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Material point method for large deformation seismic response analysis

Landslides triggered by earthquakes are one of the major seismic hazards and can cause large damages and fatalities. The material point method (MPM) has become a popular technique to model such large mass movements. A limitation of existing MPM implementations is the lack of appropriate boundary conditions to perform seismic response analysis of slopes. To bridge this gap, an extension to the basic MPM framework is presented for simulating the seismic triggering and subsequent collapse of slopes within a single analysis step. The concepts of a compliant base boundary and free-field columns are applied within the MPM framework enabling the direct application of input ground motions and accounting for the absorption of outgoing waves. The presented methodology is applied to an example slope to illustrate the proposed procedure and to benchmark it against the results obtained using an alternative technique, based on a coupled Eulerian Lagrangian (CEL) finite element approach. With the latter approach, the seismic triggering is analysed using a Lagrangian analysis step, followed by an Eulerian step to model the large deformation run-out process. With this procedure, however, the input motion cannot be applied during the runout analysis leading to a potential underestimation of the predicted displacements. This disadvantage can be overcome by the presented “all-in-one” MPM approach. The comparison shows that for short duration ground motions both methodologies lead to almost identical results. For longer earthquake events, on the other hand, the failure mechanism propagates further downand uphill into stable parts of the slope, when applying the input ground motion throughout the entire analysis, resulting in a considerably larger landslide. Finally, the capability of the presented MPM approach is demonstrated by a simulation of the Tsaoling landslides induced by the 1999 Chi-Chi earthquake in Taiwan. Marc Kohler, Andreas Stoecklin and Alexander M. Puzrin