Analysis of the characteristics of progressive erosion and the formation mechanism of debris flow inrush: Numerical simulation and its application

Unlike water inrush occurring in karst and faults, debris flow inrush involves a greater number of debris such as mud and sand, and exhibit a more complex evolution process of disaster, characterized by significant progressive erosion phenomenon. At present, the progressive erosion characteristics from fine particles to coarse particles before the burst of debris flow inrush is still unclear, and there is a lack of model to predict the volume of debris flow inrush. In this study, the debris flow inrush accidents of Anshi tunnel crossing the contact zone are introduced. Then, using a coupled computational fluid dynamics and discrete element method (CFD-DEM), the debris flow inrush is simulated in multi-scales: from sample-scale to engineering-scale. The erosion characteristics and friction angle degradation during progressive erosion in sample-scale, and the formation mechanism of debris flow inrush in engineering-scale are studied. Finally, based on the results of multi-scale simulations, a model to predict the volume of debris flow inrush considering progressive erosion is established. The reliability of the model is verified by comparison with volume of debris flow inrush of Anshi tunnel. The results of this study contribute to understanding the formation mechanism of debris flow inrush and predicting its volume.