CIE 352 – Soil Mechanics Practice Questions
1. Prove the following relationships
2. A sample of saturated clay was placed in a container and weighed. The weight
was 612g. The clay in its container was placed in an oven for 24 hours at 105◦C.
The weight reduced to a constant value of 510g. The weight of the container is
102g. If Gs=2.7, determine the (a) water content, (b) void ratio, (c) bulk unit
weight, (d) dry unit weight, and (e) effective unit weight.
3. A soil sample is proposed to be used for the construction of a road sub-base, upon
sampling and extracting the specimen, it is found that the volume of the soil
specimen is 60cmᶾ, and its mass is 180g. After being dried, the mass of the sample
is 93.43g. The particle specific gravity is 2.7.
Calculate (a) Wet density, (b) Dry density, (c) Saturated density, (d) Water
content, (e) Porosity (f) Degree of saturation.
4. Aggregates from a material storage site are required for the embankment of a
roadway. The porosity of the aggregates at the storage site is 80%, and the desired
porosity of the compacted aggregates in the embankment is 20%. For a section of
the embankment 7.6 m wide * 0.61 m compacted thickness * 305 m long,
calculate the volume of aggregates required.
5. A sample of a dry, coarse-grained material of mass 500 grams was shaken
through a nest of sieves, and the following results were obtained:
Sieve No.
4
10
20
40
100
200
Pan
Opening (mm)
4.75
2
0.85
0.425
0.15
0.075
Mass retained (grams)
0
14.8
98
90.1
181.9
108
6.1
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(a) Plot the particle size distribution (gradation) curve.
(b) Determine (1) the effective size, (2) the average particle size, (3) the
uniformity coefficient, and (4) the coefficient of curvature.
(c) Determine the textural composition of the soil (i.e., the amount of gravel, sand,
etc.).
6. An Embankment for a highway 30m wide and 1.5m in compacted thickness is to
be constructed from sandy soil trucked from a borrow pit. The water content of
the sandy soil in the borrow pit is 15% and its void ratio is 0.69. The swell is 1.2.
The specifications requires the embankment to be compacted to a dry unit weight
of 18kN/mᶾ. Determine, for a 1km length of embankment, the following: (5
marks)
a) The weight of the sandy soil from the borrow pit required to construct the
embankment.
b) The number of truckloads of the sandy soil required for the construction. The
full capacity of each truck is 22.2mᶾ, and the local government regulations
require a maximum loaded capacity of 90%.
c) Weight of water per truckload of sandy soil.
d) Degree of saturation of the sandy soil in situ.
7. A fine-grained soil has a liquid limit of 300% and a plastic limit of 55%. The
natural water content of the soil in the field is 80% and the clay content is 60%.
(a) Determine the plasticity index, the liquidity index, and the activity.
(b) What is the soil state in the field?
(c) What is the predominant mineral in this soil?
(d) If this soil were under a concrete slab used as a foundation for a building and
water were to seep into it from watering of a lawn, what would you expect to
happen to the foundation?
8. An earth dam requires 1 million cubic meters of soil compacted to a void ratio of
0.8. In the vicinity of the proposed dam, three borrow pits were identified as
having suitable materials. The cost of purchasing the soil and the cost of
excavation are the same for each borrow pit. The only cost difference is
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transportation cost. The table below provides the void ratio and the transportation
cost for each borrow pit. Which borrow pit would be the most economical?
Borrow
pit
1
2
3
Void
Ratio
1.8
0.9
1.5
Swell
factor
1.1
1.2
1.1
Transportation cost
(K/m3)
9.30
15.50
11.63
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