Examination of Present Subsurface Investigation Data for Valuation of Liquefaction Potential for Ahmadabad City by Means of SPT-N Value

Abstract

In the area of geotechnical earthquake engineering, liquefaction is most imperative, difficult, and notorious matter. It is a major contributor to urban risk. Liquefaction is the process whereby soil loses its strength and stiffness under the application of stress, where stresses get developed due to ground vibrations during earthquakes. The subsoil strata of Ahmedabad region consist of silty sand, which is one of the responsible factors for the liquefaction susceptibility. In the present study, Idriss and Boulanger [1] method is used which is based on SPT-N value. Before attempting the rigorous investigation of the liquefaction potential for Ahmedabad region, first qualitative assessment of liquefiable soils was carried out based on the geotechnical characteristics such as SPT-N value, depth of water table, grain size analysis, liquid limit, plasticity index, etc. The qualitative assessment of liquefaction potential was done by SPT method using subsurface data and PGA values were generated The different hazard maps were generated using SPT values of different depths for the quantitative assessment of liquefaction potential. Analysis reveals that Madhupura, Shyamal, and Vatva area are likely to be liquefied. If groundwater table is assumed to be at ground level in Ahmedabad region, the results show that the severity of liquefaction would be moderate to high due to the thick shallow liquefied deposits.