Approximation of Equivalent Linear Ground Response Analysis at Low Strain by Strain Dependent Linear Ground Response Analysis for Typical Site at Delhi, India

摘要

The applicability of available dynamic soil property curves (G/G_(max) and Dcurves) from other regions in region specific local site effect is a matter of debate. Authors in previous studies have clearly shown that in widely followed equivalent linear ground response analysis (ELGRA), solutions are governed by one set of dynamic soil properties (shear modulus 'G' and damping ratio 'D') for each soil layer corresponding to one value of shear strain (y). Thus, complete G/G_(max) and D curves are not required in final response at a known γ. Further, this value of γ up to 0.5% is a function of depth of that soil layer (z) as well as input bedrock motion (PHA) as per recent studies by the authors. In this work, empirical correlations between γ, z, and PHA are proposed for a typical site in Delhi based on 300 ELGRAs for sand and clay. Further, to verify the feasibility of proposed correlation, linear ground response analysis (LGRA) of one typical borehole near to earlier used boreholes, using above proposed correlations, based on known z, and PHA are performed using 2 randomly selected ground motions and found comparable with ELGRA for these both boreholes. Thus, avoiding dependence of ELGRA upon complete G/G_(max) and D curves, not available on regional scale, LGRA which uses in situ test properties, is a better and site specific approximation as proposed in this work.