’

JE – 942

*JE942*

I Semester M.E. (Civil) (Geotechnical Engineering/EQ. Engg.) Degree Examination, July/August 2013 (Semester Scheme) 2k8 Gt 104/2k8 EQ104 : ADVANCED SOIL MECHANICS (Common to GT/EQ) Time : 3 Hours

Max. Marks : 100

Instructions : i) Answer any five full questions. ii) Missing data, if any may be assumed suitably. 1. a) List the basic Engineering properties of soil and critically comment on their use. 10 b) What are clay forming minerals ? Explain the structure of important clay forming minerals.

10

2. a) What is diffused double layer ? Explain the Guoy-Chapman diffused double layer theory. 10 b) In a hydrometer analysis, the corrected hydrometer reading at the start of sedimentation was 28. After a lapse of 30 minutes, the corrected hydrometer reading was 12 and the corresponding effective depth 10.5 cm. Take G = 2.70, η = 0.001 N-S/m2 and determine the weight of solids mixed in the suspension, the effective diameter corresponding to 30 minutes reading and the percentage of particles finer than this size. 10 3. a) State and explain Bragg’s law. How is it useful in the qualitative determination of clay minerals ? 6 b) What is base exchange capacity of soils ? How is it determined in the laboratory ? Explain.

6

c) Explain the “Texture” and “Structure” of soils.

8

4. a) Explain briefly the Engineering properties of ‘Compacted soils’. b) What is field compaction control ? Explain different methods for field compaction control.

6 6 P.T.O.

*JE942*

JE – 942

c) The soil in a borrow pit has a void ratio of 0.90. A fill-in-place volume of 20,000 m3 is to be constructed with an in-place dry density of 18.9 kN/m3. If the cost of compensation is Rs. 100/- per cubic metre of soil, determine the total compensation. 5. a) What is “pressure bulb” ? What are its uses in soil Engineering practice ?

8 6

b) Explain and construct Newmark’s chart with an influence value of 0.005. A raft of size (4m×4m) carries a uniform load of 200 kPa. Using the Newmarks, chart, calculate the stress increment at a point in the soil which is 4m below the centre of the loaded area. 14 6. a) Briefly explain the mechanism of shear strength of soils.

6

b) Differentiate between shear strength parameters obtained from total and effective stress considerations.

6

c) A particular soil failed under a major principal stress of 300 kN/m2. If for the same soil, the minor principal stress had been 200 kN/m2, determine what the major principal stress would have been if :(i) φ = 30° and (ii) φ = 0°.

8

7. a) Differentiate between “Total settlement” and “Differential settlement”. What are the harmful effects of differential settlement on structures ? What are the probable remedial measures ? 10 b) A boring indicates the existence of a 20 m thick clay stratum above sand. The hydrostatic pressure at the top of the clay layer is 600 kPa. The pore pressure at the bottom of the clay layer is reduced permanently by 600 kPa by pumping. If the void ratio of the clay is reduced from 1.00 to 0.975 by pumping, estimate the ultimate settlement due to this. 10 8. Write notes on the following : i) SEM studies ii) Effective stress iii) Pore-pressure co-efficients iv) Soil deposits in India. _______________

(5×4=20)