Abstract
Soil response under earthquake loading is highly nonlinear even at low strain. The aim of this study is to determine the effect of soil non-linearity on seismic response of layered soil deposit under a considered bed rock motion. 1D effective stress-based ground response analysis has been conducted using the nonlinear finite element program Cyclic1D. Two different sites of Kolkata metropolitan city having two distinct soil formations such as Normal Kolkata Deposit (NKD) and River Channel Deposit (RCD) are selected for ground response analysis. Three different earthquake motions such as the 1940 Imperial Valley, 2001 Bhuj and 2011 Sikkim are used as input motions .The reliability of the present model is performed by comparing the results of peak ground acceleration (PGA) and its magnification factor profile with that predicted using SHAKE 2000 computer program based on equivalent linear approach. The results show that PGA at surface ranges from 0.109 g to 0.119 g for NKD soil and 0.072 g to 0.091 g for RCD soil. The range of variation of peak spectral acceleration for 5% damping ratio is 0.51 g to 0.67 g for NKD soil and 0.33 g to 0.46 g for RCD soil of Kolkata. The effects of fluctuation of ground water table and mildly-inclined infinite slope has also been studied. It is observed that properties of input earthquake motion, local site condition, topography and location of ground water table have profound influence on ground response. Further, liquefaction potential of Kolkata soil has been assessed using the results obtained from the present analysis. It is found that top 12 m of RCD soil is susceptible to liquefaction if these considered input earthquake motions are experienced at bedrock.