PART - A

  1. Bring out the points of difference between compaction and consolidations
  2. Explain ‘secondary consolidation ‘.
  3. What are the types of tests that could be conducted in triaxial test based on drainage?
  4. Distinguish between normally consolidated and over consolidated soils
  5. Define OCR.
  6. Explain the Mohr-Coulomb failure theory.
  7. What are the assumptions made in Terzaghi’s one dimensional consolidation Theory.
  8. How will you find the shear strength of cohesive soil?
  9. List the components of settlement in soil.
  10. What are the advantages of Triaxial Compression Test?
  11. Explain with neat sketch Direct Shear method of finding shear strength.
  12. What are isobars
  13. When a soil mass is said to be homogeneous.
  14. Write down the Coulomb’s expression for Shear Strength
  15. What is shear strength of Soil
  16. Define Sensitivity of Clay

PART – B

  1. A normally consolidated clay layer of 10 m thickness has a unit weight of 20 kN/m³ and specific gravity 2.72. The liquid limit of the clay is 58%. A structure constructed on this clay increase the overburden by 10%. Estimate the ultimate consolidation settlement. There is no secondary compression
  2. The total anticipated settlement due to consolidation of a clay layer under a certain Pressure is 150 mm. If 45 mm of settlement has occurred in 9 months, what is the expected settlement in 18 months?
  3. A sample of cohesionless sand in a direct shear test fails under a shear stress of 600 kPa when the normal stress is 800 kPa. Find the principal stresses and locate the principal planes.
  4. Obtain the differential equation defining the one-dimensional consolidation as given by Terzaghi.
  5. In a consolidation test, the following results have been obtained. When the load was changed from 50 kN/m² to 100 kN/m², the void ratio changed from 0.70 to 0.65. Determine the coefficient of volume decrease, and the compression index.
  6. A cylinder of soil fails under an axial vertical stress of 200 kPa when it is laterallyunconfined. The failure plane makes an angle of 490 with the horizontal. Find the values of cohesion and angle of internal friction
  7. The void ratio of a clay is 1.56, and its compression index is found to be 0.8 at Pressure of 180 kN/m². What will be the void ratio if the pressure is increased to 240 kN/m²?
  8. The results of a series of Consolidated Undrained tests on undisturbed samples of overconsolidated clay were as below:

Cell Pressure (kPa) / 100 / 200 / 400 / 600
Deviator stress at failure(kPa) / 300 / 410 / 610 / 850
Pore pressure at failure (kPa) / -45 / -15 / 50 / 110

Determine the shear strength parameters in terms of effective stresses

  1. Obtain the relationship between the principal stresses in Triaxial Compression test using Mohr – Coulomb Theory
  2. Two identical soil specimen were tested in a triaxial apparatus. First specimen failed at a deviator stress of 770 kN/m2when the cell pressure was 2000 kN/m2. Second specimen failed at a deviator stress of 1370 kN/m2 under a cell pressure of 400 kN/m2. Determine the value of c and øanalytically. If the same soil is tested in a direct shear apparatus with a normal stress of 600 kN/m2, estimate the shear stress at failure
  1. A stratum of clay with an average liquid limit of 45% is 6m thick. Its surface is located at a depth of 8m below the ground surface. The natural water content of the clay is 40% and the specific gravity is 2.7. Between ground surface and clay, the subsoil consists of fine sand. The water table is located at a depth of 4m below the ground surface. The average submerged unit weight of sand is 10.5 kN/m3and unit weight of sand above the water table is 17.0 kN/m3. The weight of the building that will be constructed on the sand above clay increases the overburden pressure on the clay by 40 kN/m2. Estimate the settlement
  1. An undrained soil sample 30cm thick got 50% consolidation in 20 minutes with drainage allowed at top and bottom in the laboratory. If the clay layer from which the sample was obtained is 3m thick in field condition, estimate the time it will take to consolidate 50% with double surface drainage and in both cases, consolidation pressureis uniform.

13. A Cylindrical specimen of dry sand was tested in a triaxial test. Failure occurred under a cell pressure of 1.2 kg/cm2 and at a deviator stress of 4.0kg/cm2. Find

(i) Angle of shearing resistance of the soil.

(ii) Normal and shear stresses on the failure plane.

(iii) The angle made by the plane with the minor principal plane.

(iv) The maximum shear stress on any plane in the specimen at the instant of failure.

  1. How will you determine coefficient of compression index (CC) from an oedomoter test
  2. How will you determine pre consolidation pressure.
  3. A vane, 10 cm long and 8 cm in diameter, was pressed into soft clayat the bottom of a bore hole. Torque was applied and gradually increased to 45 N-m when failure took place. Subsequently, the vane rotated rapidly so as to completely remould the soil. The remoulded soil was sheared at a torque of 18 N-m. Calculate the cohesion of the clay in the natural and remoulded states and also the value of the sensitivity
  4. 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 5 m thickness at the site for 50% compression if there is drainage only towards the top. What is the time required for the clay layer to reach 50% consolidation if the layer has double drainage instead of single drainage
  1. What are the various components of a settlement? How are these estimated?
  1. Describe the triaxial shear test. What are the advantages of triaxial shear test over the direct shear test