深部开采底板破坏及高承压突水模式、前兆与防治

Mining-induced floor failure and the model,precursor and prevention of confined water inrush with high pressure in deep mining

以深部开采底板承压超过5 MPa的特殊条件为研究对象,围绕复杂结构底板隔水层采动破坏及其诱发高承压突水这一核心问题,以大量突水资料为背景,分析了底板突水的形成及影响因素、水岩相互作用、时空分布及规律,总结了底板突水的两类基本模式,即完整型底板突水模式和断裂构造型底板突水模式。采用现场实测、数值模拟及物理模拟等手段,揭示了深部开采条件下底板隔水层的采动破坏规律,即在底板承压超过5 MPa条件下,工作面底板隔水层受超前应力破坏明显,深度一般在25 m左右;在相同底板隔水层结构和开采条件下,随着水压的升高,底板破坏深度及范围不断增大;工作面底板不同位置的破坏范围具有差异性,从工作面正下方往采空区方向由"倒马鞍形"逐步过渡到"倒梯形"。利用高承压矿井突水模拟试验系统,设计并完成了单一结构、多层组合结构以及断裂结构底板隔水层条件的底板高承压突水模拟试验,揭示了不同底板结构模型突水的压力及孔隙水压力变化特征,试验结果表明:采动引起的底板压力及孔隙水压力呈周期性波动,与工作面推进距离有关。突水通道形成过程中,各参数均表现为较大幅度升高并剧烈波动;通道一旦形成并发生突水时,压力和孔隙水压力均急剧下降,并稳定在某一范围,试验结果表明,底板压力和孔隙水压力信息是较为理想的底板突水监测预报信息源。以典型底板隔水层条件为基础,建立了深部高承压厚隔水层条件下安全开采评价方法以及薄隔水层条件下"底板富水性探查-注浆改造-物探钻探验证-安全开采评价-回采"的决策及实践范例;发现了豫中矿区寒武系石灰岩上段20～30 m层段岩溶不发育的特点,并具有良好的隔水性,分析了该层段隔水性的地质成因,将寒武系石灰岩上段岩溶不发育段作为隔水层考虑,并成功应用于马陵山井田井巷工程布置,实现了-350 m上车场进入寒武系石灰岩上段垂深55.5 m,合计320 m长度巷道的安全施工并投入使用2 a。

Presented the models,precursors and characteristics of complex structure aquifuge failure in the floor and the confined water inrush with high pressure over 5 MPa in deep underground coal mining.The occurrence and influencing factors of floor water inruch,interaction between water and rock,temporal-spatial distribution were analyzed based on numerous water inruch data.And then,two basic patterns of floor water inruch,including integrated and fractured floor water inrush pattern,were concluded and summarized.The characteristics of floor failure under deep mining conditions were revealed according to field measurements,numerical and physical simulations.The results show that,with the condition of confined water pressure over 5 MPa that the aquifuge is subjected to,the floor failure is influenced significantly by advance stress and the failure depth is about 25 m.The failure depth and range are enlarged with the increasing of water pressure under the same floor structure and mining conditions.There are some differences of the failure range exist from the area under the working face to the goaf,the ranges change gradually from ＂inverted saddle shape＂ to ＂inverted ladder shape＂.Three scaled models,including simplex structure,multilayer structure and faultage structure for floor water inruch with high pressure were then designed and established with the high pressure water inruch simulation equipment.And then,the basic characteristics and laws of stress and pore water pressure variation during the water inruch process with high pressure induced by coal mining under different floor aquifuge structures were also systematically summarized on the basis of the experimental results.The periodic fluctuation of the floor stress and pore water pressure due to coal mining are closely related to the mining progress.During the conformation of mining-induced water inrush pathway,all the parameters increase sharply and fluctuate violently.When the water inrush into the working face,all the parameters decrease considerably and then at a certain range of a low level for a long period.It can be deduced from these results that the floor stress and pore water pressure can be significant precursors for monitoring and forecasting the water inrush hazards in coalmines.Safety mining practices under typical floor acquifuge conditions were then summarized.Evaluation method of safety deep mining under high pressure and thick acquifuge condition was established.Then,the example of ＂floor water abundance exploration-grouting for aquifer alteration-physical and drilling exploration verification-safety mining evaluation-coal mining＂ under high pressure and thin aquifuge condition was put into practice.It was found that at least 20~30 m of the upper Cambrian limestone can be considered as aquifuge because of its poor karst development characteristics and impermeability.And then,the viewpoint has been successfully applied to the decision making of excavating the shaft bottom at-350 m level and 55.5 m deep into the upper Cambrian limestone at a coalmine of central Henan Province and a total 320 m long tunnel in the shaft bottom has been excavated safely and put into practice for 2 years.