along thecapping/subgrade interface. For thinner capping thepipe will be below sub-formation level anyway (seeHCD and HA 39/89: Edge of Pavement Detail). Although the drainage will always extend belowsub-formation level, it should be remembered that it not a requirement of capping materials that they are draining. If the capping is free draining, waterpercolating through it will be disposed of by thedrainage, but the drainage will still have a beneficialeffect if the capping is relatively impermeable. Incuttings where appreciable inflows of ground water aexpected additional `cut-off' drains should be provide

10.26 In moisture sensitive soils it is consideredbeneficial to install sub-surface drainage prior toplacement of capping which for 600mm capping wouresult in drains deeper than the minimum specified inHCD. Measures should be taken to ensure these drare not used as surface water drains during construcas they may become choked and unable to perform long-term function.



nt

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rr

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ld

ains

10.27 For cuttings in cohesive soils of lowpermeability (all those in Table 10/3), it is unlikely that`cut-off' and sub-surface drains can be set in sufficiendeep to economically and efficiently lower the `watertable' to ensure the `Low Water Table' conditionsdiscussed in LR 1132 and denoted in Table 10/2. Because of this and the discussion in Paragraph 10.2is recommended that `High Water Table' conditions adesigned for and drainage is provided accordingly. Inembankments, the Designer should consider if lower`Water Table' conditions will be appropriate for thedesign, in which case CBRs should be interpolated froTable 10/2. For heavy clay a change in `Water Tablelevel does not change the CBRs given in Table 10/2. Changes do occur, however, for silty clay and sandyclay.

Lime Stabilisation

10.28 Lime and cement stabilisation are defined inClause 601 of SHW. The second edition of the `LimeStabilisation Manual' (referred to below as the`Manual') was jointly published by ICI and BLA inJanuary 1990. Except in cases where it may conflictwith this Advice Note, the SHW or other DTpdocuments, the Manual can be regarded as a guide togood practice and to the current `State of the Art', andreflects the liaison between the Department and thelime-producing industry. It should be noted that limestabilisation as described in Clause 615 (SHW) depenon both the initial and long-term chemical reactionsdescribed in Section 3 of the `Manual'.

Materials and Chemical Reactions

Suitability of soil for stabilisation

10.29 The values of mc or MCV to be inserted inSHW Appendix 6/1 for Class 7E should be determinedin the same way as for Class 2, general cohesive fill,except where it is desired to `modify' wet material byadding extra lime before the normal processing andcompaction takes place. By using quicklime themoisture content can be reduced by the order of 5%. this case the minimum and maximum mc or MCVs forAppendix 6/1 should be established by laboratorytesting followed if necessary by site trials.




n the

witheveralay

e soil.

e

%

sth.

s

e

10.30 Organic matter interferes with the normalreaction between the lime and the soil. The maximumacceptability limit for Class 7E in Table 6/1 has beenset at 2%. This is based on DTp experience andinformation from the literature. Oxford Clay is,however, an example of variation in this limit, since itcontains up to 10% of finely divided bituminous matteand it can be successfully stabilised with 3% lime. It possible, therefore, that some relaxation may bepossible for some materials following experience andfeedback.

10.31 At a high pH value, when lime is introduced, reaction occurs between the clay fraction and thesulphates in the soil causing expansion and disruptioThe value of total sulphate content to be inserted inAppendix 6/1 should normally be 1.0% except wherecase histories or a prolonged trial indicate that a highvalue is acceptable.

10.32 There are a few clay soils, otherwise complywith Class 7E, which may not develop the requiredstrength after lime stabilisation. These includeoccurrences of Weald Clay and other silty clays in Keand East Sussex and some Upper Coal Measure clasuch as fireclays. In such cases preliminary laboratotests are recommended.

Choice of Lime

10.33 The `Manual' discusses the advantages ofquicklime (para 4.1 p 19). Semi-hydraulic quicklime,while having a low àvailable lime' content, behaveslike a weak cement: if it is proposed to take advantagof its cementitious properties in the design, a trial wobe required. In the case of quicklime a high reactivitydesirable (BS 6463: Part 3: 1987). This is measuredterms of the temperature rise when the quicklime reawith water.

Chemical Reactions

10.34 The `Manual' (Section 3 pp15-18) refers to thdrying out effect of lime but this is only strictly true inthe case of quicklime. Hydrated lime addition makesthe soil appear drier due to an increase in plastic limibut real moisture content reduction is only of the ordeof 0.5% for a 4% addition. This initial or short-termeffect is referred to as `lime modification'.



y

d

10.35 The long-term pozzolanic reaction betweelime and the clay particles (referred to as `limestabilisation') leads to a linear increase in strengthrespect to the logarithm of time up to an age of s

months. After this period the increase in strength mcontinue or become less marked, depending on th

ris

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ing

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Lime content and strength

10.36 A bearing ratio of up to 8% can be expectedimmediately following final compaction, equivalent toan upper limit for MCV of 12. The addition of aminimum of 2E% available lime should result in theCBR rising to a minimum value of 15% in theshort-term after compaction and it should not fall belowa minimum value of 7-8% in the long-term. Thisallows for some degree of softening which may occur.

10.37 For clay soils amenable to lime stabilisation thlong-term strength increases with lime content up to alime percentage roughly equal to one tenth of thepercentage clay content of the soil. However, above 4lime content the increase in strength for each 1%increase in lime content becomes less marked.

Temperature

10.38 The strength developed due to long-termpozzolanic reactions increases with temperature. Thufor laboratory specimens cured for 56 days, the strengat 25 C is about 25% greater than the strength at 15 CHowever, at 0 C little or no strength increase takesplace. The use of lime as a construction expedient onwaterlogged sites, relies only on the effect that lime haon plasticity in the short-term. This is not temperaturesensitive and in fact this process is most likely to findapplication in winter months. This certainly is not thecase for lime stabilisation as defined in the SHW wherthe long-term temperature sensitive effects areimportant, and hence the strict temperaturerequirements given in Clause 615 must be compliedwith.

Processing and Compaction

Spreading the Lime

10.39 In order to perform to the SHW, the àpprovedspreading machine' referred to in Clause 615.6 is likelto be one with a device capable of accurately meteringthe lime supplied, gearing to allow for variation inspeed of travel, large capacity and spreading width, anprovide precautions against dusting.




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Rotovation and Mixing

10.40 Clause 615.10 SHW requires the stabilisingmachine to have an integral spray bar. This is to ensthat water can be added evenly at the first or secondpass of the machine which is particularly importantwhen quicklime is used. Machines which do notincorporate their own integral water supply are unliketo be able to properly operate the integral spray barspecified in SHW.

10.41 It is important to maintain close sitesupervision to ensure that the depth processed and tfinal compacted thickness are correct, particularly forlayers thicker than 250mm.

10.42 Whenever there is a delay between passes the stabilising machine or before final compaction thesurface must be sealed as described in the SHW ClaThis is to minimise evaporation loss, reducecarbonation of the lime and reduce rain damage.

Addition of Water

10.43 If the soil is too dry for slaking quicklimeand/or mixing purposes, water should be added throthe spray-bar during the first or second pass of thestabilising machine.

10.44 The MCV required for Class 9D immediatelybefore compaction is such that 5% air voids, or bettewill be achieved following compaction to Method 7. The maximum MCV to be inserted in SHW Appendix6/1 should normally be 12. It has been asserted thatsome soils (eg Oxford Clay) an MCV of 12 representtoo wet a condition for satisfactory compaction. However recent experience suggests that compactioClass 9D material in the dry condition represented byMCV greater than 12 has led to inadequate compactresulting in swelling and softening at a later stage whwater is available. Hence, a maximum MCV of 12should be specified unless there are strong grounds choosing a higher value, in which case thedemonstration area should be carefully assessed toensure that compaction to 5% air voids has beenachieved. The minimum value to be inserted inAppendix 6/1 may be 9 or other value as the Engineeconsiders appropriate. The minimum value should bbased on the achievement of the desired bearingcapacity within an appropriate curing period.



Mellowing

10.45 This is the interruption in processing referreure in Clause 615.11. It was originally based on Amer

practice. Combined with the light compaction requfor sealing, it allows the diffusion of lime in thepresence of water and by progressive base exchang

ly reaction breaks down the clay lumps to a more friabstructure. This process also serves to correct any

original unevenness in the distribution of the lime and

is no risk of expansion from this cause afterhe compaction.

f

use.

will be necessary before such a roller can be approvegh The heavier pneumatic tyred rollers are unsuitable

the 150mm layer because there is evidence that seoverstressing of clay soils could occur under the high

weight of the heavier vibratory rollers, particularlyr, when dealing with thick layers, thicker than 250mm

10.47 Where the Engineer agrees that layers more for than 250mm thick can be constructed, the Contracs required to demonstrate that such an operation is

feasible with the plant he proposes to use. In then of demonstration area, therefore, the state of compa an the bottom of the thicker layer must be shown to be

ion adequate; normally an air void content not exceeden per cent should be achieved in the bottom 150mm

layer. To reach this level of compaction in layers offor such thickness will require the soil-lime mixture to

prepared at a lower MCV (higher moisture content)than the maximum value compatible with thinner l

as specified in Appendix 6/1. The MCV of the matin the demonstration area should be determined,

r therefore, immediately prior to final compaction. If e construction of the proposed thicker layers is appro

the soil-lime mixture in the subsequent constructiowork should be compacted at a MCV no greater than

ensures that quicklime is completely slaked so that there

Compaction

10.46 Method 7 has been introduced as anamendment to SHW Table 6/4 for Classes 9B and 9D toproduce 5% air voids at an MCV of 12. It is based onTRRL data and takes account of the fact that thetamping roller is much more effective on cohesivematerials, including lime stabilised cohesive materials,than it is on granular materials. There is evidence thatvibrating tamping rollers are effective but a site trial

loads exerted. Care is needed in correctly assessing th

that of the demonstration area. For a 350mm thicklayer, only heavy pneumatic rollers exceeding 6,000kgmass per wheel are usually considered to be suitable.




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Environmental and Health Aspects

10.48 Safety and health are fully dealt with in Sectio5.11 of the `Manual' (pp30-31).

10.49 Dust can be a problem when powdered lime used. Lime which has been spread should be coveremixed into the soil within 6 hours of application toprevent wind loss and carbonation (reversion toCaCO3).

10.50 Dust produced when granulated quicklime waused at a site in Yorkshire in 1979 was investigated bTRRL. It was found that the wind distribution effectswere mainly confined to an area close to the workingarea and that further away, the dust levels were similto other construction sites during conventionalearthmoving operations. In the measurements it wasnot possible to separate lime and soil dust.

Durability

Softening due to Soaking

10.51 Lime stabilised clays lose strength due tosoaking, even after the long-term pozzolanic reactionhave taken place, because there will always be particor patches of unreacted clay in between the areascontaining cementitious reaction products. The loss ostrength is not easy to predict because it depends onnumber of factors including:-

I. stage at which the soaking takes place;ii. confining conditions;iii. lime content;iv. permeability.

10.52 Laboratory tests often show a complete loss strength in unconfined compression when specimensstablised with less than 5% lime are soaked withoutlateral support at curing ages less than about 26 weeOn the other hand, specimens soaked and tested in tCBR mould show a 30% to 50% reduction in CBRregardless of the curing age. Because of thisuncertainty about the effect of soaking, it is importantensure that lime stabilised cappings are kept free ofwater by appropriate design of drainage and thecross-section. Cases on schemes have occurred whlime stablised cappings have lost strength and poordrainage has been a factor. This also demonstrates confining pressure is important. Proper attention musbe shown to compaction and protection.



Frost Susceptibility

n 10.53 The test specified in Clause 602.19 SHWBS 812: Part 124 test which should be carried out o

is the lime stabilisation during the ground investigad or Further tests should also be carried out on spec

cured for at least 28 days after mixing with lime.

10.54 Lime stabilised capping can be damaged eith

s unprotected material before the pavement is cony or by frost-heave when water is drawn in from be

freezing conditions. The BS 812 test will establishsusceptibility of the material to the latter type of

ar damage.

10.55 Lime stabilised cappings should be coveduring the period October to February by a weath

sles

f a

of

ks. he

to

ere

lime stabilised specimens of the materials proposed fo

by the freezing of water entering the surface of the

protection at least 300mm thick if the overlayingpavement has not been constructed, unless the resultthe BS 812 tests demonstrate that the stabilised mateis non frost-susceptible. This should be established athe ground investigation stage so that if weatherprotection is required it can be included in the ContracThe sub-base is not sufficient as weather protection ifis less than 300mm thick.

10.56 The reaction of lime with clay soils initiallyproduces a silt-like material which is more frostsusceptible than the original clay. However, thepozzolanic reaction which also occurs leads to theprogressive growth of cementitious compounds and aresulting reduction in permeability and increase intensile strength, which may make the material nonfrost-susceptible after 28 days cure or longer dependion the percentage of lime added. But some stabilisedmaterials may remain frost-susceptible even afterconsiderable curing periods.

10.57 If the design indicates that the lime-stabilisedcapping will occur within the top 450mm below roadsurface (Clause 602.19) and the results of the BS 812test show it to be frost susceptible at 28 days, then thoption of lime stabilisation in the Contract should berestricted to the lower layer of capping or deletedaltogether. Where there has been a reduction in frostsusceptibility after 28 days cure but the results still faithe test, consideration should be given to carrying outfurther tests after 56 days cure.




ious

ed hee

o

Case Histories

10.58 A number of important case histories are givein the Proceedings of the Lime Stabilisation Symposiaof 1988 and 1990, arranged by the British AggregatesConstruction Materials Industries (BACMI) and theBritish Lime Association (BLA). These include earlyschemes, and the more recently completed M40Sections which contained considerable lengths of limstabilisation.

Rain Damage

10.59 Heavy rain falling immediately afterstabilisation can cause leaching out of lime in the top50mm of construction. The leached material should bremoved before further construction and designmodified if necessary.

Stabilisation with lime plus another additive

10.60 The following combinations have been used:

i. lime plus cement;ii. lime plus PFA;iii. lime plus gypsum (Japan, Scandinavia);iv. lime plus salt (Lees, Abdelkader and Hamdani,The Highway Engineer, December 1982).

Lime plus cement

10.61 This is a two-stage process which is quite weestablished. It is applicable to clay soils, which do nonormally benefit from cement stabilisation. A commoprocedure is:-

i. process with 3% lime in a similar manner toClause 615;

ii. 2-3 days interruption for mellowing,

iii. process with 4-7% cement in a similar manner toClause 614.

10.62 The reaction with lime gives the clay a moregranular texture so that it can be cement stabilised anthe final product has a strength 50-80% greater than obtained using either lime or cement alone.



Lime plus PFA

n 10.63 The lime and PFA react to form a cementitmaterial, which can be used in place of cement forstabilising granular soils.

10.64 If the Contractor wishes to produce a stabiliscapping using any of the combinations given above

e must demonstrate that the required strengths can bobtained by:-

e

-

lltn

dthat

i. pre-contract laboratory trial tests as described inthe following Section on Testing;

ii. constructing a demonstration area as required inSHW Clause 613.

Testing

10.65 If preliminary laboratory trials are required, inorder to determine the stabilisation method, they shouldbe carried out by the Engineer or the Contractor asappropriate. The strength of laboratory compactionspecimens can be determined either by the bearing ratitest of BS 1924 or by the BS 1924 unconfinedcompressive strength tests, unsoaked and soaked. Ingeneral, the bearing ratio is approximately equivalent toone twentieth of the compressive strength (in units ofkN/m2) but a calibration should be performed for eachtype of soil. For laboratory mixing a mechanical mixerwith a high speed blade will give the best results. Itshould be noted that the strength or bearing ratio oflaboratory mixed material will be significantly greaterthan that of site-mixed material, and will need to bescaled down for design purposes, on the basis of`mixing efficiency' which is defined below.

Mixing = Strength of material mixed on-site andcompacted in laboratory

Efficiency Strength of material mixed andcompacted in laboratory.

If a trial is not conducted, the strength of the site mixedmaterial is taken as 60% of the strength achieved in thelaboratory.

10.66 The Engineer's tests on the demonstration areamay comprise:-




be. For

ment

2%. in BS the withwas

ill

e

ryr

t.

ay

th

n.

i. BS 1924 laboratory tests for strength (as describabove) on processed material obtained beforecompaction or on cores cut immediately aftercompaction;

ii. MCV to establish values to be met immediatelyprior to compaction, required for Appendix 6/1 andTable 6/1;

iii. in-situ CBR tests;

iv. dynamic or cone penetrometer tests;

v. BS 1924 tests to determine the dry density of thfull thickness of the stablised layer, excavating a pit inecessary.

10.67 There is evidence that the lime stabilisation oclays with small percentages of lime can increase thevoids ratio of the material, and therefore itspermeability, after compaction. Care should be takenavoid the softening of underlying untreated layers bypercolation of surface water through the stabilisedmaterial.

Cement Stabilisation

Materials and Chemical Reactions

Suitability for stabilisation

10.68 The grading envelope for Class 6E materialcomprises essentially granular materials for cementstabilisation whereas Class 7F material has beenintroduced so as to include the silty sands, sandy siltand mixtures of sand, silt and clay, all capable of beinstabilised with cement. High percentages of cement required for the stabilisation of uniformly gradedmaterials, either because the total surface area of thegrains is large or because the cement is required to fthe voids. This may lead to uneconomic design and cause difficulties when the material is compacted. Consequently a uniformity coefficient of greater than is advisable for Class 6E material in addition to thegrading limits given in SHW. Stabilisation ofpulverised fuel ash Class 7G material, when not ruledout by a high sulphate content, has been an accepteprocedure for many years, but may not always beeconomic. The values of mc or MCV for Class 7F to inserted in Appendix 6/1 should be determined in thesame way as for Class 1 and Class 2 (general cohesfill). There is no sharp cut-off between Class 7Fmaterial for cement stabilisation and Class 7E materi



ed for lime stabilisation and some of these soils can stabilised satisfactorily using either cement of lime

the two-stage process employing both lime and cesee Paragraph 10.61.

ef

f

to

sg

are

illcan

5

Effects of other constituents

d

be 10.71 A safe upper limit is generally regarded asIf there is any doubt, the total organic content test

ive 1924: Part 1 should be carried out. This detectspresence in soils of organic matter able to interfere

al the hydration of Portland cement. Since this test

Cement content and strength

10.69 The minimum bearing ratio to be inserted inAppendix 6/1 for Classes 9A, 9B and 9C will normallybe 15% at 7 days. This is the strength required in theshort term during construction when the capping has toact as a `platform'. In the long term a design bearingratio of 7-8% will allow for possible softening effects. A cement content of 2% added to Class 6E material wnormally give the required 7 day strength for strengthfor Class 9A material, but this should be checked on thdemonstration area. Class 7F and 7G materials will ingeneral require larger additions of cement to produceClass 9B and 9C cappings respectively. In nearly evecase there should be a requirement in Appendix 6/7 fothe construction and testing of a demonstration area,unless pre-Contract trials have already been carried ouExcept for uniformly graded materials, the strength of acement-stabilised material is directly proportional tocement content.

Variation of strength with temperature and time

10.70 For granular materials, strength increases withcuring temperature in a linear manner similar toconcrete, but there is a larger increase in strength withincrease in curing temperature for materials containingsome clay due to a pozzolanic reaction between the cland the lime released by the cement during hydration. The normal laboratory curing temperature is 20 C. Thestrength of cement-stabilisation materials increases wiincrease in curing period and a linear relation isgenerally obtained up to an age of 1-2 months betweethe strength and the logarithm of the age the specimenAfter 2 months the relation is no longer linear againstthe logarithm of time if the soil contains any clay.

Organic matter




rePart

te of

nt notf

e,

ved,tionn

.

developed, however, changes in the composition ofcements has caused difficulties in the interpretationthe test's results. Also the type of organic material, well as the amount, is important as explained forOxford Clay in Paragraph 10.30. Until a suitablealternative test is developed and until more informatbecomes available an organic contents, the aboverecommendations should continue to be used.

Total sulphate

10.72 For Class 6E materials a maximum totalsulphate limit of 1% is given in the SHW. In thepresence of lime and excess water, sulphates may rwith clay minerals to form products that occupy agreater volume than the combined volume of thereactants. The result is expansion and cracking of tmaterial. This reaction can only be avoided by theexclusion of water. This applies to some materialsfalling in Class 7F and for such materials the upperlimit for total sulphate is 0.25% rather than the moreusual value of 1% used for non-cohesive materials. Class 7F material the Engineer should indicate whethe upper limit for total sulphate is 1% or 0.25%. Sealso `Lime-induced heave in sulfate-bearing clay soby D Hunter.

Processing and Compaction

Spreading the cement

10.73 The spreading machine likely to perform to SHW is given in Paragraph 10.39.

Rotovation and water addition

10.74 It is important to maintain close sitesupervision to ensure that the depth processed andfinal compacted thickness are correct, particularly folayers thicker than 250mm. The limiting values ofmoisture content to be inserted in Appendix 6/1 forClass 9A and Class 9B materials are those that will obtained after pulverising and mixing immediatelybefore compaction and should be chosen so that thpermissible range is close to the optimum for thestabilisation mixture (as determined by BS 1924, 4.5rammer method or vibrating hammer method). TheMCV requirement for Class 9B immediately beforecompaction is as described in Paragraphs 10.75 an10.76 for Class 9D, and will override the moisturecontent requirements if there is a conflict. Similarly



Class 9C which has an end product compaction of specification will need to be compacted at a moistuas content close to the optimum obtained in BS 1924

2 (2.5kg rammer method).

ion

to use. In the demonstration area, therefore, the stacompaction at the bottom of the thicker layer must be

eact shown to be adequate; normally an air void conteexceeding 5 per cent should be achieved in layers osuch thickness and this will require the soil-cement

he mixture to be prepared at a lower MCV (highermoisture content) than the maximum specified inClause 614.10. The MCV of the material in thedemonstration area should be determined, thereforimmediately prior to final compaction. If the

For construction of the proposed thicker layers is approther the soil-cement mixture in the subsequent construce work should be compacted at a MCV no greater thails' that of the demonstration area.

the

ther

be

e

kg

d

Compaction

10.75 Where it is proposed to construct layers ofClass 9A or 9B material with thicknesses greater than250mm, the Contractor is required to demonstrate thatsuch an operation is feasible with the plant he proposes

10.76 If processed material is not compacted as soonas mixing is complete, some of the hardening effects ofthe cement will be lost and, in addition, extracompactive effort will be required to break down thecement bonds that have formed. These effects areadditive and may lead to a serious reduction in strengthThe rapidity of the MCV determination will assist inreducing the time scale between mixing and compactionto a minimum.

Testing

10.77 Preliminary laboratory trials, if required, maybe carried out as described in Paragraphs 10.65 and10.66. The type of laboratory mixer used will dependon whether the soil being stablised is granular orcohesive. It should be noted that the strength or bearingratio of laboratory mixed material will be significantlygreater than that of site mixed material and will need tobe scaled down for design purposes, on the basis of`mixing efficiency'. If a trial is not conducted, thestrength of the site-mixed material may be taken as 60%of the strength of laboratory mixed material.

10.78 Tests on the demonstration area may comprisethose listed under Paragraphs 10.65 and 10.66.




d

g

d

Durability

Softening due to soaking

10.79 Some cement stabilised soils containing claymay lose strength due to soaking as described inParagraphs 10.51 and 10.52. This can be checked inconfined conditions by determining the bearing ratio,unsoaked and soaked, in accordance with BS 1924 anfor unconfined cylindrical specimens by the BS 1924test. A soaked test has the added benefit of determininthose soils with a high sulphate content as the additionof water allows the expansive reaction, mentioned inParagraph 10.72 take place in the laboratory.

Frost susceptibility

10.80 Although soil-cement CBM 1 for sub-bases anroadbases (SHW Clause 1035) is generally non-frostsusceptible, the same is not always true for cappingwhere the cement content is lower. In particular,stabilised PFA (Class 9C) is known to be frostsusceptible. All cement stablised materials should betested after 28 days curing using the procedures inClause 602.19 SHW. Weather protection during thewinter months, as described in Paragraphs 10.53 to10.57, should be provided for doubtful Class 9Bmaterials and all Class 9C materials.



Volume 4 Section 1 Chapter 11Part 1 HA 44/91 Soil Structures

11. SOIL STRUCTURES

n

,rsd

Soil Reinforcement

11.1 The variety and range of application for soilreinforcement is almost unlimited. Therefore onlythose applications which apply directly to highways wbe mentioned. Some of the materials used are descrin Paragraphs 5.72 to 5.89.

Structures

11.2 Reinforced and anchored earth techniques are in the construction of retaining walls and bridgeabutments. The term `reinforced earth' describes a tof soil structure and does not refer to the product of aparticular organisation. These types of soil structurecomprise a mass of fill which is reinforced by tensileelements and retained by facings which are attachedthose elements. Design criteria and other informatiogiven in the Department's Technical Memorandum B3/78 (Revised 1987), Reinforced and Anchored EarthRetaining Walls and Bridge Abutments forEmbankments.

11.3 Alternative retaining wall facings could includegabions (metal or geonet baskets), tyres fastenedtogether with steel pins, or geotextile.

Embankments

11.4 Geosynthetics such as geotextiles, geowebs,geonets, geogrids etc may be used as reinforcementembankments in order to:-

i. increase the embankment overall stiffness;

ii. allow the embankment side slopes to be steepenThe reinforcement layers are usually only placed in thouter layers of the embankment; see also Paragraphto 8.13;

iii. improve the internal stability of the embankmentThe reinforcement layers will need to be placed acropossible slip planes which could occur wholly withinthe embankment;

iv. improve overall stability of the embankment andsubsoil. Where a slip plane could extend into the soibeneath the embankment, reinforcement would berequired across the base;



illibed

used

ypeny

ton isE

in

Cuttings

ed. e

s 8.9

. ss

l

v. improve foundation stability where the subsoil isweak enough to deform appreciably under the imposedload of the embankment. This should be achieved bythe use of geocell mattresses laid under theembankment or stone columns in geogrid tubes underthe embankment edges.

11.5 In applications where the polymer reinforcementis taken to the face of the embankment slope, it can bereturned back into the fill either at the level of the nextreinforcement layer above or at an intermediate level. This will stabilise the face of a steep sided slopesusceptible to erosion.

11.6 It should be noted that the presence of a geogridusually reduces the efficiency of the earthworks'compaction. There may also be practical problems ifthe geogrid is to be returned back into the fill; theseinclude:-

i. the area involved;

ii. the need to trim the slope to shape after fillingoperations are complete;

iii. the geogrid being exposed to plant working on theslope during topsoiling etc;

iv. the geogrid being exposed to ultraviolet light untilcovered by topsoil;

v. deep services being more difficult to install, egdrainage.

11.7 The reinforcement may be used insitu or placed ia layered construction similar to embankments. Techniques for insitu reinforcement include soil nailingand ground anchorages in which the reinforcing anchoare prestressed. BS 8081, Code of Practice for GrounAnchorages is referred to in the Notes for Guidance NG624.2.

Reinforcement Properties

11.8 The principle requirements of reinforcingmaterials are strength, stability (low creep), durability,ease of handling, high coefficient of friction/adhesivewith the fill, combined with low cost and highavailability.



Chapter 11 Volume 4 Section 1Soil Structures Part 1 HA 44/91

or thee of

ise ontainedf

nd

k. s

ct/87

al

r on

11.9 Since the design life of soil structures may be aslong as 120 years, the durability of the reinforcementand its resistance to degradation is very important anmust be considered by the Designer. Where metalliccomponents are used a sacrificial thickness of the meis usually necessary and a corrosion allowance formetallic components exposed to various environmentis given in Table 4 of BE 3/78 (Revised 1987). Theseallowances should be increased by the appropriateamount in areas where the metallic reinforcementoverlaps. Care should also be taken with galvanisedreinforcements in cohesive soils as zinc is sensitive toillite and therefore may not fulfil its intended functionleaving the metal unprotected (Earth Reinforcement aSoil Structures by Colin J P F Jones: Butterworths). Glass-fibre reinforced plastic (GRP) is not affected byelectrolytic corrosion, although some loss of strengthmay occur when the material is kept in wet conditionsover long periods of time. Geosynthetics appearunaffected by electrolytic corrosion or biological attacTable 5/1 gives details of the resistance of the varioupolymers to degradation from various sources.

Fill to Structures and Retaining Walls

11.10 Detailed information and criteria on this subjemay be obtained from Departmental Standard BD 30- Backfilled Retaining Walls and Bridge Abutments. Bedding and backfilling requirements for buriedconcrete box type structures are given in BD 31/87.

Fill to Corrugated Steel Buried Structures

11.11 Where it is intended to construct corrugatedsteel buried structures in partial or total trenchcondition, tests must be carried out to measure thecorrosivity of the insitu material as well as for theproposed imported bedding and surround material. Ifthese tests have not been carried out by any reason, provisional sum should be detailed in the Contract Bilof Quantities in case it is later found that the soil isaggressive. This provisional sum can be based eithe



sacrificial thickness of steel for the structure, or fprovision of additional surround material either sid

d the structure and above it. Detailed information given in Departmental Standard BD 12/88. Advic

tal firms carrying out soil corrosivity tests may be obfrom Bridges Engineering Division, Department o

s Transport.



Volume 4 Section 1 Chapter 12Part 1 HA 44/91 Landscaping and Planting

12. LANDSCAPING AND PLANTING

l andthe

poseseredf

ual toce

leave

fies.

nces

be

wings

t of

hersoil

in 2,lace

.

W

Planning

12.1 As with other parts of the scheme developmentliaison is very important to avoid abortive design worand last minute pre-contract additions. In this case tProject Manager, GE, GLE, Regional LandscapeArchitect and Horticultural Officer will be involved. Outlines of landscaping and planting will need to havbeen developed prior to the consultation stage as thenecessary plans will be made available at any PublicExhibition that may be held.

12.2 The design of earthworks, environmental bundsand structures should not be carried out purely from engineering viewpoint. The blending of these into thsurroundings may be carried out at only smalladditional cost and makes the scheme more acceptato the public and less environmentally intrusive. Theare a number of ways in which the earthworks may benhanced environmentally, many of which should beconsidered good engineering practice, including:-

i. slackening slopes at the top of deep cuttings;

ii. providing berms in deep cuttings in sympathy wthe strata and local topography;

iii. rounding slopes and bottoms of embankments acuttings;

iv. slackening cutting and embankment slopes toreturn to agriculture and placing the fenceline besideroad verge;

v. avoiding fencelines on skylines, tops of bunds e

vi. avoiding the use of imposing concrete retainingwalls by the use of strengthened embankments,reinforced soil, gabions, etc;

vii. tree planting as a visual and noise barrier with thadded benefit of stabilising slopes in certaincircumstances.

12.3 Other factors requiring attention during the earldesign stages include:-

i. the possible difficulties of planting and topsoilingsteep slopes;



khe

e

12.4 The relation between soils in the agriculturathe engineering sense is shown in Figure 12/1. For

horizons which support plant growth. For the puran of this section of this Note, `sub-soil' is the weatheir `C' horizon. The depth of topsoil and availability o

sub-soil will need to be established during the GI. ble When assessing volumes of topsoil strip, it is usre neglect volumes in wooded areas where disturbane from site clearance invariably renders any topsoil

unsuitable. Where soft foundation soils existunderneath proposed embankments it is usual to

ith topsoils may be either acid, neutral or alkaline, all owhich are capable of supporting different plant spec

nd or alkaline, or stoney or clayey) and the consequeof using variable topsoil types are serious then

placed should be made in the Contract. This may the particularly relevant to imported topsoil and to

accommodation works affecting farms and market

tc; show the extent and depths of topsoiling. The dra

SHW Clause 618.4. Other details on the treatmentopsoil should be set out in SHW Appendix 6/8.

Further information on topsoil may be found in BS

e12.6 The minimum depth of topsoil for planting, ot

than grassing and seeding, is generally 300mm. Top

y prior to good root growth on slopes greater than 1and thicknesses of 150mm likewise are difficult to p

requires only cutting slopes to be harrowed prior totopsoiling. The exception to this will be for

ii. ensuring that sufficient topsoil of the local type isavailable;

iii. ensuring that sub-soils are suitable for plantingand are not toxic or restrictive to plant life.

Topsoil

purposes of this Advice Note, topsoil is the À' and `B'

the topsoil to avoid disturbing the desiccated crust.

12.5 Depending on the underlying sub-soil types,

If the soil types on a scheme are very variable (eg acid

restrictions on where different types of topsoil are to be

gardens etc. It is usual for the earthworks drawings to

will also show the treatment type in accordance with

3882, Recommendations and Classification for topsoil

of this thickness tends to be unstable in wet weather

and maintain on slopes steeper than 1 in 1.5. The SH



Chapter 12 Volume 4 Section 1Landscaping and Planting Part 1 HA 44/91

AGRICULTURAL SOIL

AHorizon

TOPSOIL

SUB -SOIL

BHorizon

CHorizon

ROCK

Weathered top of the geological deposits,not converted to soil suitable for plantgrowth, including the horizon in whichcolumnar structure may be developed inclays.

(Leached horizon

(Horizon of accumulation(sometimes cemented to(hardpan

These twohorizons arehumus -bearing

Hard and rigid geological deposits

Fig 12/1 The relation between agricultural and engineering soil

SOILIN THE

ENGINEERINGSENSE

Soft and loose geological depositseither solid or drift, such as gravels,sands, clays, peats etc. These may beinterbedded with rock.




sandbothientnular

5.66. ve a

oil.

nt

oy

rial.

ofd.

y

in

cuttings in rock or hard materials where consideratiowill be required to maintaining the stability of thetopsoil. Where harrowing is not required in cuttingsthis should be noted in SHW Appendix 6/8.

12.7 The requirements of SHW Clause 618.3 onlyapply when the sub-soil is a heavy clay. Where thisoccurs then the extent of the restriction will need to bset out in SHW Appendix 6/8. The rainfall figurequoted in SHW Clause 618.3 is satisfactory for mostsoils likely to be encountered in this country.

Sub-soils

12.8 Most plants require water-retentive soils and hthe ability to send down tap roots (anchor roots). Growing plants on areas of rock, rock fill and granulamaterials may therefore prove difficult and so ifplanting is required a topping layer of a more acceptsub-soil is necessary. The sub-soil used will need tocohesive in order to retain nutrients and moisture, anfor most planting requirements, the depth, includingtopsoil, will need to be at least 1m.

12.9 A depth of topsoil of 300mm is normally requirefor planting, although pits for individual trees andshrubs may be used. The interface between a claymarl and the topsoil should be broken up to preventtopsoil slip and promote root penetration. Some clacan be very hard and these may require moredisturbance to allow root penetration. If the soil aroupits is not sufficiently broken up, tree roots will berestricted to the original pit resulting in sub-standardgrowth.

Waste Materials and Industrial By-products

12.10 There is increasing pressure for available wmaterials and industrial by-products to be used inhighway construction. Possible sources of thesematerials, either occurring on site or as possible impshould be identified. These materials will effectdifferent plant species in different ways, as do naturaoccurring soils. They can be toxic to plant life andspecial precautions may need to be taken.

12.11 The following comments on waste, and othematerials which may be encountered, should be not


June 1991 PAPER COPIES OF THIS ELECTR

n 12.12 China Clay waste is the waste quartzitic from the production of China Clay and is suitable, chemically and physically, for planting using suffictopsoil and nutrients. However, because of its gra

retention characteristics.

e 12.13 PFA is described in Paragraphs 5.58 to Pozzolanic action can form a hard-pan. It may ha

high boron content and high pH. It is generallyacceptable if covered with 1m of sub-soil and tops

ave

r

able bed,

d

or

ys

nd

aste

ort,

lly

red:-

nature it is liable to erosion and lacks water and nutrie

12.14 Minestone is described in Paragraphs 5.27 t5.30. This material may contain trace elements, heavmetals, sulphates and sulphides. Fresh colliery wastemay well be neutral or alkaline (pH 7.0 or higher). However on exposure to air and moisture, sulphuricacid is produced and the pH falls. The rate ofproduction of acid is very variable and will, to a largeextent, depend on the constituents of the waste mateThe leaching out of sulphuric acid into streams andwaterways can have a devastating effect on plant andanimal life. Depending on the likely severity of theproblem a topping of 1m sub-soil may be required. Consideration may be given to biotechnical methods restoration, although these are not yet fully establisheBiotechnical methods include; symbiotic association,where the association of a fungus around the roots oftrees acts as a sheath and protects the roots fromaggressive agents; and pelletized refuse, whereincinerated refuse pellets which achieve high pH areused to neutralize the acids produced in the fill. Heavmetals are likely to be present in all mining wastematerials.

12.15 Foundry Sand may have a low pH and contaheavy metals resulting from the casting process. Consequently, a topping of sub-soil may be required.

12.16 Blastfurnace Slag is usually a basic limestoneflux and unlikely to be a problem except inenvironmentally sensitive areas particularly near towatercourses where leached sulphates can causeproblems.

12.17 Useful references are given in Chapter 14.

Landscape Areas

12.18 The presence of a landscape area may bebeneficial to the earthworks balance by providing areserve of fill material if there is a shortfall, or asuitable on-site location for placing excess material.


ONIC DOCUMENT ARE UNCONTROLLED 12/3


aintainhould beccording

ntal

d;

rea

rtrees yew,

wthlin PFA or

endixg a

ide andopriatessible.

lly

ntails

forhe

Therefore, the design contours should, if possible, learoom for movement and only the general shape ouroutline of the area provided on the drawings. Howevthe basic functions of the landscape area such asscreening, protection etc should never be compromisby removal of too much material. If a particular featuwas shown at, or required by, the Public Inquiry thenthis feature must remain unchanged.

12.19 The shape of the landscape area should be sas to adequately discourage squatters and includeditches across potential access routes. Surface waterun-off should also be considered and drainage provias appropriate to protect adjacent roads or propertiesfrom flooding.

12.20 All that is required in Clause 620 SHW forcompaction purposes, unless there is a specificrequirement such as a picnic area, is that thecompaction shall be sufficient to remove large voidsand produce a coherent mass. The act of placing anmoulding materials into the desired landscape shapeusing tracked plant usually provides sufficientcompaction for the landscape area's intended use. Where particular requirements are needed for theconstruction of landscape areas according to SHWClause 620, they should be included in SHW Append6/9.

Environmental Bunds

12.21 Earthworks for environmental bunds arecovered by SHW Clause 619 with particularrequirements being set out in SHW Appendix 6/3. ThAppendix will need to set out the location, particularmaterials, construction and compaction requirementsand topsoiling and seeding or turfing requirements.

12.22 The usual practice is to site environmentalbunds as close as possible to the noise and visual soin order to make them as effective as possible: they cbe placed close to the area to be protected, but this isgenerally an inferior solution. In general,environmental bunds constructed near the source areonly effective in ameliorating problems within adistance of about 330m of the carriageway edge. Acommon solution is to build a steep sided bund closethe carriageway using soil reinforcing or strengthenintechniques. In many cases fences will have to be plaon top of the bunds and therefore sufficient room forconstruction and stability of the fence should beprovided. There may be a conflict between locating afence on top of a bund to reduce noise, and thevisualimpact of such a fence (Paragraph 12.2(v)). ThDesigner will then have to choose the best course of



ve action for the scheme.

er, 12.23 The best form of noise protection is to mthe road in cuttings. A minimum depth of 2m s

ed adequate although the depth should increase are to the distance to the nearest buildings. The

Departmental of Transport Manual of EnvironmeAppraisal gives further advice.

uch

rded

d

ix

iv. low-lying areas should be adequately drainee

v. excessive compaction should be avoided.

12.25 Whilst only appropriate species for the a

should include avoiding spread into sight lines ource neighbouring property, and avoiding planting an which may be toxic to grazing animals, such as

where there is a risk of encroachment.

12.26 A number of factors affecting plant grohave been identified. When dealing with chemica

content of the soil or toxicity it is difficult to obta to objective advice. If imported materials such asg Minestone are likely then restrictions should beced identified in the contract documents (SHW App

6/3). This will normally take the form of providintopping material of sufficient thickness and withsufficient nutrients to encourage plant growth. However, the notes below may be used as a gu

e where relevant materials are encountered apprtests should be carried out at the GI stage if po

Planting

12.24 Planting is mostly labour intensive and veryexpensive. Not all trees and shrubs grow successfuin the first round of planting so a limited number offailures is to be expected. The number of failures cabe reduced by paying attention to the earthworks deset out below:-

i. sufficient pre-planning and design should beprovided to ensure stable side slopes, topsoil andsub-soil;

ii. the depth of topsoil and sub-soil should beadequate to maintain plant growth and allow rooting the species proposed; protective measures against teffects of deleterious waste and refuse may benecessary.

iii. the correct topsoil and sub-soil types should beused which are appropriate to the proposed area andspecies;

concerned should be planted, other considerations




d,d,

urse.

ring.

le fork

of a

l oute side

duringneed

xisting

g to be

eding

secure

re

o

t

to

fore

te

so

i. Acidity is critical: a pH of 5 or below will be tooacid for most plants;

ii. Traces of heavy metals should not be greater tha1000ppm and traces of aluminium, zinc and coppercombined should be less than 20ppm. (Broadshaw aChadwick, `The Restoration of Land').

iii. The percentage of CaC03 or acid neutralisationcoefficient, should be greater than the percentage ofpyrites.

iv. Extractable boron should be less than 20ppm.

v. Materials with pozzolanic action require a toppinto allow plant growth.

12.27 The judicious use of planting will not onlyassist in erosion control but can have positive benefitby reducing the long-term maintenance costs causedshallow failures. See Barker DH 1986 ÈnhancemenSlope Stability by Vegetation' and Greenway DR 198`Vegetation and Slope Stability'. The following pointswill encourage healthy, stable plants thus improving tstability of earthworks.

i. Do not plant where root wedging may disrupt soiand rocks leading to instability or water ingress.

ii. Current horticultural/forestry practice is to havetree stakes one-third of the height of the tree with onetie to encourage early bole development.

iii. All tree ties to be removed as soon as possible (years maximum) to ensure a stable plant.

12.28 A wide range of applications for vegetation inCivil Engineering and methods of cultivation of plantsand grasses are given in Coppin and Richards (1990

Watercourses

12.29 Rivers, streams and watercourses are importecological corridors and when cleaning out, regradingor altering the alignment is required, positive measuretowards conservation should be taken. The LandscaArchitect can provide advice. The concrete lining ofwatercourses and ditches is often very much out ofsympathy with the landscape and surroundings and sthe need for lining ditches and the materials used shobe carefully considered. Geosynthetics can beparticularly good at controlling erosion of river bankswithout being obtrusive.



12.30 Where rivers and streams are to be regradecareful attention should be paid to the profile adopte

n in keeping with the nature of the original waterco

nd 12.31 Useful advice is given in the NatureConservancy Council publication on River Enginee

line watercourses should be avoided. There arecurrently many materials and techniques availab

protecting river banks from erosion which allow a quic

g out is required, attention to detail in the contractdocumentation may avoid the wholesale destruction

purpose. It is preferable to coppice rather than puls shrubs and trees. It will also help to work from th by of the watercourse which will be the least spoilt t of the regrading or cleaning out. The drawings will 7 to clearly define the extent of work required.

he 12.33 Treatment and construction of new and ewatercourses is covered by SHW Clause 606 and

ls Appendix 6/3.

Turfing and Grass Seed Mixtures

12.34 The grass seed mixture and rate of sowin

3 mixes are considered appropriate to suit localconditions, approval must be obtained from the

in SHW Appendix 6/8. SHW Appendix 6/8, and thdrawings, should be used to show the areas of see

). and turfing and also the measures to be used to

ant

spe

ould

both in plan and in cross section, to ensure that they a

The excessive use of sand-bags, riprap and gabions t

covering of plant life to develop.

12.32 When regrading of a watercourse or cleaning

natural habitat and still serve the required engineering

special requirements should be set out in SHW

used are set out in SHW Clause 618. If alternative

Horticultural Officer. Amendments are to be included

turfing on slopes where appropriate. The mowing planand mowing requirements shall be set out in SHWAppendix 6/8.

12.35 Propagation of grass on steep slopes, subjecterosion, can be improved by the use of geosyntheticsheets or jute. These materials provide a stable face grass to become established and hence make the slopmore stable.

12.36 The optimum time for sowing grass seed is laAugust or early September; April or May are almost assuitable. However priority must be given toestablishing some grass growth whatever the season as to prevent erosion of susceptible soils.




o

of

g

re

12.37 Weed control is important to avoid difficultieswith adjacent landowners. A number of weedsincluding ragwort and wild oats are notifiable andsome, particularly ragwort, are extremely poisonous tgrazing stock, especially when cut down. The WeedsAct 1959 should be consulted and complied with.

12.38 Turves are extremely useful where immediatesurface stability is required or difficulties areencountered maintaining topsoil whilst growth fromseed takes place. If a particular seed mix is requiredand not available in turf form the turves may be laidup-side-down and the root side sown with theappropriate mixture. There are a number of methodsfixing turves involving pegging individual turves orusing netting, pegged over a number of turves. Nettinshould be of a type that degrades after two years.

12.39 In some cases, wildflower swards may be moin keeping with the surroundings than grass. Furtheradvice on this subject can be obtained from theHorticultural Officer.



Volume 4 Section 1 Chapter 13Part 1 HA 44/91 Use of Computers in Design



13. USE OF COMPUTERS IN DESIGN

13.1 A number of computer programs are available forearthworks design and soil-structure interaction, someof which were developed by the Department ofTransport. There are programs available for use inslope stability, consolidation settlement and finiteelement analysis. Advice on selection and use ofprograms should be sought in the first instance fromHighways Engineering Division. For analysis of pilegroups, reference should be made to Departmental ofTransport Departmental Advice Note BA 25/88 `Piledfoundations'. Finite element programs are particularlyuseful for analyzing problems involving soil-structureinteraction and also stability of slopes wheredeformations are required.

Volume 4 Section 1 Chapter 14Part 1 HA 44/91 References

14. REFERENCES

n

d

te

For ease of use the references have been listed undeChapters referred to in the text.

2. Ground Investigations

(a) DTp. HA 34/87 Ground Investigation Procedure

(b) TRRL. Soil Mechanics for Road Engineers. Chapters 3, 4 and 8. HMSO. 1968.

(c) DTp. Specification and Method of Measuremenfor Ground Investigation. HMSO 1987.

(d) BS 5930: 1981. Code of Practice for SiteInvestigation.

(e) Site Investigation Practice: Assessing BS 5930.Vols 1, 2. Proc Conf September 1984, EngineeringGroup of the Geological Society, 20th RegionalConference, University of Surrey.

(f) TRRL. The Reproducibility of the Results of SoiClassification and Compaction Tests. LR 339. P TSherwood.

(g) BS 1377: 1990. Methods of Test for Soils forCivil Engineering Purposes.

(h) Rowe P W. The relevance of soil fabric to siteinvestigation practice. Geotechnique 22, No 2,195-300. (1972).

(i) See also the list of references in HA 34/87.

3. Specification and Method of Measurement forHighway Works

(a) Specification for Highway Works, as detailed inParagraph 1.7.

(b) Notes for Guidance on the Specification forHighway Works, as detailed in Paragraph 1.8.

(c) Method of Measurement for Highway Works, asdetailed in Paragraph 1.9.



r the (d) Highway Construction Details as detailed iParagraph 1.10.

.

t

Reinforced Earth Retaining Walls and BridgeAbutments for Embankments (Revised 1987).

(b) DTp. BD 30/87 Backfilled Retaining Walls anBridge Abutments.

(c) DTp. Highways Circular 3/87. The Use of Was

l(d) TRRL. The effect of Soil Conditions on the

Operation of Earthmoving Plant. LR 1034. A W

(e) TRRL. The Moisture Condition Test and its

Parsons and J B Boden.

(f) TRRL. The Precision of the Moisture Condition

Since these documents are referred to frequentlythroughout the document, they are listed only once tosave repetition.

(e) DTp. Specification for Road and Bridge Works. 5th Edition. HMSO. 1976. (SRBW).

4. Use of Materials and Construction

(a) DTp. Technical Memorandum (Bridges) BE 3/78

Material for Road Fill.

Parsons and P Darley.

Potential Applications in Earthworks. SR 522. A W

Test. RR 90. A W Parsons and A F Toombs.

(g) TRRL. Pilot Scale Studies of the Trafficability ofSoil by Earthmoving vehicles. RR 130. A W Parsonsand A F Toombs.

(h) SDD. Soil Suitability for Earthworking - Use ofthe Moisture Condition Apparatus. TechnicalMemorandum SH 7/83.

(i) BS 812 Testing Aggregates.

(j) BS 1377: 1990. Methods of Test for Soils forCivil Engineering Purposes.

(k) BS 1924: 1990. Stabilized Materials for CivilEngineering Purposes.



Chapter 14 Volume 4 Section 1References Part 1 HA 44/91

).

.

9.

(l) Manual of Soil Laboratory Testing,Volume 2. K H Head, Pentech Press.

(m) Snedker A. Choice of an Upper Limit of MoisturContent for Highway Works. Highways Design andConstruction, January 1973.

(n) Arrowsmith E J. Roadwork Fills - A MaterialsEngineer's Viewpoint. Clay Fills. Institution of CivilEngineers, London, 25-36. (1978).

(o) Al-Shaikh-Ali M M H. The Behaviour ofCheshire Basin Lodgement Till in MotorwayConstruction. Clay Fills. Institution of Civil EngineerLondon, 15-23. (1978).

5. Information on some Specific Materials

(a) DTp. Highways Circular 3/87. The Use of WasMaterial for Road Fill.

(b) DTp. HA 34/87. Ground Investigation Procedur

(c) DTp. Technical Memorandum (Highways) H4/74. The use of Colliery Shale as Filling Material inEmbankments.

(d) DTp. Technical Memorandum (Bridges) BE 3/7(Revised 1987).

(e) DTp. BD 30/87 Backfilled Retaining Walls andBridge Abutments.

(f) TRRL. The Use of Waste and Low-GradeMaterials in Road Construction. LR 647. P TSherwood.

(g) TRRL. The Rapid Measurement of the MoistureCondition of Earthworks Material. LR 750. A WParsons.

(h) TRRL. The Classification of Chalk for Use as aFill Material. LR 806. H C Ingoldby and A W Parson

(i) TRRL. Geotextile Test Procedures: Backgroundand Sustained Load Testing. Application Guide 5. RMurray and A McGown.

(j) TRRL. A Survey of Slope Condition onMotorway Earthworks in England and Wales. RR 19J Perry.



(k) CIRIA/PSA. Construction over AbandonedMineworkings. CIRIA Special Publication 32. (1984

e(l) CIRIA. Further work on the Engineering

Properties of Keuper Marl. CIRIA Report 47. (1973)

(m) BRE. A survey on the Locations, Disposal andProspective Uses of the Major Industrial By-Products

J Nixon, M A Smith and W H Harrison.

s, (n) BS 5930: 1981. Code of Practice for SiteInvestigation.

te

e.

8

s.

T

P R Healey and M Head.

R J Chandler and A G Davis.

and Waste Materials. Paper 19/74. (1974). W Gutt, P

(o) BS 8004: 1986. Foundations.

(p) BS 6031: 1981. Earthworks.

(q) BS 6906. Methods of Test for Geotextiles.

(r) British Coal. Mining Dept. The Treatment ofDisused Mineshafts and Adits.

(s) Meigh A C. The Triassic Rocks. Rankine Lecture1976. Geotechnique 26, No 3, 391-452. (1976).

(t) Ingold T S. Reinforced Earth. Telford, London. (1982).

(u) ICE. Clay Fills Conference 14-15 November1978. (Papers by Arrowsmith, Donnehy, Kennard etc).

(v) Hawkins A B and Pinches G M. SulphateAnalysis on Black Mudstones. Geotechnique 37, No 2,191-196. (1987).

(w) Hobbs N B. Mire Morphology and the Propertiesand Behaviour of Some British and Foreign Peats. Quart. Journ. Eng. Geol., 19, No 1, 7-80. (1986).

(x) Cairney T. Reclaiming Contaminated Land. Blackie, London. (1987).

(y) ICE. Building on Marginal and Derelict Land. Telford, London. (1987).




983).

ry. G

,

(z) Fleming G. Recycling Derelict Land. Telford,London. (1991).

(A) Howell F T and Jenkins P L. Some Aspects of thSubsidences in the Rocksalt Districts of Cheshire. 3rInternational Land Subsidence Symposium, USA. (1976).

(B) McGown A. Excavated Slopes in Fissured Tills. Symposium on Failures in Earthworks, London. (1985).

(C) Symposium on the Engineering Behaviour ofGlacial Materials, University of Birmingham. (1975).

(D) Quaternary Engineering Geology, 25th AnnualConference of the Engineering Group of the GeologicSociety, Heriot-Watt University, Edinburgh. (1989).

6. Slope Stability Analysis

(a) TRRL. Rock Stability Assessment in PreliminarySite Investigations - Graphical Methods. LR 1039. GD Matheson.

(b) TRRL. A survey of Slope Condition onMotorway Earthworks in England and Wales. RR 199J Perry.

(c) Bishop A W and Morgenstern N R. StabilityCoefficients for Earth Slopes. Geotechnique 10, No 1(1960).

(d) Bishop A W. The Use of the Slip Circle in theStability Analysis of Slopes. Geotechnique 15, 7-17. (1955).

(e) Fellenius W. Calculation of the Stability of EarthDams. Trans 2nd Congress Large Dams 4, 445-459.(1936).

(f) Morgenstern N R and Price V E. The Analysis othe Stability of General Slip Surfaces. Geotechnique15, No 1, 79-93. (1965).

(g) Turnbull W J and Hvorslev M J. SpecialProblems in Slope Stability. Proc ASCE, Vol 93, SM4499-528. (1967).

(h) Janbu N. Embankment Dam Engineering:Casagrande Volume. R C Hirschfield and S J PoulosJohn Wiley and Sons, 47-86, (1973).



(i) Sarma S K. Stability Analyis of Embankmentsand Slopes. Proc ASCE GT12, 1511-1524. (1979).

e (j) Greenwood J R. A Simple Approach to Sloped Stability. Ground Engineering 16, No 4, 45-48. (1

(k) Morrison I M and Greenwood J R. Assumptions

Slices. Geotechnique 39, 503-509. (1989).

(l) Greenwood J R. Design Approach for Slope

Embankments. Telford, London. (1990).

Embankments Using Parallel Inter-slice Forces. al Geotechnique 17, No 1, 11-26. (1967).

.

.

(a) DTp. HA 34/87 Ground Investigation Procedure.

f (b) TRRL. Rock Stability Assessment in PreliminaSite Investigations - Graphical Methods. LR 1039

D Matheson.

(c) TRRL. Presplit Blasting for Highway Rock, Excavation. LR 1094. G D Matheson.

in Simplified Slope Stability Analysis by the Method of

Repairs and Embankment Widening. Reinforced

(m) Spencer E E. A method of analysis for stability of

(n) Skempton A W and Hutchinson J N. Stability ofNatural Slopes and Embankment Foundations. Proc.7th Int Conf. Soil Mech. Found. Enging., 291-340. (1969).

(o) Hoek E and Bray J W. Rock Slope Engineering.3rd Edition. Institution of Mining and Metallurgy. (1981).

(p) Hudson J A. Rock Mechanics Principles inEngineering Practice. CIRIA. (1989).

(q) Hoek E and Wood D F. Rock support. MiningMagazine, October 1988.

(r) Matheson G D. The Collection and Use of FieldDiscontinuity Data in Rock Slope Design. QuarterlyJournal of Engineering Geology 22, No 1. (1989).

7. Cuttings



Chapter 14 Volume 4 Section 1References Part 1 HA 44/91

.

d

.

e

(d) TRRL. Ground Vibration caused by CivilEngineering Works. RR 53. B M New.

(e) BS 5607: 1988. Code of Practice for the Safe Uof Explosives in the Construction Industry.

(f) BS 6472: 1984. Guide to Evaluation of HumanExposure to Vibration in Buildings (1Hz to 80 Hz).

(g) ISO Standard 2631 (1978). Guide toMeasurement and Evaluation of Human Exposure toWhole-Body Mechanical Vibration and Repeatedshock. (Also BS 6841).

(h) Nobel Explosives Co Ltd. Explosives - SafePractice and Storage.

8. Embankments

(a) TRRL. A Survey of Slope Condition onMotorway Earthworks in England and Wales. RR 19J Perry.

(b) TRRL. Maintenance and Repair of HighwayEmbankments: Studies of Seven Methods of TreatmRR 30. P E Johnson.

(c) Finlayson D M, Greenwood J R, Cooper C G anSimons N E. Lessons to be learnt from an EmbankmFailure. ICE Proceedings Part I, 76, 207-220. (1984

(d) Greenwood J R, Holt D A and Herrick G W. Shallow Slips in Embankment Highways Constructedof Over-consolidated Clay. Earthworks FailuresConference, ICE. 6-7 March 1985. (1985).

(e) Whyte I L and Vakalis I G. Shear SurfacesInduced in Clay Fills by Compaction Plant. Compaction Technology Conference, ICE. 29 Octob1987. (1988).

9. Ground Conditions Requiring SpecialTreatments

(a) DTp. HA 34/87 Ground Investigation Procedur

(b) DTp. BD 10/82. The Design of HighwayStructures in Areas of Mining Subsidence.

14/4

(c) DTp. BD 24/84. Design of Concrete Bridges:Use of BS 5400: Part 4: 1984.

se (d) CIRIA/PSA. Construction over AbandonedMineworkings. CIRIA Special Publication 32. (1984)

(e) BS 3837: Part 1: 1986. Specification for

Expandable Beads.

(f) BS 5400: Part 4: 1978. Code of Practice for theDesign of Concrete Bridges.

(g) BS 8004: 1986. Foundations.

9.

ent. (a) DTp. HD 14/87 Structural Design of New RoaPavements.

d (b) DTp. HA 35/87 Structural Design of New Roadent Pavements.).

Prediction in Relation to Road Performance. LR 889W P M Black and N W Lister.

(d) TRRL. The Structural Design of Bituminous

Mayhew, and M E Nunn.

er (e) TRRL. Specification for the TRRL Frost HeavTest. SR 829. P G Roe and D C Webster.

e.

P R Healy and M Head.

Expanded Polystyrene Board Manufactured from

(h) ICE. Specification and Notes for Guidance andGround Treatment. Telford, London. (1987).

(i) DTp. HA 41/90 A Permeameter for RoadDrainage Layers.

10. Subgrade and Capping

(c) TRRL. Strength of Clay Fill Sub-Grade: Its

Roads. LR 1132. W D Powell, J F Potter, H C

(f) BS 1377: 1990. Methods of Test for Soils forCivil Engineering Purposes.

(g) BS 1924: 1990. Stabilized Materials for CivilEngineering Purposes.

(h) Wood C E J & Boud J P. IHT National Workshopon Design and Construction of Pavement Foundations. (1987).

June 1991


.

n

e. nd

(i) Blood J D & Lord J A. IHT National Workshopon Design and Construction of Pavement Foundation(1987).

(j) Hight D W & Stevens M H G. An Analysis of theCalifornia Bearing Ratio Test in Saturated Soils. Geotechnique 32, No 4, 315-322. (1982).

(k) Lees G, Abdelkater M O & Hamdani S K. Effectof the Clay Fraction on Some Mechanical Properties Lime-Soil Mixtures. The Highway Engineer,December 1982.

(l) ICI/BLA. Lime Stabilisation Manual. 2ndEdition. (1990).

(m) BACMI. Proceedings of the First BACMITechnical Symposium, Lime Stabilisation '88. (1988)

(n) BLA. Proceedings of the Second BACMITechnical Symposium, Lime Stabilisation '90. (1990)

(o) HMSO. The Design and Performance of RoadPavements D Croney. (1977).

(p) Hunter D. Lime-induced Heave in Sulfate-beariClay Soils. Journal of Geotechnical Engineering,ASCE 114, No 2. (1988).

11. Soil Structures

(a) DTp. BE 3/78 (Revised 1987).

(b) DTp. BD 12/88. Corrugated Steel BuriedStructures.

(c) DTP. BD 30/87 Backfilled Retaining Walls andBridge Abutments.

(d) DTp. BD 31/87 Buried Concrete Box TypeStructures.

(e) Jones C J P F. Earth Reinforcement and SoilStructures. Butterworths. 1985.



s.

of

.

.

ng

12. Landscaping and Planting

(a) DTp. HA 13/81 Planting of Trees and Shrubs.

(b) BS 3882: 1978. Recommendations andClassification for Topsoil.

(c) Nature Conservancy Council. River Engineering

(d) Jobbing J & Stevens F. Establishing Trees inRegraded Colliery Spoil Heaps. Forestry CommissioOccasional Paper No 7.

(e) Barker D H. Enhancement of Slope Stability byVegetation. Ground Engineering, April 1986, Volume19, No 8.

(f) Greenway D R. Vegetation and Slope Stability. In: Slope Stability Ed. Anderson M G and Richards KS. Wiley and Sons. (1987).

(g) Norton P J. Biotechnical Methods in theTreatment, Restoration and Use of Coal Mining WastProc. 2nd. Int. Conf. on the Reclamation, Treatment autilization of Coal Mining Wastes. (1987).

(h) Coppin N J and Richards I G. Use of Vegetationin Civil Engineering. CIRIA. (1990).

13. Use of Computers in Design

(a) DTp. BA 25/88. Piled Foundations.



Volume 4 Section 1 Chapter 15Part 1 HA 44/91 Enquiries



15. ENQUIRIES

All technical enquiries or comments on this Advice Note should be sent in writing to:

Head of DivisionRoad Engineering and Environmental DivisionThe Highways AgencySt Christopher House N ORGAN Southwark Street Head of Road Engineering andLondon SE1 OTE Environmental Division

The Deputy Chief EngineerThe Scottish Office Industry DepartmentRoads DirectorateNew St Andrew's House N B MACKENZIEEdinburgh EH1 3TA Deputy Chief Engineer

Head of Roads Engineering (Construction) DivisionWelsh OfficeY Swyddfa GymreigGovernment BuildingsTy Glas RoadLlanishen B H HAWKERCardiff CF4 5PL Head of Roads Engineering

(Construction) Division

Assistant Chief Engineer (Works)Department of the Environment forNorthern IrelandRoads Service HeadquartersClarence Court10-18 Adelaide Street D O'HAGANBelfast BT2 8GB Assistant Chief Engineer (Works)

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A** HERNCASTER BYPASS

APPENDIX 6/1CLASSIFICATION AND ACCEPTABILITY CRITERIA

CLASS

GENERALMATERIALDESCRIPTION

TYPICALUSE

PERMITTEDCONSTITUENTS

MATERIAL PROPERTIES COMPACTIONREQUIREMENTS

PROPERTY TEST LIMITS

LOWER UPPER

1B UniformlyGraded

GeneralFillDrawingsNos305/6/1B-5

Any materialsother thanClass 3

grading BS 1377: Part 2 Tab 6/2 Tab 6/2 Tab 6/4Method 3

uniformitycoeff

ratio of D to60

D10

- 10

optimum mc BS 1377: Part 4(2.5kg rammermethod)

- -

mc BS 1377: Part 2 Opt mc -2%

Opt mc +2%

1C CoarseGranularMaterial

GeneralFillDrawingNos305/6/1B-5



uniformitycoeff

ratio of D to60

D10

5 -

10% finesvalue

Clause 635 50 kN -

2B DryCohesiveMaterial




MCV Clause 632 13 16

2D SiltyCohesive




MCV Clause 632 8 15

4 Various LandscapeArea Fill

Any materials grading BS 1377: Part 2Passing 500 mmPassing 63 mm

- 10%

100% 100%

Clause 620.2

MCV Clause 632 6 18

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APPENDIX 6/1 (Cont'd)CLASSIFICATION AND ACCEPTABILITY CRITERIA

CLASS


TYPICALUSE




LOWER UPPER

6J SelectedUniformlyGradedGranular

Fill toReinforcedEarthDrawing No305/10/1305/10/2B

See Table6/1


uniformity ratio of D to 60

D10

5 10

mc BS 1377: Part 2 17% 21%

effective c'effective o /'

Clause 632 50 kN/m 25 E 2 - -

coeff offrictionadhesion

Clause 639 0.6 50kN/m2

-

6P SelectedUniformlyGradedGranular

Fill toStructuresDrawingNos:305/9/1/5305/9/2/4305/9/3/6305/9/4/5&6305/9/6/4

See Table6/1

grading BS 1377: Part 2 Tab 6/2 Tab 6/2 95% maximumdry density ofBS 1377: Part 4(VibratingHammer Method)

uniformitycoeff

ratio of D to60

D10

5 -

10% finesvalue

Clause 635 30 kN -

undrained cshear o/

Clause 633 50 kN/m 20 E2 -

-

effective c'shear o/'

Clause 636 40 kN/m 25 E2 -

coefficientofpermeability

Clause 640 5 x 10 4

m/sec - -

mc BS 1377: Part 2 17% 21%

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CLASS


TYPICALUSE




LOWER UPPER 7F Selected

SiltyCohesiveMaterial

ForStabilisationWith CementTo Form ACapping(Class 9B)

Any material, orcombination ofmaterials, otherthan chalk,unburnt collieryspoil andargillaceousrock

grading BS 1377: Part 2 Tab Tab Notapplicable

uniformitycoefficient

ratio of D to60

D10

5 -

MCV Clause 632 8 15

Liquid Limit BS 1377: Part 2 - 45

PlasticityIndex

BS 1377: Part 2 - 20

organic BS 1377: Part 3 - 2%

total BS 1377: Part 3 - 1%

7G SelectedConditionedPulverisedFuel Ash.CohesiveMaterial

ForStabilisationWith CementTo Form ACapping(Class 9C)

Conditionedmaterial directfrom powerstation dust-collectionsystem and towhich acontrolledquantity ofwater has beenadded

mc BS 1377: Part 2 15% 35% Notapplicable

totalsulphatecontent

BS 1377: Part 3 - 1%

9B CementStabisedSiltyCohesiveMaterial

Capping Class 7F withaddition ofcementaccording toClause 614

pulverisation BS 1924: Part 2 30% - Tab 6/4Method 7

MCVimmediatelybeforecompaciton

Clause 632 8 12

bearing ratio BS 1924: Part 2 15% -

9C CementStabilisedConditionedPulverisedFuel Ash.CohesiveMaterial

Capping Class 7G withaddition ofcementaccording toClause 614

pulverisation BS 1924: Part 2 60% - End Product95% ofmaximumdry denistyofBS 1924 (2.5kgrammermethod)


mc BS 1924: Part 1 To enable compactionto Clause 612

9D LimeStabilisedCohesiveMaterial

Capping Class 7E withaddition of limeaccording toClause 615

pulverisation BS 1924: Part 2 30% - Tab 6/4Method 7

MCVimmediatelybefore

Clause 632 8 12


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APPENDIX 6/1 (Cont'd)

Classification

The classification and confirmation of acceptability ofthe earthworks materials shall be carried out by theContractor at the point of excavation for on-sitematerials, and at the point of deposition for importedmaterials. Trial pit locations for classification purposeshall be agreed with the Engineer in advance. If in thopinion of the Engineer the material has altered itsclassification or become unacceptable for whateverreason, he may require the Contractor to repeat theclassification and acceptability tests given in Table 6/and this Appendix. The rate of testing required shall as stated in Additional Clause 656 AR, Appendix 0/1.

The Contractor shall submit two copies of all test resuto the Engineer within one working day of thecompletion of the test. The copies shall be signed bythe Contractor's responsible engineer/ technician.

Class 3 Material

No material is designated as Class 3.

Ground Water Lowering - Cut No 3 (sub-Clause602.17)

After stripping topsoil, but before commencing anybulk excavation between Ch 3570 and Ch 4090 in cuNo 3, the Contractor shall construct a deep temporarycut-off filter drain in the position and to the invert leveas shown on Drawing No 305/5/17A. This drain shallbe maintained to allow ground water to outfall freelyinto the stream at Ch 3570 (South side) until thepermanent road drainage through Cut No 3 iscompleted. A full description of these works is given Additional Clause 652 AR, Appendix 0/1.

Permeability Test (Clause 640)

The permeability test referred to in Clause 640 shall bthe constant head or constant hydraulic gradientpermeability test as described in BS 1377: Part 5 andPart 6 for vertical permeability. The permeability boxtest described in HA 41/90 is to be used for horizontapermeability.


PAPER COPIES OF THIS ELECTROA/iv

APPENDIX 6/3

EARTHWORKS REQUIREMENTS

Drawings

305/6/1B /2

s /3Ae /4

/5

General earthworks drawings showing quantities, 1 and fill numbering and chainages, selected fill locatbe location of unacceptable material, simplified GI

borehole information and soil strata.

lts Blasting

Blasting is a permitted alternative within the confinCut No 4 (Ch 5200 to Ch 6500) for the excavation

limestone is to be excavated by bulk blasting. Deta

pre-split drill holes together with the minimum panelsize and face lift are given in Additional Clause 643

for pre-split blasting including the trial are given int Additional Clause 644 AR, Appendix 0/1.

ls (Note: For details of pre-split blasting procedures,specifications etc see TRRL LR 1094; pre-split blasfor highway rock excavation, and also TRRL SR 817device for measuring drill rod and drill holeorientations).

inBlasting of any kind shall only take place between the

Fridays, and 1000-1200 Saturdays. No blasting shall be

eCutting Faces

In Cut No 2 (Ch 2900-3340) South side, the vergel drains within the silty cohesive material shall beexcavated in such a manner that only 20 m of drain

the Lower Lincolnshire Limestone only.

Pre-split blasting shall also be employed if the

of the diameter, dip, azimuth, spacing and depth of the

AR, Appendix 0/1. Other specification requirements

hours of 0930-1130 and 1430-1630 Mondays to

carried out on Sundays or Bank Holidays.

trench over 1 m deep may be open at any one time.

Excavation of further lengths of trench may notcommence until a sufficient length of any existing



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trench has been backfilled and fully compacted so thathe 20 m length of open trench is not exceeded.

All cut-off drains and ditches alongside cuttings andembankments shall be completed and outfalls provideprior to the commencement of any adjacent earthworexcavation or filling operations.

The faces of cuttings requiring attention prior totopsoiling shall be treated in accordance withsub-Clause 603.7(i)(a), with the exception of Cut No 4where the cut faces in limestone shall not be topsoilebut treated in accordance with sub-Clause 603.6(i).

Watercourses

The existing stream at Ch 2010-2040 North side shalbe realigned and regraded to the line and level as shoon Drawing No: 305/5/6. Concrete lining, 150 mmthick, as shown on Drawing No: HBS/5/17B shall beplaced on the invert and that side slope adjacent to thembankment from Ch 2005-2050. The redundantstream bed shall be treated in accordance withsub-Clause 606.4 and backfilled with Class 1B materDrainage pipes along the redundant stream bed shallas detailed in Drawing No: 305/5/6.

Embankment Construction

The Contractor shall not allow fills of more than 2 mheight to remain at side slopes of 1:2.5 or steeper formore than 48 hours before trimming back to the desigslope, and in any event the side slope shall not besteeper than 1:2 at any stage of construction.

No surcharging of embankments is required, and theContractor shall not stockpile material on fill areas to height greater than that of the finished embankment. See also Additional Clause 649 AR, Appendix 0/1.

The minimum thickness of capping material when useas a weather protection layer shall be 450 mm and thminimum thickness of sub-base when used as a weaprotection layer shall be 150 mm. See sub-Clause 60

Compaction

The additional compaction for the top 600 mm belowsub-formation is not required for the farm access tracat Ch 8052 and Ch 4990. Elsewhere sub-Clause612.10(ii) shall apply.

Nuclear Density/Moisture gauges may be used for themeasurement of field dry density. In Classes 6P and



t materials, BS 1377: Part 4 (vibrating hammer meand BS 1924: Part 2 (2.5 kg rammer method)

compliance.d

ksAPPENDIX 6/5

GEOTEXTILE SEPARATORS

Drawingsd

305/6/1B

lwn A geotextile shall be used under the fill material

full width of Bank No 1. It shall be laid directly on of the existing ground surface after topsoil has bee

e stripped between Ch 1500 and Ch 1800. The geshall be manufactured from synthetic fibres and shave a life expectancy of 40 years.

ial. be Design Criteria (sub-Clause 609.4)

than 10 kN/m and have a minimum axial strain of 20%

through it at right angles to its principal plane, in edirection, of 50 litres/m2/S. See Substitute Claus

n SR, Appendix 0/1.

Sampling

Samples for testing in accordance with Clause 6a be taken at the rate of 1 set of samples per 400 m

set of samples shall consist of that minimum numtest pieces sufficient to carry out all the tests requ

de Installationther8.7. The geotextile shall be laid from rolls in a longitu

be by lapping only. Physical jointing is not permitted.

location. See Substitute Clause 659 SR, Appendi

respectively shall also be used as a basis for

/6

Location

The geotextile shall sustain a tensile load of not less

at failure. It shall also, have a minimum water flow rat

Clause 609.

direction along the line of the bypass, and jointing sha

The lap width shall be 500 mm minimum at any


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APPENDIX 6/6

FILL TO STRUCTURES

Drawings

305/9/1/5 Bridge No 1 - Fill to Abutments /2/4A No 2 - Fill to Abutments and Piers /3/6 No 3 - Fill to Abutments and Piers /4/6B No 4 - Fill to Abutments /5/5 No 5 - Fill to Abutments /5/6 No 5 - Fill to Piers

Location and extent of selected granular fill Class 6Pmaterial.

The Contractor is required to show that his proposedmaterial is stable when compacted and trimmed to aslope of 1 vertical to 1.5 horizontal as described insub-Clause 610.6.

APPENDIX 6/7

SUB-FORMATION AND CAPPING

Drawings

305/7/2 305/6/3A HBS/7/1 /3B /4 to /4 /5 HBS/7/12 /5B

Pavement drawings, earthworks drawings and standdetail drawings showing the extent, locations, widthsand thickness of Capping materials.

Sub-formation shall have the same shaping requiremas formation as shown in Drawing Nos HBS/7/1 toHBS/7/12.

Where formation is formed in the Lower LincolnshireLimestone in Cut No 4 between Ch 5200 and Ch 650the material shall, in accordance with sub-Clause 61be either:

1) excavated to a depth of 500 mm and the matericrushed to give a maximum particle size of 500mm or

2) where the surface is tabular, it shall be regulatewhere necessary with a cement bound materialClass CBM2 as specified in Clause 1037.


PAPER COPIES OF THIS ELECTROA/vi

APPENDIX 6/8

TOPSOILING AND SEEDING

Drawings

305/11/1A /2B /3A

Topsoil

No imported topsoil Class 5B is required.

excavated from stockpiles which have been exposaccumulative rainfall of 150 mm over the precedin

days measured at the main site offices. For detailprotection of topsoil stockpiles see Additional Clause

The areas to be grassed and the treatment each area

and 2B.

Topsoil depths to be deposited in Treatments I and II

on Drawing No: 305/11/3A as being areas of treeplanting where the topsoil depth shall be 300 mm.

All turfing on slopes of gradient of 1:3 or steeper shall

ard Appendix 0/1.

The hydraulic mulch seeding used in Treatment III s

entAreas of grass which require to be mown 3 times in

vicinity of Bridge No 5, East abutment are detailed in

0 The locations, access points and approximate6.4, contouring of permanent topsoil storage areas are

shown on Drawing No: 305/11/3A.

As stated in sub-Clause 618.3, topsoil shall not be

655 AR, Appendix 0/1.

shall receive are shown on Drawing Nos: 305/11/1A

are 225 mm on slopes of 10 except those areas show

be pegged as described in Additional Clause 656 AR,

contain glass fibre as a retaining agent.

Drawing No: 305/11/3A.



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APPENDIX 6/9

LANDSCAPE AREAS ETC

Drawings

305/10/1 /2B /3 /4 /5

Location of noise bunds and landscape areas,cross-sections and contours, details of dense plantingareas.

Environmental Bunds

Environmental Bund No 1 shall be constructed using strengthened embankment to Clause 621. Environmental Bund No 2 shall be constructed as anormal embankment to Clause 619 except thatAppendix 6/1 shall apply instead of Table 6/1, usingClass 1B material.

Environmental Bund No 1 is detailed on Drawing Nos305/10/1 and 2B using a geosynthetic reinforcementmaterial at the vertical spacings as shown. Thereinforcing material shall comply with the requiremenof Additional Clause 660 AR, Appendix 0/1 and shallbe laid and jointed as detailed in Additional Clause 66AR, Appendix 0/1. The fill material shall be Class 6Jmaterial as detailed in Appendix 6/1, laid andcompacted in accordance with Clauses 608 and 612.

The reinforcing material shall comply with thefollowing additional requirements:-

1. Tensile strength of 20 kN/m at a maximum strainof 10% according to BS 6906: Part 1 (1987)except that the strain rate shall be set at 2% perminute ± 0.4% per minute.

2. Water flow of 30 litres/m2/s minimum under aconstant 100 mm head of water according to BS6906: Part 3 (1989).

3. Minimum Tear Strength of 400 N when tested inaccordance with ASTM D-4533-85 (Geotextilesonly).

4. Minimum Puncture Resistance of 2kN when testin accordance with BS 6906: Part 4 (1989).



5. Be unaffected by acid/alkali or biological attack.

6. Contain an UV inhibitor if left exposed for more

Landscape Areas

Locations of Landscape Area Nos 1-4 together withdetails of access points and contours are given in

Compaction of Landscape Area Nos 1, 2 and 4 in accordance with sub-Clause 620.2. Compaction o

6/4 Method 4.

a Construction of Landscape Area No 3 may be caout at the same time as the adjacent Fill No 4 suthe conditions described in sub-Clause 620.4.

All landscape areas shall be topsoiled and seedeaccordance with Treatment I, Clause 618. The

than 7 days in cumulative time.

7. Have a design life of 40 years.

Drawing Nos 305/10/3, 4 and 5.

Landscape Area No 3 shall be in accordance with Ta

minimum depth of topsoil shall be 300 mm throughou


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