煤层底板含隐伏溶洞滞后突水机理

Mechanism of delayed groundwater inrush from covered karst cave in coal seam floor

为了避免华北煤田底板含隐伏溶洞滞后突水事故的发生,以丰沛矿区三河尖矿特大水害为例,通过特殊环境下岩溶溶洞的形成原因与滞后突水的物理过程分析。数值软件模拟与事故现场观测资料对比,综合研究含隐伏溶洞底板的滞后突水机理,结果表明:新构造断裂对原始封闭地下水系统的打破及高温高压高矿化度岩溶水对白云岩的融化剥蚀是溶洞形成并不断扩大的主要原因;受采动应力与高岩溶水压力影响,隐伏溶洞顶部不断形成新岩溶塌陷且破坏隔水层的现象客观存在,是突水通道形成的关键因素;工作面推过隐伏溶洞上方一定距离,受岩溶塌陷持续剥蚀而逐渐变薄的残余隔水层因强度不足以抵抗高岩溶水压力而瞬间破断,致使采动裂隙与岩溶塌陷相互贯通,引发滞后性突水。

Abstract：In order to prevent the delayed groundwater inrush occurring from covered karst cave in coal seam floor in north China coalfield, with the example of the mega-groundwater inrush in Sanhejian Coal Mine in Fengpei coalfield, the authors investigated the mechanism of delayed groundwater inrush from covered karst cave in coal seam floor through the analysis of the formation of karst cave with special environment and physical process, numerical simulation and actual observation data comparison. The results indicate that：（1） The material causes for the formation of the en- larged karst cave are that the original closed groundwater system is broken by new structure fracture and the dolomite is denuded by the water with high temperature, high pressure and high salinity ; （2） Due to the excavation-induced stress and high water pressure inside karst, new karst collapse occurs at the top of cave, and the water-resisting layer is gradually broken down, which becomes the dominated factor of forming water passages ; （3） When the working face advances away a certain distance from covered karst, the remnant of water-resisting layer is continuously denuded by karst collapse and is instantly broken as its strength is hard to resist the high water pressure. Eventually, the water-resisting layer is penetrated and the delayed groundwater inrush occurs. Key words： covered karst cave ; delayed groundwater inrush ; floor; water-resisting layer