Material Point Method Modeling of Granular Flow Considering Phase Transition From Solid‐Like to Fluid‐Like States

Granular flow is ubiquitous in various engineering scenarios, such as landslides, avalanches, and industrial processes. Reliable modeling of granular flow is crucial for mitigating potential hazards and optimizing process efficiency. However, the complex behavior of granular media, which transitions between solid‐like and fluid‐like states, poses a significant challenge in their modeling, particularly when involving rapid mobilization. To address this challenge, we propose an innovative constitutive model capable of capturing the highly nonlinear behavior of granular flow by integrating frictional and collisional mechanisms under varying states. The proposed model incorporates two distinct stress components: frictional stress and collisional stress. The frictional stress is governed by a critical‐state‐based elastoplasticity model, which accurately describes the solid‐like behavior of granular media. On the other hand, the collisional stress is formulated using a well‐established kinetic theory, which effectively captures the fluid‐like behavior of granular media. To seamlessly transition between these two states, we introduce a novel state variable, the granular temperature, which serves as a measure of the kinetic energy of the granular system. This innovative transition model is further incorporated into a GPU‐based material point method (MPM) and used to model two types of granular flows, including column collapse and flume test on an inclined surface. The numerical results show good agreement with available experimental data, highlighting the efficacy of our proposed phase transition model with the MPM modeling approach in effectively capturing the transition of granular materials from solid‐like to fluid‐like states throughout the mobilization process, from initiation to final deposition.