Runout Mechanism of Flow-like Landslides Based on Granular Flow Physics

Characterized by sudden occurrence, high velocity and long runout distance, flow-like landslides pose great threats to human communities. In essence, flow-like landslides can be regarded as the flow of granular materials under different topographic conditions, driven by external triggers or internal state changes. During the movement of landslides, the motion behavior transitions from a solid-like state to a fluid-like state, finally resulting in its extreme mobility. Based on the granular flow physics, we investigate the dynamic process of flow-like landslides from a rheological perspective, thereby exploring the motion transition from a solid-like state to a fluid-like state and its hypermobility feature. We utilize an elastic viscoplastic constitutive model to capture the changes in the motion behavior of landslides during their movement. This model accounts for both the elastic response of the material under low-strain conditions and the viscoplastic behavior under large strains, and incorporates both stress and strain rate dependencies, which help in describing the progressive transition from a solid-like deformation to a fluid- like flow. For practice, numerical analyses of column collapse are conducted using the Material Point Method (MPM), a numerical technique well-suited for simulating large deformations. Moreover, a typical flow-like landslide in China, the Luanshibao landslide, is well studied to investigate its long runout mechanism.