Dynamic fragmentation and entrainment characteristics of a heavily Jointed Landslide: DEM simulation, field seismic signal and UAV image analysis

Characteristics of the dynamic rock fragmentation and granular-flow entrainment occurred in a heavily jointed landslide have been analyzed through a multidimensional framework consisting of the discrete element method (DEM), the landslide-induced field seismic signal and the UAV image recognition. First, DEM results reveal that the acceleration of rock mass occurs in its initial stage and the first half of the entrainment process, consistent with the analysis result of the seismic signal. Second, it was founded that the characteristic diameter (dc) and shape parameter (β) of rock fragments decreased rapidly during this period. On the contrary, the particle roundness (R), fractal dimension (D), unbalanced force (Ubf) and bond breakage energy (Eb) continuously increased in this period. These findings from landslide monitoring indicate that the fragmentation of the jointed source rock mass mainly occurs during the initial and first half of the entrainment stage. Furthermore, the evolution of the scraping intensity parameter indicates that two violent entrainment accidents occurred during the landslide movement. Meanwhile, the extremely high particle spin and roundness was founded in the middle depth of the granular flow during the entrainment process. Based on the comprehensive analysis above, we suggest that the drag reduction effect of the landslide movement is caused by two key factors, the rock fragmentation, and the particle rotational grinding occurring near the contact surface between the sliding mass and the entrainment mass.