**Quiz: Civil EngineeringExam: DFCCILTopic: Soil Mechanics**

**Each question carries 1 markNegative marking: 1/4 markTime: 10 Minutes**

Q1. A soil sample is having a specific gravity 2.60 and a void ratio of 0.78. The water content required to fully saturate, the soil at the void ratio would be

(a) 10%

(b) 30%

(c) 50%

(d) 70%

Q2. If D_60,D_30 and D_10 of sizes of a soil grading are 4 mm, 2 mm and 0.5 mm, what will be the coefficient of uniformity of this soil?

(a) 0.5

(b) 1

(c) 2

(d) 8

Q3. For a sand having an internal friction of 30° the ratio of passive to active lateral earth pressure will be

(a) 1

(b) 3

(c) 6

(d) 9

Q4. With respect to c-ϕ soil in an infinite slope, identify if the following two statements are True of False:

I. The stable slop angel can be greater than ϕ

II. The factor of safety of the slope does not depend on the height of soil in the slope.

(a) Both statements are false

(b) I is true but II is false

(c) I is false but II is true

(d) Both statements are true

Q5. Which of the following assumptions is wrongly stated in regard to the Rankine’s theory of earth pressure?

(a) The back of the wall is smooth

(b) The soil mass in semi-infinite and homogeneous

(c) The ground surface is plane

(d) The retaining wall yields about the base

Q6. Test used to determine ultimate bearing capacity and probable settlement under a given loading is

(a) Plate load

(b) Bearing Load

(c) Settlement load

(d) Field load

Q7. Find the width of grillage foundation if the total load is 650 kN and safe bearing capacity of soil is 65 kN/m^2.

(a) 10 m

(b) 12 m

(c) 14 m

(d) 16 m

Q8. What will be the seepage velocity of soil having discharge velocity of 5×10^(-7) m/s and a void ratio of 0.50?

(a) 15×10^(-7) m/sec

(b) 30×10^(-7) m/sec

(c) 20×10^(-7) m/sec

(d) 10×10^(-7) m/sec

Q9. The rate of flow of water through a soil is proportional to the hydraulic gradient is demonstrated experimentally by:

(a) Atterberg

(b) Henry Darcy

(c) Casagrande

(d) Terzaghi

Q10. The relationship between air content of soil (a_c) and its degree of saturation (S_r) is expressed as

(a) a_c=1+S_r

(b) a_c=S_r-1

(c) a_c=1-S_r

(d) None of these

Solutions

S1. Ans.(b)

Sol.

Specific gravity (G)=2.60

Void ratio (e)=0.78

Water content (w)=?

Fully saturated i.e. S=1

se=wG

1×0.78=w×2.60

▭(w=30%)

S2. Ans.(d)

Sol.

D_60=4mm

D_30=2mm

D_10=0.5mm

Coefficient of uniformity (C_u )=D_60/D_10

=4/0.5

=8

S3. Ans.(d)

Sol. Given, ϕ=30°

Active earth pressure coefficient k_a=(1-sinϕ)/(1+sinϕ)=(1-sin30)/(1+sin30)=0.5/1.5=1/3

〖Passive earth pressure coefficient 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)

S4. Ans.(b)

Sol. → In stable slope angle is greater than critical angle (ϕ)

→ Factor of safety depend on Height of soil in slope

S5. Ans.(a)

Sol. Rankine assumption in earth pressure analysis

→ soil is cohesionless.

→ Face of the wall in contact with backfill is vertical & smooth

→ ground surface is planer that may be horizontal & inclined

S6. Ans.(a)

Sol. Plate load test used to determine ultimate bearing capacity and probable settlement under given loading.

S7. Ans.(a)

Sol. Width of footing =(total load)/(safe bearing capacity)

=650/65

=10 meter

S8. Ans.(a)

Sol. Discharge velocity (V)=5×10^(-7) m\/sec

Void ratio (e)=0.50

Porosity (n)=e/(1+e)=0.5/1.5=0.33

Seepage velocity (V_s )=V/n

=(5×10^(-7))/0.33

=15×10^(-7) m\/sec

S9. Ans.(b)

Sol. According to darcy law.

▭Vαi

▭(V=K.i)

K= coefficient of permeability

S10. Ans.(c)

Sol. ▭(S+a_c=1)

S → degree of saturation

a_c → air content