What does consolidation in engineering refer to?

Consolidation in engineering specifically refers to the process where the volume of soil decreases due to the expulsion of water from its voids when subjected to applied stress. This phenomenon occurs primarily in saturated soils, where the pore water pressure is gradually reduced over time as the load on the soil increases.

When external loads are applied to saturated soil, the water within the soil matrix cannot immediately escape, leading to an increase in pore water pressure. As the water is expelled from the soil voids, the solid particles move closer together, resulting in a reduction in volume — this is the consolidation process. It is critical in geotechnical engineering, particularly in the analysis of foundations, embankments, and retaining structures, as it affects the settlement and stability of structures.

The other choices do not correctly define consolidation. The first option suggests an increase in water in voids, which contradicts the nature of consolidation as a process that involves water removal. The third option discusses soil stabilization through compaction, which is related but distinct from consolidation, as compaction involves reducing air voids and increases soil density without the drainage of pore water. The last option mentions soil expansion due to moisture, which instead describes a different soil behavior known as swelling or heaving,