Effects of Groundwater Level on Seismic Response of Soil–Foundation Systems

Abstract

A set of dynamic centrifuge experiments was performed to assess the effect of the depth of the groundwater table on the seismic site response and kinematic interaction of a foundation on unsaturated sandy soil. The experimental program consisted of centrifuge tests on dry soils, saturated soils, and soils having groundwater level at various depths. Results show that as the groundwater level was lowered, (1) seismically induced soil settlement, the mean period of the free-field motion, and the midperiod amplification factor generally decreased; (2) the lateral incoherence parameter, soil strain–dependent natural frequency, and amplification factors for peak ground acceleration, Arias Intensity, and short period roughly increased; while (3) the rocking incoherence parameter stayed approximately constant. Assuming soils in a fully saturated state for seismic design may either over- or underpredict different aspects of the seismic soil–foundation response, in comparison with partially unsaturated ground. Thus, this assumption may not always lead to safe or economical designs, especially with regard to seismically induced soil settlement, seismic site response analysis, and kinematic soil–foundation interaction.