坚硬主控覆岩预裂弱化控制导水裂缝带高度机制研究

Mechanism study of thick-hard overburden pre-cracking weakening to control the height of water conducted fracture zone

煤矿顶板水害防控与水资源保护的核心是控制导水裂缝带发育高度,降低煤层开采对上覆含水层扰动。基于覆岩破坏控制技术和顶板预裂弱化控制矿山压力显现方面研究现状,提出通过主动预裂弱化坚硬主控岩层,在不影响开采效率和资源回收率的情况下控制采动导水裂缝带发育高度的低损害开采技术构想。采用相似模拟,理论分析和数值模拟分析相结合的研究方法探究预裂弱化坚硬主控岩层控制导水裂缝带发育高度作用机制,并根据数值模拟结果提出含水层下坚硬覆岩预裂层位确定方法。研究结果表明:坚硬岩层相较于软弱岩层采动破断块度较大,采动破坏后整齐堆积于采空区,采动破坏膨胀量较小;不同层位坚硬岩层预裂弱化条件下采动响应存在显著差异,因此预裂层位选择将直接决定预裂弱化控制导水裂缝带高度效果;数值模拟结果显示中位岩层预裂和中、低位岩层同时预裂时导水裂缝带发育高度控制效果较好。研究成果为含水层下煤炭资源安全、高效和绿色开采提供了新的技术途径。

The key of roof water inrush prevention and water resources protection of coal mine is to control the height of the water conducted fracture zone and reduce mining disturbance of the overlying aquifer.Based on the current research status of overburden damage control technology and pre-cracking weakening control of ground pressure in coal mine,a method to control overburden damage by actively weakening the hard rock layer is proposed.This method does not affect mining efficiency and coal resource recovery rate.Combined with similar simulation,theoretical analysis and numerical simulation analysis,the mechanism of pre-cracking weakening thick-hard roof to control the height of water conducted fracture zone was studied.According to the numerical simulation results,a method for determining the pre-cracking hard overburden under the aquifer is proposed.The results of the study indicate that:Due to the hard rock disintegrate into larger pieces during mining,and after mining,these broken pieces will be neatly piled up in goaf,therefore the bulking coefficient of hard roof after mining is smaller than normal roof.Pre-cracking can increase the bulking coefficient of hard stratum,reduce the subsidence of overlaying strata,and thus reduce the height of water conducted fractures zone.The response of the overlying strata to mining damage varies significantly under different pre-cracking for hard rock layers in different layer positions.Therefore,the selection of the pre-cracking position will directly determine whether pre-cracking weakening control of the water conducted fracture zone height is effective.The simulation results indicate that pre-cracking the middle thick hard rock layer and pre-cracking the middle and low level rock layers simultaneously can effectively control the height of water conducted fracture zone.The study results provide a new technical path for the safe,efficient,and green mining of coal resources under aquifer.