TRANSPORT AND ROAD RESEARCH LABORATORY Department of Transport

Contractor Report 172

R R L

Testing of soil samples f rom Bell Common Tunnel

by J E Hellings (Pell Frischman Consulting Engineers Ltd)* J B Burland (Imperial College, London) & I F Symons (TRRL)

*Formerly with Golder Associates (UK) Ltd

The work reported herein was carded out under a contract placed on the first two authors by the Transport and Road Research Laboratory.

The views expressed are not necessarily those of the DepadJuent of Transport.

This report, like others in the series, is reproduced with the authors' own text and illustrations. No attempt has been made to prepare a standardised format or style of presentation.

Ground Engineering Division Structures Group Transport and Road Research Laboratory Old Wokingham Road Crowthorne, Berkshire RG11 6AU

1990

ISSN 0266-7045

Ownership of the Transport Research Laboratory was transferred from the Department of Transport to a subsidiary of the Transport Research Foundation o n 1 st

April 1996.

This report has been reproduced by permission of the Controller of HMSO. Extracts from the text may be reproduced, except for commercial purposes, provided the source is acknowledged.

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LIST OF CONTENTS

1. I N T R O D U C T I O N

2. SOIL SAMPLING

P A G E NO

.

2.1

2.2

2.3

Introduction

Drilling rig and sampling tubes

Drilling and sampling procedures

T H E G R O U N D PROFILE

3.1

3.2

3.3

3.4

Borehole profile

Classification profile

Undrained strength profile

In situ stresses

3

3

4

4

4. TRIAXIAL TESTS

.

4.1

4.2

4.3

4.4

4.5

4.6

Equipment

Calibration of instrumentation

Membrane correciions

Data retrieval and computer control

Specimen preparations and set-up

Types of triaxial test

NEW PLANE STRAIN APPARATUS 11

6. EF F ECTIVE S T R E N G T H ENVE LO P ES - L O N D O N CLAY 13

6.1

6.2

6.3

6.4

Undrained extension tests

Special tests

Passive stress relief tests

Plane-strain passive stress relief test

13

13

14

14

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LIST O F CONTENTS(cont . . )

P A G E NO

.

.

6.5 Triaxial compression tests

6.6 Comparison between triaxial extension

and compression failure envelopes

U N D R A I N E D STIFFNESS - L O N D O N C L A Y

7.1

7.2

7.3

7.4

General

Undrained extension from initial isotropic stress

Undrained extension from initial K o stresses

Undrained compression from initial K o stresses

15

15

15

16

16

16

16

17

V O L U M E T R I C STRAINS - L O N D O N CLAY 17

8.1 General 17

8.2 Swelling from high initial effective stress 18

8.3 Swelling at constant q 18

8.4 Swelling to initial K o stresses 19

8.5 Drained tests 19-

9. U N D R A I N E D STIFFNESS - C L A Y G A T E BEDS

10. D E S I G N P A R A M E T E R S

19

19

10.1 General 19

10.2 Effective strength - Claygate Beds 20

10.3 Effective strength - London Clay 20

10.4 Initial vertical and horizontal s t r e s s e s 20

10.5 The undrained stiffness properties of London Clay and Claygate Beds 20

10.6 Compressibility of London clay and Claygate Beds 20

11. A C K N O W L E D G E M E N T S 21

12. R E F E R E N C E S 21

TABLES

F IGURES

CROWN C O P Y R I G H T 1990. Extracts from the text may be reproduced cxccpt for commerc ia l

purposes provided the source is acknowledged.

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1. INTRODUCTION

The work described in this report forms part of a wider co-ordinated programme of research into the

behaviour and design of embedded retaining walls which is being carried out by the Transport and

Road Research Laboratory (TRRL) on behalf of the Department of Transport.

During the design of the cut and cover tunnel at Bell Common, Epping, Essex, for the M25 orbital

motorway, several geotechnical problems emerged with respect to the design of the in-situ retaining

walls. This led to theoretical investigations of the stability, ground displacements and working stresses

in the structure (Hubbard et al., 1984, Potts and Burland, 1983).

In an attempt to clarify and extend knowledge of the interaction between an in-situ wall and the

surrounding soil, a small section of one of the BeU Common walls has been jointly monitored by the

TRRL and the Building Research Establishment. The field instrumentation has provided information

on wall and soil displacements, strains in the wall, horizontal total stresses and pore water pressures in

the soil both during construction and in the longer term (Tedd et al., 1983, Symons and Tedd, 1989).

Comparisons between the measured and predicted behaviour revealed differences which could be

attributed to a number of causes (Symons et al., 1985).

This report describes a series of laboratory tests on samples of Claygate Beds and London Clay from

Bell Common. The objective of the work was to use the most up-to-date laboratory techniques to

measure the appropriate stiffness and strength parameters. These have since been used for further

finite element analyses to obtain revised predictions of the Bell Common Tunnel and the results

compared with the field observations (Higgins et al., 1989).

The laboratory tests were designed to shear the test specimens along stress paths similar to those to

which soil in the vicinity of an embedded retaining wall are subjected. The dependence of strength and

stiffness parameters on stress path is well known. For example, Hight et al., (1985) show decreased

stiffness and peak shear strengths for specimens of clay tested from an isotropic stress state compared

to those tested from an at-rest state. Stiffnesses were also found to increase significantly where the

stress path changed direction. Researchers have often found strength of a soil to be dependent on

stress level. Bishop et al., (1965) found a curved envelope of shear strength versus stress level for

London clay.

A further factor affecting stress and strain changes to failure is the relative magnitude of the initial

stresses in the ground as represented by the in situ earth pressure coefficient at rest K o . For example,

an overconsolidated soil with a high I( o will be close to passive failure, and will be much further in stress

space from active failure (Symons 1983). It would, therefore, be expected that the form of the stiffness-

strain curves would be different for specimens tested to passive or active failure.

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For an embedded retaining wall the final equilibrium condition and hence the magnitude of the wall

deformations and pressure acting on the structure, will be controlled by the initial stresses, strengths

and stiffnesses in the surrounding ground. It is therefore necessary for the effect of the factors given

above to be investigated if reliable predictions of behaviour are to be obtained from numerical analyses.

2. SOIL SAMPLING

2.1 Introduction

A borehole was drilled to a depth of 21m at the Bell Common Tunnel on the M25 motorway. The

borehole was located about half way along the tunnel, 40m to the north side, to the rear of Wensley

House. Figure 2.1 shows the location of the borehole along with those of other boreholes which were

drilled as part of the site investigation programmes conducted at Bell Common during 1972 and

1977-1988.

2.2 Drilling rig and sampling tubes

A Pilcon Wayfairer Mark 1 rig belonging to Kingston Polytechnic was used to drill the new borehole.

The rig was modified to use thin wall steel sampling tubes. These steel tubes were nominally 100mm

diameter by 700mm long, although often they were shorter. The wall thickness of 1.6mm was less than

the maximum recommended by Hvorslev (1949)for a satisfactory area ratio of the cutting head.

2.3 Drilling and sampling procedures

Concrete anchors were cast in holes which had been excavated near the rig and the rig was tied down

to the anchors.

Generally, the drilling procedure was first to take a sample by pushing the sampling tube in a

continuous motion into the soil. On completion the rods were twisted, the tube withdrawn, detached

and labelled and the ends waxed. The borehole was then augered out to the bottom and the sampling

process repeated.

At the end of each day the samples were transported to Imperial College and stored in the C;onstant

Temperature Store (20 ° C) until used.

Considerable problems were encountered in attempting to sample between depths of 3m and 8m due

to alternating layers of gravel, sand and clay below the water table which was between 3m and 4m deep.

Over these depths it was possible to take only disturbed bag samples.

-3-

In order to overcome the problem of collapse and to seal off the water, casing was driven initially to

8m then further to 8.75m, and finally to 9.01m.

Altogether 31 samples were taken, 3 of them bag samples and the rest tube samples. A drilling record

is shown in Table 2.1 recording the sampling depths, hydraulic 'push' pressure during sampling and the

sample number. The triaxial and plane strain tests carried out on the clay are also listed against the

core lengths in Table 2.1.

3. THE GROUND PROFILE

3.1 Borehole profile

The cores and bag samples are described in Figure 3.1 where the profile is shown. Figure 3.2 is a

photograph of core pieces typical of horizons at 1.5m., 2.5m., 4.5m., 10.9m., 14.0m., and 17.6m.

The top 2m is an Older Head deposit and comprises a firm yellowish - brown sandy, silty clay. From

2m to 8m are the Claygate Beds, a light yellowish brown soft to firm intact clay interbedded with sand

and gravel.

The water table was encountered between 3m and 4m. London Clay forms the remainder of the profile,

starting stiff and jointed and becoming very stiff at about 17m. There are, however, silty horizons, in

particular one just below 11m and another at 14m. Two types of jointing were apparent: a random

small-scale jointing where the joints are clean and often appear slickensided and larger joints passing

across the core with a silty covering.

3.2 Classification profile

A profile of moisture content (liquid and plastic limits and natural moisture content), bulk unit weight

and clay fraction are shown in Figure 3.3. No analyses were carried out on the soil between 3 and 9m.

As expected, the sandy Claygate material has a relatively low plasticity index, unit weight and a clay

fraction less than 40%.

The silty horizons within the London Clay are evident from the profiles on Figures 3.3. A typical clay

fraction of around 50% or more, drops to 30 to 40 for the less plastic material and the plasticity index

reduces from about 50 to about 25 to 30 for the silty horizons. The horizon at around l l m to 12m is

seen to be less silty than that between 13m and 15m.

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In general the natural moisture content was close to the plastic limit, typical o f a stiff overconsolidated

clay.

A study of the adjacent commercial boreholes suggests that the silty horizons are not continuous from

borehole to borehole.

3.3 Undrained strength profile

Undrained strengths from triaxial extension tests are plotted against depth in Figure 3.4. Also shown

are results of undrained extension tests (all tested from an isotropic stress state) carried out on samples

of London Clay (from Bell Common) and reported by Fourie (1984) and Maswoswe (1985). No

plasticity data is available for Fourie's and Maswoswe's tests. Note the exceptionally high strength at

a depth of 13m in the silty horizon.

Figure 3.5 shows the commercial undrained compression tests results from all boreholes at Bell

Common and also the Hellings/Fourie/Maswoswe undrained extension tests superimposed, in addition

those results from the boreholes closest to the new borehole are highlighted.

As would be expected the scatter for results is high due to (a) scale effect duc to the use of 38ram

diameter samples and (b) the natural variability of the clay.

It is of interest to note that the extension tests fall within the spread of results from the compression

tests. Also that the results from boreholes closest to the new borehole are not noticeably different from

those of all the boreholes at the Bell Common Tunnel.

3.4 In situ stresses

An oedometer test carried out on a sample from 15.2m depth (Hellings, 1989) indicated that the present

ground has been overlain by a maximum of 60m of soil corresponding to an overconsolidation ratio of

about 4 at this depth.

In situ horizontal stresses (0" h) have been assessed using both in situ instrumentation and testing and

also indirectly from laboratory suction measurements on triaxial samples.

In situ horizontal stresses at Bell Common between 4m and 15m have been measured by the

Camkometer self boring pressuremeter and also by the C'amkonieter sell" Ix)ring load cell (Windlc and

Wroth, 1977). In addition, push-in Glotzl type spade cells were installed at 6m, 9m and 12m depth

(Tedd and Charles, 1981).

-5-

.,¢

The measurements are shown on Figure 3.6. Note that the spade cell readings are known to over-

read and the given pressures incorporate a correction of half the estimated undrained shear strength

(Tedd et al., 1984).

The water levels in the London Clay were hydrostatic and varied seasonally between 3m and 4m below

the surface, (Hubbard et al., 1984). The profile of porewater pressure ( u ) for a water table at 3m has

been plotted in Fig 3.6. The vertical stress ( Cr v ) has been estimated from bulk density values and

is also shown.

Both the self boring pressuremeter and self boring load cell stress values show a wide scatter.

A full line has been drawn in, lying below the spade cell pressures, and has been extrapolated

downwards. This line is taken to represent the in situ values of 0" h . It should be noted that this line

is shown slightly curved, recognising that the soil will become normally consolidated at some depth

(Hellings, 1989). This is a reinterpretation of the stress distribution used by Ports and Burland (1983).

Suction measurements on triaxial samples were made after the method of Skempton (1961) and Burland;

and Maswoswe (1982) and are described in more detail in a subsequent Section.

Figure 3.7 shows the suction values P°k measured during this investigation. The scatter is large and

the very high values in the silty horizon between 13 and 14m should be noted. In Figure 3.8 the mean

effective in situ stress P'o has been plotted against P'k, the P'o values being estimated from Figure 3.6.:

The points fall to the right of the 45 ° line and lie in 2 clusters, one with an average P'k about t00 kPa t greater than Po and another about 350 kPa greater. Several of those in the latter group appear to be

from silty samples. Very high values of p~could also indicate a negative porewater pressure parameter

(As) which may be compatible with silty material (Bishop and Henkel, 1962),

It is of interest to note that Jardine (1985) also measured suction values for London clay samples from

Canons Park about 100kPa greater than actual in situ values of P'o" He ascribed this mostly to

disturbance during sampling operations. It is, however, likely that the high suction values are also due

to a drying out of the samples during preparation prior to testing (ie. during trimming a 38mm sample

from 100 mm core). The four black points in Figure 3.7 were obtained by Burland and Maswoswe

(1982) on 100mm samples and are all on the lower limit of the scatter, presumably due to the fact that

very little sample preparation was necessary. The at rest earth pressure coefficient can be deduced from

the measured values of P'kusing the expression given by Skempton (1961):

K o = ( p ' k / O ' v - A s ) / ( 1 - A s ) 3.1

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Using this expression Burland and Maswoswe calculated two values of K o corresponding to A s = 0.5

(likely for London clay for the stress range involved) and A s = 0.3. The corresponding values of O" h

are shown in Figure 3.6 as crosses.

d

It is interesting to com pa re the theoretical values of Pk deduced from equation 3.1 with the expression i

for Po derived f rom a knowledge of K o :

f

P k = cr',, [ K o • A s ( I - K o )] 3.2

Po = cr' v ( I ÷ 2 K o ) 1 3 3.3

e

According to these expressions p k and p o will be equal only for values of K o = 1 and A s = 1/3. Also e m r

the difference between p k and p o will vary for different values of K o and A s. Thus the values of Pk #

should not necessarily be equal to p o"

4. T R I A X I A L TESTS

4.1 Equipment

All the testing was carried out in the research laboratories at Imperial College (I.C.), which are

t e m p e r a t u r e controlled to 20 ° ± 1C. Two stress path ceils were used and the general arrangement is

shown in Figure 4.1.

Each cell had 3 pressure transducers, one each to measure cell, pore water and ram pressure. The pore

water volume changes were recorded by a 50cc I.C. automatic volume gauge, one for each cell. The

axial loads were measured by means of 450 kg capacity I.C. internal load cells.

Mid-height surface mounted Druck piezometer probes were used for all the tests (Hight, 1982). The

p robe is 6.5mm diameter and incorporates a small silicon diaphragm into which is diffused a full semi-

conductor strain gauge bridge.

Measu remen t s of local vertical strains were made with a pair of electrolevel gauges attached to

diametrically opposi te sides of the sample (Burland and Symes, 1982). During the test programme the

electrolevel gauges were replaced by new strain gauged pendulum gauges.

4.2 Calibration of instrumentat ion

M a n y of the tests described in this report were carried out at low effective stresses. The accuracy of

the calibration was thus even more important than might usually be the case. Frequent recalibrations

were carried out with no significant changes encountered.

2

-7-

The load cells were calibrated using a Budenberg dead weight calibrator. Three cycles of loading and

unloading were used. For tension calibration the load cell was suspended in a heavy duty steel f rame

and dead weights applied through a hangar. Most of the tests were carried out with deviatoric loads

rarely above 1000N and usually below 100N. The error over this range never exceeded + 0.5N and was

usually less than +0.1N.

Although local strain measurements were made for most of the tests, nevertheless each load cell was

calibrated for its compliance so that the externally measured deflections could be corrected. Correct ions

were also made for the compliance of the porous stones.

The volume gauges were calibrated against a burette over the whole range of 50ml. The mean er ror

was found to be approximately +0.05ml.

4.3 Membrane corrections

Two expressions for axial and radial stress corrections for membrane restraint that are presently in use

are: that derived by Henkel and Gilbert (1952) and that by Duncan and Seed (1967).

Hellings (1989) has carried out an extensive investigation on membrane restraint which included

numerous laboratory tests on rubber dummy triaxial specimens in tension and compression and also

finite element analyses. The following conclusions were drawn:

(i) The Duncan and Seed expressions are appropriate for most situations.

(ii) The corrections must be applied in compression as well as extension even though the m em b rane

often buckles in compression.

(iii) Young's modulus for latex membrane decreases during soaking in water from about 1400kPa to

about l l00kPa after one month.

The Duncan and Seed expressions for axial and radial stress corrections respectively are as follows:

A(T a = ( -BEre t o) (2E:a÷E: r} 1 311o(1 - Er )2 (1 - E a ) 4.1

A(T r = ( - 4 E m t o ) ( E a - Z E r ) / 3 D o ( i - E~r )2 ( 1 - E: a } 4.2

Where E a and E r are the specimen axial and radial strains respectively (E a is positive

for compression and EriS negative for bulging),Emis Young's modulus for the membrane

and t o and D o are the initial membrane thickness and specimen diameter .

-8-

It should be noted that the specimen radial strain can be expressed in terms of its volumetric (gv) and

axial (g a ) strains as follows:

E r = (1 - E v)1/2 / ( 1 - E a)1/2 _1 4.3

Note that E v will be positive for specimen contraction.

All the triaxial test results repor ted here are corrected using the Duncan and Seed theory.

As an example consider test TLPS1 (see Section 4.6) for which E m = l l00kPa (long duration test),

membrane thickness = 0.3mm, initial sample diameter = 38.26mm and the final axial and volumetric

strains = -16% and -9% respectively. The axial and radial stress corrections are 6.5 kPa and 2.1 kPa

respectively. The radial stress correct ion includes the effect of the unstressed membrane diameter being

less than the initial specimen diameter .

4.4 Data retrieval and computer control

The data retrieval system consists of a Solartron Orion connected to a Prime computer. The system

is shown diagrammatically in Figure 4.2. A Solartron 3530 Orion A unit logs the data. Each

measurement by the analogue/digi tal converter is a continuous integration of 150 readings per second.

The range for each channel is automatically established leading to high sensitivity.

The transducers are linked to the Orion by a work station containing its own power supply and signal

conditioning cards.

The Orion is connected to the Prime computer using two lines: one line for sending commands to the

Orion, the other for outputt ing all logged data.

A pen plotter, line printer and magnetic tape drive are accessible through the Prime computer as are

a graphics terminal and a printer.

The computer control system is shown schematically in Figure 4.3 and comprises a microcomputer,

analogue to digital converter and two types of controller (air valve or ram pump) driven by a stepper

motor drive unit.

T h e r e are three air valve controllers, Box 1 to 3, for the pore water, cell and ram pressures. The

controllers are step motor driven manostat air regulators adjustable in increments of 0.07 kPa.

-9-

A constant rate of strain 'ram' pump was manufactured for this test programme. Its volume can be

adjusted in steps of 0.0002ml and its control is labelled 'box 4' in Figure 4.3.

4.5 Specimen preparations and set-up

The core was extracted from the sample tube by pushing in the same direction of travel as the sampling

operation. Specimen trimming was carried out using a wire saw and frame. Triaxial specimens were

trimmed to 38mm diameter, 76mm long. When the sides had been t r immed the specimen was placed

in a split former and the ends cut square.

Saturated porous stones together with a soaked filter paper disc were used at the lop and bottom of

each sample. A small coil of fuse wire, as recommended by Burland and Maswoswe (1982), was used

at each end of the sample to separate it from the saturated stones and so prevent the high suction in

the clay from drawing water into the sample from the stones. On application of the cell pressure the

wire coils embed themselves in the sample as contact is established between stone and sample.

The rubber membrane was checked for holes and a rubber grommet for holding the pore pressure

probe was fitted at the mid-height and sealed with three coats of liquid latex. Three 0- rings were used

top and bottom to seal the membrane to the end plattens. The mid-height pore pressure probe was

installed in the grommet; the ceramic face having first been coated with a kaolin slurry to prevent

cavitation. The probe was then pushed into the grommet to touch the sample side. Two 0-rings were

used to clamp the grommet to the probe and the assembly was then coated with Ihrce layers of latex

solution.

The local strain measuring devices were attached and the cell was lowered over the specimen and

clamped. The cell was filled with de-aired water and pressurised without drainage. A high pressure

of about 700 kPa was used to saturate the sample and permit the measuremenl of the initial suction

P'k • The pore water pressures, as recorded by the probe and base transducers, usually equalised (and

stabilised) within about a day, and this reading was then used in the calculation of P'k " The values of

Skempton's pore water pressure parameter B were usually in excess of 0.95.

4.6 Types of triaxial test

The strain rates employed for the drained and undrained tests were 0.5% and 5% per day respectively

and were based on previous work on the London Clay. Pore pressure gradients were checked using the

mid-height probe and the pore pressure differences between mid-height and the ends were kept below

5 kPa.

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The following types of tests were carried out, listing the terminology:

TX---Y

UU

CU

D

T denotes triaxial and X the matcrial, L for London Clay, C

for Claygate beds. Y is the test number and --- the type of test

as follows:

Unconsolidated undrained extension tests from the initial

isotropic effective stress.

Specimens swelled isotropically and sheared undrained in

extension.

Specimens swelled back isotropically and sheared drained in

extension.

In order to return some of the specimens to in situ stress conditions and so to minimise sampling

effects, they were allowed to swell or consolidate from the initial isotropic stress state to the estimated

in situ stress conditions (Ko). The following five types of test were then carried out:

D R U L

SU

A

U A

SUD

PS

Drained shear under, decreasing axial stress and zero lateral

strain conditions.

Undrained shear in extension.

Drained shear in compression with the vertical stress constant

and lateral stress reducing to simulate active conditions.

Undrained shear in compression with the vertical stress

constant and lateral stress reducing to simulate active

conditions.

Undrained shear in extension to almost 80% estimated failure

stress. Pore pressure then increased at constant deviator stress

until failure achieved.

Passive stress relief tests. The specimens were sheared

undrained in extension to about 80% failure stress. The cell

pressure line was then switched to the mercury stand pipe and

a passive stress relief test carried out drained as described by

Burland and Fourie (1985). One mercury tube of 7.92mm 2

area was used for the passive stress relief tests. Two of the

passive stress relief tests (TLPS4 and 5) were carried ou! using

computer control. For these two tests a constant rate of axial

extension was applied and the cell pressure was set to redt, cc

in a fixed proportion to the axial strain.

-11-

Table 4.1 gives a complete summary of all the triaxial tests carried o u t on the Claygate Beds and

London Clay and Figure 4.4 shows the failure modes of all the specimens.

In reading Table 4.1, the following points should be noted:

Extension tests were conducted by decreasing the vertical stress and maintaining the

horizontal stress.

q'-- {0"~ - 0"~) is zero under Koconditions for the Claygate specimens as gohas been taken

as unity.

gostresses are not given where the specimen has been sheared from an isotropic stress

state.

The phrase'ff after isotropic swell or consolidation'refers to the isotropic stresses prior

to swelling anisotropically to K o or shearing.

the TLD1 test is labelled 'Drained/Undrained ' as some pore water pressures were

generated during shearing, although the specimen was nominally drained.

The tests modelled the stress paths followed by elements of soil in the vicinity of an embedded retaining

wall at the following locations:

• Behind the wall - test A or UA depending on the amount of drainage allowed.

• In front of the wall - test PS or test SUD, depending on drainage allowed

• In front but remote from the wall - test DRUL, corresponding to full drainage.

5. NEW PLANE STRAIN APPARATUS

A new plane strain apparatus was designed and constructed with the express purpose of determining

the behaviour of soils subject to passive stress relief under conditions of plane strain. Although a plane

strain device was available at I.C. (Atkinson, 1973) it only had limited travel and, more importantly, it

was not adapted for extension tests - a pre-requisite for passive stress relief testing.

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Figure 5.1 is a drawing of the new apparatus set up in the stress path cell and Figure 5.2 shows an

elevation and sectional plan of the apparatus. Photographs of the equipment are shown in Figures 5.3

and 5.4. A full description of the equipment is given by Hellings (1989) and only the essential features

will be described here.

The primary design requirements were:

(i) that both compression and extension tests could be carried out and

(ii) that it should be possible to test a prismatic specimen cut from a nominal 100mm

diameter tube sample.

A key feature of the new apparatus is that the top and bottom platens (4) and (5) (see Fig. 5.2) are

enclosed within the membrane surrounding the sample. The membrane is open at either end

horizontally and is splayed so that it is clamped to the polished side platens (10) and (11). This

ar rangement permits extension tests to be carried out.

In summary, therefore, the vertical stress is applied through the top and bottom platens (4) and (5).

The lateral stress is applied through the membrane by means of the cell fluid. Plane strain is

maintained by ensuring that the distance between the polished side platens (10) and (11) is fixed by

means of the tie rods (20).

Provision is made for one of the side platens (11) to be adjustable so that during isotropic consolidation

the platen will move laterally but on commencement of plane strain testing it is fixed. The intermediate

stress in the direction of zero horizontal strain is measured by means of a load cell (9).

The apparatus is housed in a large stress path cell that was originally developed for testing 100mm

diameter samples. The great advantage of the type of cell construction is being able to assemble the

plane strain apparatus and specimen prior to encasing them in the perspex surround. Figures 5.3 and

5.4 show photographs of the apparatus in pieces and of the whole assembly.

The apparatus was used to carry out a passive stress-relief test on a sample of London Clay from Bell

Common. The size of the specimen was 83mm long by 77mm high by 40mm wide. The test took over

six months to carry out due to the small area of the porous stones in the top and bottom platens. The

specimen was fitted with a local pore pressure probe and also local strain measuring devices. In

processing the results corrections were made for membrane restraint and for side friction on the side

platens.

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The failure mode of the specimen is shown in Figure 4.4 (Specimen labelled PLPS1) and a photograph

of the failed specimen is shown in Figure 5.3 The stresses are detailed in Table 4.1.

6. E F F E C T I V E S T R E N G T H ENVELOPES - LO N D O N CLAY

6.1 Undrained extension tests

Figure 6.1 shows the undrained effective stress paths in q-p 'space for the undrained extension tests on

London Clay ( q is the deviator, or shear stress (0" 1' -0"~ ) and I 3' the mean normal effective stress

L (0"~÷0"~÷0"~)). The majority of tests were sheared from initially isotropic stress conditions. Samples 3

TLCU1 and 2 were allowed to swell isotropically to low stresses prior to undrained shearing. Samples

TLSU1 and 2 were swelled to at rest pressure conditions prior to shearing. It can be seen that during

undrained shear [3' remains approximately constant and the stress path reaches failure with very little

deviation from the pre-failure path.

Figure 6.2 shows the points of maximum shear stress plotted in q-p ' space. Most of the points lie on

a well defined envelope shown by the thick broken line. It can be seen that the envelope is curved. The

chain dotted lines correspond to various values of effective angle of friction qb ° . At values of

p' less than about 100 kN/m 2 the envelope corresponds to qb'= 32 °.

6.2 Special Tests

Two special extension tests (TI_,SUDLA and 2B) were carried out in which an at tempt was madc to

simulate the process of undrained unloading followed by pore pressure increase at constant shear stress.

Figure 6.3 shows the stress paths for these two tests in q -p ' space . The broken line in this Figure

represents the failure envelope for the undrained extension tests (Figure 6.2). It can be seen that one

failure point lies slightly below the undrained failure line, while the other lies above it.

Also shown in Figure 6.3 are the stress paths for the tests in which an at tempt was made to maintain

zero lateral strain conditions during drained shearing under decreasing axial stress (tcsts T L D R U LI

and 2). It can be seen that the stress paths for both tests touch the undrained failure envelope in

extension but do not cross it.

Test TLD1 is also shown on Figure 6.3. This specimen was nominally sheared drained in extension, but

excess pore water pressures in the early part of the test caused the stress path to deviate from the

normal drained stress path.

-14-

6.3 Passive stress relief tests

Al together five passive stress relief tests were carried out such that the strength of the soil was fully

mobilised (TLPS1 to 4 and 6). The stress paths for each of these tests is plotted in Figure 6.4. The

broken line represents the failure envelope for the undrained extension tests (Figure 6.2).

It can be seen that the stress paths for the passive stress relief tests all cross the undrained failure line

giving values of ~' well in excess of the undrained values. Tests 1 and 4 give stress paths which move

a long way down towards the origin remaining outside the undrained envelope and then move back

inside it as failure progresses with decreasing values of p'.

The reason for the passive stress relief paths lying outside the undrained failure envelope, when the

results from the special tests described in the preceding section apparently coincide with it, is not

unders tood at this time. The phenomenon may indicate an important element of conservatism in the

use of traditional methods for deriving strength parameters, for use in designs involving this type of

stress path.

6.4 Plane-strain passive stress relief test

A single passive stress relief test was carried out in the plane-strain apparatus. The results of the test

are plotted in Figure 6.5 in terms of q*-p where q* is the three-dimensional deviator stress and p is

the mean of the three principal effective stresses.

q. _ 1 ~'1 [ ( O'h _ O'p' )2 ÷ ( C)'; - 0" v )2 ÷ (0. , v _ (7 h }2 ] 112 (L l

Where O~,O 0 and O' v are the horizontal, plane strain (also horizontal) and vertical effective stresses

respectively.

The broken line represents the failure envelope for the undrained triaxial extension test (Figure 6.2).

It can be seen that, as for the triaxial passive stress relief tests, the stress path moves well outside the

failure envelope for the undrained extension tests.

This single test result provides important additional evidence to support the notion that the strength

under conditions of passive stress relief may be significantly greater than that inferred from conventional

extension tests.

-15-

6.5 Triaxial compression tests

This study has been directed principally towards a study of the soil properties in the passive zone on

the excavation side of the wall - hence the emphasis on extension tests. Only three compression tests

were carried out - two drained tests following active stress paths with O" v constant and 0"~ decreasing

(TLA1 and 2A) and an active undrained test (TLUA1).

The above data from this study has been supplemented with three consolidated undrained tests carried

out by Fourie and three consolidated drained tests by Maswoswe on high quality samples from Bell

Common. In addition a number of commercial consolidated drained triaxial compression tests were

carried out during the original site investigation.

Figure 6.6 shows the peak values of q against p' for these data. There is good agreement between

Fourie's undrained tests and Maswoswe's drained tests. The two active drained tests (TLA1 and 2A)

appear to agree with the standard tests but the consolidated undrained test TLUA1 gives a high

strength, although within the scatter of other test results. The commercial tests on samples from nearby

boreholes show a significant scatter.

The broken line in Figure 6.6 represents the best estimate of the failure envelope for triaxial

compression tests on the London Clay at Bell Common.

6.6 Comparison between triaxial extension and compression failure envelopes

The failure envelopes in Figures 6.2 and 6.6 for extension and compression respectively cannot be

directly compared because of the characteristics of a q - p° plot. However, they may be superimposed

i n a p l o t of t - s ' where t - -q /2 and s'= (0"°h÷ 0" v ) / 2

Figure 6.7 shows the two failure envelopes transformed to such a plot. It can be seen that for any given

average stress s ' , the strength in extension is between 10kN/m 2 and 20kN/m 2 weaker than in

compression. This difference appears to b~ due largely to an apparent cohesive intercept on the

compression side.

Figure 6.8 shows the mobilised friction angle plotted against shear strain from extension, compression

and passive stress relief tests on specimens from similar depths and initial in situ stress conditions. This

illustrates that for small shear strains the qb' mobilised in the passive direction is likely to exceed that

in the active.

-16-

7. U N D R A I N E D STIFFNESS - L O N D O N CLAY

7.1 Genera l

The following three types of undrained triaxial test were carried out:

(i)

(ii)

(iii)

Undra ined extension from initial isotropic stress

Undra ined extension from initial K o stresses

Undra ined compression from initial g o stresses

The majority of tests were for type (ii) and only one was of type (iii).

The results for (i) are presented separately in a plot of normalised secant undrained shear modulus

Gu/p ' versus log shear strain (Figure 7.1). Stiffness for undrained extension and compression tests from

K o are plotted together in Figure 7.2. Claygate tests are also shown on this plot and the results arc

discussed later in Section 9.

7.2 Undra ined extension from initial isotropic stress

Figure 7.1 shows a composi te plot of Gu/p' versus log shear strain for four of the tests TLUU1, 3,4 and

5. It can be seen that the results fall in quite a narrow range. The values of Gu/p' at 0.01 per cent

strain range from 97 to 166.

7.3 Undra ined extension from initial Ko stresses

Figure 7.2 shows a composite plot of secant Gu/p' versus log shear strain for the undrained shearing

stage of the following tests: TLSU1 and 2, TLPS1, 3,4 and 6 and TLSUDIA and 2B. Values of Gu/p'

at .01 per cent strain range from 130 to about 300. For comparison, ranges for the undrained extension

tests from an isotropic stress state at 0.01 per cent strain are shown. The stiffness at 0.(ll per cent strain

for the tests from K o is about twice that for the tests from initial isotropic stress. However, for strains

in excess of about 0.1 per cent the stiffnesses are much more comparable.

For comparison the results of the drained phase of test TLPS2 are shown in Figure 7.2. The agreement

with the undrained results is very reasonable.

-17-

7.4 Undrained compression from initial Ko stresses

Only one undrained compression test of this type was carried out (TLUA1) and the result is shown in

Figure 7.2. The result compares reasonably well with the extension tests at low stains but the stiffness

in compression reduces less rapidly with increase in strain. This phenomenon simply reflects the larger

changes in shear stress and hence strain that are required to bring the sample to failure in compression

from an initial stress state with K o greater than unity.

For comparison the results of drained compression tests from K o conditions (TLAI and TLA2A) are

shown in Figure 7.2. The agreement with the undrained test is seen to be very reasonable.

8. VOLUMETRIC STRAINS - LONDON CLAY

8.1 General

The five phases of the various tests that were carried out may be used to study the volumetric behaviour

of the London Clay:

(i)

(ii)

(iii)

(iv)

(v)

Swelling from high initial effective stress under approximately one-dimensional

conditions.

Swelling under conditions of constant shear stress.

Swelling from initial stress to in situ l( o stresses

Drained triaxial tests

Swelling under passive stress relief

For most of the phases, sufficient readings are not available from the early portions of the tests to

examine the bulk modulus at very low volumetric strains. However, data from 7 tests has been plotted

in Figure 8.1 against axes of normalised effective secant bulk modulus (K'Ip') versus volumetric strain

[E v ) : TLPS passive stress relief phase and also anisotropic swelling phase and anisotropic swelling

phases from the following tests - TLPS1, 2, 3 and 4, TI_,SU1, TLSUDIA and TLDRUL2. Although

the apparent very high stiffness for some of the tests may be due to incomplete drainage during the

early part of the phase and despite the scatter between the tests being high, the results nevertheless

show decreasing normalised bulk modulus at higher volumetric strains. This is similar to results

obtained by Jardine (1987) on triaxial tests on London Clay.

In order to examine the large volumetric strain region in more detail the entire phases (i) to (iv)

mentioned above have been examined further. These are discussed separately in the following sections.

-18-

Jardine et al., (1986) have shown that a logarithmic function can be fitted to the measured relationship

between secant K'Ip' and volumetric strain E v. The function is written:

K' /p ' = R * Scos [ 5 (toglo ~,,/T) 3k] 8.] where R, S, T, 8 and ~k are all constants

The tangent K'Ip' can be obtained by differentiating the above expression with respect to E v ,

If the secant K'Io' is called X , then

tangent K' / p' = X - ( S 5 3k / 2. 303) ( loglo E,, / T )~.-1 [ sin 5( lOglo E: v / T)X ] 8.2

8.2 Swelling from high initial effective stress

Figures 8.2 and 8.3 show the results of tests T L D R U L 1 and 2 plotted in terms of volumetric strain

versus log p' during swelling under K o conditions from high initial values of p' . It can be seen that

for most practical purposes these portions of the swelling curves are linear. The normalised tangent

bulk modulus can be calculated from the following expression:

K' /p ' = 2 ( p l - P~) / A E v (p l " P'f)

Where Pl , P'f are the effective stresses at the beginning and end of the swelling phase and ~:v

is the resulting volumetric strain.

values of tangent K'/p' = 58 and 50 are obtained for tests TLDRUL1 and 2 respectively.

T h r e e tests (TLD1, CU1 and CU2) entailed isotropic swelling from high initial values of 13' No

measurements of volumetric strain were made during the swelling process bul the equilibrium values

were recorded. The associated values of tangent K'lp' were 26, 44 and 25 respectively.

8.3 Swellin~ at constant q

T h e two tests for which swelling took place at constant shear stress were T L S U D I A and 2B and the

associated stress paths are shown in Figure 6.3. The relationships between volumetric strain and log

p' are plotted in Figures 8.4 and 8.5. In both cases the relationship is remarkably linear. The values

of tangent K'/p' for the two tests are 24 and 13 respectively.

-19-

8.4 Swelling to initial K o stresses

A large number of tests were carried out in which the samples were swelled from initial isotropic stress

to K o conditions prior to carrying out other tests. The swelling characteristics of these tests are given

in Table 8.1.

8.5 Drained Tests

Three drained tests were carried out. The initial stages of test TLPS2 were drained prior to passive

stress relief testing. Also two active drained tests were carried out from initial K o conditions (TLA1

and 2A). The swelling characteristics of these latter two tests are plotted in Figures 8.6 and 8.7 in terms

of volumetric strain versus log p'. It can be seen that over the initial part of the tests, when the samples

are remote from failure, there is a linear relationship between volumetric strain and log p' .

All the values of K'/p' mentioned in the above sections are shown in Tables 8.1 and plotted against

depth in Figure 8.8. It can be seen that most of the values lie between 20 and 40. However , in the

more silty layer between 13m and 15m depth distinctly higher values of between 60 and 100 were

measured.

9. U N D R A I N E D STIFFNESS - C L A Y G A T E BEDS

As described in Section 2 sampling in the Claygate Beds proved very difficult. However samples were

taken from depths of between 1.8m and 2.9m. Three undrained tests were carried out. Test T C U A I

was an undrained active test carried out from isotropic stress conditions. Test T C U U I was an

undrained extension test carried out from isotropic stress conditions. Test TCPSI was a passive stress

relief test but the initial part of the test was undrained from isotropic stress conditions. The results are

plotted on Figure 7.2. It can be seen that the results fall in a narrow range. The value of Gu/p' at [).()1

per cent strain is about 600. Hence, at this level of strain, the material is two to three t imes stiffer

than the London Clay.

10. D E S I G N P A R A M E T E R S

10.1 General

In this Section the results of the test programme, together with the results of previous investigations,

are summarised to provide the best estimates of the soil parameters needed for carrying out a finite

element analysis of the Bell Common Tunnel retaining walls. The emphasis of this analysis is directed

towards the deformations anti stresses set up during and subsequent to construction (Higgins ct al

1989).

-20-

10.2 Effective strength - Claygate Beds

Two tests are available from this programme. These results together with some from the commercial

tests are plotted in Figure 10.1 in terms of t versus s ' . An envelope drawn through the tests gives

a v a l u e o f ~ ' = 32.7 ° a n d c' = 0.

10.3 Effective strength - London Clay

Figure 6.7 shows the effective strength failure envelopes for the London Clay for compression and

extension.

10.4 Initial vertical and horizontal stresses

The full lines in Figure 3.6 give the variation in both cr v and cr h with depth. The pore water pressures

are also shown.

10.5 The undrained stiffness properties of London Clay and Claygate Beds

Jardine et al (1986) have shown that a logarithmic function can be fitted to the measured relationship

between secant 6u/p' and axial strain E a observed in undrained triaxial tests.

The function is written:

6u/p' -- A* Bc0s [0t{10gl0Ea/C) Y ]

where A, 13, C, 0; and Y are constants

10.1

The values of constants to give a fit for an above expression are listed in Table 10.1. The resulting

curves drawn through the data, are shown in Figure 7.2 in terms of shear strain E s (equal to axial strain

in undrained tests). The non linearity of the three curves should be noted, showing stiffness to be

dependent on the strain level.

10.6 Compressibility of the London Clay and Claygate Beds

A mean line drawn through the results of Figure 8.1 is almost exactly coincident with a curve derived

by Jardine (1987) for tests on London Clay of the form of the logarithmic function given in .";ection

8.1. The values of the constants for the function are given in Table 10.1. A volumetric strain cut off

limit of maximum Ev (ie. elastic limit) of 0.185 per cent has been selected as the point at which the

tangent modulus of the normalised bulk modulus equals the mean K'/p' of 30 derived from Figure 8.8.

-21-

No measurements of K' were made for the Claygate Beds. With the stiffness for the Claygate around

2.5 times more than that of the London Clay it is suggested that a bulk modulus expression equally

stiffer than that derived for the London Clay be adopted. The constants are given in Table 10.1.

11. ACKNOWLEDGEMENTS

The work described in this report forms part of the programme of research of the Ground Engineering

Division (Division Head Dr. M.P. O'Reilly) of the Structures Group of the Transport and Road

Research Laboratory. The report is published by permission of the Director.

12. REFERENCES

Atkinson J.H., (1973): The Deformation of Undisturbed London Clay. Ph.D. Thesis. University of

London.

Bishop A.W., Webb D.L., and Lewin P.I., (1965): Undisturbed Samples of London Clay from the

Ashford Common Shaft: Strength-Effective Stress Relationships. Geotechnique 15 ; no. 1; 1-31

Bishop A.W., and Henkel D.J., (1962):

Edward Arnold, London.

The Measurement of Soil Properties in the Triaxial Tests.

Burland J.B., and Maswoswe J., (1982): Discussion. Geotechnique 32; 3; 285 - 286.

Burland J.B., and Symes M., (1982). A Simple Axial Displacement Gauge for use in the Triaxial

Apparatus. Geotechnique 32; 1; 62-65.

Burland J.B., and Fourie A.B., (1985): The Testing of Soils under Conditions of Passive Stress Relief.

Geotechnique 35; 2; 193-198.

Duncan J.M., and Seed H.B., (1967): Corrections for Strength Test Data. Journal S.M., and F. Div.,

ASCE., 93; SM5; 121-137.

Fourie A.B., (1984): The Behaviour of Retaining Walls in Stiff Clay. Ph.D. Thesis. University of

London.

Henkel D.J., and Gilbert G.D., (1952): The Effect of Rubber Membrane on the Measured Triaxial

Compression Strength of Clay Samples. Geotechnique 3; 1; 20-29.

-22-

Hellings, J.E. (1989): The Strength and Stiffness of Soils Associated with Excavations. Ph.D. Thesis,

University of London.

Higgins, K., Potts, D.M., and Symons I.F. (1989): Comparison of Predicted and Measured Performance

of the Retaining Walls of the Bell Common Tunnel. Contractors Report no. 124; Transport and Road

Research Laboratory; Department of Transport.

Hight D.W., (1982): A simple Piezometer Probe for the Routine Measurement of Pore Pressures in

Triaxial Tests on Saturated Soils. Geotechnique 32; 4; 396-402.

Hight D.W., Gens A. and Jardine R.J., (1985): Evaluation of Geotechnical Parameters from Triaxial

Test on Offshore Clay. Advances in Underwater Technology and Offshore Engineering 3; 253-268.

Published by Graham and Trotman Ltd..

Hubbard H.W., Potts D.M., Miller D., and Burland J.B., (1984) : Design of the Retaining Walls for

the M25 Cut and Cover Tunnel at Bell Common. Geotechnique 34; 4; 495-512.

Hvorslev M.J., (1949): Subsurface Exploration and Sampling of Soils for Civil Engineering Purposes.

US Waterways Experimental Station.

Jardine R.J., (1985): Investigation of Pile-Soil Behaviour, with Special Reference to the Foundations

of Offshore Structures, Ph.D. Thesis, University of London.

Jardine R.J., Potts D.M., Fourie A.B., and Burland J.B., (1986): Studies of the Influence of non-linear

Stress-Strain Characteristics in Soil-Structure Interaction. Geotechnique 36; 3; 377-396.

Jardine R.J., (1987): Personal Communication.

Maswoswe J., (1985) : Stress Paths for a Compacted Soil during Collapse due to Swelling. Ph.D.,

Thesis, University of London.

Potts D.M., and Burland J.B., (1983): A Numerical Investigation c-f the Retaining Walls of the Bell

Common Tunnel. TRRL Supplementary Report 783. Crowthorne, Berks., UK..

Skempton A.W., (1961): Horizontal Stresses in an Overconsolidated Eocene Clay.

Conf., SMFE, Paris, Vol., 1, 351-387.

Proc., 5th Int.,

Symons I.F., (1983): Assessing the Stability of a Propped, in situ Retaining Wall in Over-consolidated

Clay. Proc. Inst. Civ. Engrs., Part 2, December, 617-633.

-23-

Symons I.F., and Tedd P., (1989): Behaviour of a Propped Unbedded Retaining Wall at Bell Common

in the Longer Term. Geotechnique 39;4.

Symons I.F., Potts D.M., and Charles J.A., (1985): Predicted and Measured Behaviour of a Propped

Retaining Wall in Stiff Clay. Proc., l l th Int. Conf. SMFE, San Francisco, Volume 4, 2265-2268.

Tedd P., and Charles J.A., (1981): In Situ Measurement of Horizontal Stress in Over-consolidated Clay

using Push-in Spade-Shaped Pressure Cells. Geotechnique 31; 4; 554-558.

Tedd P., Chard B.M., Charles J.A., and Symons I.F., (1984): Behaviour of a Propped Embedded

Retaining Wall in Stiff Clay at Bell Common Tunnel. Geotechnique 34; 4; 513-532.

Windle D., and Wroth C.P., (1977): The use of a Self-Boring Pressuremeter to Determine the

Undrained Properties of Clays. Ground Eng., 10; 6; 37-46.

%z~ILY~S

D a t e

I TRANSPORT & ROAD RESEARCH LABORATORY

D e p t h ( m ) f r o m

1 9 . 8 . 8 5 0 0.6

t . 2 1 . 8 2 . 3

2 . 9 3

4 . 0 S.O

8 . 0

2 1 . 8 . 8 5

2 2 . 8 . 8 5 8 . 8

9 . 3 1 0 . 2 1 0 . 7 11

1 1 . 9

1 2 . 5 13 .1 13 14 14

2 7 . 8 . 8 5 16

t o

!

D r i l l i n g R e c o r d f o r New R o r e h o l o at: B e l l Common (NOTE: A l l t u b e s a m p l e s u n l e s s o t h e r w i s e : ' t i t L e d )

r

llydraulic p r e s s u r e (Ibs/inch 2)

0.6 700 1.2 1000

1.8 1600

2.3 I000

2.93 2400

4.0 2400

4 . 5 2 4 0 0 . 0

8 . 6 1 2 0 0

8 . 1 6 8 . 6 6 1400

9.3 1400

10.2 1500 1 0 . 8 8 I000

11.52 1200 .52 11.85 2400

12.5

1 3 . 0 5 2400

13.67 1600 .67 14.24 1800 .24 14.83 2 1 0 0 . 8 3 1 5 . 3 5 2300 .21 16.61 2400

1 7 . 1 4 2 2 0 0 1 7 . 6 7 2 2 0 0 1 7 . 9 3 2 0 0 0 1 8 . 5 3 2 2 0 0 1 8 . 9 4 i 2400 I 1 9 . 3 5 I 2 2 0 0

2 0 . 0 0 2 1 0 0 2 0 . 5 4 2 4 0 0 2 1 . 0 2 2 3 0 0

1 6 . 7 1 7 . 2 1 7 . 4 5 1 7 . 9 3

2 8 . 8 . 8 5 1 8 . 5 9 1 8 . 9 4

1 9 . 5 5 2 0 . 1 1 2 0 . 6 9

C o n n f l e n t S

T o p s o i l , r o o t s . S a n d y c l a y . O b s t r u c t i o n ( s t o n e s ? ) C l a y g a L C o O b s t r u c t i o n ( s t o n e s ) n e a r

b o t t o m . A u g e r t h r u ' g r a v e l . Bag

s a m p l e . W a t e r a t a b o u t 4m.

H o s t l y g r a v e l , c l a y m a t r l x . T u b e s a m p l e n o t p o s s i b l e :

s a n d a n d s t o n e s . Bag s a m p l e f r o m a u g e r .

Tube s a m p l e t a k e n : S a n d c l a y m i x t u r e ( d i s t u r b e d ) . R o r e h o l e c a v l n E b a d l y . Hove 0 . S m , r e d r t l l a t l a r g e r d J a m e t e r t o 8m a n d c a s e h o l e .

C o r e s a m p l e f r o m 8 . 1 6 m : a g a i n m o s t l y s a n d a n d s t o n e s .

C a s i n g d r i v e n f u r t h e r t o 8 . 7 5 m . L o n d o n c l a y .

L o n d o n c l a y . L o n d o n c l a y . L o n d o n c l a y .

C l a y s t o n e o b s t r u c t i o n : A u g e r t o 1 2 . 4 8 m .

C l a y s t o n e / L o n d o n c l a y : b a g s a m p l e .

L o n d o n c l a y L o n d o n c l a y L o n d o n c l a y L o n d o n c l a y L o n d o n c l a y Saml, l e t u b e f , l l o f s i l t / s a n d . D e e p e n c a a i n g t o 9 . 0 m . L o n d o n c l a y . L o n d o n c l a y . L o n d o n c l a y . LondoH c l a y . London c l a y . ] .ondut~ c l a y : t h e c o r e t ~

d r y d u e t o p o o r waking. London c l=y . Lo=.Jo~ c l a y . l . ondon c l a y : d r y c o r e ( I J o o r u a x i = t E ) . EI . I o f b A r e h o I e .

S a m p l e n o .

T e s t s p e c i m e n s f r o m t h i s c o r e

l e n g t h

Q

TCUUt, TCPSI TCUAI

7 8

9

10

I1

12 13 14 15

16

17 18 19 20 21 22

23 24 25 26 27 28

29 3O 31

TLA2 ( t e s t s p o i l e d )

TLA2A, TLSU2 TLPSS , TLUU4, TLSUD2B TLCU 1 TI.CII2

TLUU5 TLPS2b TLDRUL2 TLDRULI, TLUUI TLPSI TLA] , TLUU2

TLPS4 . TLDI TLSU! PLPSI TLSUDI . TLSUOIA TLtIU3

TI.UA 1 *rI.PS3. "rLPS6

TABLE

21

4 J *

m :>, "o

4-i ,-.i 4.1 u o

C

(~ 0 (u "13 m

¢J C .r~

,-.1

,-~ ~ 0

, J >., .rt

X t~ X ~ 0 ~

~ E 0 "~ vl

U ~

"0

~ 0 ~ U .<

~ v

u

u

O ~

k

c 0

3

o

o.

o0 P

g

o

X U

iJ

I:

J~ f~ ~J u ,'-- II ~

0 ~

TRANSPORT & ROAD RESEARCH LABORATORY

, T T T T T T T T

r ,1 N

" ~ o t ! I I I I I ! ! I

¢.4 r 4

I I I I I

t~ r4 ..~ r4

a

r l r t ~ ~ P~

0

r l r~ ( ' t r l .2 r l t~l

0 I0

r t r t 1'4 PII

r3 r l tr~ ~ t "4) r t ~ I"1 *'1 *-, Pc ~ r t N

r l 0 0 0 0 ~ f~ P~ ~ 0 0 0

E o I 1 = l

,..4 I • I l

o k l

ill (J I I 1 I

"o 0 C ~

I , o u

I t ( : • ,re

"0 4 "O ~' ~ ~ . -4 I ¢ I .,.4 ~* I

I* k,

O " 0 : 3 O O U W M .-4 U I~ U ~1

t* -,4 :) >

o o

S~ e g IP r" ll~ K3 k :3 J* :~ J* :3 I*

• ~/ , 41

v u ~,, ~ v u N • o It •

0 0 o

• :~ 0 ) 0 • 4 ,.4 r,~ ,,4 ~, ,.-( .-4 I . • -4 It ~ I US ,"* I t U

• U r . t , ~1 • 0 s, • u i i

JD U ~

,,,4 ,~, I : "10 U *0 ".,.

I . . . - *

. ~ ~ ~, 4 0

0 b t . I~

o : ~ . . o . , , :~ , t / Z. 0 U : t aO I

,.-( I t w It

¢,

,~ v u 00 E oo

>~ c 0 C

: ~ ~

o E D-, : 0~9: o o z :

u ~ O,U O U 0 1 .

u U C C 1 >

~ v ~ v ~ v ~ v ~ v ~ v ~ v v ~ v ~ v v ~ v ~ v

. J n Q n

.J , J . J ,,J P' t " P' P '

0 r~ , - - ~ ,f, __ "-~ ;~ ,'C ,< V)

TABLE

Table 8. i

Swelling Characteristics of London Clay

Swelling Characteristics to Initial K o conditions

Depth

(m)

14.8

13.4

20.4

10.3

20.5

17 5

94-

I0 7

18 5

19 9

15 2

98

t Test Po Pf

(kN/m 2) (kN/m 2)

TLPSI 338 231

TLPS2 401 223

TLPS3 350 280

TLPS5 247 205

TLPS6 353 283

TLSUI 331 251

TLSU2 280 207

TLSUD2B 255 212

TLSUDIA 317 259

TLUAI 350 281

TLAI 338 234

TLA2A 245 197

(per cent)

-0.39

-0.84

-0.73

-0.81

-1.28

-1.05

-I 60

-0 92

-0 55

-0 33

-0 91

-0 66

K w

(MN/m 2 )

27

21

i0

5

5

8

5

5

I0

21

ii

7

K'/p'

96

68

30

23

17

26

19

20

37

66

40

33

Swelling Characteristics during Drained Tests

15.2

9.8

13.4

TLAI

TLA2A

TLPS2

233 130 -I.ii 8

197 115 -0.96 8

223 205 -0.14 13

48

56

60

Table i0.i

Non-Linear undrained stiffness and effective bulk modulus

stiffness parameters

undrained stiffness parameters

i-~I/P' versus )

Description A B C a 7 (%) ( r a d s ) ( r a d s )

London Clay 570 557 0.00007 1.47 0.453 Compression

London Clay 317 350 0.000105 1.22 0.61 Extension

Claygate Beds 633 647 0.0005 1.36 0.62

~Q (min) (%)

0.0003

0.0005

0.0007

~Q (max)

(%)

2.0

0.ii

0.i

Effective bulk modulus stiffness parameters

( K ' / p ' versus v~

Description R S T ~

(%) ( r a d s ) (mads)

London C l a y 520 495 0 .0006 1 .8 0 .44

C l a y g a t e Beds 1300 1238 0 . 0 0 0 6 1 .8 0 . 4 4

~v (min)

%

0.0007

0.0007

~v (max)

%

0.185

0.185

TRANSPORT& ROAD RESEARCH LABORATORY

LOCATION PLAN FOR NEW BOREHOLE AT BELL COMMON

""106,

,//I 0 " . .~"

.

,z ' ~ J ./o J ,,. ~ . / /

,,~.-'~\~., / / Mill X\/'--"---v~H°use Farm :a?- " ~' 0 £" ~",-~"a--JWinT / . , , ~ / ~ Jmill

H OU..Sp_ 2d, Reservoir ...~ t 0.. iWensley . .

I, "--4 '~.. ,=~

~-~-- .;,~ ,//: / 971 PP 972 j , ~ . ' ~ ~_ / / / l ~ 9 7 0 P P ~ 1 4 1 0 / " ' , J . " T..a~ v-" / ~-~0/-%,.'" ,,-,

, ~ 4 0 9 / .973 f "" ""

, / ' / . 4 0 8 \ , " 4 ~ " .-"" " ~ f . R o k~

) , . . . . -

Theydon Copt.

160 o

o 0 o J Eppin{ Thicks idorenole I pre 1977-78

Trial pit j.t investigation Borehole 1977-78 investigation

o II

50 100

metres

150

FIG. 2.1

200 !

LOG

O l d e r H e a d

FIG. 3.1

e l

w

o

,=?,

>, 6

.=

= E

- ..2 .,,,, . j ,

__ - - :..,

_ : , ,

t J 3

10

12

I 'J

1/.,. ¢,,..

O

c -

O . - I

16

o

t"l *i

2 - - e l

1"3 e l - , - , i

x l

e l

x l

8 .-1 e l

e l , - - - , I

e l

l " l i ° l

e l

e l

e l

e l

e l

18

20

B o r e h o l e d r i l l e d w i t h P i l c o n Mark I T r a v e l l e r Rig

4

O I

O I

x l

*! !

o

TRANSPORT& ROAD RESEARCH LABORATORY

BOREHOLE

Yellowish brown becoming lighter with depth with light grey - blue mottling, firm, vague horizontal bedding, sandy, silty CLAY with some gravel, shells and roots.

Light yellow - brown mottled blue grey soft to firm CLAY. Intact, interbedded with large quartz pebbles and dark golden brown loose clayey SAND with quartz pebbles. Note: Borehole collapsing from 3m to 8m due to several layers o£ sand with large pebbles. Augered and cased.

Grey-blue stiff, horizontally bedded - jointed with thin covering of silt in joints. Core breaks at joints. Some shells.

As above but more silty

As above but more silty

Claystone nodules. 10mm to 20nun, angular

Clay becoming very stiff. Joints less silty. Some joints appear to be slickenslded.

E n d o f b o r e h o l e

• lOOmm d i a t u b e s a m p l e

x B a g g e d s a m p l e

S t a n d i n g w a t e r

FIGURE 3.2

PHOTOGRAPHS OF SPLIT SAMPLES FROM VARIOUS DEPTHS

I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I o , 2 ~ , ~ 6 7 8 9 , o

CM

TRANSPORT & ROAD I::ESEARCH LABORATORY

P R O F I L E O F [ N D E X P R O P E R T I E S F,G. 3.3

Moisture content Bu lk unit weight c lay f ract ion Borehole (%} ( k N / m 3} ( % ) log

00 20 /.O 60 80 19.5 20 20.5 21.0 30 /.0 50 I I ~ I I , I = I i |

~ TOPSOILand 1 - older Head

' CLAY

2 I. o , ~ ~ - - O i ! :_.--~.--. o , ~ i . ' . - Q ~

3 - _V. ~ Soft to fire i ~'--~...~ i n ~ t c l ~

- - /" --..-~_-. interbedded E !'._~:Z w i th sand

5;- !E i~ " and grovel o. I : "--.----- C LAYGATE

i I ; - - - Z -

8 ! - " " ------ St i f f

9 - ----'-~'----- f issured c~_ , -_..---- LON DON CLAY

:C : ------- - - - - - : TO . . R : --~-~

• u .--.."-~ 11 - r~.~.~. AS above

: 0 : ~I -~-~'~ but mo re 0 I E n ~ "

~ . ;-Tr'~ s~lty

13 - : c ; -=-_---- , ~..~_ - - " As a b o v e b u t

- . - - , more si l ty

15 - ; 0 :

17 - 0 London Clay ;c, :_--_- becoming less

le- , o ~_-~1 sil~ and very - ~ ' ~ S ' ,v -:-Z='-i s t i f f

~ m

20 - " : ---'2-~-~" : -"-_%-

2+ - I t ~---- PL LL

TRANSPORT& ROAD RESEARCH LABORATORY UNDRAINED STRENGTH v DEPTH FROM TRIAXIAL

EXTENSION TESTS F,G. 3./,

E ¢-

Q .

£ 3

Su (k Po}

-20 -40 -60 -80 I I I I

O • M

11-

12-

t 3 -

lZ,-

15-

1 6 -

17-

18-

19 -

2 0 -

-100 -120 -140 -160 -180 -200 -220 -2z, O -260 -280 I I I I I I I I I I

O From iso~ropic

• From K•

F • Fourie (1984) { from is•tropic)

M• Meswoswe (1981}(from is•tropic)

• M

O

• F

O

O

M O • F

O

o M

TRANSPORT & ROAD RESEARCH LABORATORY

UNDRAINED COMPRESSION AND EXTENSION TEST RESULTS

Su [kPa)

0, 20 40 60 I I • I

; II-

S2- i-

n 4"

'~.

8"

£-

1C"

11"

12"

13"

II,"

15"

16

17

18

19

20

21

22

23

2~

25

26" i

27'-

28.

30:-

31-

32

33

3~

35

0

fr- o-I- oo -~-

® @

0

0

e©oO @°

® .+

0

°eo® -e l - •

®

80 100 120 1~0 160 180 200 220 2/.,0 260 280 300 I i I | I | I ! 5 I | |

• 1972

o o 1977/78

o 4- H ell ings/Fourie/Moswoswe

(E), (~) Represents neorest commemiol boreholes ( 16/.. 165.97l..975.976}

• 0

+

©

+ ©

0

+ 0

@

0

.

O

0 0

0

®

© O

O

-I-

• O

Q

O

@

O

© O

O

FIG. 3 . 5

TRANSPORT& ROAD RESEARCH LABORATORY

VARIATION OF VERTICAL AND HORIZONTAL STRESSES WITH DEPTH

O Push in pressure cells 0 Camkometer SBP r-I Camkometer SBL • Pore water pressure

~ X Deduced from P'K

.¢..~

. 0

0 •

6

10

12

14

16

\ \

- \

100

Stress ( k N / m 2 )

200 300

O 0 \ a •

\ \ \ L \ \ \ \

400

I I I I

500

Assumed ¢r h variat ion

r-1

~ 'U

\ \ \ \

'\ , 0

\o \

0

0

0

\

O C e

\

0

0

Older head

Claygate beds

London clay

F,G. 3.6

TRANSPORT& ROAD RESEARCH LABORATORY

VARIATION OFMEASURED Pk' WITH DEPTH F,G. 3.7

0 0

E

.=:2 ¸- ( 3 .

O -

Z. -

6 -

8-

10-

1 2 -

m

1 / . -

1 6 -

w,-.

18.--

I !

2o L

Suct ion p ; ( - k N I m 2

100 200 300 A00 500 600 700 I I I I I I I

O O

• Represents Burland and Maswoswe (1982)

0

0 0

0 0

0 0

O O

O O

o o

O

O

O

O

O O

O

O O

O

TRANSPORT & ROAD RESEARCH LABORATORY

COMPARISON BETWEEN MEASURED VALUES Pk' AND VALUES OF P'o nG. 3.8

• .~ 0 t~ " m O

• • o - 0

O ~

• o

o ~ . " • - o

u O

o ;

o e , i

i

I I I I \ i o 0 0 0 0 0 0 0 0 0

(od>l) n ~ . s u ! ,~I

L,

8

TRANSPORT& ROAD RESEARCH LABORATORY

GENERAL ARRANGEMENT OF HYDRAULIC TRIAXlAL CELL CONNECTED TO SELF COMPENSATING MERCURY CONTROL

A

e = 0

121 X

.o_

t )

121

> , -r"

2 ~ 0 0

n

U

111

¢-

g . ~ £ a . c ~

U D ~D Ul

-e-

S

if} if)

II I -

l- '-

0

~c

LO ~ o>.

_o o- ~'i===#

F,G. /,.I

TRANSPORT& ROAD RESEARCH LABORATORY

THE ORION DATA LOGGING SYSTEM FIG. ~ . 2

o ~

---~-6 ¢'~ e-

D

N

f

8

¢- o ~

he" t-: '~ ~ L e- ..~oo , • o o

• ~__~l __~J I ~=o

o .o ~

t -

2 o -

s s ~ o o t t l a

o

o-,~

~ o , X " C 0

~-" o ~

I--

O

. _ E c~

o_~ "i

TRANSPORT& ROAD RESEARCH LABORATORY

GENERAL ARRANGEMENT OF THE NEW SYSTEM DRIVING A STRESS

MICROCOMPUTER PATH CELL

t

CONTRO FIG. ~ . 3

"13

O

(,_~l "O U

~ ~ Y_~E- ~_ .

::::, - 5 -~ ,,,.... ~ ," x ~. O Q,,. U ..~3

ll ~ .o ,.,,,

II

S. 8

i

U I'~ i @t} r'r'l

: i ! d

TRANSPORT & ROAD RESEARCH LABORATORY

FAILURE MODES OF SPECIMENS F,G. ~,.~,

,X

\ \

\ b

i

t

c

\

\ B

i ~

<

i~1 .1=: ~ , c

g ..9

/ F.; ~, I

i

- i

i -

P

- , p_ i -

"RANSPORT& ROAD RESEARCH LABORATORY

APPARATUS ENCLOSED FIG. 5.1 THE NEW PLANE STRAIN IN A STRESS PATH CELL

A~just/rtg n u t

!

A,+~stct>l+ pl~te SCreW control rod

SuppOrt ~[tar

P c r s p e x

Soc31ing plot¢

- - C >

| ~ t for S4~l;ng

L.ood ten

CmssD~r s~gS~rt

~O1t om soccer

Pore ~ u n ~ leodl

B4rllo/rcm SGCll

Loadinq mm

O;spSacemt nt

BellofrQm se¢ll. JI F

O;u! gcugt

Arm ¢~,+.-...;11cl t:o r+Gm lor Str¢~ mms~.~ement

I.;r, ear bccr~ng

~ - - q ~ R G ~ m 9roSS urt

]

TRANSPORT& ROAD RESEARCH LABORATORY

SECTIONAL ELEVATION AND PLAN OF NEW PLANE STRAIN APPARATUS

FIG. 5 . 2

~ ~_~ ~ ~ % ~.~--.~-~:-~ ~ /, ~ ~ ~-7>~< ~- ~-~_~ ~ ~

~:~ ~ ~=~ ~® -- ~

/ , , , , .~.W; " ~ I l T I " - ~ I IF-//-'::X) "V . ' ~ , - , l i ' ~ I

~/ ~< / v ,,. . . . . . . . . . . . . . . . . . . . . . . . . . . ,q \ \ \ " i

Vertical Section Through SpecimcnCentr¢ line ~ # . ~ .~,., . . ; . . . ~ ,e .-

= ,z - , \ - N

- / . ~ / / \ \ N ~ ",~1 - ! / x . ! ~ I i I _~~/ s~e~,~o ~ll~l', 1o,, ,,1

® f ~" ~'~V. :\\\'4 i il V. , i~\\c.-X,,+

; (~ " ~ Sect ion A - A (~ (~ 0 10 20 30 60 50

Scale L

1 Top spacer 14 Gear support piece 2 Bolt 15 Gears 3 Topmembron¢ sealing platen 16 Stud & Top platen 1"7 Gears 5 Bottom platen 18 Screw controlrod 6 Bottom membrane sealing platen 19 Support plate "7 Bottom loading head 20 End platentie rods 8 Back-up platen 21 Support rail crossbars 9 Load c¢11 22 Support roils

10 Make--up platen 23 Support roils 11 Adjustable platen 24 Supporting plate 12 End plate 25 Wheels 13 Screw shaft 26 Adjustable plate guide

29 Drainage

F I G U R E 5.3

P H O T O G R A P H S OF C O M P O N E N T S O F T H E P L A N E S T R A I N A P P A R A T U S

(TOP) A N D S P E C I M E N OF L O N D O N C L A Y A F T E R T E S T I N G IN P L A N E

S T R A I N - T E S T PLPSI ( B O T T O M )

4

t ~ ~ J

I ' 1 ' 1 ' i ' i ' 1 0 1 2 3 4 5

CM

FIGURE 5.4

PHOTOGRAPHS OF NEW PLANE STRAIN APPARATUS

b~

TRANSPORT & ROAD RESEARCH LABORATORY

RESULTS OF UNDRAINED TRIAXlAL EXTENSION

TESTS ON LONDON CLAY F,O 6.1

O

O

O 0"

O--

C~

o~

D D ~ D DD~D DDDDD U U ~ J ~ J ~ J~JJ

o

w

1"0

6-

Q-o o -

o t o-

o

G

O .,-i

c-.

o o

D 0

I I ' 0 0 ~ - " 0 0 ~ -

I 1 • 00~- . 00~-

(ed~) b

i i L' • Or) c;-- " 0 0 9 - " O 0 -

Z 0 H

CO Z I,I ~--

X I,I

0 I,I Z

rF E] Z -D

T R A ~ R T & ROAD RESEARCH LABORATORY

PEAK STRENGTHS FROM UNDRAINED TRIAXlAL EXTENSION TESTS ON LONDON CLAY

0

8 -

0

0

0 0

0 0

I// / o /" "~

• 1 ° 1 , . / I ' " . I

_

? . , - /

k ÷ /

/

/ 0

o :) 0 u //o

/ / / , 3 / / . 0 / " /,,//° 0 c~

,I I I I I I O O O O O O O O O O O O

("4 ("3 ,,4' I.f") I r , J i i

(ZUJIN)l) ({0 - °.D)

I F I G . 6 . 2

TRANSF:~3RT & ROAD RESEARCH I~BC)F::~ATORY

STRESS PATHS FOR CONSTANT q SWELLING TESTS AND Ko SWELLING TESTS AND AN UNDRAINEDIDFb~INED

TEST ON LONDON CLAY

o

1 o ,,,"I rO

~ . J ~ ~ O C D

C C ~ Q J J J J J

B O ~ + X

0

rr)

o

(3,

V

0 o _

( 3

0

0 O J _ ,-q

c " (:O

o . ,%-

o I

/

/

/ /

I I I I

/

, / /

/

i I " 0 0 ~ - - " 0 ~ - - " 0 ~ - 0 " 0 ~ ' - " 0 8 - O ~ T - " 0 9 T -

(ed>t) b

FIG. 6.3

T R A ~ R T & ROAD RESEARCH LABORATORY

RESULTS OF TRIAXlAL PASSIVE STRESS RELIEF TESTS ON LONDON CLAY

0

0

0

0

e~

~ 0

Ck ,u

v

0 O _

121. etl

0 ~D

\

0

• 0

T / .

...4" l l 3

0 I'M - - i

2 L?.

\

,#

O _

0 I I I 1 I I • 00~- • 0 ~ - "0 "01~- " 0 8 - " O ~ T - . ' o 9 T -

Cede) b

FIG. 6

~JJJJ~g

I Be~.~x0

• Oe~-

ITRANSPORT & ROAD RESEARCH LABORATORY

RESULTS OF PLANE STRAIN PASSIVE STRESS RELIEF TEST ON LONDON CLAY

I I I : 0

C~

0 0

0 l / : ) - -

I

~E ° - l - - =

Z

~ o _

I/)

I/)

~o- I - 0 c -

O

:~ O o

/ /

,.U i I

i i /

/ /

/

I I

I

I I I I I 0 0 0 0

{zUJ IN> i ) ~ ssea~S 3!JO]D!Aa( ] C] X

I I

I I

I

I F,G. 6 . 5

TRAhEE~AT& ROAD RESEARCH LABORATORY

PEAK STRENGTHS FROM DRAINED AND UNDRAINED TRIAXlAL COMPRESSION TESTS ON LONDON CLAY I FIG. 6 . 6

O o

• \ \ ~ , o ~ \ \ E ~'-

N

V

\ I I ! 1 I ! I -

_0 0 0 0 0 0 0 C~ ° 0 O 0 0 0 0

(z tU lN) l ) {"_0 - ~OI

TRANSPORT& ROAD RESEARCH LABORATORY

COMPARISON BETWEEN FAILURE ENVELOPES FROM TRIAXlAL COMPRESSION AND EXTENSION TESTS ON LONDON CLAY

C: O u}

O_ E O

CP

O - O

O - o

O - O

O ~ O

_Oo

O - O

"4r

O O

m o

Z

O

I I I I ~Io O 0 0 O O O O O O ,4" CO ~

(Z uJ / N)I )

FIG. 6 . 7

TRANSPORT & ROAD RESEARCH LABORATORY

¢1' versus SHEAR STRENGTH (gs) - EXTENSION AND COMPRESSION TESTS FROM Ko

F,O. 6.8

LEGEllO

.................. TLA1 TLA2A TLPS2 TLPS& TLUA1 TLS01 TLSU2

-10 - 9 L

36,.

3L,-

32"

39

DEPTH pl 28"

(m) I 15.2 223 26-

9.8 197 2~,

15.2 223 ~' 22.

16.3 242 (degrees) 20. ACTIVE ZONE

19.9 330 18.

17.5 251 16

9.4 206 1~-

12-

10-

6"

£s ( percent ) -8 -7 -~ -s -~ -3 -2 -1 COMPRES~ON

EXTENSION i i I. 5 li .2 E s ( percent )

, '8

qO

142

PASSIVE ZONE | -16

, 48 ~'

:-20 (degrees)

" " ~ J I --2f, I

I ,-26 I / '-28

"" I

~ -30 I

" '-32

I "-3/, I /

\ / "-36

TRANSPORT& ROAD RESEARCH LABORATORY

GulP' vs. LOG ~ FOR UNDRAINED EXTENSION TESTS FROM

INITIAL ISOTROPIC STRESS- LONDON CLAY

0 O (D O O 0 ur~ 0 IF) 0

] l l I I

~S Z) u~ ~-) "r" ._l 13 F-- Q.

~B O t_ -J o l--~-

dJ F- 0 Z

O

I

C'3

I°

C'd

F- d

(D _A I--

/

F-

,I 7 /" / / / //

._I _j ._I F- I-- I--

O c~

I F,G 7. I

c . _

(3

Ill

(-- Or)

TRANSPORT & ROAD RESEARCH LABORATORY

LONDON CLAY AND CLAYGATE BEDS: G u/p~ vs. LOG E; FOR UNDRAINED EXTENSION TESTS FROM K o AND UNDRAINED

COMPRESSION TESTS FROM K o

Mean curve Cloygate

Legend for London Clay extension tests

TLPS1 TLPS2(Dr) TLPS3 o - - o - - - o - TLPSL. o - - o ~0 TLPS6 "" ~ := TLSUI .a---o a TLSU2 . x ~ x ~ x

TLSUD1A TLSUD2B

Compression test TLUA1

Mean curves for London Clay- extension

compression

\

E W

Range for undrained extension tests an London Cloy fro--'m---" Isotropic.

T LA1 (Dr)

I

0.01 0.1

TCUA1

L •

°

TL 2ACD.,I O

1.0

Shear strain (%}

I F,G 7.2

700

550

5OO

i

55O

- 500

- c.50

- & O 0

- 350 Gu( ~J

P - 3 0 ( :

25(

20(3

1S0

100

50

0 10.0

TRANSPORT & ROAD RESEARCH LABORATORY

K'ISec) vs. LOG E v FOR SWELLING PHASES OF p' EXTENSION TESTS ON LONDON CLAY

FIG. 8.1

TLPS 2(anisotr. swell} TLDRUL2 (anisotr. swel l)

~ TLPS1 (anisotr . swe l l ) TLPS1 (p'os.str re l ie f } TLSU1 ( an•sort, swel l } TLSUDIA (on•sort. swell)

z ~ - - z ~ - - Z~ TLPS3 (on•sort. swell } - - 0 • • • i - T L P S 4 (an•sort. swell)

, Mean l ine

I 0.01

X \

%

° h

• \

ql

0 .05

I I w'~"t"~ I 0.1 0.5

Vo lume t r i c s t r o i n ' ~

- 320

280

- 2/.0

180 K a S¢c

160 pn

120

K 1 80__ sec = 75

pn

(ie Klton =30) Z,O

pl

0 1.0

TRANSPORT& ROAD RESEARCH LABORATORY

RELATIONSHIP BETWEEN VOLUMETRIC STRAIN AND LOG p' FOR Ko SWELLING TEST TLDRUL1 I FIG. 8 . 2

i

OL~" 0

'.D

~"; 7

, ; , j

,;,;-i

""t \ ,.,.~_ ' ~

,-,.j E : • i

,.-,.j

r , • • ...- r , j

,-, '.D

tD )j'-.

' .D , :O

, . ~ r ' , .

C l O'., i....i

b " l ~ - -1 I - -

I I I I I ]

00"1"I O-'_z'O- O 0 " L - O ~ ' L - On' ,~- nc-,:~- on ' : : ' -

,.'.:-..} u !~..~,-_-'. -~u,~l,:,f -,

, f

TRANSPORT& ROAD RESEARCH LABORATORY

RELATIONSHIP BETWEEN VOLUMETRIC STRAIN AND LOG p' FOR K O SWELLING TEST TLDRUL2

I

Oq "0

" 'J 7

"£' (i b'l

03

,.'x]

oJ

£,J

,-, ,'d ' ; ' J 13- ,:~"

,='4

o.~-

,.-,j

I

'-D r-,.o

• ' : K '

Z

I I I I •

i:;n 0 0'_:'0- O0"L- n,_~'L- 00"~- 0'_--'~- orI";'-

Q -.J t--

FiG. 8.3

T R A N S P O R T & ROAD RESEARCH LABORATORY

RELATIONSHIP BETWEEN VOLUMETRIC STRAIN AND LOG p' FOR CONSTANT q SWELLING TEST TLSUD 1A

FIG. 8.

,-:,

I J ' l

,:,.] -

,:o.°'] k I ,J

. ':g\ j...~ - •

,.,;- ~~~ . . - : h - !

,~ ::r J

r . ,-, .~.

r-2i :,

,'*..i i i ,"r: ,CC

,;,.J

, - " , °

,:,.~-i

i~-o I f"l ,.T.

I I',.~ I t i I I i I 0 Z ' 0 i'iFi FI- r l ? ' o - - " ' " o - p ' - " o - n : : : ' o - r l o ' ~ - n,-]"

'-'Z ~-. i:: u ! .=..~ -~ # a :JJT~ I. 0 r'i

o'.i

,r-,

,_s I

I

I--

TRANSPORT& ROAD RESEARCH LABORATORY

RELATIONSHIP BETWEEN VOLUMETRIC STRAIN AND LOG p' FOR CONSTANT q SWELLING TEST TLSUD 2B

I

,:,J LI - i

3-

~ J ,

[ '3

p.j -

.~ P ' I r l " - -..-- ,.~.J

~,.s • i

: : : t- r t J

£'.1

°a.J

i _ £,.J

-~J

I.l.j --

r,-,

-,~ I I I I 1 I

I~ i:l "1"1 I'~'-% " [ - I.'1 I.'1 " ' ; ' - I;l'-- " h - - 01.'1 . i ~ _ I:1~ . 2 _ r i o "~,

< ;-~ .-., u ! ~_.~ -). ~ . . ~ , m I o ( l

o.~ 0:, i--.i

r,-, ,:,J ,---, - - , ,'1-., . J I - -

FIG, 8 . 5

TRANSPORT& ROAD RESEARCH LABORATORY

RELATIONSHIP BETWEEN VOLUMETRIC STRAIN AND LOG p' FOR DRAINED ACTIVE TEST TLA1

FIG, 8.6

F I

r

I f f f p

! ! I !

0 0 " 0 - ;:,E'O-

0 .cO N

o 13,.

~0 ~ C~.~

o

\ 0

,'r 0 o.

i ~ ! i l . , 7 . ( ' ,X, I 0 ' 3 " 0 - 0 6 " 0 - O,-7.'L- Oc, '~ . - O: - : 'L - rz~ -_.-

," ~.." "t I t ; "~.o~ .~ ~: ~ :JJTI "L r , i^~

TRANSPORT & ROAD RESEARCH LABORATORY

RELATIONSHIP BETWEEN VOLUMETRIC STRAIN AND LOG p' FOR DRAINED ACTIVE TEST TL,42,4

1 I ,,, T , , I I

.f...

-~ °.,

~ -~.

I .

i ° i

-1

o

o

('4

"("4

o

"c4

° - . .~ .:..

- ~ 0

-~

0 H " O - - n . ' : " O - 0 ' : - . , " ( i - 0,.~.," I - ! - n.-:. • ; - 0 ' - " ~ , - h E : " . L - . 0 [ " : : : -

;" "~" "I J..] | ~'~-..~ "l ":. ~l l~l'~ t '} l'0 ,"~ "- " • -" • '" . . . . - ' I , I

i tG. 8 . 7

TRANSPORT& ROAD RESEARCH LABORATORY

VALUES OF K'/p' PLOTTED AGAINST DEPTH

0 0

2 -

4

6 -

A 8 -- I/} I - -

E

l o - (3.

tm

1 2 -

1 / . -

1 6 -

18

2O

K I t(~n

20 /-,0 P' 60 80 100

"1-

• ÷

I I I I i

4.

O

O

÷ X

O ÷

O

• +

÷ ÷

O Swelling from high p/

Q Swelling at constant q.

+ Swelling to initial K o

x Drained tests

X

÷

O

÷

I F I G . 8.8

Silty

Stratum

0

TRANSPORT& ROAD RESEARCH LABORATORY

PEAK STRENGTHS FROM DRAINED AND UNDRAINED TRIAXIAL TESTS ON CLAYGATE BEDS

0 0

0

0 0

o

I I II

m

o x

._o

E

~°~ E

z S ~ I -- @ o

0 0

I

0 0

0 0

{ z uJ/N>I ) 1

6,1

(I)

> £ D cn¢_) e3

n u~- - .~ .~_

8

_8

0 ~ 0

i

0 - 0

0

E

Z 0

I F,G 10.1