ENGI 5723 - Geotechnical Engineering II

Laboratory Tests

Laboratory: Unconfined Compression Test

Test Date: March 3rd, 2017

Report Submittal Date: March 10th, 2017

Submitted to: Dr. Bipul Hawlader

Submitted by: Group C10

Ahmed Ahmed - 201336344

Oaies Kiblawi - 201351350
Muhammad uzair khokhar-201350949
Mohammed Yaquob Gul M Khan - 201413234
Helio Garcia 201649605

Winter 2017
Faculty of Engineering and Applied Science
Memorial University of Newfoundland

Purpose
 The purpose of this experiment was to load our soil sample with different levels of normal
loading in order to determine the undrained shear strength and unconfined compressive strength
of the specimen.

Procedure

1. Obtain prepared a sample from the lab technician.

a. Measure the sample at three points, 120 apart and average the values
b. At the top, mid-height and bottom of the sample, take three diameter measurements.
c. Find the mass of the sample

2. Determine the deformation at 15% strain of the soil sample, so that we know when to end
loading incase loading has not peaked.
i. Find the volume and density of the specimen
ii. Weigh a moisture cup so that the moisture content can be determined afterwards.

3. Align the specimen in the compression machine. Adjust so that the sample is just making contact
with both platens (loading cell reading = 0.5kg). Zero both load device and deformation dial.

4. Start the test and take load and deformation readings at 10, 25, 50, 100 and every 50 to 100 dial
divisions after, until one of the following occurs:
a. Load decreases on sample significantly
b. Load holds constant for four readings
c. Deformation is significantly past 15 percent strain, say to about 20 to 25 percent
5. Weigh the sample immediately after removing from the compression machine for water content
measurement.

6. Place cup in the oven.

7. Return the next day and weigh the dry samples to compute the water content and the dry density.

8. Compute the strain, corrected area, and stress for 8-10 spaced points and create a stress vs. strain
graph.

9. Find the values of qu and cu on the stress-strain and Mohrs circle plots.

Deviation from ASTM Standards

The samples used for testing were prepared by the TA prior to conducting the experiment,
therefore we can not conclude that standard preparation procedures were followed as per ASTM
standards.

Standards for the unconfined compression test specified by ASTM D2166 that were not followed
during the experiment include:

Zero the deformation indicator or record the initial reading of the electronic deformation device.

Apply the load so as to produce an axial strain at a rate of 12 to 2 %/min. Followed by recording
load, deformation, and time values at sufficient intervals. During the experiment, the axial strain
rate per minute was not recorded.

The rate of strain should be chosen so that the time to failure does not exceed about 15 min. As
mentioned above, the rate of strain was not recorded.

Results & Calculations

Sample 1 (Our)
Mass
Diameter Type (g)
Type (mm) Cup 9.8
Dia 1 33.42 Cup w/
Dia 2 33.4 sample 35.1
Dia 3 33.39 Sample
Average before 25.3
Dia. 33.40 drying
Sample
30.3
after drying
 Type Length (mm)
Height 1 64.68
Height 2 65.06
Height 3 65
Area (cm2) Average8.76158 23.41%
Moisture
Height 64.91
content
Chart and Graph

Tim Disp(i Disp(m %Strai Corrected Load Load Stress(k

Strain
e n) m) n Area(cm2) (lbs) (kN) Pa)
0 0 0 0 0.00 8.76 0 0 0
10 0.014 0.343 0.005 0.53 8.81 9.2 409.24 46.46
20 0.028 0.704 0.011 1.08 8.86 16.7 742.85 83.87
1023.0
30 0.040 1.024 0.016 1.58 8.90 23 114.93
9
1272.1
40 0.053 1.354 0.021 2.09 8.95 28.6 142.17
9
1490.1
50 0.067 1.697 0.026 2.61 9.00 33.5 165.63
5
1659.1
60 0.079 2.004 0.031 3.09 9.04 37.3 183.52
9
1828.2
70 0.093 2.352 0.036 3.62 9.09 41.1 201.10
2
1966.1
80 0.106 2.682 0.041 4.13 9.14 44.2 215.13
1
2086.2
90 0.118 3.007 0.046 4.63 9.19 46.9 227.08
2
2197.4
100 0.132 3.353 0.052 5.17 9.24 49.4 237.85
2
2299.7
110 0.145 3.673 0.057 5.66 9.29 51.7 247.63
3
2384.2
120 0.158 4.013 0.062 6.18 9.34 53.6 255.30
5
2468.7
130 0.171 4.348 0.067 6.70 9.39 55.5 262.90
6
2539.9
140 0.184 4.666 0.072 7.19 9.44 57.1 269.06
3
2611.1
150 0.197 5.009 0.077 7.72 9.49 58.7 275.02
1
2673.3
160 0.210 5.321 0.082 8.20 9.54 60.1 280.11
8
2731.2
170 0.222 5.646 0.087 8.70 9.60 61.4 284.61
1
2775.6
180 0.236 5.984 0.092 9.22 9.65 62.4 287.60
9
2820.1
190 0.248 6.307 0.097 9.72 9.70 63.4 290.61
7
2851.3
200 0.262 6.665 0.103 10.27 9.76 64.1 292.02
1
2873.5
210 0.274 6.970 0.107 10.74 9.82 64.6 292.76
5
 2878.0
220 0.288 7.303 0.112 11.25 9.87 64.7 291.53
0
2864.6
230 0.301 7.656 0.118 11.79 9.93 64.4 288.40
5
2637.8
240 0.313 7.938 0.122 12.23 9.98 59.3 264.25
0

Soil Sample 1
350
300
250
200
Stress (kPa) 150
100
50
0
0.00 5.00 10.00 15.00

% Strain

Mohr Circle
 qu= 292.76 kPa cu=qu/2 = 146.37 kPa

Results & Calculations

Sample 2
Mass
Type
(g)
Diameter Cup 9.8
Type (mm)
Cup w/
Dia 1 33.3 34.6
sample
Dia 2 33.28 Sample 24.8
Dia 3 33.4 Type
before Length
Average drying (mm)
Dia. 33.33 Height 1 20.3
Sample 65
Height
after 2 65.45
Height 3
drying 65.04
Average 65.16
Area (cm2) 8.7249 Height 22.17%
Moisture
content
Chart and Graph:

Disp(i Disp(m %Strai Corrected Load Stress(kP

Time Strain Load (kN)
n) m) n Area(cm2) (lbs) a)
0 0 0 0 0.00 8.72 0 0 0
0.009
10 0.251 0.004 0.39 8.76 191.27 21.84
9 4.3
0.022
20 0.566 0.009 0.87 8.80 378.10 42.96
3 8.5
0.035
30 0.894 0.014 1.37 8.85 858.51 97.05
2 19.3
0.047
40 1.201 0.018 1.84 8.89 1365.60 153.63
3 30.7
0.060
50 1.537 0.024 2.36 8.94 1703.67 190.66
5 38.3
0.073
60 1.867 0.029 2.87 8.98 1979.46 220.37
5 44.5
0.086
70 2.202 0.034 3.38 9.03 2197.42 243.34
7 49.4
0.100
80 2.550 0.039 3.91 9.08 2370.90 261.10
4 53.3
0.112
90 2.863 0.044 4.39 9.13 2504.35 274.42
7 56.3
0.126
100 3.211 0.049 4.93 9.18 2637.80 287.43
4 59.3
110 0.14 3.556 0.055 5.46 9.23 61.7 2744.55 297.40
0.152
120 3.884 0.060 5.96 9.28 2842.41 306.36
9 63.9
0.166
130 4.232 0.065 6.49 9.33 2926.93 313.68
6 65.8
0.178
140 4.531 0.070 6.95 9.38 3002.55 320.20
4 67.5
150 0.192 4.887 0.075 7.50 9.43 69.2 3078.17 326.34
 4
0.204
160 5.204 0.080 7.99 9.48 3149.34 332.13
9 70.8
0.218
170 5.552 0.085 8.52 9.54 3220.51 337.66
6 72.4
0.230
180 5.860 0.090 8.99 9.59 3278.34 341.95
7 73.7
0.243
190 6.190 0.095 9.50 9.64 3345.06 346.97
7 75.2
0.256
200 6.510 0.100 9.99 9.69 3402.89 351.05
3 76.5
0.270
210 6.863 0.105 10.53 9.75 3451.82 353.96
2 77.6
0.282
220 7.173 0.110 11.01 9.80 3496.30 356.61
4 78.6
0.295
230 7.511 0.115 11.53 9.86 3545.23 359.50
7 79.7
0.308
240 7.844 0.120 12.04 9.92 3594.16 362.36
8 80.8
0.322
250 8.184 0.126 12.56 9.98 3634.20 364.22
2 81.7
0.335
260 8.512 0.131 13.06 10.04 3669.78 365.67
1 82.5
0.348
270 8.852 0.136 13.58 10.10 3700.92 366.55
5 83.2
0.354
280 8.997 0.138 13.81 10.12 3398.44 335.73
2 76.4
 Soil Sample 2
400

350

300

250

200
Stress (kPa)
150

100

50

0
0.00 5.00 10.00 15.00

% Strain

Mohr Circle:
 qu= 366.55 kPa cu=qu/2 = 183.27 kPa

Discussion of Sample 1 (our)

The group manually recorded the data produced by the unconfined compression test until the
failure condition was met. Through plotting the stress vs. strain chart and the Mohrs circle for
specimen testing, an unconfined compressive strength of 292.76 kPa was obtained, while an
undrained shear strength value of 146.38 kPa was achieved. As per table 12.4 of the course
textbook, 200-400 kPa is an expected unconfined compressive strength value for very stiff clays.
The specimen tested in lab appeared to be very stiff as it was visibly compact and exhibited
stiffness upon handling. It is reasonable to surmise that the clay was very stiff due to the data
extracted, although the origin of the specimen was unknown, therefore it is impossible to source
the projected values for strength of the provided soil type. The moisture content for the clay
specimen was determined to be 23.41%/22.17%, respectively per two sample cans. Potential
sources of error for the lab include:

The soil sample cans were left unattended overnight in an oven to dry, thus potential disturbance
of soil samples may have occurred, skewing moisture content values.
To commence loading, the instrument must contact the face of the sample before zeroing the
instrument. For this reason, some measure of strain may have occurred prior to zeroing the
instrument.
As with all experiments requiring manual record of data, communication error may be present
through either record or statement of the experimental data. Skew in the data unexplainable by
typical experimental error may be attributable to either incorrect record or communication of
experimental values.

Conclusion

From the experiment we were able to determine the undrained shear strength (cu) and
unconfined compressive strength (qu) of our soil specimen at different levels of normal loading.
The expected results were achieved, as we increased our normal load (starting at 1 kg), and
increased the load by 10, 25, 50, 100 and 50 dial divisions thereafter until failure occurred to find
our maximum shear stress to be 146.38 kPa. We had further success in our experiment in the
plotting of our strain- stress curve and Mohr's circle. The lab helped demonstrate how the
undrained shear strength and unconfined compressive strength can be determined through the
unconfined compression test method.