Define consolidation and explain it's types.

The property of soil by virtue of which the volume decreases under applied pressure is termed as compressibility.

The compression of soil can occur due to one or more of the following causes :

1. Compression of solid particles and water in the voids.

2. Compression and expulsion of water in the voids.

3. Expulsion of water in the voids.

 The process in which gradual reduction in volume of soil mass occurs under sustained loading and is primarily due to expulsion of pure water is known as consolidation.  It is the property of fine grained soil because the fine grained soil mass has large void ratio and higher water content. 

The term consolidation applies more to fine grained soil than to coarse grained soil for the following reasons:

1. Fine grained soil are more compressible....Show More

The property of soil by virtue of which the volume decreases under applied pressure is termed as compressibility.

The compression of soil can occur due to one or more of the following causes :

1. Compression of solid particles and water in the voids.

2. Compression and expulsion of water in the voids.

3. Expulsion of water in the voids.

 The process in which gradual reduction in volume of soil mass occurs under sustained loading and is primarily due to expulsion of pure water is known as consolidation.  It is the property of fine grained soil because the fine grained soil mass has large void ratio and higher water content. 

The term consolidation applies more to fine grained soil than to coarse grained soil for the following reasons:

1. Fine grained soil are more compressible than coarse grained soil in therefore the settlement of fine grained soil are generally larger than that of coarse grained soil.

2. Consolidation of fine grained soil takes much longer time than coarse grained soils due to low permeability. Fine grained soil impose long-term problem to the super-structure.

The consolidation of soil  deposit can be divided into three stages:

1. Initial consolidation

2.  primary consolidation

3.  secondary consolidation

Initial Consolidation:

The reduction in volume of this soil just after the application of the load is known as initial consolidation or initial compression. For saturated soils, the initial consolidation is mainly due to compression of solid particles.

Primary consolidation:

After initial  consolidation, further reduction in volume occurs due to expulsion of water from the voids. This reduction in volume is called primary Consolidation which depends upon the permeability of the soil.

 In fine grained soils, the primary consolidation occurs over a long time. On the other hand, in course grained soils, the primary consolidation occurs rather quickly due to high permeability.

Secondary Consolidation:

The reduction in volume continues at a very slow rate even after the hydrostatic pressure developed by the applied pressure is fully dissipated and the primary consolidation is  complete. This additional reduction in the volume is called secondary consolidation.