Quiz: Civil Engineering 27 Nov 2020

Quiz: Civil Engineering
Exam: RSMSSB-JEn
Topic: Soil Mechanics & Foundation Engineering

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. Quick sand is a …?
(a) Type of sand
(b) Flow condition occurring in cohesive soils
(c) Flow condition occurring in cohesionless soils
(d) Flow condition in both cohesive and cohesionless soils

Q2. 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

Q3. Between seepage and discharge velocity in a soil
(a) Any one may be higher
(b) Former is always higher
(c) Later is always higher
(d) Both are equal

Q4. 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

Q5. Friction piles are most effective in
(a) Soft clay
(b) Dense sand
(c) Organic soil
(d) Filled up soil

Q6. The consistency index is greater than 1. the soil will behave as
(a) Liquid
(b) Plastic
(c) Solid
(d) None of these

Q7. The upper most line of seepage in an earth dam is also called as
(a) Water pressure line
(b) Hydraulic gradient line
(c) Phreatic line
(d) Parabolic seepage line

Q8. 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

Q9. A soil has a liquid of 40% and plasticity index of 20%. The plastic limit of the soil will be
(a) 20%
(b) 30%
(c) 40%
(d) 60%

Q10. For a soil deposit having porosity (n) = 33% and specific gravity (G) = 2.60, the critical hydraulic gradient is:
(a) 1.0
(b) 1.05
(c) 1.07
(d) 1.10

Solutions
S1. Ans.(c)
Sol. Quick sand is a flow condition occurring in cohesionless soils. In this, if seepage pressure equal to submerged unit weight of soil, then effective stress reduces to zero and soil particles leaves the soil mass and flow along with water is termed as quick sand condition or liquefaction.

S2. 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.

S3. Ans.(b)
Sol. Relation between seepage velocity (V_s ) and discharge velocity (V) is given by –
▭(V_s=V/n)
Since n < 1, then seepage velocity is always higher than discharge velocity.

S4. 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 )

S5. 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.

S6. Ans.(c)
Sol.
Consistency index (I_C )                         State
I_C>1                                         Solid or Semi-solid state
I_C<0                                                 Liquid state
0 < I_C < 1                                          Plastic state

S7. Ans.(c)
Sol. The upper most line of seepage in an earth dam is called phreatic line it separates the saturated soil mass from unsaturated soil mass and the pressure at or above phreatic line is atmospheric and below phreatic line is hydrostatic.

S8. 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

S9. 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%)

S10. Ans.(c)
Sol. Given, Porosity (n) = 33%
Specific gravity (G) = 2.60
Critical hydraulic gradient (I_C ) = ?
▭(I_C=(G-1)/(1+e))
e=n/(1-n)=0.33/(1-0.33)=0.49
I_C=(2.6-1)/(1+0.49)
▭(I_C=1.073 )

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