Characterization of the Mass Transport and Energy Conversion of a Rapid Long-Runout Loess Landslide Using the Finite–Discrete Element Method

Rapid long-runout loess landslides pose serious threats to human activities. However, associated kinematic processes, such as mass transport and energy conversion, are not fully understood, limiting disaster prediction and prevention. Herein, numerical models were established to quantitatively investigate the kinematic process of rapid long-runout loess landslides via the finite–discrete element method (FDEM). These models were calibrated according to the Dabuzi rapid long-runout loess landslide deposit and laboratory tests. We conducted systematic numerical simulations to explore the mass transport and energy conversion of a rapid long-runout landslide, focusing on the influences of the sliding volume and the traveling path topography undulation depicted by the fractal dimension. The rapid evolution of the mass structure from continuous to discontinuous, the transition from a solid state to fluid-like state, and the mutual influence of mass transport and energy conversion were quantitatively characterized during the landslide kinematic process. With increasing topographic surface's fractal dimension, the maximum displacement, maximum velocity, and volume expansion ratio of the landslide exhibited linear decreasing trends, and the accumulation morphology changed. Variations in these parameters with the sliding volume were opposite to those of the fractal dimension case, except for the deposit volume expansion ratio. Particularly, the surface mass always displayed extreme long-runout motion displacements. The mass transport characteristics, like the transition from acceleration to deceleration, were driven by the mutual conversion of potential energy to kinetic energy and the dissipation of friction and fracturing. The deceleration process was initially dominated by fracture energy dissipation and then by friction energy dissipation.