Two-phase model with dilatancy/contraction for dense solid-fluid mixture in landslide mobility

The presence of pore fluid can great change landslide dynamics, significantly enhancing sliding mobility and resulting in high velocities and long runout distances. Our study presents a two-phase model with dilatancy/contraction for dense solid-fluid mixture based on the material point method. In the constitutive model, we consider the dilatancy/contraction effect on the two-phase system and the rate-dependent frictional law derived from granular flow rheology (the μ(K) and Φ(K) relationships). Numerical benchmarks including saturated granular column collapse and flume experiments were conducted to see the performance of the model. Furthermore, simulations of the 2014 Oso landslide in Washington State, USA, were performed to investigate the mechanisms governing its high mobility. The liquefaction of saturated sediment and the induced excess pore pressure at the base of the slide, which contributes to the high mobility of the landslide, were well captured in our simulations.