Soil Mechanics and Foundation Sheet 20

1) Question.

In case of coarse grained sand having high permeability and low plasticity, 95% of consolidation occurs within...... after application of load.
Answer.
- 1
  
  1 minute
- 2
  
  30 minutes
- 3
  
  1 hour
- 4
  
  2 hour
Answer: 1

Explanation:
2) Question.

The time factor corresponding to 25% degree of consolidation is given by
Answer.
- 1
  
  π/8
- 2
  
  π/16
- 3
  
  π/32
- 4
  
  π/64
Answer: 4

Explanation:
3) Question.

The relation between coefficient of consolidation ( $c_{v}$ ), time factor $(T_{v})$ , drainage path (d) and time (t) is given by
Answer.
- 1
  
  $c_{v} = \frac{d^{2} . T_{v}}{t}$
- 2
  
  $c_{v} = \frac{d^{2} . t}{T_{v}}$
- 3
  
  $c_{v} = \frac{T_{v} . t}{d^{2}}$
- 4
  
  $c_{v} = \frac{T_{v}}{d^{2} . t}$
Answer: 1

Explanation:
4) Question.

The ratio of settlement at any time (t) to the final settlement is known as
Answer.
- 1
  
  compression index
- 2
  
  coefficient of consolidation
- 3
  
  degree of consolidation
- 4
  
  none of these
Answer: 3

Explanation:
5) Question.

The relation between coefficient of consolidation $(c_{v})$ , coefficient of volume change $(m_{v})$ and coefficient of permeability (k) is given by
Answer.
- 1
  
  $c_{v} = \frac{k}{m_{v} . γ_{w}}$
- 2
  
  $c_{v} = \frac{k . m_{v}}{γ_{w}}$
- 3
  
  $c_{v} = \frac{γ_{w}}{k . m_{v}}$
- 4
  
  $c_{v} = \frac{γ_{w .} γ_{w}}{k}$
Answer: 1

Explanation:
6) Question.

The time factor for a clay layer is
Answer.
- 1
  
  a dimensionless parameter
- 2
  
  directly proportional to permeability
- 3
  
  directly proportional to drainage path
- 4
  
  none of these
Answer: 1

Explanation:
7) Question.

The degree of consolidation is proportional directly
Answer.
- 1
  
  to time and inversely to drainage path
- 2
  
  to drainage path and inversely to time
- 3
  
  to time and inversely to the square of drainage path
- 4
  
  to square of drainage path and inversely to time
Answer: 3

Explanation:
8) Question.

The rate of consolidation...... with the increase in temperature.
Answer.
- 1
  
  increases
- 2
  
  decreases
- 3
  
  does not change
Answer: 1

Explanation:
9) Question.

The coefficient of consolidation is used for evaluating
Answer.
- 1
  
  stress in the soil
- 2
  
  total settlement
- 3
  
  over consolidation ratio
- 4
  
  time rate of settlement
Answer: 4

Explanation:
10) Question.

The decrease in voids ratio per unit increase of pressure is called
Answer.
- 1
  
  coefficient of permeability
- 2
  
  coefficient of compressibility
- 3
  
  coefficient of volume compressibility
- 4
  
  coefficient of curvature
Answer: 2

Explanation:
11) Question.

As per converse Labarre formula, group efficiency of friction piles is given by:

where

m = number of columns

n = number of rows

$α = \tan^{- 1} (d / s) (i n d e g r e e)$

d = diameter of pile

s = c/c spacing of pile
Answer.
- 1
  
  $1 - \frac{α}{90} [\frac{(n - 1) m + (m - 1) n}{m n}]$
- 2
  
  $1 - \frac{α}{90} [\frac{(n + 1) m + (m + 1) n}{m n}]$
- 3
  
  $1 - \frac{α}{90} [\frac{(n - 1) m - (m - 1) n}{m n}]$
- 4
  
  $1 - \frac{α}{90} [\frac{(n + 1) m - (m + 1) n}{m n}]$
Answer: 1

Explanation:
12) Question.

In care of free over damped vibration,
Answer.
- 1
  
  $C = \sqrt{k . m}$
- 2
  
  $C = 2 \sqrt{k . m}$
- 3
  
  $C > 2 \sqrt{k . m}$
- 4
  
  $C < 2 \sqrt{k . m}$
Answer: 3

Explanation:
13) Question.

The natural frequency of a vibrating foundation system

i) increases as the square root of the spring stiffness

ii) decreases with the square root of the spring stiffiness

iii) increases as the square root of the mass of the body

iv) decreases with the square root of the mass of the body

of these statements:
Answer.
- 1
  
  (i) and (iii) are correct
- 2
  
  (i) and (iv) are correct
- 3
  
  (ii) and (iii) are correct
- 4
  
  (ii) and (iv) are correct
Answer: 2

Explanation:
14) Question.

The soils most susceptible to liquefaction are
Answer.
- 1
  
  saturated dense sands
- 2
  
  saturated fine and medium sands of uniform particle size
- 3
  
  saturated clays of uniform size
- 4
  
  saturated gravels and cobbles
Answer: 2

Explanation:
15) Question.

The unit weight of a soil at zero air voids depends on:
Answer.
- 1
  
  specific gravity
- 2
  
  water content
- 3
  
  unit weight of water
- 4
  
  all the above
Answer: 4

Explanation:
16) Question.

A soil having particles of nearly the same size is known as:
Answer.
- 1
  
  well graded
- 2
  
  uniformly graded
- 3
  
  poorly graded
- 4
  
  gap graded
Answer: 2

Explanation:
17) Question.

Select the incorrect statement
Answer.
- 1
  
  Bearing capacity of a soil depends upon the amount and direction of load
- 2
  
  Bearing capacity of soil depends on the type of soil.
- 3
  
  Bearing capacity of a soil depends upon shape and size of footing.
- 4
  
  Bearing capacity of a soil is independent of rate of loading.
Answer: 1

Explanation:
18) Question.

In the plate loading test for determining the bearing capacity of soil, the size of square bearing plate should be
Answer.
- 1
  
  less than 300 mm
- 2
  
  between 300 mm and 750 mm
- 3
  
  between 750 mm and 1 m
- 4
  
  greater than 1 m
Answer: 2

Explanation:
Bearing plate : The bearing plate is either circular or square, made of mild steel of not less than 25 mm in thickness and varying in size from 300 to 750 mm with chequered or grooved bottom.
19) Question.

Terzaghi's bearing capacity factors Nc, Nq and Ny are functions of
Answer.
- 1
  
  cohesion only
- 2
  
  angle of internal friction only
- 3
  
  borth cohesion and angle of internal friction
- 4
  
  none of the above
Answer: 2
Explanation:
Terzaghi’s bearing capacity factors Nc, Nq and Nγ depend only on the angle of internal friction (φ) of the soil.

For example:
- φ = 0° → Nc = 5.7, Nq = 1, Nγ = 0
- As φ increases, the bearing capacity factors also increase.
They do not directly depend on cohesion (c).
20) Question.

Terzaghi's general bearing capacity formula for a strip footing

C NC+y D Nq+0.5 y NyB gives

where C = unit cohesion

y = unit weight of soil

D = depth of foundation

B = width of foundation

Nc, </m
Answer.
- 1
  
  safe bearing capacity
- 2
  
  net safe bearing capacity
- 3
  
  ultimate bearing capacity
- 4
  
  net ultimate bearing capaicty
Answer: 3
Explanation:
This is Terzaghi’s ultimate bearing capacity equation for a strip footing.

Where:
- c = unit cohesion of soil
- γ = unit weight of soil
- D = depth of foundation
- B = width of foundation
- Nc, Nq, Nγ = bearing capacity factors
The three terms represent:

cNc → contribution due to cohesion

γDNq → contribution due to surcharge/overburden

0.5γBNγ → contribution due to soil weight

Therefore,

Ultimate bearing capacity = cNc + γDNq + 0.5γBNγ

📌 Remember for MCQ
- qu → Ultimate bearing capacity
- qnu = qu − γD → Net ultimate bearing capacity
✅ Answer: C. Ultimate bearing capacity

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