Soil Mechanics MCQ Questions and Answers

Soil Mechanics MCQ 1

The active earth pressure of a soil is proportional to (where φ is the angle of friction of the soil)

1. tan(45°- φ)
2. tan²(45°+φ/2)
3. tan²(45°-φ/2)
4. tan(45°+φ)

Answer:  3. tan²(45°-φ/2)

Solution

Active earth pressure,

p_a=k_aγH

where, 

k_a=(1- Sinφ)/(1+ Sinφ)=tan²(45°-φ/2)

Soil Mechanics MCQ 2

The quantity of seepage of water through soils is proportional to

1. coefficient of permeability of soil
2. total head loss through the soil
3. neither (a) nor (b)
4. both (a) and (b)

Answer: 4. both (a) and (b)

Solution

We know that

Seepage,

Q=kH(N_f/N_d)

where, 

k = coefficient of permeability of the soil

H = Total head loss through the soil

N_f = number of flow channels

N_d = number of equipotential drops

Therefore, seepage quantity is proportional to both coefficients of permeability of the soil and total head loss through the soil.

Soil Mechanics MCQ 3

When drainage is permitted under initially applied normal stress only and full primarily consolidation is allowed to take place, the test is known as

1. quick test
2. drained test
3. consolidated undrained test
4. none of these

Answer: 3. Consolidated undrained test

Solution

Three different types of triaxial tests can be performed:

Unconsolidated Undrained Test (UU test) or quick test: Drainage is not permitted in both the consolidation and shearing stage.

Consolidated Drained Test (CD test): Drainage is permitted in both the consolidation and shearing stages.

Consolidated Undrained Test (CU test): Drainage is only permitted in the consolidation stage but not in the shearing stage.

Soil Mechanics MCQ 4

The maximum value of effective stress in the past divided by the present value is defined as the over consolidation ratio (OCR). The O.C.R. of an over consolidated clay is

1. less than 1
2. 1
3. more than 1
4. none of these

Answer: 3. more than 1

Solution

OCR=(Maximum applied effective stress in the past) /(effective stress applied in the present)

If OCR <= 1, soil is normally consolidated

If OCR >1, soil is over consolidated

Soil Mechanics MCQ 5

If N_f, N_d and H are total number flow channels, total number of potential drops and total hydraulic head differences respectively, the discharge q through the complete flow is given by (where K is a constant)

1. q=√H(N_f/N_d)
2. q=KH(N_d/N_f)
3. q=KH(N_f/N_d)
4. q=KH√(N_f/N_d)

Answer: 3.  q=KH(N_f/N_d)

Solution

Seepage quantity is given by

q=KH(N_f/N_d)

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