Soil liquefaction

Liquefaction at Niigata

Chuetsu earthquake-earthquake liquefaction1

Liquefaction in Peterborough St

Giddy House

Christchurch quake, 2011-02-22

SFBALiqufactionMap

Soil liquefaction occurs when a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, such as shaking during an earthquake, in such a way that it behaves like a liquid. The phenomenon is most often observed in sandy soils with a high water table, but it can also occur in other types of soils under specific conditions.

Causes and Mechanism

The primary cause of soil liquefaction is the increase in pore water pressure and the reduction of effective stress in the soil particles, which leads to a temporary or permanent loss of soil strength. This process is typically triggered by ground shaking during an earthquake, rapid loading, or changes in water level. When the soil particles are rearranged or densified, and the water pressure increases, the soil may begin to flow if the stress conditions exceed the soil's ability to support the load.

Effects

The effects of soil liquefaction can be devastating, leading to significant ground deformation, settlement, and damage to buildings and infrastructure. Structures may tilt or sink if the soil beneath them liquefies, and underground pipes and tanks may float to the surface. Liquefaction-induced ground failures include flow slides, lateral spreads, and ground oscillation.

Mitigation and Engineering Considerations

To mitigate the risks associated with soil liquefaction, engineers and geologists assess the potential for liquefaction through site-specific soil investigations and use various ground improvement techniques to increase soil strength and reduce water content. These techniques may include compaction, dewatering, and the addition of chemical stabilizers. Building codes in areas prone to earthquakes often include requirements for assessing liquefaction hazards and designing foundations to withstand potential soil liquefaction.

Historical Examples

Notable examples of soil liquefaction include the 1964 Niigata earthquake in Japan, the 1989 Loma Prieta earthquake in California, and the 2011 Christchurch earthquake in New Zealand. These events highlighted the importance of understanding soil liquefaction in earthquake-prone regions and have led to significant advancements in earthquake engineering and soil mechanics.