JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III SOIL MECHANICS Previous Question Paper (July - 2023 - R16)
i) Question paper consists of Part A, Part B.
ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions.
iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Describe briefly the formation of soils.
Answer
Soils are formed through the process of weathering, which involves the physical disintegration and chemical decomposition of parent rocks. Physical weathering (mechanical) breaks rocks into smaller particles through temperature changes, frost action, or abrasion, while chemical weathering alters the mineral composition through processes like oxidation, carbonation, and hydration. The resulting weathered material is then transported by agents such as water, wind, ice, or gravity and deposited to form soil profiles.
Explain the soil three phase system with a neat diagram.
Answer
Soil is a complex material consisting of solid particles, water, and air. The three-phase system represents these components as distinct, separated volumes to facilitate geotechnical calculations. The system is typically illustrated by a block diagram showing the three phases stacked vertically: air at the top, water in the middle, and soil solids at the bottom.
The diagram components are defined as follows:
- Air (Va): The volume of voids occupied by air, with a mass of zero.
- Water (Vw): The volume of voids occupied by water, with a corresponding mass (Mw).
- Solids (Vs): The volume of the soil particles themselves, with a corresponding mass (Ms).
The total volume (V) is the sum of the volumes of air, water, and solids (V = Va + Vw + Vs), while the total mass (M) is the sum of the masses of water and solids (M = Mw + Ms). The volume of voids (Vv) is the sum of the air and water volumes (Vv = Va + Vw).
What is quick sand condition?
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List out the uses of flownets.
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Draw the compaction curve.
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Give the affects of compaction on soil properties.
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Explain the Secondary consolidation of soil.
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Discuss the significance of Over Consolidation Ratio.
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Explain the shear strength parameters.
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What is critical void ratio?
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Part B
Explain different types of soil structures and its effect on soil properties.
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Discuss Atterberg’s limits and their significance.
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Define: i) Porosity ii) Void Ratio iii) Degree of saturation iv) water content v) Specific Gravity.
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Determine the degree of saturation of a natural soil deposit having water content 18% specific gravity 2.60 and void ratio 0.5.
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Discuss the factors affecting permeability in detail.
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Explain the significance of capillary rise in soil.
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Derive an expression to determine coefficient of permeability of soil by laboratory falling head permeability test.
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In a variable head permeability test the initial head of 80cm dropped to 45cm in 2 hours 10 min. The diameter of the stand pipe being 2.5cm. The soil specimen was 120mm long and 100mm diameter. What is the coefficient of permeability of the soil?
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Explain the principle and working procedure of Proctor’s compaction test.
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The in-situ void ratio of a granular soil deposit is 0.5. The maximum and minimum void ratios of the soil were determined to be 0.75 and 0.35.G=2.67. Determine the relative density and relative compaction of the deposit.
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Outline the Boussinesq’s formula for vertical stress distribution in soil under a point load.
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List various field compaction equipments along with its suitability.
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Explain in detail the determination of coefficient of consolidation using log t method.
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In a laboratory consolidometer test on a 20 mm thick sample of saturated clay taken from a site, 50% consolidation point was reached in 10 minutes. Estimate the time required for the clay layer of 5m thickness at the site for 50% compression if there is drainage only towards the top.
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Discuss Terzaghi’s theory of consolidation, stating the various assumptions and their validity.
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Explain the computation of total settlement in soil.
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Describe direct Shear test. What are its merits and demerits?
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A direct shear test was performed on 60 mm × 60 mm sample of dry sand. The normal load was 360 N. The failure occurred at a shear load of 180 N. Plot the Mohr strength envelope and determine ϕ. Assume c = 0. Also, identify the principal stresses at failure.
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Explain any one laboratory method of determining shear strength of soil.
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Discuss the Mohr-Coulomb failure envelope of soils.
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