Jawaharlal Nehru Technological University Hyderabad B.Tech III GEOTECHNICAL ENGINEERING Previous Question Paper (November/December - 2018 - R13)

Draw typical grain-size distribution curves for (i) uniform (ii) gap graded (iii) well graded soils.

List the common clay minerals and summarize their key properties.

Explain the terms quick condition and critical hydraulic condition.

What are the assumptions for Darcy’s law to be valid? Discuss each of them.

State the basic requirements to be satisfied for the validity of Boussinesq’s equation for stress distribution.

Explain the concept of ‘Pressure Bulb’ in soils. List the various factors that influence the compaction of soils, show their influence with illustrative sketches of compaction curves.

Define the terms ‘Compression index’, ‘coefficient of consolidation’, and ‘coefficient of compressibility’.

What are the assumption’s in Terzaghi’s theory of one-dimensional consolidation?

Differentiate between unconsolidated undrained test and a drained test.

Explain basic differences between a box shear test and a triaxial shear test for soils.

A soil sample is partially saturated. Its natural moisture content was found to be 22% and bulk density 2 g/cm³. If the specific gravity of the solid particles be 2.65 and the density of water be taken as 1 g/cm³., find out the degree of saturation and the void ratio. If the soil is saturated what will be its saturated unit weight?

An undisturbed saturated specimen of clay has a volume of 18.9 cm³ and a mass of 30.2 g. on oven drying, the mass reduces to 18.0 g. the volume of dry specimen as determined by displacement of mercury is 9.9 cm³. Determine shrinkage limit, specific gravity, shrinkage ratio and volumetric shrinkage.

The liquid limit of a soil is 59%, the plastic limit is 23% and the natural moisture content is 46%. What is the liquidity index? What is its significance? Define shrinkage limit and shrinkage ratio.

A clayey soil has natural moisture content of 15.8%. The specific gravity of soil is 2.72. Its saturation percentage is 70.8%. The soil is allowed to soak up water. After some time, the saturation increases to 90.8%. Find out the water content of the soil in latter case.

In a falling head permeability test on sample 12.2 cm high and 44.41 cm² in cross-sectional area, the water level in a standpipe of 6.25 mm internal diameter dropped from a height of 75 cm to 24.7 cm in 15 minutes. Find the coefficient of permeability.

Give the characteristics of Flow nets. What is the theoretical height of capillary rise and the capillary pressure in a fine grained soil with effective size D₁₀ of 0.002 mm.

In a deposit of fine sand, the water table is 3 m below the ground surface. But the sand upto a height of 1 m above the water table is saturated by capillary water. The sand above this height may be considered dry. For the sand, Gs is 2.68 and porosity is 40%. Calculate the effective stress at the depth of 8 m.

What are the factors affecting permeability? A horizontal stratified deposit consists of three layers each uniform in itself. The permeability of the layers are 8 × 10^-6 m/s, 50 × 10^-6 m/s and 15 × 10^-4 m/s and their thicknesses are 6 m, 3 m and 18 m respectively. Find effective average permeability of the deposit in horizontal and vertical direction.

Explain Newmark's influence chart for finding vertical stresses in soil.

During a compaction test, a soil attains MDD of 18.6 kN/m³ at a moisture content of 15%. Taking specific gravity of soils as 2.7, find the degree of saturation and percentage air voids at MDD. What will be the dry density corresponding to zero air voids at OMC. How does compaction improve the engineering properties of soils?

A strip footing 3 m wide is loaded on the ground surface with a pressure of 100 kN/m². A 4m thick soft clay layer exits at a depth of 10 m below the foundation. Find the average increase in vertical stress at the clay layer under the centre line and edge of the building.

From Proctor's compaction test, the maximum dry density of a soil was found to be 1.75 g/cc and OMC 14.5%. The specific gravity of the soil grains was 2.6. Find out the degree of saturation and percentage air voids at the optimum state. What is zero air voids line?

Explain square root time fitting methods for Cv estimation.

A clay soil, tested in a consolidometer, showed a decrease in void ratio from 1.20 to 1.10 when the pressure was increased from 0.25 to 0.50 kgf/cm². Calculate the coefficient of compressibility and the coefficient of volume compressibility. If the coefficient of consolidation determined in the test for the given stress increment was 10 m²/ year, calculate the coefficient of permeability in cm/s. If the samples tested at the site was taken from a clay layer 3 m in thickness, determine the consolidation settlement resulting from the given stress increment.

Explain height of solids method for void ratio estimation.

A certain clay layer has a thickness of 5 m. After 1 year, when the clay was 50% consolidated, 8 cm of settlement had occurred. For a similar and loading conditions, how much settlement would occur at the end of 1 year and 4 years respectively, if the thickness of this new layer is 25 m?

In an insitu vane shear test on a saturated clay, a torque of 35 Nm was required to shear the soil. The diameter of the vane was 50 mm and length 100 mm. Calculate the undrained shear strength of the clay. The vane was then rotated rapidly to cause remoulding of the soil. The torque required to shear the soil in the remoulded state was 5 Nm. Determine the sensitivity of the clay.

Explain unconfined compression test and Vane shear test.

In a direct shear test on a sand sample, the normal stress was 200 kN/m² and the sample failed at a shear stress of 120 kN/m². Draw the mohr circle and the strength envelope. Determine (i) the angle of shearing resistance of the soil, (ii) the magnitude of the major and the minor principle stresses, (iii) the orientation of the principal planes.

Write the Mohr Coulomb failure criterion.