7/30/2019 r7320101 Geotechnical Engineering i

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Code :R7320101 R07III B.Tech II Semester (R07) Supplementary Examinations, December 2010

GEOTECHNICAL ENGINEERING-I(Civil Engineering)

Time: 3 hours Max Marks: 80Answer any FIVE questions

All questions carry equal marks

1. A soil is to be excavated from a borrow pit which has a density of 1.75 g/cc and water contentof 12%. The G=2.7. the soil is compacted so that the water content is 18% and dry density1.65 g/cc for 1000m3 of soil, estimate

(a) quantity of soil to be excavated from the pit,

(b) Amount of water to be added, also determine the void ratios of soil in borrow pit and fill.

2. (a) Define stokes law and mention the corrections applied in hydrometer analysis.

(b) A soil sample has wL

=20% wP

=12% classify the soil as per IS classification system.Sieve size %passing2.032mm 1000.422mm 850.075mm 38

3. Define Darcys law? Explain the factors effecting permeability of soil.

4. (a) What is quick sand condition? Derive the expression for hydraulic gradient in quick sandcondition.

(b) A granular soil deposit is 7m deep over a impermeable layer. The ground water table is4m below ground level. The deposit has a zone of capillary rise of 1.2m with saturation

of 50%. Plot the variation of total stress, pore water pressure, effective stress with e=0.6,G=2.65.

5. (a) Explain about pressure bulb concept?

(b) A line load of 100 kN/meter run extends to a long distance. Determine the intensity ofvertical stress at the point 2m below the surface and

i. directly under the line load andii. at a distance 2m perpendicular to line load

6. (a) Define:

i. Relative compaction

ii. Placement water contentiii. Dry side of optimum and wet side of optimum

(b) What are the factors that effect compaction of soil?

7. (a) Explain any one of the graphical method for getting coefficient of consolidation

(b) The void ratio of clay A decreased from 0.572 to 0.505 under the change in pressure from120 to 180 kg/m2. The void ratio of clay B decreased from 0.612 to 0.597 under sameincrease in pressure. The thickness of soil sample A is 1.5 times that of B. The timerequired for 50% consolidation is 3 times longer for sample B than for A. What is theratios of their coefficient of permetabilities.

8. (a) Explain Mohr-Coulombs failure theory.

(b) In an unconfined compression apparatus a cylindrical soil sample of clay 8cm long and 4cmdiameter fails under the load of 80N. Determine the shearing resistance if failure occursat 10% strain.

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