1. What is a soil in an engineering context? Define.
2. (a) What is a clay?
(b) What are the major properties and characteristics of clay? Discuss.
(c) Define the terms Diffused Double layer, adsorbed water and absorbed water.
3. What are the three major clay groups? Discuss their chemistry.
4. A dry soil sample of 525 g is subjected to particle size analysis (sieve analysis and hydrometer analysis).
The sieve analysis data are given below.
|
Sieve mesh aperture size (mm)
|
Mass of soil retained (g)
|
|
4.75
|
50.0
|
|
2.00
|
36.3
|
|
0.84
|
42.1
|
|
0.425
|
40.4
|
|
0.25
|
23.5
|
|
0.106
|
91.5
|
|
0.075
|
10.2
|
|
Pan
|
231.0
|
Hydrometer analysis results are as follows.
|
Diameter of the particle (mm)
|
% Finer
|
|
0.03
|
37.8
|
|
0.02
|
31.6
|
|
0.01
|
24.1
|
|
0.008
|
20.8
|
|
0.004
|
15.0
|
|
0.001
|
8.4
|
5. Complete the particle size distribution calculations, draw the grading curve and classify the soil according to the Unified Soil Classification System.
Soil excavated from a borrow site is being used to build an embankment. The void ratio of the soil at the borrow is 1.07 and the porosity of the compacted soil in the embankment is 43%. If the volume of excavation is 220,000m3, how many cubic meters of embankment can be built using this soil?
6. Soil for a compacted earth fill is available from three different borrow sites. At the earth fill the soil is to be compacted to a void ratio of 0.65 with finished volume of 150,000m3. The in situ void ratios and the costs (soil and transportation) per cubic metre for the three sites are given below. Which site would be economical?
|
Borrow
|
Void ratio
|
Cost/m3
|
|
A
|
0.85
|
7.80
|
|
B
|
1.1
|
7.20
|
|
C
|
1.4
|
6.60
|
7. A sub-base for an airport runway, 100 m wide, 2000 m long and 500 mm thick, is to be constructed out of a clayey sand excavated from a nearby borrow, where the in situ water content is 6%. This soil is being transported in trucks having capacity of 8 m3, where each load weighs 13.2 tonnes. In the sub-base course, the soil will be placed at a water content of 14.2% to a dry density of 1.89 t/m3.
(a) How many truck loads will be required to complete the job?
(b) How many litres of water should be added to each truck load?
(c) If the sub-base becomes saturated later, without any change in volume, what would be the water content? (Assume Gs = 2.7).