Shear Strength and Earth Pressure

JKSSB Junior Engineer (Civil) · Soil Mechanics · 9 practice questions with answers and explanations: 4 Easy, 5 Medium, 0 Hard.

Sample questions

Sample Easy question 1

A clean dry sand has a cohesion of:

  1. Equal to the friction angle
  2. Equal to its unit weight
  3. High
  4. Zero
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Answer: D. Sands are cohesionless, and their strength comes from friction alone.

Sample Easy question 2

For a square footing, Terzaghi's cohesion term in the bearing capacity equation uses a shape factor of:

  1. 1.3
  2. 1.0
  3. 2.0
  4. 0.5
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Answer: A. qu = 1.3 c Nc + γ D Nq + 0.4 γ B Nγ.

Sample Easy question 3

A drained test on a sand in a direct shear box measures the angle of internal friction φ as the:

  1. Angle whose tangent is the ratio of shear strength to normal stress
  2. Angle of repose of the slope
  3. Angle of the shear box
  4. Angle of the failure plane to the vertical
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Answer: A. For dry sand, tan φ = τ ÷ σ.

Sample Medium question 4

The Rankine active earth pressure coefficient for φ = 30° is:

  1. 2/3
  2. 1/2
  3. 1/3
  4. 3
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Answer: C. Ka = (1 − sin 30°) ÷ (1 + sin 30°) = 0.5 ÷ 1.5 = 1/3.

Sample Medium question 5

The active thrust on a 4 m high smooth wall retaining dry cohesionless soil of unit weight 18 kN/m³ and φ = 30° is:

  1. 96 kN per metre
  2. 144 kN per metre
  3. 48 kN per metre
  4. 24 kN per metre
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Answer: C. Pa = ½ Ka γ H² = ½ × (1/3) × 18 × 16 = 48 kN/m.

Sample Medium question 6

A soil has c = 20 kPa and φ = 30°. Under an effective normal stress of 100 kPa, the shear strength is about:

  1. 50 kPa
  2. 120 kPa
  3. 57.7 kPa
  4. 77.7 kPa
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Answer: D. τ = c + σ' tan φ = 20 + 100 × 0.577 = 77.7 kPa.

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