Dynamic response of slopes under near-field seismic excitation using the material point method

Abstract

Seismic-induced landslides exhibit distinct instability mechanisms compared to gravitational landslides, characterized by dynamic features such as tension, projection, and directionality. This study investigates the dynamic response and instability mechanisms of near-fault slopes under seismic excitation using a simplified bedrock-slide body dual-structure slope, with failure process simulations conducted through the Material Point Method (MPM). The results indicate that periodic seismic vibrations lead to alternating deep shear and shallow tensile failures, facilitating the formation of a continuous sliding surface. Analyzing the instantaneous unbalanced force direction of particles under seismic load reveals a correlation between slope instability and seismic wave directionality. Seismic P-waves primarily cause tensile plastic failure in the geotechnical body, with smaller slope deformation but a greater potential for ejection toward the free surface. Conversely, S-waves cause considerable deformation, driving shear plastic failure within the slope and the formation of the sliding surface. The tensile and shear plastic responses lag behind the seismic vibrations. This paper discusses the correspondence between the slope’s dynamic response under seismic action and the progressive formation process of the sliding surface, where the interaction between the seismic driving force and inertial force results in a significant accumulation of plastic strain, directly affecting the mode of sliding surface formation. Studying the inherent driving mechanisms of slope dynamic failure reveals the dynamic response characteristics of the slope under seismic excitation from multiple perspectives, offering significant implications for explaining the typical directional failure patterns of earthquake-induced landslides.