UC Berkeley

The influence of diatoms on clayey soils behavior has been shown to be important through studies of these soil deposits in Japan, Mexico, Thailand, among others. In Guayaquil city, the presence of diatom assemblages in soil samples was identified in the deltaic estuarine deposition found throughout the urban area.

A new geotechnical characterization scheme for the Guayaquil soils was proposed based on geological studies, historical data of geotechnical explorations, in situ microtemor measurements, and Spectral Analysis of Surface Waves (SASW) tests performed at representative sites. Geotechnical parameters, such as plasticity, sensitivity, and void ratio, depend on the amount of cementation in the soils. This influences the static behavior of Guayaquil soils by producing an apparent overconsolidation ratio and high anisotropy ratio in some areas, which in turns, affect the seismic response of these deposits. Accordingly, some correlations were developed between geotechnical parameters and seismic response properties such as shear wave velocity for each geotechnical zone to characterize the Guayaquil soil deposits for dynamic analyses. The Construction Ecuadorian Norm requires that site-specific geotechnical investigations and seismic response analyses be performed for the high plasticity deltaic estuarine clays, which are the predominant soils in Guayaquil.

Select soil constitutive models can capture the Guayaquil clay behavior as reflected in the results of advanced monotonic and cyclic test performed as part of this study. The analysis of these results provides a framework for understanding the mechanical behavior of the estuarine-deltaic, high plasticity, diatomaceous, naturally cemented clay in Guayaquil. Seismic response analyses using non-linear and linear equivalent models were also performed that provided useful insights.

Based on the calculated elastic and inelastic responses of the Guayaquil soils, a seismic zonation for the city was proposed where the appropriate seismic demand for a structure can be developed. In addition, a detailed procedure for estimating a design site response spectrum for Guayaquil City's prevalent soil conditions was developed. The experimental results and numerical procedures presented in this research provide key information for the design of engineered systems in Guayaquil and provide insights for cities worldwide, with similar geomorphological, seismic, and geotechnical characteristics