Simulating Earthquake-triggered Runout using Higher-order Hydromechanical MPM and PM4Sand

Abstract

Earthquake-triggered landslides pose a significant risk to society and infrastructure. Despite the catastrophic consequences, significant questions remain regarding their manifestation and have rarely been analyzed in large-strain numerical frameworks. There is a need to simulate earthquake-triggered landslides within a unified framework that can incorporate geometrical and material nonlinearities, while having the capability to simulate the runout process, from triggering to post-failure cyclic mobility. The Material Point Method (MPM) is a particle-based computational technique that has achieved significant success in simulating geotechnical problems; however, it suffers from numerical errors that have prevented it from realizing its full potential in geotechnical earthquake engineering. The aim of this research is to develop and validate an MPM framework that facilitates a deeper understanding of earthquake-triggered landslides. To achieve this goal, a higher-order multiphase isogeometric MPM framework is proposed. Non-zero kinematic and periodic boundary conditions are developed to simulate shaking table loading and free-field modes. Finally, the PM4Sand constitutive model is implemented in the hydromechanical MPM to enable the model to capture the cyclic behavior of sand, including liquefaction triggering and cyclic mobility. Verification and validation of the framework are performed by comparing the results with those obtained using the Finite Element Method (FEM), analytical solutions including Newmark-type techniques, and shaking table tests. A centrifuge test of a clay embankment overlying saturated sand is simulated using the computational framework. The accelerometer and pore water pressure trends are satisfactorily matched with experimental data, and the deformation mechanism is well captured. The MPM framework proposed in this dissertation presents promising advancements toward a stable hydromechanical large-strain methodology that can capture material and geometric nonlinearity, simulating the entire runout process from triggering to post-failure stabilization to ultimately better understand earthquake-triggered landslide manifestations.