JNTU B.Tech II SOIL MECHANICS Previous Question Paper (December - 2017 - R13)

A clay soil has void ratio 0.7 and specific gravity 2.7, estimate its shrinkage limit.

A cohesionless soil has maximum and minimum void ratios are 0.8 and 0.4. In a natural state the same soil has a dry unit weight of 16.5 kN/m³. If the specific gravity of soil is 2.65, estimate the density index of soil.

What is the speciality of Westergaard’s approach as compared to Boussinesq’s analysis?

Define pressure bulb and write its importance. Also draw a typical pressure bulb under isolated footing and group of closely placed isolated footings.

Write the parameters, which are imparting shear strength in soil.

A cohesionless soil has failed at a deviator stress of 200 kPa corresponding to a cell pressure of 100 kPa. Estimate the angle of internal friction of soil.

Write the specifications of standard compaction and also estimate its compaction effort.

Distinguish single drainage and double drainage systems with clear illustrations.

A clay soil has undrained cohesion of 50 kPa and unit weight 20 kN/m³, Estimate the depth of tension crack.

List the factors that influence the failure of slopes.

Derive from fundamentals:

The dry unit weight of a sand sample in the loosest state is 13.34 kN/m³ and in the densest state, it is 21.19 kN/m³. Determine the density index of this sand when it has a porosity of 33%. Assume the grain specific gravity as 2.68.

Define and distinguish the following: (i) Adsorbed and Absorbed water (ii) Discharge velocity and seepage velocity.

An earth dam of 80 m wide is built on an impervious foundation with a horizontal filter at the base near the toe. The permeability of the soil in the horizontal and vertical directions is 8 × 10^-3 mm/s and 2 × 10^-3 mm/s respectively. The full reservoir level is 40 m above the filter. A flow net constructed for the transformed section of the dam, consists of four flow channels and 12 head drops. Estimate the seepage loss for the entire length of dam.

Explain how the vertical stress is estimated at a given depth and at the center of uniformly loaded large rectangular area, if vertical stress formula for corner of the area is given.

A raft of the size 4 m × 4 m carries a uniform load of 180 kN/m². Using the point load approximation with four equivalent point loads, calculate the stress increment at a point in the soil which is 4m below the centre of the loaded area.

Discuss the pore pressure, volume and stress-strain variations in cohesionless soils with neat graphical presentations.

A series of box shear (area of box = 3600 mm²) tests were conducted on a soil sample. For the results presented in below table, estimate the ‘cohesion’ and ‘angle of internal friction’ of soil.

What are the drained and undrained shear tests? Under what conditions should the drained shear strength or the undrained shear strength parameters are used? Explain.

The following data relate to a triaxial compression tests performed on a soil sample. Determine the shear parameters such as cohesion and angle of internal friction from the above data using the relation of σ1 and σ3.

What is preconsolidation pressure? Discuss its determination from the Casagrande’s graphical method.

There is a bed of compressible clay of 4 m thickness with pervious sand on top and impervious rock at the bottom. Consolidation test conducted on an undisturbed specimen of clay of 20 mm thick obtained from the same deposit showed that 90% settlement has reached in 4 hours. Estimate the time in years for the building founded over this deposit to reach 90% of its final settlement.

Define the following: (i) Immediate consolidation settlement, (ii) Primary consolidation settlement (iii) Degree of consolidation and (iv) Compression index.

Standard compaction test results on a soil sample as follows:

Explain Fellinius method for location of critical center of rotation.

A gravity retaining wall retains 9 m of a backfill, γ = 18 kN/m³ and φ = 30° with a uniform horizontal surface. Assume the wall interface to be vertical, determine the magnitude and point of application of the total active earth pressure force. Assume water table is at 3m below the backfill surface.

Differentiate both Rankine’s and Coulomb’s earth pressure theories. Explain the limitations of both the theories.

An embankment is inclined at an angle of 35° and its height is 15 m. The angle of shearing resistance is 15° and the cohesion intercept is 200 kN/m². The unit weight of soil is 18 kN/m³. If the Taylor’s stability number is 0.06, find the factor of safety with respect to cohesion.