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 their 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 become unusable causing severe damages. Hence, as some tremors have been reported in and around Sri Lanka [2,3] and even a minor earthquake can cause soil liquefaction, it is important to consider possible mitigation measures prepare for liquefaction. In Sri Lanka, it is rare to find historical data of liquefaction related incidents. Recent studies demonstrated that there is a potential for liquefaction in some places of the island [5]. This could be evaluated by analyzing the basic geotechnical investigation data, according to the simplified procedure proposed by Seed and Idriss (1971). This paper proposes a procedure to prepare a liquefaction hazard map for Sri Lanka by identifying the hazard zones using an extensive geotechnical investigation data base. In this analysis 384 locations were identified as susceptible for liquefaction out of 3282 locations analyzed. It is to be noted that the research has given a special attention to the variation of ground water table and the maximum possible ground accelerations.