Seismic response characterization of high plasticity clays

Abstract

An experimental study was undertaken to characterize the seismic response of high plasticity clays found in the Texoco Lake region of the Mexico City valley. Series of resonant column and triaxial tests were carried out in twin samples, and empirically-derived well known modulus degradation and damping ratio models were used to simulate the measured response. A total of forty three tests were conducted in twin samples. The results gathered appear to indicate that the reference strain, γr, instead of the plasticity index, PI, constitutes the best parameter to properly establish the modulus degradation and damping curves for high plasticity clays, increasing the accuracy of the model predictions. Appropriate values of γr were obtained for the high plasticity Texcoco clays directly from the experimental data, to determined modulus degradation and damping curves. The approach was validated throughout the analysis of four cases study. Site response analysis predictions were compared with actual measurements at three seismological stations and one vertical array, considering several recorded moderate to large seismic events. The computed ground motions are in good agreement with the measured response.