Tuesday, March 2, 2010

Soil liquefaction, earthquakes and Haiti

In addition to poor design and defective construction, one of the causes of the mass destruction we saw during last month’s earthquake in Haiti is “liquefaction”. Liquefaction is a naturally occurring event in which the strength of soil is reduced by earthquake shaking. Specifically, the earthquake shaking causes a drop in the soil’s bearing capacity. Liquefaction is more likely to occur in low lying areas where the soil is saturated. When liquefaction occurs, the ability of a soil to support the foundation of a building is reduced, thereby causing catastrophic damage to the building itself. In a nutshell, the soil turns into a liquid allowing everything it previously supported to sink. Many buildings in Haiti were built in low lying areas where liquefaction is likely to occur. Buildings can be designed to withstand liquefaction. Through laboratory and field testing, it can be determined how the building should be designed to withstand liquefaction. The tragedy that occurred in Haiti underlines the importance of developing a thorough building code and strictly enforcing it.