Soil Mechanics and Foundation Sheet 15

1) Question.

The critical gradient of the seepage of water
Answer.
- 1
  
  directly proportional to void ratio
- 2
  
  increases with the decrease in void ratio
- 3
  
  inversely proportional to specific gravity
- 4
  
  increases with the decrease in specific gravity of soil
Answer: 2

Explanation:
2) Question.

The direction of seepage is always ...... to the equipotential lines.
Answer.
- 1
  
  parallel
- 2
  
  perpendicular
Answer: 2

Explanation:
3) Question.

A deposit of fine sand has a porosity n and the specific gravity of soil solids is G. The hydraulic gradient of the deposit to develop boiling condition of sand is given by
Answer.
- 1
  
  $(G - 1) (1 - n)$
- 2
  
  $(G - 1) (1 + n)$
- 3
  
  $\frac{G - 1}{1 - n}$
- 4
  
  $\frac{G - 1}{1 + n}$
Answer: 1

Explanation:
4) Question.

The critical gradient of the seepage of water in a soil medium is

[ G= specific gravity of soil, e= void ratio]
Answer.
- 1
  
  $\frac{1 + G}{1 + e}$
- 2
  
  $\frac{G - 1}{1 + e}$
- 3
  
  $\frac{1 + e}{1 - G}$
- 4
  
  $\frac{1 + e}{G - 1}$
Answer: 2

Explanation:
5) Question.

The hydraulic gradient provided at the downstream side of a hydraulic structure such as a dam, is called
Answer.
- 1
  
  downstream gradient
- 2
  
  tail water gradient
- 3
  
  exit gradient
- 4
  
  any one of these
Answer: 4

Explanation:
6) Question.

The exit gradient of the seepage of water through a soil medium is the
Answer.
- 1
  
  slope of the flow line
- 2
  
  slope of the equi-potential line
- 3
  
  ratio of total head to the length of seepage
- 4
  
  ratio of the head loss to the length of seepage
Answer: 4

Explanation:
7) Question.

A flow net is used to determine the
Answer.
- 1
  
  seepage flow
- 2
  
  seepage pressure
- 3
  
  exit gradient
- 4
  
  all of these
Answer: 4

Explanation:
8) Question.

The flow net in the seepage of water through a soil medium is a network of
Answer.
- 1
  
  flow lines
- 2
  
  equi-potential lines
- 3
  
  flow lines and equi-potential lines
- 4
  
  water particles and their movement in the soil
Answer: 3

Explanation:
9) Question.

Flow lines and equi-potential lines are
Answer.
- 1
  
  perpendicular to each other
- 2
  
  parallel to each other
- 3
  
  intersecting lines at $90^{0}$ to each other
- 4
  
  intersecting lines at $45^{0}$ to each other
Answer: 3

Explanation:
10) Question.

Quick sand is a
Answer.
- 1
  
  moist sand containing small particles
- 2
  
  condition which occurs in coarse sand
- 3
  
  condition in which a cohesionless soil loses all its strength because of upward flow of water
- 4
  
  none of the above
Answer: 3

Explanation:
11) Question.

According to Rankine's alalysis, minimum depth of foundation is equal to

where q = imtemsotu of loading

y = unit weight of soil

$ϕ$ = angle of internal friction
Answer.
- 1
  
  $\frac{q}{y} {(\frac{1 + \sin ϕ}{1 - \sin ϕ})}^{2}$
- 2
  
  $\frac{q}{y} {(\frac{1 - \sin ϕ}{1 + \sin ϕ})}^{2}$
- 3
  
  $\frac{q}{y} (\frac{1 + \sin ϕ}{1 - \sin ϕ})$
- 4
  
  $\frac{q}{y} (\frac{1 - \sin ϕ}{1 + \sin ϕ})$
Answer: 2

Explanation:
12) Question.

Allowable bearing pressure of a foundation depends upon
Answer.
- 1
  
  allowable settlement only
- 2
  
  ultimate bearing capacity of soil only
- 3
  
  both allowable settlement and ultimate bearing capacity
- 4
  
  none of above
Answer: 3

Explanation:
13) Question.

Bishop's method of stability analysis
Answer.
- 1
  
  is more conservative
- 2
  
  neglects the effect of forces acting on the sides of the slices
- 3
  
  assumes the slip surface as an arc of a circle
- 4
  
  all of the above
Answer: 3

Explanation:
14) Question.

Which of the following earth pressure theories is directly applicable to bulkheads?
Answer.
- 1
  
  Rankine's theory
- 2
  
  Coulomb's theory
- 3
  
  both
- 4
  
  none of the above
Answer: 4

Explanation:
15) Question.

Cohesive soils are
Answer.
- 1
  
  good for backfill because of low lateral pressure
- 2
  
  good for backfill because of high shear strenth
- 3
  
  poor for backfill because of large lateral pressure
- 4
  
  none of the above
Answer: 3

Explanation:
16) Question.

Total lateral earth pressure is proportional to
Answer.
- 1
  
  depth of soil
- 2
  
  square of depth of soil
- 3
  
  angle of internal friction of soil
- 4
  
  none of above
Answer: 2

Explanation:
17) Question.

If the top surface of the backfill of a retaining wall is inclined to the horizontal at an angle $β$ , then the coefficient of passive earth pressure is equal to

Where $ϕ$ is the angle of internal friction of soil
Answer.
- 1
  
  $\frac{\cos β (\cos β - \sqrt{\cos^{2} β - \cos^{2} ϕ})}{\cos β + \sqrt{\cos^{2} - \cos^{2} ϕ}}$
- 2
  
  $\frac{\cos β (\cos β + \sqrt{\cos^{2} β - \cos^{2} ϕ})}{\cos β + \sqrt{\cos^{2} - \cos^{2} ϕ}}$
- 3
  
  $\frac{\cos β + \sqrt{\cos^{2} β - \cos^{2} ϕ}}{\cos β (\cos β + \sqrt{\cos^{2} - \cos^{2} ϕ})}$
- 4
  
  $\frac{\cos β - \sqrt{\cos^{2} β - \cos^{2} ϕ}}{\cos β (\cos β + \sqrt{\cos^{2} - \cos^{2} ϕ})}$
Answer: 2

Explanation:
18) Question.

Coefficient of earth pressure at rest is
Answer.
- 1
  
  less than active earth pressure but greater than passive earth pressure
- 2
  
  greater than active earth pressure but less than passive earth pressure
- 3
  
  greater than both the active earth pressure and passive earth pressure
- 4
  
  less than both the active and passive earth pressures
Answer: 2

Explanation:
19) Question.

The effect of cohesion on a soil is to
Answer.
- 1
  
  reduce both the active earth pressure intensity and passive earth pressure intensity
- 2
  
  increase both the active earth pressure intensity and passive earth pressure intensity
- 3
  
  reduce the active earth pressure in tensity but to increase the passive earth pressure intensity
- 4
  
  increase the active earth pressure intensity but to increase the passive earth pressure intensity
Answer: 3

Explanation:
20) Question.

The major pricipal stress in an element of cohesionless soil within the backfill of a retaining wall is
Answer.
- 1
  
  vertical if the soil is in an active state of plastic equilibrium
- 2
  
  vertical if the soil is in a passive state of plastic equilibrium
- 3
  
  inclined at $45^{o}$ to the vertical plane
- 4
  
  none of the above
Answer: 1

Explanation:

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