Granular Material Point Method: unsaturated soil modelling

The paper proposed an enhancement to the Granular Material Point Method extending the original framework for unsaturated granular materials. It discusses briefly the key processes occurring during unsaturated flows and gives a set of assumptions for simplified analysis of such flows with the Granular Material Point Method. Then it proposes an algorithm for the Granular Material Point Method for unsaturated materials and shows how to adjust the original Granular Material Point Method code. Finally, the paper presents two sets of simulations involving unsaturated flows comparing outcomes from the previously proposed Granular Generalized Interpolation Material Point Method (Granular GIMP), original GIMP, as well as two newly proposed Granular GIMP simulations with an enhancement for unsaturated soils. The results show that the proposed formulation leads to improved and qualitatively different results and confirm that considering partial saturation is essential, also when the flow of material is of interest. The paper uniquely illustrates the developments not only with figures but also with videos, giving the whole extent of simulation instead of just a timestamped image. •Granular Material Point Method framework for unsaturated soils.•Simple assumptions leading to robust calculations.•Outflow from a silo simulation.•Simulation of granular avalanche.•Partial saturation leads to qualitatively different results during flow.