Macro and Micro Analysis on Coal-bearing Soil Slopes Instability Based on CFD-DEM Coupling Method

By combining the discrete element method (DEM) with computational fluid dynamics (CFD), a three-dimensional CFD–DEM fluid–solid coupling microscopic computational model was established to analyse the micro-mechanism of instability and failure in a coal-bearing soil slope during rainfall. According to the results, the main failure mode of coal-bearing soil slopes simulated by the CFD–DEM fluid–solid coupling model was rainwater washing, and the slope sliding surface was predicted as an approximately linear segment. The adaptability of this numerical method was verified by considering its similarity to a range of rain-washed slopes in an outdoor model test. During rainfall, microscopic parameters, such as force chain and coordination number slope soil particles, changed, as confirmed by changes in the coordination number of the slope’s top particles from 6.0 in the initial state to 3.2 in the unstable state. This was directly related to the macroscopic mechanics of the slope soil. In this study, based on the analysis of the changes in the microscopic parameters of the particles, the law of failure evolution of coal-bearing soil slopes during rainfall was explored from the microscopic perspective. This study not only provides a theoretical basis for the protection design and construction of coal-bearing soil slopes in the region but also encourages an effective analytical method for the macroscopic mechanical law of discrete media from a micro-macro perspective in geotechnical engineering.