4/9/2016

UNDRAINED SHEAR
STRENGTH WITH A
TRIAXIAL
COMPRESSION TEST
Date of lab: Wednesday 30th march 2016
Instructor’s name: Mrs Jacob Jittina
Group members: CARYLL, HAAFIZ, BULAMA

EMMANUEL ODERA IGWEBUIKE

CIE 5005 GROUND AND WATER STUDIES
CONTENTS

ABSTRACT .................................................................................................................
INTRODUCTION ........................................................................................................ 1
AIM ............................................................................................................................. 3
OBJECTIVES ............................................................................................................. 3
THEORY .................................................................................................................... 4
METHODOLOGY ....................................................................................................... 6
LAB TEST PROCEDURE .......................................................................................... 8
EQUIPMENT .............................................................................................................. 9
RESULTS AND CALCULATIONS........................................................................... 14
DIMENSIONS .......................................................................................................... 17
WATER CONTENT OF EACH SPECIMEN ............................................................. 17
SAMPLE CALCULATIONS ...................................................................................... 18
GRAPH .................................................................................................................... 20
FAILURE MODE ...................................................................................................... 22
ANALYSIS AND CONCLUSION ............................................................................. 23
REFERENCES ......................................................................................................... 25
ABSTRACT

Understanding the nature of soils plays a huge role in ground construction, as the
knowing the behaviour of the soils can lead to the estimate on the stability of a
foundation and TRIAXIAL test is one of the best methods for obtaining the behaviour
of a soil. A lab experiment was done by 2nd year civil engineering students to test the
UNDRAINED shear strength parameters within a TRIAXIAL compression test. This
experiment tested different soil samples in order to obtain the shear strength
parameters by applying various elements of soils and various confining pressures.
Readings were observed and taking down in the lab. Stress-strain graphs were
plotted to aid in analysing the behaviour of the specimen. A Mohr’s circle was also
plotted to obtain the cohesion factor and angle of shearing resistance of the soil.
Initially there will be an increase in pore water pressure and as consolidation occurs
over time, the pore water and effective stress also increase, but seeing as this is a
fully saturated specimen none of that occurs. The TRIAXIAL imposed stresses in 2
different dimensions, which were the vertical and lateral stresses. From analysing
the test, it was observed that the test was indeed a failed test. In this lab report you
will come to find out in proper detail about the TRIAXIAL test, the analysis discussed,
theory, equipment used, results, errors observed in the lab, and how these errors
can be avoided in the future.
TRIAXIAL COMPRESSION TEST Emmanuel Odera Igwebuike

INTRODUCTION
Laboratory testing is a major part and an important concept of engineering.
The test can depend on the project needs and can be difficult. A laboratory test should
be prepared and completed vigilantly to improve the test data for design and
construction. The shear strength of a soil is a very vital part to foundation design, it
aids designers when designing foundations, as they need to be aware of the shear
strength at which the soil can bear a foundation. In addition, all kinds of slopes,
including river banks, hills, and man-made cuts and fills in transportation engineering,
stay in place only because of the shear strength of the material of which they are
composed. Deep understanding and knowledge of the shear strength of soil is
important for the design of structural foundations, embankments, retaining walls,
pavements, and cuts. In this laboratory testing, the type of test being adopted is known
as a TRIAXIAL compression test.

According to Jacob, J (2016), the TRIAXIL compression test is a test widely

known all over the world. It is a test used to determine the shear strength behaviour in
the soil. The TRIAXIAL test also, aids in informing the behaviour of soils. It was test
first introduced during the 1930’s in the United States of America by two men called
CASAGRANDE and TERZAGHI. In testing for the shear strength of a saturated soil,
the TRIAXIAL compression is dependent upon the applied stresses, strain rate, time
of solidification, and preceding stress the soil faced. Other known tests are the CBR
test, shear box test, unconfined compression test and the compaction tests.

Saturated soils are tested using the TRIAXIAL compression test under 2 different soil
tests-

CONSOLIDATED AND UNCONSOLIDATED UNDRAINED TEST

CONSOLIDATED DRAINED TEST

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CONSOLIDATED AND UNCONSOLIDATED UNDRAINED TEST - In this test

method, there are two different, conditions to which the soil is tested
o Consolidated UNDRAINED TEST (CU) - According to ASTM standard
method D2850, Using the pore-water pressure measured during the test,
the shear strength determined from this test method can be expressed
in terms of effective stress.
This shear strength may be applied to field conditions where full drainage
can occur or where pressure is induced by loading pore can be
estimated, and the field stress conditions are similar to those in this test
method. During testing, drainage of the specimen is not permitted.
o Unconsolidated UNDRAINED TEST (UU) - According to ASTM
standard method D2850, the shear characteristics of the soil are
assessed under UNDRAINED conditions and is capable of being applied
to field conditions where soils have been fully consolidated under a
stress and is subjected to a change in stress without time for further
consolidation to take place and the field stress conditions are similar to
those in the test method. During testing, the loads are applied quickly
and the sample is not allowed to consolidate during the test.
CONSOLIDATED DRAINED TEST - According to ASTM standard method
D6467, in a consolidated drained test the sample is consolidated and sheared
in compression slowly to allow pore pressures built up by the shearing to
dissipate. The rate of axial deformation is kept constant, i.e., is strain controlled.
The idea is that the test allows the sample and the pore pressures to fully
consolidate (i.e., adjust) to the surrounding stresses. The test may take a long
time to allow the sample to adjust, in particular low permeability samples need
a long time to drain and adjust strain to stress levels.

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AIM
The main aims of the lab test were to:

Find the shear strength parameters by applying various elements of soils and
various confining pressures.
Determine the apparent cohesion and angle of shearing resistance of a given
sample of cohesive soil by means of an UNDRAINED TRIAXIAL compression
test with the aid of a Mohr’s circle.

OBJECTIVES
At the end of the experiment the students were able to

Develop laboratory and experimental skills

Understand both practical and theoretical concepts in relation to the shear
strength of the soils

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THEORY

The type of TRIAXIAL test used in this method is an unconsolidated

UNDRAINED test. In this type of UNDRAINED test method, the compressive strength
of a soil is determined in terms of stress, therefore, the resulting strength depends on
the pressure developed in the pore fluid during loading. In this test method, fluid flow
was not permitted from or into the soil specimen as the load is applied, therefore the
resulting pore pressure, and hence strength, differs from that developed in the case
where drainage can occur. If the test specimens is 100 % saturated, consolidation
cannot occur when the confining pressure is applied nor during the shear portion of
the test since drainage is not permitted. Therefore, if several specimens of the same
material are tested, and if they are all at approximately the same water content and
void ratio when they are tested, they will have approximately the same unconsolidated-
UNDRAINED shear strength. If the test specimens are partially saturated, or
compacted/reconstituted specimens, where the degree of saturation is less than
100 %, consolidation may occur when the confining pressure is applied and during
application of axial load, even though drainage is not permitted. Therefore, if several
partially saturated specimens of the same material are tested at different confining
stresses, they will not have the same unconsolidated-UNDRAINED shear strength.
Mohr failure envelopes may be plotted from a series of unconsolidated UNDRAINED
TRIAXIAL tests.

The Mohr’s circles at failure based on total stresses are constructed by

plotting a half circle with a radius of half the principal stress difference (deviator stress)
beginning at the axial stress (major principal stress) and ending at the confining stress
(minor principal stress) on a graph with principal stresses as the abscissa and shear
stress as the ordinate and equal scale in both directions. The failure envelopes will
usually be a horizontal line for saturated specimens and a curved line for partially
saturated specimens. The unconsolidated-UNDRAINED shear strength is applicable
to situations where the loads are assumed to take place so rapidly that there is
insufficient time for the induced pore-water pressure to dissipate and for consolidation
to occur during the loading period (that is, drainage does not occur).

(ASTM D2850, 1999)

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Difficulties in geotechnical design require only shear strength parameters

that are in relation to consolidate soils or to measure the peak stress. In this case
Mohr’s circle is created for each peak or failing stress. The tangent to these circles is
then drawn to provide a reasonable good observation. Strength envelope and angle
of friction can all be determined from the Mohr’s circle graph that was produced on
graph sheet as shown in figure 2.5. In the Mohr’s circle, major principle stress will be
the deviator stress which is in addition to the cell pressure (denoted as σ1f), then the
minor principle stress will be the cell pressure (denoted as σ3), both of these values
were of high importance when creating the failure envelope, as they determine the
size of the circles. The soil has an UNDRAINED strength known as Su, this is taken
as the interception of the shear stress which is on the y axis, after this the slope is
obtained, which is done by on the failure envelope line. Compressive strengths
determined using this procedure may not apply in cases where the loading conditions
in the field differ significantly from those used in this test method.

(ASTM D2850, 1999)

Advantages Disadvantages

The test can be performed, with The test set up is more

complete control, under all the complicated than any other
three drainage conditions. shear test. It requires a skilled
It is possible to take pore person to handle the apparatus
pressure measurements during precisely.
the test. Tests on small diameter
The distribution of stress on the samples of stiff fissured clays
failure plane is uniform. give very high strength. Hence to
It is possible to determine the obtain accurate result for such
state of stress within the type of soils, large diameter
specimen at any stage of the specimens should be tested.
test. Consolidation of cohesive soil
specimens take more time than
in the shear box test.

(Z. Khan, 2016)

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 METHODOLOGY

Figure 1.0 TRIAXIAL test apparatus (POWRIE. W, 2014)

TRIAXIAL COMPRESSION TEST Emmanuel Odera Igwebuike

According to POWRIE, W. (2014), in every TRIAXIAL test, there are two

stages, the consolidation stage and the shear stage. In the consolidation stage, the
cell pressure is increased to a chosen amount, which provides a uniform confining
stress all around the specimen, which signifies the preliminary point of the next stage
which is the shear stage. In the shear stage a load is applied vertical through the ram,
this loads causes an increase in stress at the top of the specimen. In the test there are
two stress, σ1 and σ3. The major stress σ1 is acting vertically on the specimen, σ3 is
the minor stress acting horizontally on the specimen. The vertical stress is increased
until the specimen fails.

Samples of saturated soil, about 38mm diameter were obtained from a larger
sample, most likely from a trial pit or a borehole investigation. Each of the samples
obtained were pushed the end of its tube, with the aid of a screw jack extruder fixed
to the bench. The end square is then cut using a palette knife when the first 10mm has
been extruded. After this a further 76 mm was cautiously extruded and this 76mm of
the specimen was then cut off from the clay remaining in the tube. In order to prevent
any drying out the sample is then wrapped in cling film. Since this was an UNDRAINED
test, there are two more identical samples required, and these samples are indicated
lightly by 1, 2 and 3.

The first sample was fixed on the Perspex disc which was placed on the base
plate of the TRIAXIAL mechanism. After which a base loading cap was then placed
on top. A rubber membrane was then placed upon the loading cap, pedestal and
sample. This was done initially, by placing the membrane inside the membrane
stretcher tube and bending the ends over outside ends of the tube. In order for the
membrane to be slipped over the sample, suction was required. The ends of the
membrane were released onto pedestal and loading cap when the membrane is in
position. After this, two rubber ‘O’ rings as shown in Figure 1.3, were used to secure
the membrane to the pedestal and loading cap using the ends of the membrane
stretcher tube while cautiously avoiding and damage to the sample. Then the Perspex
cylinder and cell top was slowly raised over the sample, and on top of the three bolts
which it is secured firmly with wing nuts.

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LAB TEST PROCEDURE

The loading ram was brought into contact with the loading cap. Then cautiously
the TRIAXIAL cell was raised to bring the loading ram in contact with the proving
ring. (This is shown by small deflection, maybe 2 divisions, as observed from
the dial gauge).
A cell pressure was then applied, this was done by opening the cell pressure
supply valve.
Proper adjustment was giving to the proving ring’s position, to make contact
with the loading ram, then zero the dial gauge.
The strain rate was set to 1.25 mm/min, after this the machine was turned on.
The proving ring dial gauge readings (divisions) were recorded subsequent to
the vertical defection.
The machine is to be switched off when either the proving ring gauge goes
backwards or if a 16mm deformation is achieved. In this lab test, the machine
was switched off when the proving ring gauge started going backwards.
The cell pressure valve was closed and drained of water into the water cylinder.
Then cautiously the cell was lowered and the loading ram discharged. Then the
Perspex cylinder top was removed and the soil sample extracted.
The whole tested soil specimen was then used to determine a water content.
Then the above steps were repeated at the desired cell pressures.

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EQUIPMENT

Figure 1.1 The Perspex cylinder being filled up

Figure 1.2 the TRIAXIAL system strain rates and setup

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Rubber membrane

‘O’ rings
Perspex disc

Figure 1.3 the specimen fixed on the TRIAXIAL base plate

Figure 1.4 the soil specimen sample

Figure 1.5 The soil specimen being positioned on the TRIAXIAL base plate

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Figure 1.6 strain adjustment valve

Figure 1.7 the Perspex cylinder

Figure 1.8 the Palette knife

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Cell pressure
valve

Figure 1.9 the cell pressure valve connection to the TRIAXIAL system

Figure 2.0 the vertical loading ram

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Figure 2.1 the deflection gauge

Figure 2.2 the proving ring gauge

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RESULTS AND CALCULATIONS

Cell pressure- 2 kg⁄cm2 - 200 kN⁄M 2

Table 1: Observed and calculated readings for specimen 3

∆H Proving Proving E= ∆𝐇/ 1-E F(KN) 𝐙=𝐅/𝐀𝟎 Z(1-E)

(0.01mm) ring ring dial 𝐇𝐨 (a*7) (KN/m²) (KN/m²)
reading gauge
(DIVS) (a)
0 0 0 0.000 1.000 0.000 0.0000 0.00000
20 0.6 3 0.003 0.997 0.021 18.5185 18.46979
40 0.6 3 0.005 0.995 0.021 18.5185 18.42105
60 0.6 3 0.008 0.992 0.021 18.5185 18.37232
80 1 5 0.011 0.989 0.035 30.8642 30.53931
100 1.1 5.5 0.013 0.987 0.039 33.9506 33.50390
150 1.4 7 0.020 0.980 0.049 43.2099 42.35705
200 1.7 8.5 0.026 0.974 0.060 52.4691 51.08837
250 1.8 9 0.033 0.967 0.063 55.5556 53.72807
300 1.9 9.5 0.039 0.961 0.067 58.6420 56.32716
350 2 10 0.046 0.954 0.070 61.7284 58.88564
400 2.1 10.5 0.053 0.947 0.074 64.8148 61.40351
450 2.2 11 0.059 0.941 0.077 67.9012 63.88077
500 2.2 11 0.066 0.934 0.077 67.9012 63.43405
600 2.5 12.5 0.079 0.921 0.088 77.1605 71.06888
700 2.6 13 0.092 0.908 0.091 80.2469 72.85575
800 2.65 13.25 0.105 0.895 0.093 81.7901 73.18064
900 2.7 13.5 0.118 0.882 0.095 83.3333 73.46491
1000 2.8 14 0.132 0.868 0.098 86.4198 75.04873
1100 2.85 14.25 0.145 0.855 0.100 87.9630 75.23148
1200 2.9 14.5 0.158 0.842 0.102 89.5062 75.37362
1300 2.95 14.75 0.171 0.829 0.103 91.0494 75.47515
1400 2.95 14.75 0.184 0.816 0.103 91.0494 74.27713
1500 2.95 14.75 0.197 0.803 0.103 91.0494 73.07911
1600 2.95 14.75 0.211 0.789 0.103 91.0494 71.88109

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Cell pressure- 0.5 kg⁄cm2 - 50 kN⁄M 2

Table 2: Observed and calculated readings for specimen 1

∆H (0.01mm) Proving Proving E= ∆𝐇/𝐇𝐨 1-E F(KN) 𝐙=𝐅/𝐀𝟎 Z(1-E)

ring ring dial (a*7) (KN/m²) (KN/m²)
reading gauge
(DIVS) (a)
0 0 0 0.000 1.000 0.000 0.000 0.000
20 1 5 0.003 0.997 0.035 30.864 30.783
40 1.2 6 0.005 0.995 0.042 37.037 36.842
60 1.4 7 0.008 0.992 0.049 43.210 42.869
80 1.4 7 0.011 0.989 0.049 43.210 42.755
100 1.4 7 0.013 0.987 0.049 43.210 42.641
150 1.6 8 0.020 0.980 0.056 49.383 48.408
200 1.7 8.5 0.026 0.974 0.060 52.469 51.088
250 1.8 9 0.033 0.967 0.063 55.556 53.728
300 1.8 9 0.039 0.961 0.063 55.556 53.363
350 1.85 9.25 0.046 0.954 0.065 57.099 54.469
400 1.95 9.75 0.053 0.947 0.068 60.185 57.018
450 2 10 0.059 0.941 0.070 61.728 58.073
500 2 10 0.066 0.934 0.070 61.728 57.667
600 2.05 10.25 0.079 0.921 0.072 63.272 58.276
700 2.1 10.5 0.092 0.908 0.074 64.815 58.845
800 2.2 11 0.105 0.895 0.077 67.901 60.754
900 2.2 11 0.118 0.882 0.077 67.901 59.860
1000 2.2 11 0.132 0.868 0.077 67.901 58.967
1100 2.2 11 0.145 0.855 0.077 67.901 58.073
1200 2.25 11.25 0.158 0.842 0.079 69.444 58.480
1300 2.25 11.25 0.171 0.829 0.079 69.444 57.566
1400 2.3 11.5 0.184 0.816 0.081 70.988 57.911
1500 2.3 11.5 0.197 0.803 0.081 70.988 56.977
1600 2.3 11.5 0.211 0.789 0.081 70.988 56.043

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Cell pressure- 1 kg⁄cm2 - 100 kN⁄M 2

Table 3: Observed and calculated readings for specimen 2

∆H Proving Proving E= ∆𝐇/𝐇𝐨 1-E F(KN) 𝐙=𝐅/𝐀𝟎 Z(1-E)

(0.01mm) ring ring dial (a*7) (KN/m²) (KN/m²)
reading gauge
(DIVS) (a)
0 0 0 0.000 1.000 0.000 0.000 0.000
20 1.2 6 0.003 0.997 0.042 37.037 36.940
40 1.3 6.5 0.005 0.995 0.046 40.123 39.912
60 1.3 6.5 0.008 0.992 0.046 40.123 39.807
80 1.4 7 0.011 0.989 0.049 43.210 42.755
100 1.4 7 0.013 0.987 0.049 43.210 42.641
150 1.5 7.5 0.020 0.980 0.053 46.296 45.383
200 1.6 8 0.026 0.974 0.056 49.383 48.083
250 1.8 9 0.033 0.967 0.063 55.556 53.728
300 1.9 9.5 0.039 0.961 0.067 58.642 56.327
350 2 10 0.046 0.954 0.070 61.728 58.886
400 2.1 10.5 0.053 0.947 0.074 64.815 61.404
450 2.2 11 0.059 0.941 0.077 67.901 63.881
500 2.3 11.5 0.066 0.934 0.081 70.988 66.317
600 2.4 12 0.079 0.921 0.084 74.074 68.226
700 2.5 12.5 0.092 0.908 0.088 77.160 70.054
800 2.6 13 0.105 0.895 0.091 80.247 71.800
900 2.6 13 0.118 0.882 0.091 80.247 70.744
1000 2.6 13 0.132 0.868 0.091 80.247 69.688
1100 2.7 13.5 0.145 0.855 0.095 83.333 71.272
1200 2.7 13.5 0.158 0.842 0.095 83.333 70.175
1300 2.7 13.5 0.171 0.829 0.095 83.333 69.079
1400 2.7 13.5 0.184 0.816 0.095 83.333 67.982
1500 2.7 13.5 0.197 0.803 0.095 83.333 66.886
1600 2.7 13.5 0.211 0.789 0.095 83.333 65.789

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DIMENSIONS

All specimens have the same constant dimensions below:

Diameter: 38.0mm – 0.038m
Area: 1134.45mm – 1.134 ∗ 10−3 m
Length (Ho ): 76mm – 0.076m
Proving ring constant: 0.007 KN/DIV

WATER CONTENT OF EACH SPECIMEN

Table 4: Water content of each specimen

Specimen Specimen 1 Specimen 2 Specimen 3

Container number 2 3 1
Mass of container, M1 (g) 14 13 15
Mass of container + wet soil , M2 (g) 31 30 31
Mass of container + dry soil , M3 (g) 28 27 28
Mass of water, M4 = M2 -M3 (g) 3 3 3
Mass of dry soil, M5 = M3 -M1 (g) 14 14 13
Water content, M4 ⁄M5 ∗ 100% 20 21.43 23.08

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SAMPLE CALCULATIONS

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GRAPH

Stress-strain graph of all specimens

80.00

70.00 Specimen 1
60.00 Specimen 2
Specimen 3
50.00

40.00

30.00

20.00

10.00

0.00
0.000 0.050 0.100 0.150 0.200 0.250

Figure 2.3. A graph of Stress against strain plotted for all specimen

Figure 2.4 Multi stage UU test (adopted from Barnes. G, 2000)

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FAILURE MODE

Figure 2.6. Shear strength of fissured clays (adopted from Barnes. G, 2000)

Figure 2.7. Failure mode observed in the lab specimen

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ANALYSIS AND CONCLUSION

As the axial load on the specimen increases a shortening in length takes place with a
corresponding increase in diameter. When drainage becomes allowable, the volume
of the sample will decrease. This was measured by the strain dial gauge which
indicates the change in length of the specimen. Drainage conditions during shearing
will heavily affect the strength parameters of the soils. The specimen in the experiment
was subject to compressive stresses set along three orthogonal axes, applied in two
stages. The test was continued by increasing the axial load as the cell pressure is held
constant. The compressive stress is increased with deviator stress. Graphs were used
to analyse the data, as plots shows the stress condition at failure for each test. Failure
occurs at the peak of the graph as shown above on the different specimens used.

Ultimate strength- From the graph it is observed that there is an increase cell
pressure applied, in proportional to the peak strength. This is due to the resistance of
the soil. The soil with the greatest cell pressure 200 is having the greatest resistance
as seen in figure 2.3.

Residual strength- It is observed that there is an increase cell pressure applied, in

proportional to the residual strength. This is due to the resistance of the soil. The soil
with the greatest cell pressure 200 is having the greatest resistance as seen in figure
2.3.

Critical state strength- Sometimes referred to as to the ultimate strength (mostly in

loose sand or soft clay). After a significant amount of shear strain, a soil will achieve a
constant volume state and it will continue to shear at this constant volume without
change in volume or void ratio. It is observed that specimen with the intermediate cell
pressure (specimen 2) has the greatest critical state strength, due to the specimen
having the longest constant shear.

There is no shear stress developed on the sides, but only on the vertical and lateral
axial planes, these were then referred to as the principal stresses. As the specimen
shortens under the load, the diameter will increase in dense or over consolidated
samples in which the specimen may shear clearly along the slip surface as the peak
stress is reached. In lightly over-consolidated soil the shear will be less clear.

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From the failure mode of the specimen it is observed that the soil is an over
consolidated soil with physical evidence of fissures. Fissures exists in most over
consolidation clays producing planes of weakness. The type of fissure observed in this
lab test is a single smooth fissure inclining at a 45° to the horizontal as seen in figure
2.6 and figure 2.7.

The shear strength of a cohesive soil depends upon the degree of saturation,
pressure and drainage conditions. During testing, the drainage valve was closed
during the consolidation stage, this caused the soil not to gain any strength during this
phase. A Mohr’s circle was then drawn to obtain the shear strength and the gradient
of the test specimen. In the Mohr’s circle drawn, it observed that the slope obtained is
not in relation to the expected theoretical slope. This then proves that this was a failed
lab test. From the Mohr’s circle plotted, it was observed that the 1 st circle plotted had
errors while it was performed in the lab which is why the circle is not reaching the
failure envelope, also the gradient is >0. The expected theoretical value is equal to
zero. Failure is due to the soils being compacted with few air void contents present
and the test being a multistage UU test. In a multistage process, shear stress is applied
under confining pressure at a slower rate to allow more readings to be taken. The soil
structure of the soil will be disturbed to a certain degree, which was observed in the
Mohr’s circle. If the soil was tested to a constant moisture content it is meant to attain
one failure strength regardless of the cell pressure. The steps in stress-strain curve
are as a result of the initial stiffness increase caused when the cell pressure was
increased. There is a tendency to imagine three different Mohr’s circles when really
the stress-strain plot is continuous. Thus the results are often reported with three
different Mohr’s circles giving a reduced cohesion intercept 𝐶𝑈 and gradient ø𝑈 value
greater than zero, which is inaccurate, as seen in figure 2.4. Using these small values
in a shallow foundations can be dangerous overestimate of stability. The lab
experienced failure, to ensure this does not occur in the future, better attention should
be allocated to the reliability of the results. For example if more than one person reads
the value and confirms the reading this will make our results more reliable, thus,
increasing the accuracy of our results and minimising the error. The chance of
equipment error can be reduced by checking the equipment before conducting the
experiment. Also taking more readings will increase the reliability of our results, but if
the procedure is not well adopted, then the lab would be completed in a wrong trend.

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REFERENCES

ASTM D2850-95(1999), Standard Test Method for Unconsolidated-UNDRAINED

TRIAXIAL COMPRESSIONTEST on Cohesive Soils, ASTM International, West
Conshohocken, PA, 1999, www.astm.org

ASTM D6467-13, Standard Test Method for Torsional Ring Shear Test to Determine
Drained Residual Shear Strength of Cohesive Soils, ASTM International, West
Conshohocken, PA, 2013, www.astm.org

Barnes, G. (2000) Soil Mechanics: principles and practice. 2nd ed. Hampshire:
Palgrave Macmillan.

D. Y. F. HO and D. G. FREDLUND (1982) A multistage TRIAXIAL test for

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