Soil Mechanics and Foundation Sheet 17

1) Question.

The rate of expulsion of pore fluid is directly dependent on the....... of the soil.
Answer.
- 1
  
  shear strength
- 2
  
  void ratio
- 3
  
  permeability
Answer: 3

Explanation:
2) Question.

The vertical deformation of soil mass consists of
Answer.
- 1
  
  deformation of soil grains
- 2
  
  compression of pore fluid
- 3
  
  reduction of pore space
- 4
  
  all of these
Answer: 4

Explanation:
3) Question.

The consolidation of a soil is defined as the
Answer.
- 1
  
  process of compression by gradual reduction of pore space under steady load
- 2
  
  process which gives gradual decrease of water content at constant load
- 3
  
  change in volume of soil due to expulsion of pure water under an applied load
- 4
  
  any one of the above
Answer: 4

Explanation:
4) Question.

The neutral stress is..... if the water is flowing from downward on the soil mass.
Answer.
- 1
  
  increased
- 2
  
  decreased
Answer: 2

Explanation:
5) Question.

The effective stress is..... if the water is flowing from upward on the soil mass.
Answer.
- 1
  
  increased
- 2
  
  decreased
Answer: 1

Explanation:
6) Question.

The total stress is equal to the sum of the effective stress and pore water pressure.
Answer.
- 1
  
  True
- 2
  
  False.
Answer: 1

Explanation:
7) Question.

The removal of neutral pressure...... the effective pressure.
Answer.
- 1
  
  increases
- 2
  
  decreases
- 3
  
  does not change
Answer: 1

Explanation:
8) Question.

The neutral stress is
Answer.
- 1
  
  transmitted through the points of contact of the interconnected particles of soil
- 2
  
  trasmitted to the soil base through the pore water
- 3
  
  independent of the depth of water above the soil mass
- 4
  
  due to weight of soil particles
Answer: 2

Explanation:
9) Question.

The effective stress on the soil mass ..... void ratio.
Answer.
- 1
  
  increases
- 2
  
  decreases
Answer: 2

Explanation:
10) Question.

The effective stress is also called pore-water pressure.
Answer.
- 1
  
  Agree
- 2
  
  Disagree
Answer: 2

Explanation:
11) Question.

Rankine's theory of earth pressure assumes that the back of the wall is
Answer.
- 1
  
  plane and smooth
- 2
  
  plane and rough
- 3
  
  vertical and smooth
- 4
  
  vertical and rough
Answer: 3

Explanation:
12) Question.

Sensitivity of a soil can be defined as
Answer.
- 1
  
  percentage of volume change of soil under saturated condition
- 2
  
  ratio of compressive strength of unconfined undisturbed soil to that of soil in a remoulded state
- 3
  
  ratio of volume of voids to volume of solids
- 4
  
  none of the above
Answer: 2

Explanation:
13) Question.

During the first stage of triaxial test when the cell pressure is increased from $0.10 N / m m^{2} t o 0.26 N / m m^{2}$ , the pore water pressure increases from $0.07 N / m m^{2} t o 0.15 N / m m^{2}$ . Skempoton'
Answer.
- 1
  
  0.5
- 2
  
  -0.5
- 3
  
  2.0
- 4
  
  -2.0
Answer: 1

Explanation:
14) Question.

The ratio of the undisturbed shear strenth to the remoulded shear strength in cohesive soils under undrained conditions is
Answer.
- 1
  
  zero
- 2
  
  1
- 3
  
  greater than 1
- 4
  
  between 0 and 1
Answer: 3

Explanation:
15) Question.

When a sample of sand is sheared under undrained condition, then
Answer.
- 1
  
  volume of dense sand increases and that of loose sand decreases
- 2
  
  volume of dense sand decreases and that of loose sand increases
- 3
  
  volume of both dense sand and loose sand decreases
- 4
  
  volume does not change
Answer: 4
Explanation:
In an undrained shear test, drainage is not permitted during shearing. Therefore, no volume change can occur, regardless of whether the sand is dense or loose.
- Dense sand tends to dilate (increase in volume) during shear under drained conditions.
- Loose sand tends to contract (decrease in volume) during shear under drained conditions.
However, under undrained conditions, these volume changes are prevented, and instead pore water pressure changes develop:
- Dense sand → negative pore pressure (suction) tendency.
- Loose sand → positive pore pressure tendency.
Hence, the actual volume remains constant.
16) Question.

In a trixial compression test when drainage is allowed during the first state (i.e. application of cell pressure) only and not during the second state (i.e. application of deviator stress at constant cell pressure), the t est is known as
Answer.
- 1
  
  consolidated drained test
- 2
  
  consolidated undrrained test
- 3
  
  unconsolidated drained test
- 4
  
  unconsolidated undrained test
Answer: 2

Explanation:
17) Question.

The state of stress on a plane inclined at an angle of $45^{o}$ to the horizontal plane is represented on the Mohr's circle by a point at which

where $σ_{1} a n d σ_{3}$ are major and minor principal stresses respectively
Answer.
- 1
  
  $n o r m a l s t r e s s i s \frac{σ_{1} + σ_{3}}{2} a n d s h e a r s t r e s s i s \frac{σ_{1} - σ_{3}}{2}$
- 2
  
  $n o r m a l s t r e s s i s \frac{σ_{1} - σ_{3}}{2} a n d s h e a r s t r e s s i s \frac{σ_{1} + σ_{3}}{2}$
- 3
  
  $n o r m a l s t r e s s i s \frac{σ_{1} + σ_{3}}{2} a n d s h e a r s t r e s s i s z e r o$
- 4
  
  both normal stress and shear stress are equal
Answer: 1

Explanation:
18) Question.

In the triaxial compression test, the application of additional axial stress (i.e. deviator stress) on the soil specimen produces shear stress on
Answer.
- 1
  
  horizontal plane only
- 2
  
  vertical plane only
- 3
  
  both horizontal and vertical planes
- 4
  
  all planes except horizontal and vertical planes
Answer: 4

Explanation:
19) Question.

If the shearing stress is zero on two planes, then the angle between the two planes is
Answer.
- 1
  
  45o
- 2
  
  90o
- 3
  
  135o
- 4
  
  225o
Answer: 2

Explanation:
Planes on which the shear stress is zero are called principal planes.

A fundamental property of stress analysis is that the two principal planes at a point are mutually perpendicular.

Therefore, if the shearing stress is zero on two planes, the angle between those planes is: 90 deg
20) Question.

Select the incorrect statement
Answer.
- 1
  
  In a direct shear box test, the plane of shear failure is predetermined
- 2
  
  Better control is achieved on the drainage of the soil in a triaxial compression test
- 3
  
  Stress distribution on the failure plane in the case of triaxial compression test is uniform
- 4
  
  Unconfined compression test can be carried out on all types of soils.
Answer: 4

Explanation:

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