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TitleConsolidation Test
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Page 10

Kwan Kam Hung University No.: 2004170968 10 / 20

8. Release the load and take the sample and ring from the cell. Dry the surfaces of the

sample with filter papers and re-weigh.

9. Place the sample in the oven for at least 24 hours, remove from and re-weigh.

Results and Calculations
Inner Diameter of Ring (m) 0.0763

Height of Ring (m) 0.0188
Cross Sectional Area A (m2) 0.0045723

Table 1 The dimensions of the metal ring of the consolidation cell.

1. Calculations of the Final Void Ratio ef of the Soil Samples.

Water Content w

%
m

m

%
W

W

s

w

s

w

100

100

×=

×=

where w = water content

Ww = weight of water

Ws = weight of solid

mw = mass of water

ms = mass of solid

Void Ratio e

Assume the samples are fully saturated at the beginning of the test. Therefore, the

degree of saturation, Sr is equal to 1. The volume of void is equal to the volume of

water.

e

wG
S sr =

e = wGs when Sr = 1

where e = void ratio

Sr = degree of saturation

Gs = Specific gravity = 2.65

Sample A B C D
Loading (kPa) 25 50 100 200

Mass of disc (g) 70.4 74 75.7 75.3
Mass of disc + wet soil + ring (g) 317.4 316.5 314.6 315.9
Mass of disc + dry soil + ring (g) 268.4 267.2 263.4 269.7

Mass of ring (g) 91.9 92.3 92.9 94.3

Page 20

Kwan Kam Hung University No.: 2004170968 20 / 20

6. Large air bubbles might be entrapped in the soil samples due to insufficient

compaction. The consolidation process might then be affected as extra voids were

introduced to the specimens.

7. The first few readings for the change in soil thickness were subjected to errors, as the

pore water inside the soil samples would not take up the applied load instantaneously,

but might require several minutes to complete the process.

Conclusion
In the experiment, the consolidation of the remoulded soil sample under four different

applied loadings was studied. It was found that the void ratios e of the soil samples

decreased with time due to the drainage of pore water.

The compressibility index was determined from the graph of void ratio e against

logarithm of applied pressure and was found to be 0.0612. In addition, it was discovered

that the rate of consolidation decreased with time but increased with the applied loading.

The time for 90% consolidation t90 and coefficient of consolidation Cv were found using

the root time method (Taylor’s method). The rates of consolidation under four different

applied loadings are summarized in the table below:
Sample A B C D

Load (kPa) 25 50 100 200
Coefficient of consolidation Cv (cm2/s) 0.0011169 0.0012196 0.0013793 0.0019334

Table 10 Summary of the coefficients of consolidation Cv for the remoulded soil sample

under 25, 50, 100 and 200kPa applied loadings.

Reference
1. R. F. Craig, Soil Mechanics, E & FN Spon Press, 6th Edition, 1997.

2. R. Whitlow, Basic Soil Mechanics, Addison Wesley Longman Limited, 3rd Edition,

1995.

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