51. The vertical stress at point P₁ due to the point load Q on the ground surface as shown in figure is σ_z. According to Bossiness's equation, the vertical stress at point P₂ shown in figure will be
    

1. 1. σ_z/2

   
   
   

   2. σ_z

   
   
   

   3. 2σ_z

   
   
   

   4. 4σ_z

   
   
   

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1. View Hint View Answer Discuss in Forum

   Bossiness's equation
   Vertical stress
   
   

   Correct Option: D

   Bossiness's equation
   Vertical stress
   
   

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52. A soil mass contains 40% gravel, 50% sand and 10% silt. This soil can be classified as

1. 1. silty sandy gravel having coefficient of uniformity less than 60.

   
   
   

   2. silty gravelly sand having coefficient of uniformity equal to 10.

   
   
   

   3. gravelly silty sand having coefficient of uniformity greater than 60.

   
   
   

   4. gravelly silty sand and coefficient of uniformity cannot be determined.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Gravel: 40%; Size = 4.75 mm
   ∴ D₆₀ = 4.75 mm
   S_and = 75mm
   S_and + gravel = 50 + 40 = 90%
   ∴ D₁₀ = 75 mm = 0.075 mm
   

   Cu =	D60
   	D10

   
   

   =	4.75
   	0.075

   
   = 63.33 > 60
   ∴ Soil is gravelly silty sand with C_u > 60.

   Correct Option: C

   Gravel: 40%; Size = 4.75 mm
   ∴ D₆₀ = 4.75 mm
   S_and = 75mm
   S_and + gravel = 50 + 40 = 90%
   ∴ D₁₀ = 75 mm = 0.075 mm
   

   Cu =	D60
   	D10

   
   

   =	4.75
   	0.075

   
   = 63.33 > 60
   ∴ Soil is gravelly silty sand with C_u > 60.

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53. The figure below shows two flow lines for seepage across an interface between two soil media of different co-efficient of permeability. If entrance angle α₁ = 30°, the exit angle α₂ will be
    

1. 1. 7.50°

   
   
   

   2. 14.03°

   
   
   

   3. 66.59°

   
   
   

   4. 75.96°

   
   
   

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1. View Hint View Answer Discuss in Forum

   	tanθ1	=	k1
   	tanθ2		k2

   
   

   ⇒	tan30	=	1 × 10-7
   	tanθ2		4 × 10-7

   
   ∴ tanθ₂ = 4 × tan30
   ∴ θ₂ = 66.59°

   Correct Option: C

   	tanθ1	=	k1
   	tanθ2		k2

   
   

   ⇒	tan30	=	1 × 10-7
   	tanθ2		4 × 10-7

   
   ∴ tanθ₂ = 4 × tan30
   ∴ θ₂ = 66.59°

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54. A 6 m thick clay layer undergoes 90% consolidation four times faster under two-way drainage as compared to the - drainage. In an identical clay layer of 15 m thickness, two way drainage will be faster as compared to one-way drainage by

1. 1. 8 times

   
   
   

   2. 4 times

   
   
   

   3. 2.5 times

   
   
   

   4. 2 times

   
   
   

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1. View Hint View Answer Discuss in Forum

   Time factor,
   

   Tv =	Cv.t
   	d2

   
   ∴ t ∝ d²
   d = H, for single drainage
   = H/2 for double drainage
   ∴ time taken is 1/4 times then single drainage.

   Correct Option: B

   Time factor,
   

   Tv =	Cv.t
   	d2

   
   ∴ t ∝ d²
   d = H, for single drainage
   = H/2 for double drainage
   ∴ time taken is 1/4 times then single drainage.

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55. The undrained cohesion of a remoulded clay soil is 10 kN/m². If the sensitivity of the clay is 20, the corresponding remoulded compressive strength is

1. 1. 5 kN/m²

   
   
   

   2. 10 kN/m²

   
   
   

   3. 20 kN/m²

   
   
   

   4. 200 kN/m²

   
   
   

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1. View Hint View Answer Discuss in Forum

   C_u = 10 kN/m²
   q_u = 2C_u
   = 2 × 10 = 20 kN/m²

   Correct Option: C

   C_u = 10 kN/m²
   q_u = 2C_u
   = 2 × 10 = 20 kN/m²

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