Quiz: CIVIL ENGINEERING 16 Jan 2020

Quiz: CIVIL ENGINEERING
Exam: NPCIL-SCIENTIFIC ASSISTANT (CIVIL)
Topic: SOIL MECHANICS

Each question carries 1 mark
Negative marking: No negative marking
Time: 10 Minutes

Q1. A soil has a discharge velocity of 6 × 10^(-7) m/s and void ratio of 0.5. What is its seepage velocity?
(a) 3 × 10^(-7) m/s
(b) 6 × 10^(-7) m/s
(c) 12 × 10^(-7) m/s
(d) 18 × 10^(-7) m/s

Q2. If K is coefficient of permeability, m_v is coefficient of volumetric change and γ_w is unit weight of water, then coefficient of consolidation will be
(a) C_v=K/(m_v×γ_w )
(b) C_v=(m_v×γ_w)/K
(c) C_v=(K×γ_w)/m_v
(d) None of these

Q3. The total unit weight of soil is 22 kN/m³. the specific gravity of soil particles is 2.67 and the water content of the soil is 10%. The dry unit weight would be
(a) 20 kN/m³
(b) 2 kN/m³
(c) 0.02 kN/m³
(d) 200 kN/m³

Q4. The approximate void ratio in sandy soils is
(a) 0.2
(b) 0.3
(c) 1.2
(d) 0.6

Q5. If permeability of a soil at the void ratio of e_1 and e_2 are k_1 and k_2 then which of the following relation is correct?
(a) k_1/ k_2=(1+e_1 ) / (1+e_2)
(b) k_1/ k_2=(1-e_1) / (1-e_2)
(c) k_1/ k_2=e_1 / e_2
(d) None of these

Q6. The constant head permeameter is suitable for:
(a) Silty soil
(b) Organic soil
(c) Coarse grained soils
(d) Clay

Q7. Consistency limit measured by the instrument, is known as:
(a) Plate load test
(b) Oedometer
(c) Casagrande’s apparatus
(d) Hydrometer

Q8. A clay soil sample is tested in a triaxial apparatus in consolidated-drained conditions at a cell pressure of 100 kN/m². What will be the pore water pressure at a deviator stress of 40 kN/m²?
(a) 0 kN/m²
(b) 20 kN/m²
(c) 40 kN/m²
(d) 60 kN/m²

Q9. If the coefficient of active earth pressure is 1/3 then what is the value of coefficient of passive earth pressure?
(a) 1/9
(b) 1/3
(c) 3
(d) 1

Q10. A soil has a liquid of 40% and plasticity index of 20%. The plastic limit of the soil will be
(a) 20%
(b) 30%
© 40%
(d) 60%

Solutions

S1. Ans.(d)
Sol. discharge velocity (V) = 6 × 10^(-7) m/s
Void ratio (e) = 0.5
Porosity (n) = e/(1+e)
= 0.5/(1+0.5)
= 0.5/1.5
=0.33
Seepage velocity (V_s ) = V/n
=(6×10^(-7))/0.33
V_s=18.18× 10^(-7) m/sec

S2. Ans.(a)
Sol. ▭(C_v=K/(m_v×γ_w ))
C_v→ coefficient of consolidation
K → permeability
m_v→ coefficient of volume compressibility
γ_w→ unit weight of water

S3. Ans.(a)
Sol. total unit weight = (r_b ) = 22 kN/m³
Specific gravity (G) = 2.67
Water content (w) = 10%
Dry unit weight (r_d )= ?
r_d=r_d/(1+w)=22/(1+0.1)
▭(r_d=20kN\/m^s )

S4. Ans.(b)
Sol.

Type of soilMinimum void ratioMaximum void ratio
Silty sand
Gravel
Coarse sand
Fine sand
Clay sand
0.33
0.30
0.35
0.40
0.17
0.98
0.60
0.75
0.85
0.59

S5. Ans.(d)
Sol. According to Kozney Karman equation
Permeability (k) =1/Kk (r_w/μ)(e^3/(1+e)) d^2
▭(k α e^2 )
▭(K_1/K_2 α (e_1^2)/(e_2^2 ))

S6. Ans.(c)
Sol. The constant head parameter is suitable for determination of permeability in coarse grained soil.
▭(K=2.303 aL/At log_10 h_1/h_2 )

S7. Ans.(c)
Sol. Consistency limit is measured by Casagrande’s apparatus.

S8. Ans.(a)
Sol. In consolidated drainage test, drainage is permitted during cell pressure as well as back pressure stage both, hence, the pore water pressure is zero in this case.

S9. Ans.(c)
Sol. Given,
k_a=1/3
k_p= ?
we know,
k_a.k_p=1
1/3.k_p=1
▭(k_p=3 )

S10. Ans.(a)
Sol. Given
W_L=40%
I_P = 20%
W_P= ?
I_P=W_L-W_P
20%=40%-W_P
▭(W_P=20%)

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