Experimental Validation of an Identification Procedure of Soil Profile Characteristics from Free Field Acceleration Records

Abstract

In this paper, a new approach for soil profile characterization is validated. The soil characteristics are calculated by fitting the theoretical amplification functions to those obtained experimentally. The identified characteristics have been observed to agree well with those obtained by in situ and laboratory tests. This new approach uses system identification theory and free field records. It is based on formulation of theoretical soil amplification function for two sites in terms of the different parameters of the soil profile layers (thickness, damping ratio, shear wave velocity and unit weight). The theoretical function is smoothed according to the experimental data (spectral ratios) by means of the least squares minimization technique. The function parameters are determined by solving, numerically, a non linear optimization problem. In this approach, soil profile characteristics of two sites can be identified simultaneously, from only a single soil acceleration record at free surface of each site without need of bedrock or outcropping acceleration records. Strong ground motions data recorded during the Boumerdes earthquake (Algeria) of May 21, 2003, are used for the validation.