Site response of heterogeneous natural deposits to harmonic excitation applied to more than 100 case histories

Variation of shear-wave propagation velocity (SWV) with depth was studied by analyzing more than one hundred actual SWV profiles. Linear, power, and hyperbolic variation schemes were investigated to find the most representative form for naturally occurred alluvial deposits. It was found that hyperbolic (asymptotic) variation dominates the majority of cases and it can be reliably implemented in analytical or analytical-numerical procedures. Site response analyses for a one-layer heterogeneous stratum were conducted to find an equivalent homogeneous alternative which simplifies the analysis procedure but does not compromise the accuracy of the resonance and amplification responses. Harmonic average, arithmetic average and mid-value equivalents are chosen from the literature for investigation. Furthermore, full and partial depth averaging schemes were evaluated and compared in order to verify the validity of current practices which rely upon averaging shallow depths, viz., the first 30 m of the strata. Engineering bedrock concept was discussed and the results were compared.