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VTU Civil Engineering (Semester 6)
Geotechnical Engineering 2
December 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) Discuss about the importance of sub-soil exploration program.
6 M
1 (b) Explain the method of seismic refraction.
7 M
1 (c) What are the methods available for dewatching? Explain any one method.
7 M

2 (a) Derive the expressions for vertical stress and shear stress by using Boussineq's theory. Also compare this theory with Westergaard's theory.
8 M
2 (b) Write a note on pressure distribution diagrams.
6 M
2 (c) A load of 1000kN acts as a point load at the surface of a soil mass. Estimate the stress at a point 3m above and 4m away from the point of action of the load of Boussinesq's formula. Compare the value with the result from Westergaars's theory.
6 M

3 (a) What are flows nets? Explain the characteristics of flownet with a neat sketch. What are their uses?
8 M
3 (b) Explain Graphical method for drawing flow net.
6 M
3 (c) For a homogeneous earth dam 32m high and 2m free board, a flow net was constructed with 4 flow channels. The number of potential drops was 20. The dam has a horizontal filter at the base near the toe. The coefficient of permeability of the soil was 9×10-2 mm/s. Determine the anticipated seepage, if the length of the dam is 100m.
6 M

4 (a) Define At rest, Active and Passive Earth pressures.
6 M
4 (b) Explain Rankine's theory for calculating Active pressure in cohesion less soils for no surcharge.
6 M
4 (c) A retaining wall with a smooth vertical back is 10m high and retains a 2-layers sand backfill with the following properties.
0 - 5m depth: C"=0, ϕ'=30°, r=18 kN/m3
Below:           C"=0, ϕ'=34°, r=20 kN/m3
Show that active earth pressure distribution, assuming that the water table is well below the base of the wall.
8 M

5 (a) What are the causes for failure of slopes?
6 M
5 (b) Discuss the Swedish method of slices for a cohesive frictional soil.
8 M
5 (c) An embankment is inclines at an angles of 35° and its height is 15m. The angle of shearing resistance is 15° and the cohesion intercept is 200kN/m2. The unit weight of soil is 18.0 kN/m3. If Taylor's stability number is 0.06, find the factor of safety with respect to cohesion.
6 M

6 (a) Define safe bearing capacity, safe bearing pressure and allowable bearing pressure.
6 M
6 (b) Write a note on standard penetration test and its corrections.
8 M
6 (c) Calculate the ultimate bearing capacity of a 2m wide square footing resting on the ground surface of sand deposited with the following properties:
i) Unit weight 18.6 kN/m3 ii) Angle of internal friction 35°. Also calculate URG of same footing when it is placed at depth of 1m below the ground surface. Take Nq=41.4, Nr=42.2.
6 M

7 (a) Write a note on settlement of footings.
10 M
7 (b) A saturated clay 8m thick underlies a purposed new building. The existing overburden pressure at the centre of clay layer is 300 Kpa and load due to a new building increase the pressure by 200Kpa. The liquid limit of the soil is 75%. Water content of soil is 50%. GS= 2.7. Estimate consolidation settlement.
10 M

8 (a) Explain the factors affecting the choice of foundation.
6 M
8 (b) Discuss the proportion of isolated footing.
6 M
8 (c) Write a note on classification of pile foundations.
8 M

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