What is consolidation of soil?

Consolidation is the time-dependent compression of saturated fine-grained soil due to expulsion of water from voids under sustained load. When load is applied, pore water initially carries the stress. Water slowly drains out, transferring stress to soil skeleton, causing settlement. Primary consolidation involves water expulsion; secondary compression (creep) continues after primary is complete. Consolidation rate depends on soil permeability and drainage path length. This explains why clay settlements take years.