Understanding the Seismic Response of Sheet-Pile Walls in Liquefiable Soil: key mechanisms and the role of element tests

Abstract

Seismic response of geostructures in liquefiable soils is often quite complex and may involve several factors that contribute to the key mechanisms affecting the overall performance. However, in some cases, if critical mechanisms are well understood, it might be possible to estimate the system response by using relatively simple analytical tools. This study investigates the potential use of direct simple shear (DSS) test in estimating the seismic response of sheet-pile retaining structures supporting liquefiable soils. Through a comprehensive analysis of the centrifuge experiments carried out as part of the 2022 Liquefaction Experiments and Analysis Projects (LEAP-2022), coupled with Type-C numerical simulations of the centrifuge experiments, it is observed that the sheet-pile wall response is critically related to the stress-strain response of the soil near the tip of the sheet-pile wall which is embedded in a dense layer of Ottawa F65 sand. An in-depth understanding of such stress-strain response using laboratory-based element tests might provide a means to estimate the wall rotation and its lateral displacements. To this end, simplified numerical analyses were performed to estimate the initial vertical effective stress and time-history of shear stresses caused by the earthquake near the tip of the sheet-pile wall. Then, several specimens of Ottawa F65 sand were prepared at relative densities comparable to the values achieved in the LEAP-2022 centrifuge experiments and were subjected to the estimated shear stress time-histories. By assuming a rigid body motion of the sheet-pile wall during earthquake, the rotation of the wall at the end of earthquake motion was then estimated using the permanent shear strains measured in the DSS tests. It is observed that the estimated rotations of the sheet-pile wall compare well with the rotations observed in the centrifuge tests and those obtained in Type-C numerical simulations. In these cases, DSS tests are shown to provide a relatively simple means for estimating the rotations of the sheet-pile wall.