针对山西元宝湾煤矿浅埋深上覆和下伏柱式采空区中部煤层的安全复采难题，综合采用理论分析、实验室实验、物理模拟、数值模拟和现场实测方法，探究了柱采区蹬空开采底板煤柱垂直荷载及内应力分布形态，并基于Mises等效应力探讨了柱采区蹬空煤柱潜在破坏形式；揭示了柱采区蹬空开采底板关键柱破坏形式及破坏剥落体运动特征；阐明了底板煤柱破坏次序及柱群动态失稳演化规律。提出通过柱采区注浆充填强化底板煤柱承载能力的方法来进行中层遗煤资源的回收，并据此给出了确保元宝湾煤矿6107工作面中部遗煤蹬空安全复采的底板柱采区临界充填高度。结果表明：若底板9号煤层柱式采空区不充填，层间岩层的非均匀下沉将使柱采区煤柱产生偏心压缩，导致关键柱及其剥落体出现旋转下沉的现象；当柱采区关键柱破坏失稳后，覆岩载荷呈现出双向传递的特点，整个煤柱群表现为以关键柱为中心，双向多米诺骨牌式的链式失稳特征，而三维空间中则呈现出以关键柱为圆心的外向辐射波状失稳扩展特征，柱采区关键柱的破坏失稳将诱发底板煤柱群整体失稳，导致6107工作面蹬空开采区域采掘设备及工作人员、超前煤岩体大面积塌陷等动力灾害。数值模拟及物理相似模拟结果表明，确定6107工作面蹬空段安全复采的底板柱采区临界充填高度为6 m，即充填不接顶高度为2 m，这一结论亦得到了实测结果的证实。在此基础上，针对充填效果较差且充填高度未达6 m的局部区域，进一步提出了底板空洞二次充填和加固处理方法，确保了蹬空段中层遗煤资源的安全复采。

The safety problems of the shallow buried overlying and underlying mined out areas with pillars in the Yuanbaowan Coal Mine are investigated using some theoretical analysis, laboratory experiments, physical simulation, numerical simulation and field measurement methods. In particular, the vertical load and internal stress distribution patterns of coal pillars underlying the working seam floor in the mined out area are explored, and the potential damage form of the coal pillars in the mined out area is discussed based on the Mises equivalent stress. The failure mode of key pillars and the movement characteristics of fractured flakes in the mined out areas are revealed, and the failure sequence of underlying coal pillar groups and dynamic instability evolution are clarified. Therefore, a method of strengthening the bearing capacity of the underlying coal pillars through grouting in the mined out area is proposed to recover the coal resources in the middle coal seam between the mined out seams, and the critical filling height of the mined out area to ensure a safe mining of No.6107 working face is given. The results show that if the mined out area of No. 9 coal seam is not filled, the uneven subsidence of the roof strata will lead to the eccentric compression of the coal pillars, the key pillar and its fractured bodies rotate and subside eventually. Once the key pillar is damaged, the overburden load presents the characteristics of two way transmission. A two way domino chain type collapse centered on the key pillar is shown in the entire coal pillar group, while the outward radiating wave like instability expansion characteristic with the key pillar as the center is presented in the three dimensional space. The failure and instability of the key pillars will induce the overall instability of the underlying coal pillar group, which may lead to induce such dynamic disasters as a large scale collapse of the working face and its advanced coal rock mass. The critical filling height for the safe mining of the working face No.6107 at the mined out area is 6 m, which is also confirmed by the actual measurement results. On this basis, for the regional area where the filling effect is poor and the filling height is less than 6 m, the secondary filling and re-inforcement treatment method is proposed to ensure the safe mining of remaining coal resources in the middle seam above the mined out area.

1 工作面概况

2 蹬空开采底板煤柱承载及变形特征

   2.1 力学模型

   2.2 内应力分布规律

3 煤柱破坏形式及柱群失稳扩展规律

   3.1 相似材料物理力学参数测试

   3.2 物理模拟方案

   3.3 底板煤柱破坏形式及失稳时序

4 充填率对煤柱稳定性的影响规律

   4.1 充填体对煤柱弹塑性扩展的抑制效应

   4.2 临界充填高度及蹬空开采安全评价

5 蹬空段充填效果实测及评价

   5.1 充填效果观测

   5.2 柱采区充填未接顶防治对策

6 结论