Numerical simulation of non-rigid landslide into reservoir with erodible sediment bed using SPH method

Landslide phenomenon in accumulated erodible bed sediments in a reservoir is one of the issues in hydraulic and sedimentation sciences that has received little attention. We intend to model two-dimensional changes of the water surface in a reservoir and of an erodible bed caused by a non-rigid landslide using a particle-based meshless approach. In this study, a fully explicit three-step algorithm is used. In this method, approximate numerical solution to the equations of the fluid dynamics is obtained by replacing the fluid with a set of particles. The governing equations for water flow and sand mass movement are solved for each particle. The movement of each particle, which is in interaction with other particles, is tracked. Experiments of a dam break on a dry bed, and submarine rigid and non-rigid landslides have been used to validate the method. Results indicate that the model was successfully calibrated against the measured data. Moreover, good agreement with the measured data demonstrates high capabilities of this method in simulating free-surface flows and wave-related phenomena. After the model validation, changes of erodible bed in a reservoir due to a non-rigid landslide were modelled. In this study, non-rigid landslide masses and sediment materials were modelled by non-Newtonian Carreau-Yasuda fluid, which is the novelty in the analysis of this type of natural hazard. Two possible scenarios were analyzed-one with the sliding material lighter, and the other with the sliding material heavier than the deposited sediments. The model was run until the landslide completely collapsed and its full impact was applied to the reservoir bed sediments. Additionally, we waited until the water level reached a steady state. These examples demonstrate that the model presented in this paper can be used as a reliable tool for modelling these phenomena.