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D192077 Pages:3

PART छ
Answer any two full questions, each carries 15 marks

Determine the ratio of average coefficient of permeability in the horizontal to
vertical direction for a deposit consists of three layers 6m, 1.5m and 3m and
having coefficient of permeability 2.5X107 mm/s, 3.5X10° mm/s, 4.5X10*
mm/s. Assume the layer to be isotropic.

A direct shear test was conducted on sand gave a failure shear stress of 70 kN/m?
when the normal stress was 200 kN/m*. Draw the mohr circle, mohr failure
envelope and find the angle of shear resistance. Find the principal stresses at
failure and orientation principal planes.

State and explain Darcy’ s law.

In a variable head permeability test the initial head is 50 cm. The head drops by
15cm in 15 minutes. Find the time required to run the test for the final head to
become 20 cm. Take the height and cross sectional area of the soil sample as 6
cm and 50 cm’ respectively. Take the area of stand pipe as 0.5 ണ്‌.

An unconfined compression test was conducted on clay sample 150 mm diameter
and 300 mm height. The failure load was 15014 and axial deformation at the time
of failure was 3 mm. Find the cohesive strength of the soil.

Write the merits and demerits of direct shear test

A soil profile consists of surface layer of gravel 4 m thickness having density 17
kN/m*, an intermediate layer of clay 3.5m thickness having saturated density 18
kN/m? and bottom layer of sand 4 m thickness having saturated density of 19
kN/m*. The water table is at 4m from ground level. Determine the total stress,
neutral stress and effective stress at bottom and interface layers.

PART C
Answer any two full questions, each carries 20 marks

Define normally consolidated soil, over consolidated soil and under consolidated

soil.

Write down the weight of hammer, height of fall, number of layers, volume of
the mould and number of blows per layer for 15.1.1811! compaction test.

At a site the soil consists of sand up to 3.5m depth and from 3.5m to 7m the soil
is normally consolidated clay. The water table is at 1.5m from ground level. The
density of sand is 19 KN/m* above the water table and 20 kN/m* below the water
table. The natural water content and specific gravity of clay are 60% and 2.65
respectively. The liquid limit of clay is 75%. Estimate the probable settlement of
clay layer, if the pressure at mid-height of clay layer increases by 40kPa.

Explain the method to find the preconsolidation pressure.

Explain the procedure for determination of coefficient of consolidation by
logarithm of time fitting method.

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