Evaluation of dynamic explicit mpm formulations for unsaturated soils

Abstract

Many applications in geohazards prevention involve large deformations of unsaturated soils, e.g. rainfall induced landslides, embankment collapses due to wetting etc. These phenomena can be investigated with multiphase implementations of the Material Point Method (MPM) able to account for the behaviour of unsaturated soils. This paper compares two formulations: (i) afully coupled three-phase formulation(3P)in which the governing equations are derived from the momentum balance and the mass balance equations of solid, liquid and gas phase assuming non-zero gas pressure,the primary unknowns are the absolute accelerationsof the phases (aS–aL–aG formulation); (ii)a simplified approachthatneglectsthe momentum balance equation of the gas(2P_s).Potentialities and limitations of these approaches are highlighted consideringa 1D infiltration problem.Despite the introduced simplifications, the simplified formulation gives reasonably good results in many engineering cases