In-Situ and Numerical Investigation of Groundwater Inrush Hazard from Grouted Karst Collapse Pillar in Longwall Mining
In-Situ and Numerical Investigation of Groundwater Inrush Hazard from Grouted Karst Collapse Pillar in Longwall Mining
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DOI：
10.3390/w10091187
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发表时间：
2018-09-01
期刊：
影响因子：
3.4
通讯作者：
Duan, Hongyu
中科院分区：
文献类型：
--
作者：
Ma, Dan;Cai, Xin;Duan, Hongyu
突水是矿山工程中典型的水文自然灾害。2000年至2012年，全国共发生各类矿井突水灾害1110起，死亡失踪矿工4444人。岩溶陷落柱（KCP）是华北煤田常见的地质构造，含大量颗粒岩，在高压作用下易发生迁移。因此，KCP带是地下开采中重要的突水通道。对KCP区进行灌浆可以减轻地下水突水的危险性。然而，KCP附近煤柱的断裂或失稳会引起围岩失稳甚至地下水突水的危险。为评价某采空区注浆式煤柱失稳引起的含水层突水风险，对采空区注浆式煤柱周围地层变形进行了现场调查。建立了底板-柱-顶系统对煤柱连续作用的力学模型；在此基础上，建立了连续失稳和突水风险的数值模型。楼板-柱-顶体系的总能量和刚度是判断体系稳定性的两个标准。煤柱的总能量比底板系统的总能量大，是保证底板-柱-顶系统稳定的基本因素。当底板或煤柱刚度为负值时，系统将失去稳定性；由此产生地下水突水通道。而当楼板-柱-顶体系满足时出现负值，则表明体系结构处于破坏状态；较窄的煤柱会增大系统持续失稳的风险，容易形成地下水突水通道。连续煤柱的失稳概率较低。反之，破碎煤柱的破坏概率更大。裂隙煤柱巷道顶板塑性区和变形量均大于连续煤柱，说明连续煤柱有效地缓解了突水风险。
Groundwater inrush is a typical hydrologic natural hazard in mining engineering. Since 2000 to 2012, there have been 1110 types of mine groundwater inrush hazards with 4444 miners died or missing. As a general geological structure in the northern China coalfields, the karst collapse pillar (KCP) contains a significant amount of granular rocks, which can be easily migrated under high hydraulic pressure. Therefore, the KCP zone acts as an important groundwater inrush pathway in underground mining. Grouting the KCP zone can mitigate the risk of groundwater inrush hazard. However, the fracture or instability of the coal pillar near KCP can cause the instability of surrounding rock and even groundwater inrush hazard. To evaluate the risk of groundwater inrush from the aquifer that is caused by coal pillars instability within grouted KCP in a gob, an in-situ investigation on the deformation of the surrounding strata was conducted. Besides, a mechanical model for the continuous effect on the coal pillar with the floor-pillar-roof system was established; then, a numerical model was built to evaluate the continuous instability and groundwater inrush risk. The collective energy and stiffness in the floor-pillar-roof system are the two criterions for judging the stability of the system. As a basic factor to keep the stability of floor-pillar-roof system, the collective energy in coal pillar is larger than that in floor-roof system. Moreover, if the stiffness of floor-roof or coal pillar meets a negative value, the system will lose stability; thus, the groundwater inrush pathway will be produced. However, if there is a negative value occurring in floor-pillar-roof system meets, it indicates that the system structure is situated in a damage state; a narrower coal pillar will enlarge the risk of continuous instability in the system, leading to a groundwater inrush pathway easily. Continuous coal pillars show a lower probability of instability. Conversely, the fractured coal pillars have a greater probability of failure. The plastic zone and deformation of the roadway roof in the fractured coal pillar are larger than that of continuous coal pillar, indicating that the continuous coal pillars mitigate the risk of groundwater inrush hazard effectively.