Seismic Site Classification of a Bridge Site over River Barak on Silchar Bypass Road

Abstract

Local site condition always plays a significant role in amplifying the ground motion parameters during an earthquake. To estimate site-specific earthquake hazards and to design earthquake resistant structures, it is important to characterize a site according to its class. This paper has made an effort to classify a proposed bridge site over river Barak on ‘Silchar Bypass Road’ which lies in a highly seismically active region (zone-V) of India. In the present study, in the absence of the shear wave velocity profile, the V_s30 for the top 30 m soil have been estimated using SPT-N value (collected from government agencies, PWD, Assam) for the 6 bore hole locations by proposing one new empirical equation correlating V_s and SPT-N for all soil type. The results have shown that all the bore hole locations are having their V_s30 and SPT-N between 180 to 360 m/s and 15N to 50N respectively, which conclude that the bridge site comes under the site class D according to the provisions of NEHRP (National Earthquake Hazard Reduction Programme).