Liquefaction Susceptibility Mapping of Kollam Coastal Stretch, Kerala, Considering Geotechnical Parameters

The assessment of liquefaction potential is one of the important scientific problems for the geotechnical investigators. Liquefaction of loose saturated cohesionless soil during earthquake has been a major cause of damage due to earthquake for the buildings, earth embankments and other civil engineering structures. The study area of the coastal stretch of Kollam in western Kerala, India, mainly consists of coastal alluvial deposits and marine sand. Samples were collected along the length and width of coastal stretch of Kollam and are tested to obtain water content, dry density, fines content and the gradation curves. Limiting curves-based gradation criteria proposed by Tsuchida (1970) and empirical relation for stress ratio (SR) values obtained by Chien et al. (2002) were used for the calculation of liquefaction potential at sample locations. Spatial analysis of this data is done using QGIS to delineate the region into most liquefiable, liquefiable, less likely to be liquefiable and not liquefiable zones. The susceptibility map developed based on SR criteria is found to be in agreement with the liquefaction potential map developed by overlay of the two criteria which infer the dominant influence of dry density of the deposits of Kollam coastal stretch. Further, a ground truth examination of the final susceptibility map revealed that the zones in which water table lies within 0–5 m from ground level are more vulnerable to liquefaction in the Kollam coastal stretch. The proposed liquefaction susceptibility map can be used as a firsthand info on liquefaction potential of region which can aid in site-specific studies for future development.