PARTICLE FLOW SIMULATION OF RAPID LOESS LANDSLIDES WITH FRONTAL PLOWING EFFECT

During the run-out process of certain rapid loess landslides, loose terrace materials at the slope toe can be plowed and pushed forward by the loess sliding mass, resulting in significant upheaval deformation and horizontal transport of the terrace materials, leading to the enlargement of the landslide impact area. This phenomenon is referred to as the frontal plowing effect in the literature. To investigate the dynamic evolution mechanism of the frontal plowing effect of rapid loess landslides, we conducted a case study on the Ximiaodian landslide that occurred on the northern margin slopes of the loess tableland in Xianyang City, Shaanxi Province. Field investigations were carried out to study the depositional geomorphology of the landslide and the deformation characteristics of the terrace material. Subsequently, we developed a particle flow model to analyze the frontal plowing effect formed during the run-out process of this landslide. Finally, we discussed the influence of the pre-failure slope angle on the frontal plowing mode of the landslide. The results indicate that the rapid movement of the loess landslide provides the kinematic conditions for the formation of the frontal plowing effect. The upheaval deformation and horizontal transport of the front terrace material are caused by the squeezing of the loess landslide, and during this process, the loess sliding mass does not significantly mix with the terrace materials. Based on the simulated run-out characteristics of the landslide, the frontal plowing process can be divided into four stages: (1)shoveling stage in which the landslide plows into the topsoil of the terrace, (2)squeezing-shearing stage when multiple spiral shear failure surfaces form in the terrace, (3)pushing-upheaval stage in which the pushing-induced upheaval deformation of the terrace in the front part continues, and (4)decelerating-stable stage when the frontal plowing process stops. The squeezing-shearing stage plays an important role in the formation of the multiple thrust-nappe structure in the disturbed terrace area. Additionally, it also indicates that the pre-failure slope angle determines the frontal plowing mode of the landslide. With the increase in slope angle, more loess sliding mass will cover the disturbed terrace material, and the frontal plowing mode transforms from a pure horizontal pushing mode to a covering-pushing mode. The research results of this paper could provide a useful reference for the prevention and mitigation of this type of landslide in loess areas.