Meshfree particle numerical modelling of sub-aerial and submerged landslides

•A multiphase particle continuum model was developed for sub-aerial and submerged landslides.•The model is based on WC-MPS method with pressure depended µ(I) rheology.•Comparison of numerical results with those of experiments showed good agreements.•The role of rheological model is investigated.•Results provide a better understanding of the mechanisms involved in landslides. A novel multiphase mesh-free particle numerical model is developed and applied for modeling of sub-aerial (dry) and submerged (underwater) landslides. The model is based on the weakly-compressible moving particle semi-implicit method (WC–MPS), and treats the multiphase system of water and granular materials as a multi-density multi-viscosity continuum. The viscous behaviour of the granular material is predicted using a visco-plastic rheological model (i.e. μ(I)) with a dynamic inter-grain mechanical pressure. The model is validated and evaluated for the rigid, sub-aerial and submerged landslides in comparison with the available experimental measurements and past numerical results. The granular surface profile and the evolution of the granular mass are compared. Comparisons show a good agreement between the results of the developed model and those of the experiments, and also a better accuracy comparing to the past numerical studies. The results also show the capability of the model in dealing with the shape evolution and the deformation and fragmentation of granular interface. Complementary experiments on the sub-aerial landslide are also conducted to study the relevant physics and validate the model. The role of the rheological model is also investigated. Comparing the μ(I) rheology with the widely–used Herschel–Bulkley model shows a slightly more accurate granular profiles for the μ(I) rheology, for both sub-aerial and submerged landslides.