c2-10 Site Investigation

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C2-10 Site Investigation

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National Productivity and Quality Specifications (NPQS)




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CONTENTS

Page

1.

GENERAL 3

1.1 Scope 3

1.2 Related Sections 3

1.3 Standards and Regulations 3

1.4 Trade Preambles 4

1.5 Definition 5

2. PERFORMANCE REQUIREMENTS 7

2.1 Method of Advancement and Locating of Boreholes 7

2.2 Reporting Requirements 7

2.3 Ground Movements and Vibrations 7

2.4

Noise Nuisance 7

3. MATERIALS 9

3.1 Drilling Fluid for Rotary Coring 9

3.2 Cement / Bentonite Grout for Backfilling 9

3.3 Sample Tubes 9

3.4 Standpipes 9

3.5 Piezometers 9

4. WORKMANSHIP 11

4.1 Sinking Boreholes 11

4.2 Pits and Trenches 12

4.3

Sampling 13

4.4 In-situ Testing 15

4.5 Laboratory Tests 18

4.6 Geophysical Methods of Investigation 19

4.7 Instrumentation and Monitoring Requirements 19

4.8 Noise and Disturbance 20

5. VERIFICATION AND SUBMISSIONS 21

5.1 Submissions 21

5.2 Equipment Calibration 23

5.3 Commissioning of Water Standpipes and Piezometers 23



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1. GENERAL

Read with the General Requirements section, and all other contract documents.

1.1 Scope

This section covers the requirements for ground investigation, including:

a. Sinking of boreholes

b. Excavation of trial pits

c. Probing

d. Extraction of disturbed and undisturbed soil samples

e. Testing of soils both in-situ and in the laboratory

f. Monitoring of ground water level

g. Geophysical methods of investigation

1.1.1 Provisional Schedule of Works

Refer to PSD for the provisional schedule of works to be carried out for the siteinvestigation.

1.2 Related Sections

Read this work section in conjunction with the relevant requirements of theother work sections as follows:

C2-20 General Earthworks (Excavation and Filling)

C2-50 Instrumentation and Monitoring

1.3 Standards and Regulations

Unless otherwise agreed by the SO, ensure all of the Works comply with therelevant requirements of the Standards and Codes listed below or referenced inthe body of the Specification. Alternative Standards and Codes may be

proposed for approval by the SO, provided it can be demonstrated that thealternative Standards and Codes comply with the requirements of thestandards specified. All Standards and Codes quoted are the current version,unless specific year references are noted.

SS CP 79 Safety management system for construction worksites

ISRMISRM commission on standardisation of laboratory and field tests.Suggested Methods for determining the uniaxial compressivestrength and deformability of rock materials (1979)

ISRMISRM commission on testing methods. Suggested Method fordetermining point load strength (1985)



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BRE Digest 251 Assessment of damage in low rise building

BS 1377 Methods of Test for Soils for Civil Engineering Purposes

BS 3506 Unplasticized PVC pipe for industrial purposes

BS 5930 Code of practice for Site Investigations

BS 8008Guide to safety precautions and procedures for the constructionand descent of machine-bored shaft for piling and other purposes.

In the event that the standards or Codes are revised or superceded, refer to thelatest edition or the appropriate substitution for the relevant subjects.

1.4 Trade Preambles

1.4.1 Coordination with Other Works

Co-ordinate with other contractors who may carry out other works at the sametime at the site. Take into account of site access, space occupation, safety andsafeguarding of adjoining properties and each other’s works.

1.4.2 Quality Control Plan

No item.

1.4.3 Licensed Surveyor

Employ a Licensed Surveyor who shall be responsible for surveying borehole

locations and submit the results to the SO together with the site investigationreport.

1.4.4 Supervision of the Works

Engage a competent and suitably experienced site engineer to the SO’sacceptance, to supervise the field works. Do not remove or replace thissupervisor without the prior agreement of the SO.

1.4.5 Existing Services Affected by the Works

Ensure that existing services affected by the works are detected, protected and/ or diverted. Comply with all authority requirements.

1.4.6 Upholding of Adjoining Properties

Accept responsibility for the upholding of the adjoining buildings and roads,footpaths etc., where applicable, together with the mains and services from thetime of taking possession of the site through the duration of the works.

Adequately maintain roads and footpaths within and adjacent to the site andkeep clear of mud and debris.



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1.4.7 Instrumentation and Monitoring

Provide instruments as scheduled in the PSD to monitor vibrations, noise andground movements. If necessary or as required by the authorities, propose and

provide additional instrumentation and monitoring for records.Take cognisance of and co-ordinate with other contractors on site who may becarrying out instrumentation and monitoring works to avoid duplication ofinstallation and readings.

For general requirements of the instrumentation and monitoring works refer toSection C2-50.

1.4.8 PE Endorsement

Engage a professional engineer to verify the accuracy of the findings andendorse all reports including the site investigation report and, if required, theinterpretative report.

1.4.9 Fenced Protect ion

Protect all equipment and working area using fencing or other methods asappropriate.

1.4.10 Safety

Provide safety precautions to comply with all current legislation and regulations,notably:

a. Building Control Regulations

b. Code of Practice for Traffic Control at Work Zonec. Factories (Building Operations and Works of Engineering Construction)

Regulations

d. Factories Act

e. SS CP 79 Safety management system for construction worksites

f. For works within LTA Railway Protection Zone, ensure the works complyfully with Code of Practice for Railway Protection.

Additionally, comply also with the following:

a. BRE Digest 251 (1995) Assessment of damage in low rise building

b. BS 8008: Guide to safety precautions and procedures for the constructionand descent of machine-bored shaft for piling and other purposes

1.5 Definition

a. AccreditedTestingLaboratory

Shall mean an organisation or laboratory accreditedunder the Singapore Laboratory Accreditation Scheme(SINGLAS) and fully equipped to carry out all tests andchecks required by the Specification.



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b. Hard Material Rock or hard soil defined as class I, II or III in BS 5930.



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2. PERFORMANCE REQUIREMENTS

2.1 Method of Advancement and Locating of Boreholes

The method of advancement shall be such that the boring can be completedand logged to the specified depth, with samples obtained, insitu testing carriedout and instrumentation installed as specified.

Borehole locations shall be surveyed prior to drilling commencement and thedrilled position shall be expressed in Northern and Eastern coordinates systemwith reference to the Singapore National Grid.

All elevations including ground level and top of instruments to be in the nearest50mm relative to the Ordinance Datum, where mean sea level is taken as100mOD.

2.2 Reporting Requirements

2.2.1 Digi tal Data

Refer to the PSD for requirement of providing digital data.

2.2.2 Photographs

Where colour photographs are required for records, submit gloss colour print ofapproximate size 150mm x 100mm to the SO. Where a digital camera is used,submit electronic copy of the photographs in either *.jpg or *.bmp format in

place of the photograph negatives.

The photographs shall show clearly all required details and shall contain agraduated scale and colour chart for reference. Take the photographs undernatural light condition with uniform intensity of light to reflect the natural colourof the intended object eg. cores, trenches etc. Do not use flashlights.

2.3 Ground Movements and Vibrations

Generally comply with the requirements of BS 5228 Part 1.

The vibration generated by the works in MRT structures not to exceed a peak

particle velocity of 15mm/s.Unless otherwise directed, refer to Section C2-50, Clause 4.2.2 for generalrestrictions on ground movements and vibration limits for adjacent structureswhere relevant.

2.4 Noise Nuisance

Take all necessary actions to ensure compliance with noise control regulationsimposed by the NEA or any relevant authorities.



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The noise level at the nearest occupied building outside the Site shall notexceed the following maximum permissible noise level, or shall have met thenoise control guidelines introduced by the NEA whichever is the more stringent:

Type of occupied buildings Applicable period Maximum allowableequivalent continuous noiselevel measured over aperiod of 5 minutes in dB

(a) Hospital, school, home forthe aged, sick etc

7am to 7 pm 75

7pm to 7am 55

(b) Buildings other than thosein (a) above

7am to 7 pm 90

7pm to 7am 70



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3. MATERIALS

3.1 Drilling Fluid for Rotary Coring

Use clean water, air or air mist. Drilling muds or additives may be used subjectto agreement with the SO. For ground conditions with Artesian pressure,propose the unit weight of drilling fluid to the SO’s acceptance.

3.2 Cement / Bentonite Grout for Backfill ing

Mix equal portions by weight of Ordinary Portland Cement and Bentonite byhand or machine to a uniform colour and consistency before placing. Moisturecontent shall not exceed 250%.

The mix shall provide a proper seal against the borehole wall and prevent theformation of potential seepage paths for groundwater through the borehole.

For backfilling boreholes where there is no groundwater, add just sufficientamount of water to produce a pump-able mix.

Where there is water in the exploratory hole add only sufficient water to form acohesive paste.

3.3 Sample Tubes

Use hydraulic piston type of sampler unless otherwise agreed. Do not useplastic lining tubes in substitution for steel or aluminium sampling tubes. UseMazier Sampler in place of the thin walled sampler for stiff soil with theagreement of the SO. Thin walled sampler tubes shall be made of steel oraluminium. Open tube and piston samples are to have a minimum of 75mminternal diameter.

3.4 Standpipes

3.4.1 Tube

The standpipe shall be of unplasticised Polyvinylchloride or high densityPolyethylene, of minimum internal diameter 19mm. The lower 1m shall be

perforated by holes not greater than 5mm diameter at approximately 75mmspacing or slots not greater than 5mm width giving an equivalent area.

3.4.2 Filter

Use Pea gravel or similar material, 6-10mm diameter.

3.5 Piezometers

Piezometers shall generally be the Casagrande type. Alternative types ofpiezometer may be used subject to approval. Refer to section C2-50, clause3.10 for general requirement.



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4. WORKMANSHIP

4.1 Sinking Boreholes

4.1.1 Method of advancement

Unless otherwise specified use one of the following methods:

a. Rotary coring

b. Percussion boring

c. Auger boring

Submit proposals for any other methods to the SO for approval. The minimumnominal casing diameter shall be 150mm. At ground level before boring

commences, the initial casing diameter shall be sufficiently large to ensure thatthe borehole can be completed to its scheduled depth.

4.1.2 Circulation of Drilling Fluid and Cutting Sedimentation Pits

Locate pits for circulation of drilling fluid and cutting sedimentation away fromthe borehole and connect through trenches, unless otherwise agreed with theSO for other alternative methods due to site constraint.

4.1.3 Addition of Water

Do not use water to advance the borehole other than in dry granular soils orotherwise agreed by the SO.

Maintain a positive hydraulic head in the borehole where it advances below thewater table in cases where disturbance of the soils is likely.

4.1.4 Obstructions

Use Rotary coring method where a hard stratum or obstruction is encountered.

Do not continue for more than an hour without reference to the SO andobtaining further instructions.

4.1.5 Coring Through Hard Materials

When Hard Materials are encountered, use a core-barrel with a diamond-

impregnated drill bit or other methods as agreed with the SO to obtain samplingmaterials. Take samples at the change of such hard stratum.

4.1.6 Continuation of Boreholes

Cover any borehole remaining open overnight. Before the first sample of thenew day is taken, advance the boring for at least 0.3m.

4.1.7 Backfill ing of Boreholes

Do not backfill boreholes with soil arisings, unless otherwise agreed with theSO. Backfill all boreholes with cement bentonite grout, with standpipes and



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piezometers together with their response zones installed at the depthsspecified, or as directed by the SO.

Introduce the grout using a tremie pipe which is kept below the surface of the

grout as filling proceeds. Agree the methods to be used where ground conditions make normal groutingimpracticable.

Leave the area in a clean and tidy condition.

4.2 Pits and Trenches

4.2.1 Inspect ion Pits

Unless otherwise directed or agreed, excavate pits by hand to a depth of 1.2mand hand auger for another 0.8m (i.e. Total 2m) to locate undergroundservices.

Use hand-operated power tools where necessary to assist the excavation.

Record the positions, depths and dimensions of all services encountered in thedaily reports.

4.2.2 Trial Pits and Trenches

Excavate pits by hand to a depth of 1.2m unless otherwise specified, or bymachine to the required depth to enable visual examination and sampling fromoutside the excavation. Do not allow access to excavations greater than 1.2m,unless otherwise agreed.

4.2.3 Observation Pits and Trenches

Excavate by hand or machine as required. Provide adequate support to enablesafe access for in situ examination, sampling and testing as required.

4.2.4 Dimensions of Pits and Trenches

Unless otherwise specified:

a. Pits as in Clause 4.2.1 shall have a base area not less than 1.5m².

b. Trenches other than as in Clause 4.2.1 shall be 1m wide.

4.2.5 Groundwater

Keep pits and trenches free from surface water run-off. Control ground water bypumping from a sump, but take adequate safety measures to maintain thestability of the excavation.



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4.2.6 Descrip tion of Pits and Trenches

Describe the nature of the ground encountered within the excavationsincluding:

a. the nature of the strata

b. the condition of the base

c. the presence of any water

d. suspected contamination

Photograph the excavations to show the details of the ground conditions andany unusual features identified.

4.2.7 Protection to Excavations Left Open

4.2.7.1 Protection to personnel

Provide all necessary signing and lighting, together with temporarybarriers/fencing.

4.2.7.2 Protection against inclement weather

Provide all necessary precautions to protect the excavations from the effects ofinclement weather.

4.2.8 Backfilling

Backfill as soon as practicable using excavated material unless otherwiseagreed.

Compact with excavation plant or as agreed to ensure the area remains levelafter filling.

Remove any surplus material from site. Leave the area in a clean and tidycondition.

4.3 Sampling

4.3.1 Open Tube and Piston Samples

Take samples in accordance with BS 5930.

Soil samples shall be at least 500mm long.

4.3.2 Frequency of Sampling and Testing

Requirements for sampling and testing are given in Clause 1.1.1.

For boreholes in clay soils except soft marine clay, take an SPT following everyattempt to take an open tube or piston sample. For soft marine clay, take avane shear test instead of an SPT.

For boreholes in Made Ground and granular soil, take bulk-disturbed samplefrom SPT tests at intervals as directed by the SO.



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4.3.3 Identif ication, Storage and Disposal of Samples

Remove all samples from the site of the boreholes at the end of each day'swork and protect from excessive heat by storing on or near the site under cover

and secured from interference.Label all samples clearly in accordance with BS 5930. Identify clearly anymaterial thought to be harmful.

Seal, transport and store the samples so that no change in moisture contentand soil structure occurs prior to laboratory testing.

Remove all samples from the site so as to reach the laboratory within the sameday of being taken unless otherwise agreed.

Retain samples until at least 28 days after submission of the approved finalreport. Give the SO notice of at least 1 week before the disposal of samples.

4.3.4 Disturbed Samples

Retain disturbed samples at all changes of strata from the cutting shoe of anopen tube.

Store these samples in small airtight PVC containers, correctly labelled, anddeliver to the SO’s office or other premises as directed upon completion of theWork.

4.3.5 Undisturbed Samples

Take undisturbed samples by thin walled piston or other approved sampler incohesive materials at change of strata and at appropriate intervals as directed

by the SO within each type of soil.Use a Mazier sampler to obtain stiffer soils where the thin walled sampler is notable to take undisturbed samples.

4.3.6 Standard Penetration Test Samples

When a standard penetration test (SPT) is carried out, retain the sample fromthe split barrel sampler as a small disturbed sample.

Where no sample is retained take a bulk disturbed sample from the test zone.

4.3.7 Groundwater Samples

Where directed by the SO, take a sample of not less than 0.25l from each waterstandpipe. Store each sample in a clean, dry container.

4.3.8 Description of Samples

Examine and describe all samples in accordance with BS 5930. Forweathering classifications and descriptions of soils and rocks, refer to BS 5930.

4.3.9 Recording Depths

Record the depths below ground at which all samples are taken. For open tubeand piston samples record the depth to the top and bottom of the sample andthe length obtained, for bulk samples record the depth of the sample zone.



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4.3.10 Rock Cores

4.3.10.1 Equipment for core recovery

Unless otherwise specified use a triple tube coring system, effected by the useof a double tube barrel with an approved semi-rigid liner.

Use triple tube core barrel of NX size or larger to obtain cores of not less than50mm diameter in rock.

4.3.10.2 Recovery of cores

Produce cores not less than the specified diameter throughout the length of thecore.

No drilling run shall exceed 1.5m in length. Withdraw the core barrel from thehole and remove the core as often as may be necessary to secure the highestpossible core recovery and quality. Probe rock for a minimum depth of 5metres by rotary core drilling or continue drilling until not less than 90%recovery is achieved in any 1.5m run. Core recovery of less than 90% is notacceptable. If the measured core recovery is less than 90%, the subsequentcore run shall be halved (subject to a minimum core run length of 0.5m).

4.3.10.3 Removal of cores

Carry out all operations so as to minimise disturbance to the cores.

Support the core rigidly while the liner is removed and subsequently as the coreis extruded.

4.3.10.4 Marking of coresImmediately after removal of the liner mark both ends in indelible ink or otheragreed manner. Cap and seal the liner.

4.3.10.5 Storage of cores

Immediately after removal from the core barrel, wrap selected lengths of core in3 layers of linen cloth, coat each layer with wax and place the cores in coreboxes in a consistent sequence.

Store the core boxes on or near the site under cover and secured from publicinterference.

Send all cores to the lab as soon as possible after retrieving from the ground.

4.3.10.6 Testing of cores

Carry out point load test or uniaxial compression strength test on selected coresamples as agreed by the SO to determine the grade of rock quality.

4.4 In-situ Testing

4.4.1 Equipment Calibration

Calibrate all equipment as required in accordance with the manufacturer’s

requirements.



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4.4.2 General Requirements

Carry out the in-situ tests in accordance with BS 1377.

4.4.2.1 BoreholesTake SPT at intervals specified in clause 1.1.1, or as directed by the SO.Report the water surface and casing levels in the borehole at the time of thetest.

4.4.2.2 Observation Pits and Trenches

Refer to PSD for the schedule of testing, such as:

a. Measure vane shear strength at 1m depth intervals or at change of strata incohesive soil.

b. Take In-situ density using appropriate method at 1m depth in each pit and

trench.

c. Make available Mackintosh probing equipment during the excavation of allobservation pits and trenches and test where required.

d. Cone penetration test, in-situ permeability test and trial grouting of voids tobe carried out in the pits.

4.4.3 Standard Penetration Tests (SPT)

Carry out SPT to refusal by confirmation of 3 consecutive 100 blows/0.3m at2m centres or such that bedrock has encountered. For the purpose of rockheadconfirmation, retrieve core samples of not less than 3.0m/5m length in

accordance with Clause 4.3.10.2. Terminate and backfill the borehole withbentonite-cement grout.

When an SPT test is carried out, record and include in the report the blow countfor each 75mm increment (or part) of penetration.

4.4.4 Vane Shear Tests

Carry out in-situ vane shear tests where specified to provide an estimate of theundrained shear strength of the soil tested.

The vane blade must be of size 130mm x 65mm or bigger and advancedthrough cohesive soil without the assistance of boring except through hard soillayers.

4.4.5 Pressuremeter Tests

Carry out in-situ pressuremeter tests at predetermined depths.

4.4.6 Cone Penetration Tests

Carry out in-situ Cone Penetration tests (CPT) with porewater pressuremeasurement in specified locations.

Present the following parameters together with the results:

a. Net cone resistance

b. sleeve friction



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c. pore pressure

d. friction ratio

e. pore pressure ratio.

Carry out dissipation test in silty/clayey strata when required

4.4.7 Permeabil ity Test

Carry out permeability tests at depths as directed. Indicate clearly in theinterpretation of the results whether a constant-head or variable-head methodhas been adopted for the test.

4.4.8 Packer Tests

Carry out Packer or water absorption tests in rock to measure wateracceptance by in-situ rock mass under a given pressure. Express the results in

terms of Lugeon units. A staged test consisting different water pressures ispreferable. Clearly state in each test location whether the test has been carriedout using single or double packers.

4.4.9 Plate Load Tests

Carry out the test in accordance with BS 5930 at depth below the existingground level as specific with a minimum plate size of 300mm in diameter. Loadthe plate to cause bearing failure by a constant load. The failure load is definedas the load at which the plate continues to settle at a steady rate or at least theplate have gone through 15% of the plate width, whichever is the lesser.

Account for the estimated bearing strength and deformation characteristics of

the materials to be tested as indicated in the PSD.

Apply the test load by means of a newly calibrated hydraulic jack usingkentledge or other method as accepted by SO.

Provide a certificate of calibration from an accepted testing authority before testcommencement.

4.4.9.1 Test Procedure

Load testing shall be of the Maintained Load Method. Loading shall be inincrements of producing not more than one-fifth of the design bearing pressureor smaller steps as agreed. Unloading shall be in at least three equal steps.

Each loading shall be maintained for a minimum period of 5 minutes and untilsettlement is stabilized. At the maximum load pressure, the load shall bemaintained for a minimum of 6 hours and until settlement is stabilized.

The settlement is deemed to stabilize if the rate does not exceed 0.1mm perhour or in proportion for a shorter maintaining time.

Throughout the test, make observations of vertical movement of the plate withtwo dial gauges graduated in 0.025mm divisions. Place a linear metric scalegraduated with the appropriate number of sub-divisions vertically on either sideof the plate to allow independent measurement of its vertical movement with aprecise level. Refer the dial gauge readings on stiff steel beams, the ends ofwhich shall rest on, or are fixed to reliable supports.



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The beam supports shall extend not less than one metre below ground surfaceand not be located closer than two metres from the centre of test plate. Checkthe elevation of the supports frequently with reference to a fixed benchmark.

Protect the entire measuring assembly against rain, direct sunlight and otherdisturbance that might affect its reliability. Provide all necessary facilities toenable the supervision staff to check readings during the progress of the test.Keep the test under continuous and competent supervision. Give at least 24hours notice of the commencement of each test.

4.5 Laboratory Tests

Conduct laboratory tests in accordance with BS1377 for soil samples and ISRMfor rock samples.

4.5.1 Classif ication Tests

Carry out tests for the classification of soil for the determination of basicphysical properties as specified.

a. Moisture content (BS1377-2, Clause 3)

b. Atterberg limits including liquid limit, plastic limit and plasticity index(BS1377-2, Clause 4 and 5)

c. Bulk density and dry density (BS1377-2, Clause 7)

d. Particle density or specific gravity (BS1377-2, Clause 8)

e. Particle size distribution with wet sieving and hydrometer methods

(BS1377-2, Clause 9)

4.5.2 Chemical tests

a. Carry out tests for determining the organic matter, chemical substances andcorrosivity properties of soil and water samples as specified.

b. Organic matter content (BS1377-3, Clause 3)

c. Total sulphate content of soil and sulphate content in 2:1 water-soil extract(BS1377-3, Clause 5)

d. pH value of soil (BS1377-3, Clause 9)

e. Sulphate content (BS1377-3, Clause 5) and pH value of ground water(BS1377-3, Clause 9)

f. Chloride content of soil (BS1377-3, Clause 7)

4.5.3 Compressibili ty Test

Carry out one-dimensional consolidation and swelling tests in an Oedometer fordetermining the consolidation and swelling characteristics of soil when subjectto changes in applied vertical effective stress in accordance with BS1377-5,Clauses 3 and 4.



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4.5.4 Shear Strength Tests

Carry out compression tests for the determination of the shear strengthparameters of soils in terms of total and effective stresses in compliance with

the following:a. Direct shear test (BS1377-7, Clause 4 or 5 as specified by the SO)

b. Unconfined compression test (BS1377-7, Clause 7)

c. Unconsolidated-undrained triaxial compression test by single stage ormultistage loading without measurement of pore pressure (BS1377-7,Clauses 8 and 9)

d. Consolidated-undrained triaxial compression test with measurement of porepressure (BS1377-8, Clause 7)

e. Consolidated-drained triaxial compression test with measurement of porepressure (BS1377-8, Clause 8)

Agree with the SO, the required cell pressures for triaxial tests prior to carryingout the tests.

4.5.5 Strength Tests on Rock Samples

Carry out compression tests for the determination of the shear strengthparameters of rocks in compliance with the following:

a. Uniaxial compression strength test (ISRM, 1979)

b. Point load test (ISRM, 1985)

4.6 Geophysical Methods of Investigation

When required in the specified scope, submit to the SO’s acceptance,procedures and equipment to be used for the geophysical investigation. Thefollowing methods may be used.

a. Seismic methods

b. Electrical techniques

c. Electromagnetic techniques

d. Potential field techniquese. Wireline geophysical logging.

Carry out a field trial for the survey prior to commencing the main work.

4.7 Instrumentation and Monitoring Requirements

4.7.1 Groundwater

Make careful observations of ground water conditions and levels daily duringeach boring operation.



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Record the level of the water table in each borehole twice daily: once in themorning before resumption of boring and once at the end of the day.

If artesian conditions are encountered agree with the SO the measures to be

adopted.Record the readings by an electrically operated water level indicator capable ofmeasuring the depth to water levels of up to 30 metres.

4.7.2 Standpipes and Piezometers

Typical installation details for standpipes and piezometers are shown in FiguresS1 and S2. Install standpipe and piezometer in separate boreholes asscheduled in the PSD.

Also install multilevel piezometers in separate boreholes unless otherwiseagreed.

Protect the tops of standpipes and piezometers by surface boxes as indicated.

Allow a minimum time lag of 1 hour between placing of cement bentonitegrout/bentonite pellet and filter material above to prevent probable mixing up ofthe intended permeable and impermeable layers.

Unless otherwise agreed, monitor all standpipes and piezometers daily duringthe fieldwork. After the completion of the fieldwork period, return to site once aweek to measure the water level in each and every standpipe and piezometerfor a period of one month. Give one day's notice to all occupiers on the site onwhich the piezometers and standpipes are situated.

4.7.2.1 Sand filter

Record the volume of the sand filter placed. The response zone formed by thesand filter shall extend from 0.5m below the tip of the porous element to 1.0mabove the tip of the element.

4.8 Noise and Disturbance

Carry out the work in such a manner as to minimise noise, vibration and otherdisturbance.

Comply with all current regulations and environmental controls.



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5. VERIFICATION AND SUBMISSIONS

5.1 Submissions

5.1.1 Testing laboratory

Submit the proposed testing laboratory for acceptance during tender.

5.1.2 Field reports

Submit a duplicate copy of the Daily Site Record on the following working day.For all borings, the record shall state:

a. Location (chainage where known)

b. Borehole number

c. Date and times of boring

d. Type of plant used

e. Diameter of boring casing and core as appropriate

f. Depth of base of each stratum from surface

g. Description of strata

h. Level of the bottom of the casing when each sample is taken or in situ testcarried out or each core run drilled

i. Depths at which all samples were taken and in situ tests carried out

j. Detailed test records

k. Level at which water was standing at the commencement and end of eachday's work

l. All water levels encountered and amount of water added (if any) whenboring cohesive soils

m. Length of drill runs and the actual lengths of core recovered in each drill run

n. Percentage and colour of drilling fluid returns

o. Rotary drilling penetration rate and variations

p. Remarks on any matters not referred to the above which may be of value ininterpreting and understanding the ground conditions.

5.1.3 Borehole Logs

Submit one copy of the Preliminary Borehole Logs for the preliminarydescription of the soils at each borehole. Provide a further copy with completelist of samples retrieved for Laboratory Testing within two days of thecompletion of site work at each borehole.



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5.1.4 Laboratory Testing Schedules

Prepare a blank test schedule by considering the provisional quantities inClause 1.1, including the following information:

a. borehole number

b. sample number

c. sample type

d. sample depth and on the other axis the following standard laboratory testsshall be listed:

e. Moisture content

f. Atterberg Limits

g. Bulk density and dry density

h. Specific gravity of soil particles

i. Particular size distribution by Wet sieving method

j. Particular size distribution by hydrometer method

k. Organic matter content

l. Sulphate of soil and in sample of water-soil extract

m. pH of soil

n. Sulphate and pH of water sample

o. Chloride of soil

p. Oedometer (leave space for pressure range to be specified)

q. Direct shear test

r. Unconfined compression test

s. Quick triaxial test on 38mm diameter specimen (leave space for pressurerange to be specified)

t. Consolidated-undrained and consolidated-drained triaxial compressiontests on 38mm diameter specimen (leave space for pressure range to bespecified)

u. Uniaxial compression strength test

v. Point load test

w. Three blank columns for other tests

Submit these draft schedules sheets to the SO with the preliminary logs.

5.1.5 Plate load test

Submit calculations and sketches of the test set up and method statement forthe plate load test to SO for approval before commencement of the test.Engage a PE to review and endorse all submissions.

Submit all records and plot of load versus settlement within 24 hours aftercompletion of the test. Format or records and reports to SO’s acceptance.



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5.1.6 Geophysical Methods of Investigation

Submit the field trial result for the investigation to the SO prior to commencingthe main work.

Process the data after completing the field work and calibrate the data withborehole results for interpretation of geological conditions across the monitoringpoints. Submit an interpretative report together with the site investigation reportto the SO.

5.1.7 Interpretive Report

Submit 5 copies or as directed, of the interpretive report after completion. Thereport shall contain at least information on:a. Description of the works, location etc.

b. Field log reports

c. Lab test reports

d. Interpretation of the implication of the ground condition on the following:

I. Shear strength parameters for design

II. Foundation design

III. Temporary shoring scheme

Submit the report with endorsement by the engaged PE.

5.2 Equipment Calibration

5.2.1 Field Vane Shear Tests

Provide full details of the equipment used as well as calibration record andspecimen calculation sheets.

Submit preliminary results for both virgin and remoulded shear strength to theSO within 24 hours after completion of the test.

5.2.2 Pressuremeter Tests

Provide full details of the equipment used, its range of operation includingmaximum depth below ground level and calibrations record together with

specimen calculation sheets.

Submit preliminary results for both initial loading and reloading cycles to the SOwithin 24 hours after completion of the test.

5.3 Commission ing of Water Standpipes and Piezometers

On completion of the installation, commission all standpipes and piezometersusing a falling head test by filling the standpipe or piezometer full with water tothe top of the PVC tubing.

Monitor the drop in water level in the standpipe or piezometer at intervals of

15s, 30s, 1 min, 2 min, 4 min, 8 min, 15 min, 30 min, 1 hr, 2 hr, 3 hr, 4 hr, 5 hr,



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6 hr, 7 hr, 8 hr, 16 hr, 24 hr, or when the water level has returned to its initialsteady level.

The water standpipe or piezometer must be in working condition throughout the

monitoring period. Rectify any damaged water standpipe or piezometer beforehanding over.

Take samples of ground water of not less than one litre from the standpipesand piezometer when required.

Store the water samples in clean sealed containers, clearly label and deliver tothe laboratory for chemical tests.

The tests for sulphate content (% S03), chloride content, acidity (pH value) anddegree of salinity shall be determined from the same sample.



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SURFACE BOXWITH COVER

TYPICAL DETAILS OF PIEZOMETER INSTALLATION

NTS

CAP

CEMENT BENTONITEGROUT (1 : 1 BYWEIGHT)

BENTONITE CHIPS ORPELLETS


SAND FILTER

PIEZOMETER

BOTTOM OF HOLE

TIP LEVEL

GROUND LEVEL

1 5 0 0

1 5 0 0

1 5 0 0

PLASTIC TUBE

Figure S1



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SURFACE BOXWITH COVER

TYPICAL DETAILS OF WATER STANDPIPE INSTALLATION

NTS

10mm SINGLE SIZE AGGREGATE


BOTTOM OF HOLETIP LEVEL

GROUND LEVEL

19mm PERFORATEDPVC PIPE WITH 2LAYERS OF NYLONMESH

Figure S2

CAP

1 5 0 0

Documents

c2-10 Site Investigation