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VTU Civil Engineering (Semester 5)
Geotechnical Engineering 1
June 2014
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Define: i) Void ratio; ii) Porosity; iii) Degree of saturation; iv) Water content; v) Dry unit weight; vi) Unit weight of soil solids; vii) Air content with the help of a three phase diagram; viii) %age of air voids.
5 M
1 (b) With usual notations derive the relationship; Sc=W.G.
5 M
1 (c) The volume of an undisturbed clay sample having a natural water content of 40% is 25.6×10-6 m3 and its weight is 0.435 N. Calculate the void ratio and degree of saturation of the sample, if specific gravity is 2.75. Solve by first principles.
10 M

2 (a) Define i) Liquid limit; ii) Plastic limit; iii) Shrinkage limit; iv) Relative consistency; v) Toughness index; vi) Slenderness ratio.
6 M
2 (b) A 100×10-6 m3 clay sample has natural water content of 30%. Its shrinkage limit s 18%. If the sp. gr. of solids is 2.72, what will be the volume of sample at a water content of 15%?
4 M
2 (c) In a liquid limit test specimens of certain sample of clay following readings are obtained:
The plastic limit of clay is 13% natural water content is 18%. Determine liquid limit, plasticity index, liquidity index, relative consistency, flow index and toghness index of soil.
 Water content (%) 31.93 27.62 25.51 23.3 No. of blows 5 16 23 42
10 M

3 (a) Explain the classification of fine grained soils as per Indian soil classification system.
6 M
3 (b) Define soil structure. Explain with neat sketches single grained and honey combed structures in soils.
6 M
3 (c) The following data refers to a sample of soil:
Percentage passing 4.75mm I.S. sieve = 64
percentage passing 75 micron I.S. sieve = 6
Coefficient of uniformity =7.5
Coefficient of curvatures =2.7
Plasticity index =2.5
Classify the soil
8 M

4 (a) List and explain the factors affecting the permeability of soils.
6 M
4 (b) A permeameter of 82mm diameter contains a sample of soil of length 350mm. It can be used for either constant head or falling head tests. The stand pipe used for the letter has a diameter of 25mm. In the constant head test the loss of head was 1160mm measured on a length of 250mm. When the rate of flow was 2.73 m/sec. Find the coefficient of permeability of the soil. If a falling head test was then conducted how much time would be taken for the head to drop from 1.5m to 1.0m?
8 M
4 (c) The effective sizes of two sands are 0.09 mm and 0.54 mm. The capillary rise of water in the first sand is 480mm. What is the capillary rise in second sand, if void is same for both sands?
6 M

5 (a) Explain Mohr-Coulomb theory as applied to soils.
5 M
5 (b) Explain the factors affecting the shear strength of soils.
5 M
5 (c) A deep clay stratum underlies a sand strata of 5m thick. The ground water table is found at 3m depth from GL. For sand G=2.65 and e=0.6. The sand above water table is 40% saturated. For clay if natural water content is 45% and G=2.70 draw total, effective and neutral pr. Variation diagrams up to a depth of 8m from GL.
10 M

6 (a) Explain the factors affecting compaction of soils.
8 M
6 (b) Following are the result of standard proctor test:
The sp.gr. of soil particles is 2.65.
Plot the following and determine OMC and MDD:
i) Moisture density curve.
ii) Zero air voids curve.
iii) Ten percent air content curve.
 Trial No. 1 2 3 4 5 Moisture content (%) 8.3 10.5 11.3 13.4 13.8 Bulk unit wt (kN/m3) 19.8 21.3 21.6 21.2 20.8
12 M

7 (a) Distinguish between normally consolidated soils and over consolidated soils.
6 M
7 (b) What are the assumptions made in Terzaghi's one dimensional consolidation theory?
8 M
7 (c) Explain the determination of preconsolidation pressure by casagrande method.
6 M

8 (a) With a neat sketch, explain the square root of time fitting method of determining coefficient of consolidaton.
6 M
8 (b) Explain how the shear tests are classified based on sample drainage conditions.
6 M
8 (c) A bed of compressible clay of 4m thickness has pervious sand on top and impervious rock at the bottom. In a consolidation test on an undisturbed specimen of clay from this deposit, 90% settlement was reached in 4hrs. The specimen was 20mm thick. Estimate the time in years for a building founded over this deposit to reach 90% of its final settlement.
8 M

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