JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III Year II Semester SOIL MECHANICS Previous Question Paper (May - 2019 - R16)
Note: This question paper contains two parts A and B. Part A is compulsory. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
What are the Index properties of soil?
Answer
Index properties are those physical properties of soil that help in its identification and classification. They do not indicate the engineering performance directly but provide a basis for predicting soil behavior. Key index properties include:
- Water content (natural moisture content)
- Specific gravity of soil solids
- Particle size distribution (sieve analysis and sedimentation)
- Consistency limits (Atterberg limits: Liquid, Plastic, and Shrinkage limits)
- In-situ density (unit weight)
The dry density of a sand with porosity of 0.387 is 1600 kg/m3. Find the void ratio of the soil and the specific gravity of the soil solids. [Take γw = 1000 kg/m3]
Answer
Given: Porosity (n) = 0.387, Dry density (ρd) = 1600 kg/m3, Density of water (ρw) = 1000 kg/m3.
1. Void ratio (e):
2. Specific gravity (G):
Using the relation ρd = (G * ρw) / (1 + e):
Define neutral stress and effective stress.
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What is quick sand phenomenon? How would you calculate the hydraulic gradient required to create quick sand condition in a sample sand?
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What do you mean by pressure bulb?
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What are the assumptions made in Boussinesq’s theory?
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Define normally consolidated and over consolidated soils.
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Briefly explain e-p and e-log p curves.
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What do you mean by Critical void ratio of sand?
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Draw the failure envelopes for an over-consolidated soil for the test and point out the important divergence from a normally consolidated soil.
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Part B
The dry unit weight of a soil sample in the loosest state is 13.34 KN/m3 and in the densest state, it is 21.19 KN/m3. Determine the relative density of the sand when it has porosity of 33%. Assume the grain specific gravity as 2.68.
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Differentiate between Saturated density and Bulk density.
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A soil has a porosity of 40%, the specific gravity of solids of 2.65 and water content of 12%. Determine the mass of water required to be added to 100 m3 of this soil for full saturation.
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What is relative density? How it is determined? What is its importance for coarse grained soil?
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What are the pumping out methods for the determination of coefficient of permeability in the field. What are their advantages and disadvantages? What are Dupuit’s assumptions?
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A sand deposit is 10m thick and overlies a bed of soft clay. The ground water table is 3m below the ground surface. If the sand above the ground water table has a degree of saturation of 45%, plot the diagram showing the variation of the total stress, pore water pressure and effective stress. The void ratio of the sand is 0.70. Take specific gravity (G) = 2.65.
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Explain the uses of Flow net.
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With a sketch explain the construction of Newmark’s chart.
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A line load of 100KN/m run extends to a long distance. Determine the intensity of vertical stress at a point 2m below the surface at a distance of 2m perpendicular to the line load. Use Boussinesq’s theory.
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What is field compaction? Briefly describe different methods of field compaction.
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Discuss on compaction quality control.
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Calculate the final settlement of the clay layer due to an increase of pressure of 30 kN/m2 at mid-height of the layer. Take γw = 10 kN/m3. Also calculate the settlement when the water table rises to the ground surface.
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Discuss the limitations of Terzaghi’s theory of consolidation. Why is theory used despite its limitations?
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A saturated soil stratum 4m thick lies above an impervious stratum and below a pervious stratum. It has void ratio of 1.50 at an initial pressure of 150 kN/m2.
Compute the change in void ratio due to an increase of stress of 50 kN/m2. Take Cc = 0.20
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Also compute the final settlement of the soil stratum due to above increase in stress.
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What would be the time required for 50% consolidation? Take Tv = 0.20, k = 3.0 × 10-4 cm/sec.
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Explain the types of shear test based on different drainage conditions.
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Give one example each of the use of UU(Unconsolidated undrained) strength, CD (consolidated drained) strength in engineering practice.
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A series of consolidate-undrained triaxial tests was conducted on an over-consolidated clay. Plot the strength envelopes in terms of total stresses and effective stresses, and hence determine the strength parameters. If the soil was pre-consolidated to a pressure of 1000 kN/m2, plot the variation of the pore pressure parameter Af with the over-consolidation ratio.
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