Initail Consolidation

When a load is applied to partially saturated soil, there is a decrease in the volume of soil due to expulsion and compression of the air voids. Also, a small decrease in the volume of soil occurs due to compression of solid particles The reduction in the volume of soil just after the application of load is called initial consolidation. For saturated soils, the initial consolidation is mainly due to the compression of solid particles.

Primary Consolidation

Reduction of the volume is due to the expulsion of water from voids. The decrease in volume in this stage depends on the permeability of the soil, hence it is a time-dependent process. In fine-grained soil primary consolidation occurs for a long time. But in coarse-grained soil it occurs quickly due to high permeability.

Secondary Consolidation

The reduction in volume continues at a very slow rate even after the primary consolidation is completed, this additional reduction in the volume of soil is called secondary consolidation