Liquefaction potential in Sri Lanka-preparing a liquefaction hazard map using geotechnical investigation data

Abstract

Soil Liquefaction is a process, where granular soils below the ground water table temporarily lose its strength due to cyclic loading created by an earthquake. Liquefied soil behaves as a viscous fluid rather than a solid. During liquefaction, porewater pressure is suddenly increased, forcing the soil particles to suspend in water. As a result, the buildings, utility services, natural substances and other structures are collapsed causing severe damage to the people and the nature. In some cases, the destruction due to liquefaction is not repairable. Therefore, the mitigation measures are essential to prepare for liquefaction. In Sri Lanka, it is rare to find the historical data of liquefaction or related incidents. Recent studies demonstrated that there is a potential for liquefaction in some places of the island. It could be evaluated by using the basic geotechnical investigation data, according to the simplified procedure proposed by Seed and Idriss (1971). This study is intended to prepare a liquefaction hazard map for Sri Lanka by identifying the hazard zones, using an extensive geotechnical investigation data base. As per the analysis 218 locations were identified as susceptible for liquefaction during an earthquake of magnitude 6.0 out of 3282 locations analyzed. Further, the research has given a special attention to the variation of ground water table and the maximum possible ground acceleration.