Soil Mechanics and Foundation Sheet 16

1) Question.

The effective stress on the soil is due to the
Answer.
- 1
  
  external load acting on the soil
- 2
  
  weight of the soil particles
- 3
  
  weight of water present in soil pores
- 4
  
  both (a) and (b)
Answer: 4

Explanation:
2) Question.

The piping failure in a hydraulic structure can be prevented by
Answer.
- 1
  
  diverting the seepage water into filter wells
- 2
  
  increasing the creep length of flow of water
- 3
  
  increasing the stress due to weight of the structure
- 4
  
  all of the above
Answer: 4

Explanation:
3) Question.

A flow net constructed to determine the seepage through an earth dam which is homogeneous but anisotropic, gave 4 flow channels and 16 equipotential drops. The coefficients of permeability in the horizontal and vertical directions are $4 \times 10^{- 7}$ m/s and $1 \times 10^{- 7}$ m/s respectively. If the storage head is 20 m, then the seepage per unit length of the dam in $m^{3} / s$ , will be
Answer.
- 1
  
  $5 \times 10^{- 7}$
- 2
  
  $10 \times 10^{- 7}$
- 3
  
  $20 \times 10^{- 7}$
- 4
  
  $40 \times 10^{- 7}$
Answer: 2

Explanation:
4) Question.

The expression for the discharge (Q) through a flow net for isotropic soils is given by

[ $N_{F}$ = Number of flow channels, $N_{D}$ = Number of potential drops, H= Total hydraulic head causing flow, K= A constant]
Answer.
- 1
  
  $Q = K H \times \frac{N_{F}}{N_{D}}$
- 2
  
  $K H \sqrt{\frac{N_{F}}{N_{D}}}$
- 3
  
  $Q = K H {(\frac{N_{F}}{N_{D}})}^{2}$
- 4
  
  $K H {(\frac{N_{F}}{N_{D}})}^{3}$
Answer: 1

Explanation:
5) Question.

The permissible exit gradient for safety against piping which endanger the stability of a hydraulic structure, should be
Answer.
- 1
  
  0.2
- 2
  
  0.4
- 3
  
  0.6
- 4
  
  0.8
Answer: 1

Explanation:
6) Question.

The maximum permissible exit gradient is the critical gradient divided by a factor of safety.
Answer.
- 1
  
  True.
- 2
  
  False.
Answer: 1

Explanation:
7) Question.

The critical gradient for all soils is normally
Answer.
- 1
  
  0.5
- 2
  
  1
- 3
  
  1.5
- 4
  
  2.5
Answer: 2

Explanation:
8) Question.

The seepage pressure is independent of the coefficient of permeability.
Answer.
- 1
  
  Correct
- 2
  
  Incorrect
Answer: 1

Explanation:
9) Question.

The seepage force in soils is
Answer.
- 1
  
  proportional to head loss
- 2
  
  proportional to exit gradient
- 3
  
  perpendicular to the equi-potential lines
- 4
  
  all of these
Answer: 4

Explanation:
10) Question.

The critical gradient of the seepage of water...... with the increase in specific gravity of soil.
Answer.
- 1
  
  increases
- 2
  
  decreases
- 3
  
  does not change
Answer: 1

Explanation:
11) Question.

In a consolidated drained test on a normally consolidated clay, the volume of the soil sample during shear
Answer.
- 1
  
  decreases
- 2
  
  increases
- 3
  
  remains unchanged
- 4
  
  first increases and then decreases
Answer: 1

Explanation:
12) Question.

The shear strength of a soil
Answer.
- 1
  
  is directly proportional to the angle of internal friction of the soil
- 2
  
  is inversely proportional to the angle of internal friction of the soil
- 3
  
  decreases with increase in normal stress
- 4
  
  decreases with decrease in normal stress
Answer: 4

Explanation:
13) Question.

Relationship between dry density $γ_{d}$ , percentage air voids $n_{a}$ , water content w and specific gravity G of any soil is
Answer.
- 1
  
  $γ_{d} = \frac{(1 + n_{a}) G γ_{w}}{1 + w G}$
- 2
  
  $γ_{d} = \frac{(1 + n_{a}) G γ_{w}}{1 - w G}$
- 3
  
  $γ_{d} = \frac{(1 - n_{a}) G γ_{w}}{1 + w G}$
- 4
  
  $γ_{d} = \frac{(1 - n_{a}) G γ_{w}}{1 - w G}$
Answer: 3

Explanation:
14) Question.

A normally consolidated clay settled 10 mm when effective stress was increased from $100 k N / m^{2}$ to $200 k N / m^{2}$ . If the effective stress is further increased from $200 k N / m^{2}$ to $400 k N / m^{2}$ , then the settlement of the sa
Answer.
- 1
  
  10 mm
- 2
  
  20 mm
- 3
  
  40 mm
- 4
  
  none of the above
Answer: 1

Explanation:
15) Question.

Coefficient of compressibility is
Answer.
- 1
  
  constant for any type of soil
- 2
  
  different for different types of soils and also different for a soil under different states of consolidation
- 3
  
  different for different types of soils but same for a soil under different states of consolidation
- 4
  
  independent of type of soil but depends on the stress history of soil
Answer: 2

Explanation:
16) Question.

Select the correct statement
Answer.
- 1
  
  coefficient of compressibility of an over-consolidated clay is less than that of a normally consolidated clay
- 2
  
  coefficient of compressibility of an over-consolidated clay is greater than that of a normally consolidated clay
- 3
  
  coefficient of compressibility is constant for any clay
- 4
  
  none of the above
Answer: 1

Explanation:
17) Question.

Compressibility of sandy soils is
Answer.
- 1
  
  almost equal to that of clayey soils
- 2
  
  much greater than that of clayes solis
- 3
  
  much less than that of clayey soils
- 4
  
  none of the above
Answer: 3

Explanation:
18) Question.

Direct measurement of permeability of the specimen at any stage of loading can be made
Answer.
- 1
  
  only in fixed ring type consolidometer
- 2
  
  only in floating ring type consolidometer
- 3
  
  both (A) and (b)
- 4
  
  none of the above
Answer: 1

Explanation:
19) Question.

Clay layer A with single drainage and coefficient of consolidation $C_{v}$ taken 6 months to achieve 50% consolidation. The time taken by clay layer B of the same thickness with double drainage and coefficient of consolidation $C_{v} / 2$ to achieve the same dgreee of consolidation is
Answer.
- 1
  
  3 months
- 2
  
  6 months
- 3
  
  12 months
- 4
  
  24 months
Answer: 1

Explanation:
20) Question.

Select the correct statement
Answer.
- 1
  
  The greater the viscosity, the greater is permeability
- 2
  
  The greater the unit weight, the greater is premeability
- 3
  
  The greater the unit weight, the smaller is permeability
- 4
  
  Unit weight does not affect permeability
Answer: 2

Explanation:

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