Chapter 14 Lateral Earth Pressure

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1 Page 14 1 Chapter 14 Lateral Earth Pressure 1. Which of the following is not a retaining structure? (a) Retaining wall (b) Basement wall (c) Raft (d) Bulkhead 2. When a retaining structure does not move either to the right or to the left of its initial position, the ratio of the effective horizontal stress to the effective vertical stress is generally represented by (a) K. (b) K 0. (c) K a. (d) K p. 3. For coarse grained-grained soils, the coefficient of earth pressure at rest can be estimated by using the Jaky s equation, which is given as (a) 1 sinφ (b) 1 sinφ (c) 1 sinφ φ (d) % 4. The total force per unit length of the retaining wall of height H when it does not move either to the right or to the left of its initial position is given as (b) γ. 5. The magnitude of coefficient of earth pressure at rest in most soils ranges between (a) 0.0 and 0.5. (b) 0.0 and 1.0. (c) 0.5 and 1.0. (d) 0.5 and The condition in which every point in a soil mass is on the verge of failure refers to (a) elastic equilibrium. (b) plastic equilibrium. (c) both (a) and (b) (d) none of the above

2 Page When a retaining structure moves towards the soil backfill, the stress condition within the soil backfill is called (a) at rest state. (b) active state. (c) passive state. (d) both (b) and (c) 8. The Rankine s theory of earth pressure assumes that (a) the back face of the wall in contact with the soil backfill is smooth. (b) the wall extends to an infinite depth. (c) both (a) and (b) (d) the soil is massless. 9. The coefficient of Rankine s active earth pressure (a) tan 45 φ (b) tan 45 φ (c) tan 45 φ (d) tan 45 φ 10. The coefficient of Rankine s passive earth pressure (a) tan 45 φ (b) tan 45 φ (c) tan 45 φ (d) tan 45 φ 11. In the Rankine s active state, the failure plane within the soil backfill makes an angle with the horizontal given as (a) 45. (b) φ (c) 45 φ (d) 45 φ 12. In the Rankine s passive state, the failure plane within the soil backfill makes an angle with the horizontal given as (a) 45. (b) φ (c) 45 φ (d) 45 φ

3 Page For the Rankine s active state, the active earth pressure from the cohesionless soil backfill at the bottom of a retaining wall of height H is (a) γ. (b) γ. 14. For the Rankine s passive state, the passive earth pressure from the cohesionless soil backfill at the bottom of a retaining wall of height H is (a) γ. (b) γ. 15. The total active force per unit length of the retaining wall of height H from the cohesionless soil backfill is given as (b) γ. 16. The total passive force per unit length of the retaining wall of height H from the cohesionless soil backfill is given as (b) γ. 17. The total active force on the retaining wall of height H from the cohesionless soil backfill acts above the base of the wall at a height of (a) /4. (b) /3. (c) /2. (d) 3 / The total passive force on the retaining wall of height H from the cohesionless soil backfill acts above the base of the wall at a height of (a) /4. (b) /3. (c) /2. (d) 3 /4.

4 Page For the Rankine s active state, the active earth pressure from the cohesive soil backfill at the bottom of a retaining wall of height H is (b) γ (c) γ 2 γ The typical value of wall tilt (the ratio of horizontal displacement of the wall top to its height when the wall rotates about its bottom) required for achieving Rankine s passive state in dense sand is (a) (b) (c) (d) An application of surcharge at the top of the soil backfill (a) causes no change in the earth pressure along the depth of the wall. (b) decreases the earth pressure along the depth of the wall. (c) increases the earth pressure along the depth of the wall. (d) increases the earth pressure near the top of the wall only. 22. The presence of cohesion in the soil backfill (a) causes no effect on the earth pressure along the depth of the wall. (b) decreases the active earth pressure along the depth of the wall. (c) increases the passive earth pressure along the depth of the wall. (d) both (b) and (c) 23. The depth of tension cracks in the cohesive soil backfill under undrained condition is (a). (b). (c) (d). 24. The development of tensile cracks in the upper part of the cohesive soil backfills (a) causes no effect on the earth pressure along the depth of the wall. (b) decreases the active earth pressure along the depth of the wall. (c) increases the active earth pressure along the depth of the wall. (d) both (b) and (c) 25. For a retaining wall with a rough vertical back, the total active earth pressure acts (a) horizontally. (b) in a direction making an angle greater than 90 with the vertically upward direction. (c) in a direction making an angle smaller than 90 with the vertically upward direction. (d) in any direction.

5 Page For a retaining wall with a rough vertical back, the total passive earth pressure acts (a) horizontally. (b) in a direction making an angle greater than 90 with the vertically upward direction. (c) in a direction making an angle smaller than 90 with the vertically upward direction. (d) in any direction. 27. Which of the following earth pressure theories consider the roughness of the back of the wall? (a) Rankine s active earth pressure theory (b) Rankine s passive earth pressure theory (c) Coulomb s earth pressure theory (d) all of the above 28. The Coulomb s active earth pressure coefficient becomes equal to the Rankine s active earth pressure for (a) α = 0 and θ = 0. (b) α = 0 and δ = 0. (c) θ = 0 and δ = 0. (d) α = 0, θ = 0 and δ = 0. where α is the angle made by the top surface of the soil backfill with the horizontal, θ is the inclination of the back face of the wall to the vertical, and δ is the angle of friction between the soil backfill and the wall. 29. The wall friction results in (a) reduction in the total active earth pressure. (b) increase in the total passive earth pressure. (c) both (a) and (b) (d) increase in the total earth pressure. 30. When the soil-wall interface friction angle becomes greater than about half of the soil backfill frictional angle, the Coulombs earth pressure theory overestimates the passive force, which is on (a) the unsafe side of the design. (b) the safe side of the design. (c) both (a) and (b) governed by the site conditions. (d) none of the above

6 Page 14 6 Answers, Hints and Discussion 1. (c) 2. (b) Discussion: K 0, K a and K p are called coefficient of earth pressure at rest, coefficient of active earth pressure, and coefficient of passive earth pressure, respectively. 3. (b) Hint and Discussion: See Eq. (14.3). (c) is correct for overconsolidated coarse-grained soils, see Eq. (14.4), and (d) is correct for fine-grained, normally consolidated soils. 4. (d) Hint: See Eq. (14.8). 5. (c) 6. (b) 7. (c) 8. (c) 9. (c) 10. (d) 11. (d) 12. (c) 13. (b) 14. (b) 15. (d) 16. (d) 17. (b) 18. (b) 19. (c) Hint: See Fig (d). 20. (a) Hint: See Table 14.1.

7 Page (c) Hint: See Eq. (14.32). 22. (d) Hint: See Eqs. (14.36) and (14.42). 23. (b) Hint: See Eq. (14.35). 24. (c) 25. (b) Hint: See Fig (c) Hint: See Fig (c) 28. (d) Hint: Compare Eqs. (14.18) and (14.51). 29. (c) 30. (a)

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Downloaded from Downloaded from /1 PURWANCHAL UNIVERSITY VI SEMESTER FINAL EXAMINATION-2003 LEVEL : B. E. (Civil) SUBJECT: BEG359CI, Foundation Engineering. Full Marks: 80 TIME: 03:00 hrs Pass marks: 32 Candidates are required to give their