Chapter 12: Liquefaction

Liquefaction is a phenomenon that involves the transfer of the overburden stress from the soil skeleton to the pore fluid. Multiple mechanisms can cause this load transfer, earthquake shaking being one of them. The potential for load transfer is more significant and consequential in loose, saturated, cohesionless soils due to their increased contractive tendencies. As a result, there is an increase in excess pore water pressures, a reduction in effective stress and a commensurate reduction in the strength and stiffness of the soil.

Many dams have failed as a result of liquefaction in the dam or in its foundations. The attention of the dam building profession was, however, drawn to the issue by the failure of the Lower San Fernando dam during the 9 February 1971, magnitude 6.6 San Fernando earthquake in California, USA. The dam was constructed by hydraulic filling, and its upstream slope failed due to earthquake-induced liquefaction.