DEM-CFD COUPLED ANALYSIS ON LEAKING PROCESSES OF WATER AND SAND UNDER HIGH WATER PRESSURE
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摘要: 针对不同水压条件下漏水漏砂引发的灾害问题,在室内模型试验的基础上,利用离散元和计算流体力学耦合(DEM-CFD)方法进行模拟分析。基于传统重力流试验考虑流体的耦合作用建立数值分析模型,研究水土流失形态、水土流失量、土体变形、底板结构受力及土体应力的发展变化规律。研究结果表明:漏水漏砂过程中形成的土体松动椭圆区域受土体流失与流体作用共同影响;漏点附近流场存在高流速区,最终形成贯通的水力通道,高水压将增加贯通水力通道宽度。漏水量及土体顶部颗粒的迁移均存在于缓慢增加阶段和突增阶段,高水压的影响主要发生在突增阶段,且土体损失直接导致突增阶段的发生。漏水漏砂过程中底板结构的受力分为陡降阶段、缓慢下降阶段和相对稳定阶段。漏水漏砂将诱发土拱的发生,且高水压使得土拱更易发生破坏,从而引发更多土体流失。贯通水力通道形成前、后的水土流失量及高水压的影响规律不同。Abstract: 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.
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