Quiz: Civil Engineering

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

Q1. Consider the following statements in respect of two-dimensional incompressible flow with velocity components u and v in x and y directions respectively.
1. the continuity equation is ∂u/∂x=∂v/∂y
2. the acceleration in x-direction is a_x=∂u/∂t+u ∂u/∂x+v ∂u/∂y
3. the condition of irrotationality is ∂u/∂y=∂v/∂x
4. the equation of a streamline is udy = -vdx
Which of these statements are correct?
(a) 2 and 3 only
(b) 1 and 2 only
(c) 1, 2 and 3
(d) 3 and 4

Q2. For a most economical trapezoidal channel section
(a) hydraulic mean radius equals the depth of flow
(b) hydraulic mean radius equals half the depth of flow
(c) bottom width is twice the depth of flow
(d) bottom width is half the depth of flow

Q3. Leaching is process
(a) By which alkali salts present in the soil are dissolved and drained away
(b) by which alkali salts in soil come up with water
(c) of draining excess water of irrigation
(d) which controls water-logging

Q4. When seepage takes place through the body of an earthen dam, it leads to
(a) development of pore pressures in the dam body
(b) reduction in the shear strength of the dam
(c) reduction in the developed shear stresses in the dam
(d) (a) and (b) both

Q5. In a plane stress problem there are normal tensile stresses σ_x and σ_y accompanied by shear stress τ_xy at a point along orthogonal Cartesian coordinates x and y respectively. If it is observed that the minimum principal stress on a certain plane is zero then
(a) τ_xy=√(σ_x+σ_y )
(b) τ_xy=√(σ_x-σ_y )
(c) τ_xy=√(σ_x σ_y )
(d) τ_xy=√((σ_x )/σ_y )

Q6. The collapsible soil is associated with
(a) dune sands
(b) laterite soils
(c) loess
(d) black cotton soils

Q7. Bentonite is a material obtained due to the weathering of
(a) limestone
(b) quartzite
(c) volcanic ash
(d) shales

Q8. A soil has bulk density of 22 kN/m³ and water content 10%. The dry density is
(a) 20 kN/m³
(b) 15 kN/m³
(c) 18 kN/m³
(d) 19 kN/m³

Q9. The porosity of a soil sample is 30% and specific gravity of its particles is 2.75. Then saturated unit weight is equal to
(a) 1.69 gm/cm³
(b) 1.94 gm/cm³
(c) 2.23 gm/cm³
(d) 2.46 gm/cm³

Q10. A soil has plastic limit of 20% and plasticity index of 40%. If the natural water content of the soil is 34%, then the consistency index is equal to
(a) 0.35
(b) 0.65
(c) 0.82
(d) 1.00


S1. Ans.(a)
Sol. For two dimensional incompressible flow
(i) Continuity equation ∂u/∂y+ ∂v/∂y = 0
(ii) Equation of stream line
V/dy = u/dx

S2. Ans.(b)
Sol. For most economical trapezoidal channel section
R → hydraulic mean radius
Y → depth of flow.

S3. Ans.(a)
Sol. Leaching is the process in which land is flooded with adequate depth of water. The alkali salts present in soil, get dissolved with this water, which percolate down to join the water table or are drained away by sub surface drains.

S4. Ans.(d)
Sol. When seepage takes place through the body of an earthen dam:
(i) development of pore pressures in the dam body.
(ii) reduction in the shear strength of the dam.
S5. Ans.(c)
Sol. Principal stresses
(σP_1)/(σP_2 ) = (σ_x + σ_y)/2 ± √(((σ_x – σ_y)/2)^2+τxy^2 )
Since minimum principal stress is zero therefore
((σ_x+ σ_y)/2)^2 = ((σ_x – σ_y)/2)^2+τ_xy^2
▭(τ_xy= √(σ_x σ_y ))

S6. Ans.(c)

S7. Ans.(c)
Sol. Bentonite is decomposed volcanic ash containing high percentage of clay mineral montmorillonite.

S8. Ans.(a)
Sol. γ_d = γ_b/(1+w )
= 22/(1 + 0.1 )
= 20 kN/m^3

S9. Ans.(c)
Sol. γ_sat = ((G+e) γ_w)/(1+e)
e = n/(1 -n) = 0.3/(1 –0.3) = 0.43
γ_sat = ((2.75 + 0.43) × 1)/(1 + 0.43 )
= 2.22 g/cm^3

S10. Ans.(b)
Sol. Consistency index (I_c) = (w_L –w_p)/I_p × 100
I_p = w_L –w_P
w_L = I_P+w_P
= 40 + 20
= 60%
I_c = (60 – 34)/40 = 0.65


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