Physical modeling of a liquefiable soil-sheet pile retaining wall system

Abstract

December 2024School of EngineeringSheet-pile walls are retaining structures that are prone to liquefaction-induced lateral spreading in waterfront areas. This dissertation explores the dynamic behavior of soil-sheet pile retaining wall systems under seismic loading, focusing on the effects of various parameters such as peak ground acceleration (PGA), number of peak cycles, Arias Intensity, soil density, and embedment ratio. The Liquefaction Experiments and Analysis Projects (LEAP) is a global research collaboration aimed at producing reliable test data to advance and verify numerical models for soil liquefaction studies. The study employs a series of dynamic centrifuge tests performed at the Rensselaer Polytechnic Institute (RPI) as part of the LEAP 2020 and LEAP 2022 projects. The LEAP 2020 experiments simulated the seismic response of retaining wall systems in saturated granular soil to understand the soil-structure interaction and liquefaction phenomena. The problem involved a floating sheet pile wall supporting a deposit of liquefiable soil. The experimental setup of the LEAP 2020 models featured a backfill height to embedment support ratio of 2:1. These experiments investigated the impact of varying mass density and input motions on soil-structural interaction. As part of the LEAP 2020 research campaign, test RPI-LEAP 20-E was conducted at the RPI centrifuge facility by Dr. Evangelia Korre to assess the seismic behavior of the sheet pile wall. Subsequently, the author of this thesis performed the RPI-LEAP 20-S test at the same facility as a repeat experiment, achieving results that were highly consistent with the initial test. Within the framework of LEAP 2022, a series of six centrifuge experiments, RPI-LEAP 22-5, RPI-LEAP 22-10-1, RPI-LEAP 22-10-2, RPI-LEAP 22-10-3, RPI-LEAP 22-19, and RPI-LEAP 22-36 were conducted at RPI to investigate the impact of varied input motion parameters (Number of peak cycles, motion duration and PGA) on the retaining wall models. LEAP 22 models had an increased embedment depth with an embedment ratio of 1:1. The key findings from the LEAP 22 experiments indicated that higher PGAs lead to increased soil-structure interaction, manifesting in higher accelerations, pore water pressures, and lateral displacements of the retaining walls. An increase in Arias Intensity, while maintaining a comparable number of peak cycles, resulted in greater lateral displacement of the retaining wall. The settlement of the backfill surface away from the wall was found to increase with a higher number of peak cycles. The experiments also highlighted the significant role of soil density in mitigating seismic impacts, with denser soil models showing lower displacements. Additionally, varying the embedment ratio of the sheet-pile walls significantly influences their seismic performance, with deeper embedment reducing wall displacements and rotations. The study underscores the importance of considering PGA, number of cycles, Arias Intensity, and soil properties in designing resilient geotechnical structures. The experimental results contribute to a better understanding of the complex dynamic behavior of retaining wall systems and provide valuable data for validating numerical models used in predicting soil liquefaction and seismic responses. This research highlights the critical factors influencing the stability of geotechnical structures in seismic-prone areas and offers insights for improving design and risk assessment practices.Ph