Discrete-Element Method Simulations of the Seismic Response of Flexible Retaining Walls

Abstract

In this study, an analysis of soil–retaining wall dynamic interaction is conducted using three-dimensional discrete-element method (DEM) simulations. Soil grains are treated as rigid spherical particles that are allowed to overlap one another at contact points. The flexible sheetpile-type retaining wall is simulated using rigid balls glued together by parallel bonds with specific strength and stiffness to mimic the physical properties and stiffness of a real wall. Owing to computational limitations, the high g-level concept and scaling laws for dynamic centrifuge testing are utilized to decrease the domain size and simulation time. In addition, free-field boundaries are employed at the lateral sides of the model to prevent the reflections of the propagating waves back to the assembly and enforce free-field motion. Seismic excitation is introduced to the system through the base wall, which represents the bedrock. The effects of different characteristics of the input seismic wave, such as its frequency and amplitude, on the dynamic response of the soil–sheetpile system are analyzed. Furthermore, data on the lateral thrust and bending moment on the wall and its deflection are collected. It is found that the lateral earth pressure and bending moment increase during seismic excitation and the final residual values are, in most cases, considerably larger than the initial static ones. It is also observed that the maximum amplification of ground acceleration behind the sheetpile, the amount of wall deformation, and the maximum level of internal forces and moments the sheetpile experiences during dynamic loading are strongly affected by the frequency and amplitude of the input motion. The results show that for ground acceleration stronger than a critical limit, the maximum lateral earth pressure stays almost at a constant level. However, the maximum dynamic bending moment on the wall is found to increase even for ground accelerations higher than the critical value.