浅埋煤层开采突水溃砂两相流的耦合数值研究

THE TWO-PHASE FLOW OF WATER-SAND INRUSH UNDER SHALLOW COAL SEAM MINING: A COUPLED NUMERICAL STUDY

为探究浅埋煤层开采上覆含水松散层水砂两相流动规律,采用基于离散元软件PFC3D和有限元软件GID的耦合数值方法,模拟了上覆岩层中预制理想单裂隙在不同开度和倾角条件下突水溃砂全过程,分析了裂隙通道所受接触力、水流速度、水砂间拖曳力随时步的变化规律。结果表明:裂隙开度和倾角会改变突水溃砂过程中水砂突涌类型,对覆岩所受接触力、水流速度及其稳定所需时间产生较大影响,水砂间拖曳力主要受裂隙倾角的影响。裂隙通道入口处即上覆岩层的顶层在突水溃砂初期所受接触力最大,处于最危险状态;水流速度稳定值和流动稳定所需时间分别与裂隙倾角和开度成线性相关;对比裂隙通道底面侧,倾向侧水砂间拖曳力较大,水砂突涌更加剧烈。

In order to study the flow performance of mixed water-sand two-phase flow of the overlying water bearing loose bed under the shallow coal seam mining, a coupled numerical method based on discrete element software PFC3D and finite element software GID is used to simulate the whole processes of water-sand inrush in precast ideal fracture with different opening widths and dip angles in overlying rock strata. The analysis of the contact force of the fracture channel, flow velocity of water and the drag force between water and sand variation law along with time steps show that, the opening widths and dip angles of fracture change the flow patterns of water-sand flow inrush, and have great impact on the contact force of the fracture channel, flow velocity of water and the time of mixed water-sand flow. However, the drag force is mainly influenced by the dip angles of fissure channel. The fracture channel entrance is the most dangerous position, where has the largest contact force in the process of water-sand coupled flow. The final flow velocity of water and the time steps to stabilize the water velocity in the fissure are in linear correlation with the fracture angles and the fracture opening widths, respectively. The drag force is greater and water-sand inrush is more intense in dip side than underside of the fissure channel.