LIQUEFACTION

Liquefaction is a process that converts a solid soil into liquid.

Liquefaction occurs in cohesion less soils( soils that hold firmly together) which have water in the pore spaces, and are poorly drained.

When the seismic waves from the earthquake pass through the soil, the vibrations cause the individual grains in the soil to move and separate from each other. This cause results in a lesser volume of the soil mass, as the grains pack is moved tightly together.

The pore water in those spaces becomes compressed. Water is relatively incompressible and as such it pushes back against the soil grains. The pore pressure becomes so high, that the soil grains become almost buoyant causing a significant drop in the shear strength of the soil to a very low value.

When this occurs the soil loses its ability to support loads which can cause buildings to fall and sink into the ground.

So liquefaction is a solid soil that mixes with water and becomes liquid.