深部开采底板岩体卸荷损伤的强扰动危险性分析

Strong disturbance hazard analysis of unloading damage for floor rock mass in deep coal mining

为研究深部高应力岩体强烈的卸荷效应扰动底板破坏并诱发突水的危险性,根据卸荷力学理论,研究了深部开采卸荷对底板扰动破坏的影响,运用离散元软件计算了深部开采底板卸荷损伤的强扰动特征,基于三轴卸荷试验及损伤因子概念推导了卸荷量与损伤因子的关系,获得了底板岩体卸荷的扩展破坏条件,划分了底板卸荷扰动分区,分析了深部开采底板岩体卸荷损伤破坏的强扰动危险性。结果表明:随采深增加,底板卸荷起点及卸荷应力增加,卸荷量却降低,而深部开采较小的卸荷量便造成底板严重损伤破坏;岩体卸荷量越大,卸荷速率、位移量及渗透系数越高,越易致其扩展破坏;裂隙倾角及水平应力与垂直应力比值越小,越易满足底板岩体卸荷的扩展破坏条件。

To investigate the mechanisms of floor failure and further induced risks of water inrush by the strong unloading effect of high-stress rock mass in deep coal mining, the influence of unloading on floor disturbance and failure was analysed with the theory of unloading rock mass mechanics. It calculated the strong disturbance characteristics of floor rock mass unloading damage in deep coal mining by using the discrete element method（DEM）. Based on triaxial unloading tests and the concept of damage factor, we obtained the relationship between unloading percentage and damage factor, determined the propagation and failure condition of rock mass, and achieved the unloading disturbance partition of floor. Then the disturbance hazard of floor rock mass unloading damage and failure in deep coal mining were further studied. The results show that with mining depth increasing, both unloading starting point and unloading stress of floor are increased, but the unloading percentage is reduced, in which the lower unloading percentage causes damage severely in deep coal mining. When the unloading percentage of rock mass is greater, its unloading rate and displacement and the permeability coefficient become higher, which easily induces floor rock mass instability propagation. When the dip angle of crack and the ratio of horizontal stress and vertical stress are low, it easily reaches the propagation and failure conditions of floor rock mass unloading.