DEM-CFD COUPLED ANALYSIS ON LEAKING PROCESSES OF WATER AND SAND UNDER HIGH WATER PRESSURE

To reveal the mechanisms of hazards induced by leakage of groundwater and sand under different water pressure, DEM-CFD method was adopted to simulate leaking processes based on a laboratory model test. Considering the effect of water leakage into the traditional gravity flow test, the numerical analysis model by DEM-CFD method was built. The variations of soil and water loss patterns, loss amounts, soil deformation, forces on the bottom plate of the testing chamber and soil stress were studied. The results showed that the soil zone of loose ellipse induced by a leaking process was influenced by both the soil loss and water leakage. A fast-flowing zone existed near the leaking point, and a hydraulic channel formed with the development of the leaking process. High water pressure increased the width of hydraulic channels. The amounts of leakage flow and ground surface movement went through a slow development stage and a sudden increasement stage, the high water pressure widened hydraulic channels. The loss of water and soil occured in the stages of slow development and sudden increasement, the high water pressure mainly influenced the sudden increasement stage. Besides, soil loss led to occurrence of the sudden increasement stage directly. During the water-sand leaking process, the variation process of forces on the bottom plate of the testing chamber could be divided into three stages:the steep decreasing stage, the slow decreasing stage and the relative stability stage. The leaking process induced the occurrence of soil arches. High water pressure made the soil arch more prone to be damaged, which caused more severe soil loss. The process of soil loss and the influence of high water pressure were quite different before and after formation of hydraulic channels.