Quiz: Civil Engineering 26 May 2021

Quiz: Civil Engineering
Exam: DFCCIL
Topic: Soil Mechanics

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes

Q1. Which of the following methods is more suitable for the determination of permeability of clayey soil?
(a) Constant head method
(b) Falling head method
(c) Horizontal permeability test
(d) None of these

Q2. When movement of wall under the earth pressure from the backfill was prevented the coefficient of earth pressure was recorded as 0.5. The ratio of the coefficient of passive and active earth pressure of the backfill is
(a) 1/3
(b) 3
(c) 1/9
(d) 9

Q3. Friction piles are most effective in
(a) Soft clay
(b) Dense sand
(c) Organic soil
(d) Filled up soil

Q4. Consider the following statements regarding the phenomenon of bulking of sand
1)It is due to the film of water around sand particles
2)It is due to capillary action
3)It is more in finer sands
Which of these statements is / are correct?
(a) 1,2 and 3
(b) 1 and 3
(c) 2 and 3
(d) 1 and 2

Q5. In plate load test to determine the bearing capacity if the soil is sand, then bearing capacity of the footing is
(a) Directly proportional to the width of footing
(b) Inversely proportional to width of footing
(c) Independent of the width of footing
(d) Directly proportional to square root of width of footing

Q6. If the porosity of a soil sample is 40%, void ratio for this sample is
(a) 0.50
(b) 0.70
(c) 0.60
(d) None of these

Q7. A soil sample has liquid limit = 45% plastic limit of 25% shrinkage limit = 15% for natural water content of 30% the consistency index for the sample is
(a) 40%
(b) 50%
(c) 75%
(d) 60%

Q8. The condition of zero atmospheric pressure can be expected at
(a) Sea level
(b) Mean sea level
(c) The base of sea
(d) Phreatic surface

Q9. Taylor’s stability number is equal to
(a) C/(F_C H)
(b) c/(F_C γH_C )
(c) C/γH
(d) C/(γH_C )

Q10. A line load of infinite length has an intensity q per unit length. What is the vertical stress σ_z at a depth z below the earth at the centre of the load?
(a) σ_z=2qz/π
(b) σ_z=2q/πz
(c) σ_z=2qz²/π
(d) σ_z=2q/πz²

Solutions

S1. Ans.(b)
Sol. Variable head or falling head permeability test is suitable for the determining the permeability of clayey soil.
▭(k=2.303 a/A L/t log_10 (h_1/h_2 ) )

S2. Ans.(d)
Sol. Given, co-efficient of earth pressure at rest (k_0 )=0.5
1-sinϕ=0.5
sinϕ=0.5
▭(ϕ=30°)
k_a=(1-sinϕ)/(1+sinϕ)=(1-sin30)/(1+sin30)=0.5/1.5=1/3
k_P=(1+sinϕ)/(1-sinϕ)=(1+sin30)/(1-sin30)=1.5/0.5=3
k_P/k_a =3/(1\/3)
▭(k_p/k_a =9 )

S3. Ans.(b)
Sol. Friction piles are also called as ‘floating pile’. These piles are most effective in dense sand and used to transfer load through skin friction between the embedded surface of the pile and the surrounding soil.

S4. Ans.(a)
Sol. Bulking of sand is a phenomenon due to-
1) due to the film of water around sand particles.
2) due to capillary action.
3) It is more in finer sands.

S5. Ans.(a)
Sol. Bearing capacity of footing as per shear criteria is given by-
▭(q_uf/q_up =B_f/B_p )
▭(q_up α B_f )
Where,
q_uf = ultimate bearing capacity of footing
q_up=ultimate bearing capacity of plate
B_f= width of footing
B_p=Width of plate.

S6. Ans.(d)
Sol. Given, Porosity (n) = 40% = 0.4
Void ratio (e) = ?
e=n/(1-n)=0.4/(1-0.4)=0.4/0.6=0.67

S7. Ans.(c)
Sol. Given,
W_L=45%
W_P=25%
W_s=15%
W_n=30%
I_C= ?
I_C=(W_L-W_n)/(W_L-W_P )=(45-30)/(45-25)=15/20=75%

S8. Ans.(d)
Sol. Phreatic line is the top flow line which separates the saturated soil mass from the unsaturated soil mass. Pressure below phreatic line is hydrostatic pressure but pressure on and above phreatic line is atmosphere.
So, condition of zero atmospheric pressure can be expected at phreatic surface.

S9. Ans.(d)
Sol. Taylor’s stability No. →
S_n=C_m/yH
S_n=C/(F_c.yH) (∵F_C=C/C_m )
S_n=C/(H_C.yH) (∵F_C=H_C/H)
▭(S_n=C/(yH_C ))

S10. Ans.(b)
Sol. A line load of infinite length has an intensity q per unit length then vertical stress (σ_z) at a depth Z below the earth is given by –
▭(σ_z=2q/πz)