临近水库浅埋煤层防水煤柱留设宽度数值模拟

Reasonable Width of Water Proof Coal Pillar in the Mining of Shallow Coal Seam Close to Reservoir with Numerical Simulation

留设防水煤柱是临近水库煤层保水开采最为有效的方法,而如何确定防水煤柱留设宽度是当前迫切需要解决的问题。分析保水开采问题的流固耦合机理,建立流固耦合作用的控制方程,以张家峁矿井常家沟水库周边4^(-2)煤层开采为工程依托,采用数值模拟研究煤层采动对库岸边坡变形和孔隙水压力的影响规律,分析浅埋煤层开采覆岩采动破坏特性与岸坡失稳模式,进而提出防水煤柱的合理留设宽度。结果表明:当工作面临近库岸边坡时,库岸坡体先后出现向采空区侧倾倒转动和向水库方向滑移失稳的破坏模式;当坡面顶点产生反向水平位移且竖向位移急剧增加时,岸坡开始向水库方向滑移;当煤层顶底板孔隙水压力突变为0时,顶底板开始突水;取以上两种情况下较大煤柱宽度作为临界煤柱宽度,可以保证岸坡不出现失稳破坏且煤层顶底板不发生突水事故。在此基础上确定4^(-2)煤层防水煤柱宽度为109 m,工程实践证明该宽度可以保证安全开采。研究成果可为确定临近水库煤层开采的防水煤柱宽度提供理论支撑和实践依据。

The most effective method is to retain water proof coal pillar for the water conservation mining of coal seam close to reservoir,and determining the reasonable width of water proof coal pillar has always been a common concerned problem.The fluid solid coupling mechanism of water conservation mining was analyzed,and the governing equations of fluid solid coupling were established.Then taken the mining of 4^(-2) coal seam close to Changjiagou reservoir located in Zhangjiamao mine as the project background,the research method of numerical simulation were adopted to analyze overburden strata mining failure features and the failure mode of reservoir bank slope,and research the reasonable width of water proof coal pillar.Results show that when the working face was near the reservoir bank,the reservoir bank slope occurred the failure modes of dumping rotation to goaf and slide instability to reservoir successively.In the simulation analysis,the maximum value of the width of coal pillars when the top points on slope surface experienced reverse horizontal displacement and several key points produced sharp vertical displacements or the pore pressure in the roof and floor of coal seam suddenly changed to 0 should be taken as the critical width of coal pillar.The reasonable width of waterproof coal pillar was determined to be 109 m,which could ensure the safety mining.These results could provide a theoretical support and practical basis for determining waterproof coal pillar widths in coal seam mining close to reservoirs.