# Soil Mechanics Questions and Answers – Consolidation Process – 1

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This set of Soil Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Consolidation Process – 1”.

1. The decrease in the volume of soil mass under stress is known as __________
a) compression
b) compressibility
c) tension
d) consolidation

Explanation: When a compressive load is applied to a soil mass, a decrease in its volume takes place. The decrease in volume of soil mass under stress is known as compression.

2. The property of soil mass pertaining to its susceptibility to decrease in volume under pressure is ____________
a) compression
b) compressibility
c) tension
d) consolidation

Explanation: When a compressive load is applied to a soil mass, a decrease in its volume takes place. The decrease in volume of soil mass under stress is known as compression and the property of soil mass pertaining to its susceptibility to decrease in volume under pressure is compressibility.

3. Every process involving a decrease in the water content of a saturated soil without replacement of water by air is called _________
a) compression
b) compressibility
c) tension
d) consolidation

Explanation: According to Terzaghi, every process involving a decrease in the water content of a saturated soil without replacement of water by air is the process of consolidation.

4. When stress is applied to soil mass, the elastic deformation of solid particles is ____________
a) extremely large
b) large
c) small
d) negligibly small

Explanation: When stress is applied to soil mass, the elastic deformation of solid particles is negligibly small compared to the deformation caused by change in relative position of the discrete particles and the resulting decrease in the volume of voids.

5. The compression resulting from a long term static load and consequent escape of pore water is _____________
a) compression
b) compressibility
c) tension
d) consolidation

Explanation: The compression resulting from a long term static load and consequent escape of pore water is consolidation, as according to Terzaghi, every process involving a decrease in the water content of a saturated soil without replacement of water by air is the process of consolidation.

6. If increases in the water content due to an increase in the volume of voids is known as _________
a) compression
b) compressibility
c) swelling
d) consolidation

Explanation: Swelling is the increase in the water content due to an increase in the volume of voids. According to Terzaghi, it is the opposite of consolidation. Consolidation is decrease in the water content of a saturated soil without replacement of water by air.

7. Compression of soil, under short duration of moving or vibratory loads is _________
a) saturation
b) compressibility
c) swelling
d) compaction

Explanation: Compression of soil, under short duration of moving or vibratory loads is known as compaction. Swelling is the increase in the water content due to an increase in the volume of voids. The compression resulting from a long term static load and consequent escape of pore water is consolidation.

8. Slow vertical deformation occurs when a compressive load is applied to a laterally confined layer of sand.
a) True
b) False

Explanation: When a compressive load is applied to a laterally confined layer of sand, rapid vertical deformation occurs. The rate at which this deformation can take place depends upon the permeability of soil and upon the distance the water must travel to reach a drainage surface.

9. The compressibility of clays may also be caused by the following factor.
a) changes in salinity
b) ion exchange
c) expulsion of double layer water from between the grains
d) swelling of clay

Explanation: The compressibility of clays may also be caused by the three factors:
I. expulsion of double layer water from between the grains
II. slipping of particles to new positions of greater density
III. bending of particles as elastic sheets

10. The mechanics of consolidation was demonstrated by ___________
a) Taylor
b) Skempton
c) Terzaghi
d) Darcy

Explanation: The mechanics of consolidation was demonstrated by Terzaghi, by means of the piston and spring analogy.

11. In the spring analogy of consolidation, cylinder is filled with water up to bottom of piston and spring carries 10 units of load. If external two units of load is applied and the valve closed, then the effective pressure σ’ and hydrodynamic pressure u is given by ___________ a) σ’=0, u=12
b) σ’=0, u=0
c) σ’=10, u=2
d) σ’=12, u=0

Explanation: When external two units of load is applied and the valve closed, then the effective pressure σ’ and hydrodynamic pressure u is given by σ’=10, u=2. This is because the additional pressure of 2 units is entirely borne by water.

12. In the spring analogy of consolidation, cylinder is filled with water up to bottom of piston and spring carries 10 units of load. If external two units of load is applied and the valve is partly opened, then the effective pressure σ’ and hydrodynamic pressure u is given by ___________ a) σ’=0, u=12
b) σ’=10+∆σ’, u=2-∆σ’
c) σ’=10, u=2
d) σ’=12, u=0

Explanation: When external two units of load is applied and the valve is partly opened, then the effective pressure σ’ and hydrodynamic pressure u is given by σ’=10+∆σ’, u=2-∆σ’. This is because the additional pressure of 2 units is borne both by spring as well as water.

13. In the spring analogy of consolidation, cylinder is filled with water up to bottom of piston and spring carries 10 units of load. If external two units of load is applied and the valve is opened, then the effective pressure σ’ and hydrodynamic pressure u is given by ___________ a) σ’=0, u=12
b) σ’=10+∆σ’, u=2-∆σ’
c) σ’=10, u=2
d) σ’=12, u=0

Explanation: When external two units of load is applied and the valve is opened, then the effective pressure σ’ and hydrodynamic pressure u is given by σ’=12, u=0. This is because the additional pressure of 2 units is borne by water is entirely transferred to the spring.

14. Excess pore pressure is also known as ___________
a) hydrodynamic pressure
b) seepage pressure
c) effective pressure
d) total pressure

Explanation: The pressure that builds up in pore water due to load increment in the soil is termed as excess pore pressure. Excess pore pressure is also known as excess hydrostatic pressure or hydrodynamic pressure.

15. In fluid flow calculations, water is considered as incompressible.
a) True
b) False

Explanation: Water is slightly compressible but in fluid flow calculations, water is considered as incompressible because the pressure changes involved are too small to make appreciable change to the density.

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