Seismic safety of earth or rockfill dams and embankments is strongly conditioned by permanent displacements caused by earthquakes. For a severe earthquake, the permanent displacement pattern results from the combination of displacements generated by volumetric and shear plastic strains distributed within the structure, and those caused by sliding of the soil mass along one or more failure surfaces. Numerical procedures commonly used in practice do not consider the strain localization phenomena

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... t failure surfaces and the associated mesh dependence of the solution. Typically, nonlinear finite element or finite difference codes yield an estimate of distributed deformations and dynamic response, without accounting for the plastic strain localization problem. In addition, some of the numerical approaches used in practice do not consider the change of configuration caused by large displacements. The material point method or MPM is a lagrangian "particle-mesh" numerical method. It has been previously used in modeling dynamic problems with large displacements and strain localization. With MPM, a body is discretized into a collection of lagrangian particles, which carry all the data needed to define the body's state. Interaction between particles takes place in a background fixed mesh, similar to those used in the finite element method. The MPM is applied in this paper to model the three dimensional dynamic response of Punta Negra dam, a concrete faced gravel dam which is being built in San Juan Province, Argentina.. 287