GPSC Civil Engineering (Combine Exam) Paper Solution (03-05-26) – Page 18

171) Consider the following statements about the Atterberg limits of a clayey soil:

1. Liquid limit (LL) determined by the Casagrande apparatus is defined at 25 blows of the cup.
2. Plasticity index (PI) = LL – SL, where SL is the shrinkage limit.
3. A soil with LL > 50% is classified as high plasticity (H) in the Unified Soil Classification System (USCS).
4. Sensitivity of a quick clay may exceed 100, meaning remoulded strength is less than 1% of the undisturbed strength.

Which of the statements given above are correct?

1. 1 and 3 only
2. 1 and 4 only
3. 1, 3 and 4 only
4. 1, 2, 3 and 4

172) A consolidated undrained (CU) triaxial test on a saturated clay specimen gives the following: Cell pressure σ3 = 100kPa deviator stress at failure ∆σ = 80kPa and pore water pressure at failure u = 60 kPa. What is the effective angle of internal friction (φ’) if the effective cohesion c’ = 0 ?

1. φ’ = 14.5°
2. φ’ = 19.5°
3. φ’ = 30°
4. φ’ = 23.6°

173) Consider the following statements about Terzaghi’s one-dimensional consolidation theory:

1. The theory assumes that drainage occurs only in the vertical direction.
2. The coefficient of consolidation Cv = k / (mv x γw), where k is permeability and mv is the coefficient of volume compressibility.
3. The time factor T = 90% consolidation (U = 90%) is approximately 0.848.
4. Pre-consolidation pressure (σ’p) of an overconsolidated clay can be determined from the e-logσ’ curve using the Casagrande graphical method.

Which of the statements given above are correct?

1. 1 and 2 only
2. 1, 2 and 3 only
3. 1, 2 and 4 only
4. 1, 2, 3 and 4

174) Consider the following statements about pile foundations:

1. In a friction pile, the ultimate load capacity is derived primarily from skin friction along the pile shaft.
2. The pile group efficiency factor (η) is mostly less than 1.0 for friction piles in clay.
3. Negative skin friction increases the structural load on a pile.
4. The ‘critical depth’ concept in pile design (Meyerhoff) suggests that unit skin friction and end bearing increase linearly with depth without limit.

Which of the statements given above are correct?

1. 1 and 3 only
2. 1, 2 and 4 only
3. 2 and 4 only
4. 1, 2 and 3 only

175) Consider the following statements about the Rankine’s earth pressure theory:

1. Rankine’s active earth pressure coefficient Ka = (1 – sinφ)/(1 + sinφ).
2. Rankine’s theory assumes the wall is perfectly smooth (no wall friction).
3. For a cohesive backfill, the tension crack depth is given by zc = 2c/(γ√Κa).
4. Rankine’s passive pressure coefficient Kp = tan²(45 + φ/2) and Kp = 1/Ka.

Which of the statements given above are correct?

1. 1 and 2 only
2. 1, 2 and 3 only
3. 1, 2, 3 and 4
4. 2, 3 and 4 only

176) A bar of length L is fixed at both ends and subjected to a temperature rise of ∆T. If the coefficient of linear expansion is α and modulus of elasticity is E, the thermal stress developed is

1. αΔΤ⋅Ε (compressive)
2. αΔΤ⋅Ε (tensile)
3. αΔΤ⋅Ε/2 (compressive)
4. Zero, since both ends are fixed

177) Consider the following statements about Principal Stresses:

1. On a principal plane, only normal stress acts and shear stress is zero.
2. The maximum shear stress equals half the difference of principal stresses.
3. Principal planes are always at 90° to each other.
4. Maximum shear stress plane is always at 45° to the principal plane.

Which of the above statements are CORRECT?

1. 1, 2 and 3 only
2. 1, 3 and 4 only
3. 2, 3 and 4 only
4. 1, 2, 3 and 4

178) For a solid circular shaft of diameter d and transmitting torque T, the maximum shear stress and angle of twist per unit length are respectively given by

1. τ = 16T / (πd³) and θ / L = 32T / (πGd⁴)
2. τ = 16T / (πd³) and θ / L = 64T / (πGd⁴)
3. τ = 32T / (πd³) and θ / L = 16T / (πGd⁴)
4. τ = 16T / (πd²) and θ / L = 32T / (πGd³)

179) Mohr’s circle is drawn for a 2D stress state where σx = 80 MPa, σy = 20 MPa and τxy = 30 MPa. The radius of Mohr’s circle is

1. 30 MPa
2. 50 MPa
3. √(900 + 900)
4. √(900 + 1600)

180) Consider the following statements about elastic constants E, G, K and Poisson’s ratio v:

1. E = 2G(1 + v)
2. E = 3K(1 – 2v)
3. E = 9KG / (3K + G)
4. For an incompressible material, v = 0.5 and K → ∞

Which of these statements are INCORRECT?

1. None of them
2. 1 only
3. 3 only
4. 2 and 4 only