The material Point Method (MPM) combines features of Finite Element and Discrete Particle methods. It is well suited to analyze geotechnical problems which involve large displacements and dynamic response. An explicit coupled hydro-mechanical formulation has been developed to analyze cases controlled by general loading and pore pressure generation and dissipation. The procedure has been successfully applied to reproduce the failure conditions of Aznalcóllar dam. The failure was explained by a combination of a slow dissipation of pore water pressures in impervious, high plasticity brittle clay and by a progressive failure mechanism. It was also found that the initial state of stress controlled the development and position of the failure surface. Taking Aznalcóllar as a reference case, the following aspects have been investigated: The response of brittle and non-brittle soils; the effect of a sudden loss of effective cohesion at peak strength conditions and the construction sequence and the dam geometry. The analysis of results provides a valuable insight into the significance of the set of aspects outlined above.