基于水位降速的松散承压含水层下采煤压架突水灾害预警研究

Many coal mines in east and north China exists serious support crushing and water inrush disaster during mining under unconsolidated confined aquifer. Instability of the key stratum breaking structure is the basic reason of such disasters. We can make early-warning to such disaster if we can predict instability of the key stratum breaking structure. Preliminary study shows connected effect exists between water level variation of unconsolidated confined aquifer and key stratum breaking movement. That is water level will change with key stratum’s different motion feature because of coal mining. Descending speed of water level increases significantly when key stratum breaking structure instability. So we can make descending speed of water level as an evaluation index for the stability of key stratum structure and then predict disaster. Through this research, we will research the law of connected effect between water level variation of unconsolidated confined aquifer and key stratum breaking movement. Then reveal influence factors of the connected effect. Based on above study, calculation formula for critical warming values of descending speed of water level will be given. Finally, it can provide new method for preventing support crashing and water inrush disaster. This research will promote the development and perfection of safe mining theory and technology under unconsolidated confined aquifer.

我国华北、华东矿区很多煤矿在松散承压含水层下采煤时存在严重的压架突水灾害问题。覆岩关键层破断结构失稳是导致压架突水灾害的根本原因，如能对关键层结构失稳做出预测，即可对压架突水灾害进行预警。前期研究发现，松散承压含水层水位变化与关键层的破断运动存在联动效应，即含水层水位会随关键层的不同破断运动特征表现出不同的变化状态。当关键层破断结构失稳时，松散承压含水层水位降速会明显增大，因此可以将水位降速作为关键层结构稳定性的判别指标，从而对压架突水灾害进行预警。本项目通过深入研究含水层水位变化与关键层破断运动之间的联动规律，揭示其联动效应影响因素，确定关键层破断结构失稳的临界水位降速，形成基于含水层水位降速的压架突水灾害预警方法，为松散承压含水层下采煤压架突水灾害的防治提供新手段。本项目的研究将进一步促进松散承压含水层下安全采煤理论与技术的完善和发展。

针对我国华北、华东矿区煤矿在松散承压含水层下采煤时压架突水灾害的防治问题，采用现场实测、模拟实验、理论分析等方法，开展了基于松散承压含水层水位降速的压架突水灾害预警方法研究工作。结果表明，长观孔水位变化与覆岩破断联动效应受到覆岩结构、含水层水位渗透特性等影响明显，基岩越薄，覆岩中硬岩层层越少，距离煤层10倍采高以内的顶板中存在巨厚硬岩层且距离煤层最近的硬岩层厚度越大时，覆岩越容易发生整体破断，长观孔水位必然发生明显下降。工作面初次采动较多重复采动更容易引发覆岩结构的失稳进而导致灾害发生。含水层骨架颗粒粒径越大，含水层的流动补给和渗透性能越好，作用在基岩顶界面上的载荷较大，容易导致覆岩发生整体破断和长观孔水位快速下降。结合水位变化与覆岩破断的联动规律，实测总结出了水位突降型、波动回升型、应力扰动型3种联动类型及其发生条件，其中水位突降型联动预示着覆岩结构发生失稳，最易引发压架突水灾害。在掌握水位变化与覆岩破断联动规律的基础上，基于地下水动力学原理和岩层控制的关键层理论，揭示了长观孔水位与覆岩破断失稳产生联动效应的机制，理论分析得出了关键层破断结构失稳的临界水位降速计算公式，并推导形成了单孔预警与双孔预警的时水位降速计算方法。研究成果在祁东煤矿多个具有压架突水危险的工作面进行了成功应用。