CE3404 Soil Mechanics Important Questions

CE3404 Soil Mechanics Important Questions

Unit 1 Part B

1. The mass of wet soil when compacted in a mould was 25kN. The water content of the soil was 12%. If the volume of the mould was 1100 cc. Determine,
   (i) Dry unit weight
   (ii) Void Ratio
   (iii) Degree of saturation and
   (iv) Percent air voids. Take G = 2.68.
2. A soil sample has a porosity of 45%. The specific gravity of solids 2.70, Calculate,
   (i) Void ratio
   (ii) Dry density
   (iii) Unit weight of the soil, if 50% saturated.
   (iv) Unit weight of the soil, if completely saturated.
3. Describe the structure of soil and explain phase relationship.
4. Explain the methods of field compaction of soil with any one field test carriedout.
5. Describe the phase relationship of the soil and index properties with neat illustration.
6. Explain the theory and significance of compaction of soils.

Unit 2 Part B

1. Compute the total pressure, effective pressure and pore water pressure at a depth of 20 m below the bottom of a lake 6 m deep. The bottom of lake consists of soft clay with a thickness of more than 20m. The average water content of the clay is 40% and specific gravity of the soil may be assumed to be 2.65.
2. Explain in detail the laboratory experiment to determine coefficient of permeability for coarse grained soil with neat sketch. Also derive the suitable governing equation.
3. Discuss the stress distribution in homogenous and isotropic medium for point land using Boussinesq’s theory.
4. Discuss the component of settlement with Terzaghi’s one dimensional consolidation theory.
5. Calculate the following for a sand sample of 20 cm long having a cross sectional area of 35 cm², tested under a constant head of 60 cm with a discharge of 120 ml in 6 min. Take dry mass of sand used for the test as 1320 g and specific gravity as 2.68.     (i) Coefficient of permeability, (ii) Discharge velocity,            (iii) Seepage velocity
6. Explain the procedure for field measurement of pumping out test in aquifers.

Unit 3 Part B

1. A water tank is supported by a ring foundation having outer diameter of 10 m and inner diameter of 7.5 m. The ring foundation transmits a uniform load intensity of 160 kN/m². Compute the vertical stress induced at depth of 4 m, below the centre of ring foundation, using Boussinesque analysis.
2. In a consolidation test, the void ratio of the specimen which was 1.05 under the effective pressure of 214 kN/m², changed to 0.995 when the pressure was increased to 430 kN/m². Calculate the (i) co-efficient of compressibility (ii) Compression index (iii) co-efficient of volume change.
3. Discuss the principle and procedure of tri-axial compression test with a neat sketch.
4. Compute the net safe bearing pressure using modified Teng and Meyerhof equation for a settlement of 30mm for a square footing of size 4 * 4 m to be laid at a depth of 2 m below the ground surface in loose to medium dense sand. Take corrected standard penetration test value N = 11
5. Explain the theory of estimation of stress distribution in a soil and Boussinesq’s assumptions to derive point load expression.
6. Calculate the average settlement of a clay layer for a site having a top layer of fine sand upto a depth of 10.6 m and a soft clay layer below for a depth of 7.6 m. The water table is at a depth of 4.6 m below the ground surface. The submerged unit weight of sand is 10.4kN / (m ^ 3) and wet unit weight above the water table is 17.6kN / (m ^ 3) The water content of normally consolidated clay is 40% with a liquid limit of 45% and the specific gravity of the solid particles is 2.78. The proposed construction produce a net stress of 120kN / (m ^ 2) at the centre of clay layer.

Unit 4 Part B

1. A vane shear 8cm in diameter and 12cm in length was used to measure shear strength of the clay. If a torque of 650 Nm was required in natural state and 1250 Nm in remoulded state, determine shear strength in both the cases.
2. Explain in detail the how shear strength of a soil is determined by unconfined compressive strength. Explain with neat sketch.
3. Discuss Mohr Coulomb failure theory for direct shear with a neat sketch.
4. Compute the shear strength parameters of a clay soil having the failure plane at 55 deg and failure axial stress of 240kN / (m ^ 2) an unconfined cylindrical specimen.
5. Compute the shear strength of soil along a horizontal plane at a depth of 4 m in a deposit of sand having angle of internal friction 35°, dry unit weight of 17 kN/m³, and a specific gravity of 2.7 for the following conditions of ground water table. (i)
   2.5 m depth from ground surface, (ii) at the ground surface
6. Explain the procedure for the measurement of shear strength by direct shear test.

Unit 5 Part B

1. Explain the procedure for analysis of slope stability by Bishop’s slice method.
2. Explain the causes for failure of slopes and protection measures of slope.
3. Explain the types of slopes and causes of failure of slopes with a neat sketch.
4. Describe slope stability analysis by Bishop’s simplified method of slices. with a neat sketch.
5. Write down the procedure for determining the factor of safety of a given slope by friction circle method.
6. In a sloping terrain, it was found that the soil is clayey and weak in nature, suggest any four slope protection methods to stabilize the slope.