Estimation and Application of Strength and Stiffness Reduction Factors of Liquefiable Soil

Abstract

The reduction of soil strength and stiffness caused by soil liquefaction is an important issue in designing pile or shallow foundations on liquefiable soils. In practice, strength and stiffness reduction is considered via a reduction factor ([Formula: see text]) approach in seismic design. Different sets of values of [Formula: see text] are available according to the factor of safety against liquefaction ([Formula: see text]) of the liquefiable soil; these ([Formula: see text]) values are usually calculated using simplified liquefaction analysis procedures. Each set of [Formula: see text] is calibrated and constructed for specific simplified liquefaction analysis procedures or soil conditions. Thus, engineers have difficulty in selecting [Formula: see text] when using a simplified liquefaction analysis procedure without a corresponding set of [Formula: see text]. In this study, values of [Formula: see text] for simplified liquefaction analysis procedures commonly used in Taiwan are obtained using a single element test via FLAC program and UBCSAND model. In addition, a novel application of [Formula: see text] is introduced to improve the usability of the simplified numerical procedure used to predict the liquefaction-induced settlement of a shallow foundation. Simulation results show that the simplified numerical procedure with [Formula: see text] approach yields a convincing and conservative result.