Improved Modeling of Subaerial and Subaqueous Muddy Debris Flows

In this note, a two-dimensional depth-averaged numerical model (MassFlow2D) previously developed to simulate subaerial and subaqueous muddy debris flows is further improved. The retarding effects of ambient fluid, including shear resistance, dynamic pressure, and added mass, on debris-flow movement is considered. The critical depth is reformulated by considering the role of the earth pressure gradient of debris flow. The improved model is then validated against laboratory-measured datasets from two flume experiments and a slump test. The numerical results agree well with the laboratory datasets. Afterward, the robustness of the model is demonstrated by a schematized large-scale submarine landslide. The improved model is also applied to a more realistic field scenario with real bathymetry originating from the Northern South China Sea where historical submarine landslides occurred. The results show that resistances from ambient water have significant implications on the dynamics of failed sediments. It is observed that the earth pressure gradient of debris flow plays a major role in the stage of creep deformation.