开展浅埋综采面区段窄小煤柱破坏机理及顺槽围岩控制技术的研究，对提高煤炭资源的回采率以及保证工作面的安全生产具有重要的工程价值。本文以陕煤集团神木红柳林煤矿15217综采面为工程背景，采用室内试验、理论分析、数值模拟及现场试验等方法开展研究工作，主要研究结论如下：

（1）完成了不同围压和不同卸荷速率下煤岩三轴压缩试验，试验结果表明：在一定围压范围内，随着围压的升高，煤岩峰值强度，主破裂角也随之增大。单轴压缩下，煤岩呈劈裂破坏形式，在三轴压缩条件下，随着围压的增大，煤样的破坏形式逐渐由局部剪切破坏向整体剪切破坏形式转变。声发射振铃计数显著增长主要发生在峰前弹塑性变形阶段和峰后破坏阶段；不同卸荷速率下煤岩三轴压缩试验破坏过程可以分为3个阶段：轴压加载阶段、围压卸载阶段和煤岩破坏阶段。卸荷作用下煤样破坏以拉剪混合破坏形式为主。随着卸荷速率的增加，煤岩内部裂隙发育速度越快，脆性破坏特征越明显，声发射瞬时振铃计数越高。

（2）完成了煤岩三轴压缩与三轴卸围压试验前后核磁共振试验，试验结果表明：三轴压缩和三轴卸围压试验后T₂谱曲线均出现了明显右移的现象，且T₂谱的第三波峰相对试验前显著增大，说明煤岩破坏后内部孔隙数量不断增加，孔隙尺寸不断增大。与三轴压缩试验相比，三轴卸围压试验后T₂谱的第三波峰上升幅度更大，说明煤岩内部大孔径孔隙数量显著增多，卸围压试验煤岩破坏更剧烈，脆性破坏特征显著。试验后煤岩孔径尺寸主要分布在 之间。

（3）基于极限平衡理论，得出红柳林煤矿15217综采面合理的窄煤柱留设宽度应介于7.30m~8.80m之间。采用FLAC^3D数值模拟方法，分析了双巷掘进和综采面回采期间不同煤柱宽度下煤柱的稳定性以及顺槽围岩应力、位移和塑性区分布特征。最终综合数值模拟和理论分析计算结果，得出8.5m是窄煤柱留设的最佳方案。

（4）基于“强支-强卸”结合设计理念，采用高强度托盘、高强度支护材料和高预应力锚杆（索）对顺槽围岩进行强力支护。根据极限平衡理论完成了15217综采面胶运顺槽和辅运顺槽支护参数设计，利用FLAC对支护参数合理性进行评价。结果表明：双巷掘进期间与综采面回采期间煤柱受力、变形均较小，顺槽围岩受力、变形、围岩塑性区和锚杆（索）受力均在安全许可范围内。

（5）基于“强支-强卸”结合设计理念，完成了15217综采面定向长钻孔分段水力压裂卸压方案设计及其现场卸压效果监测分析。综采面共布设四个钻场，每个钻场包含三个压裂钻孔，目标压裂层位为粉砂岩，压裂层位高度分别为18m、43m和62m。水力压裂卸压效果微震监测表明：水力压裂有效弱化了坚硬顶板的完整程度，压裂影响区内顶板基本可以随工作面推进及时垮落，减小了侧向支承压力对煤柱的影响，切断了其应力传递路径，从而优化了煤柱的受力环境。

（6）完成了15217综采面顺槽监测方案设计及现场实测工作。结果表明：15217综采面初次来压步距为47.4m，周期来压步距为17.5m，动载系数为1.27。15217综采面自2022年6月13日开始回采，2023年3月10日回采结束，工程实践表明：综采面回采期间顺槽围岩变形处于安全许可范围内，围岩未发生破坏，综采面安全回采，说明提出的支护与卸压方案合理有效。

It is of great engineering value to improve the recovery rate of coal resources and ensure the safe production of working face by studying the failure mechanism of narrow and small coal pillars and the control technology of surrounding rock in shallow buried fully mechanized mining face. In this paper, the 15217 fully mechanized mining face of Shenmu Hongliulin Coal Mine of Shaanxi Coal Group is taken as the engineering background, and the research work is carried out by means of indoor test, theoretical analysis, numerical simulation and field test. The main conclusions are as follows :

(1) The triaxial compression test of coal rock under different confining pressures and different unloading rates was completed. The test results show that within a certain confining pressure range, with the increase of confining pressure, the peak strength of coal rock and the main fracture angle also increase. Under uniaxial compression, the coal rock is in the form of splitting failure. Under triaxial compression, with the increase of confining pressure, the failure mode of coal sample gradually changes from local shear failure to overall shear failure. The significant increase of acoustic emission ringing count mainly occurs in the pre-peak elastic-plastic deformation stage and post-peak failure stage. The failure process of coal-rock triaxial compression test under different unloading rates can be divided into three stages : axial compression loading stage, confining pressure unloading stage and coal-rock failure stage. Under the action of unloading, the failure of coal samples is mainly in the form of tensile-shear mixed failure. With the increase of unloading rate, the faster the development of cracks in coal rock, the more obvious the brittle failure characteristics, and the higher the instantaneous ringing count of acoustic emission.

(2) The nuclear magnetic resonance test of coal rock before and after triaxial compression and triaxial unloading confining pressure test was completed. The test results show that the T₂ spectrum curve has obvious right shift after triaxial compression and triaxial unloading confining pressure test, and the third peak of T₂ spectrum is significantly increased compared with that before the test, indicating that the number of internal pores of coal rock is increasing after failure, and the pore size is increasing. Compared with the triaxial compression test, the third peak of the T₂ spectrum after the triaxial unloading confining pressure test rises by a larger margin, indicating that the number of large-diameter pores in the coal rock increases significantly, and the damage of the coal rock in the unloading confining pressure test is more severe and the brittle failure characteristics are significant. After the test, the pore size of coal rock is mainly distributed between .

(3) Based on the limit equilibrium theory, it is concluded that the reasonable width of narrow coal pillar should be between 7.30 m and 8.80 m. The numerical simulation method was used to analyze the stability of coal pillars and the distribution characteristics of stress, displacement and plastic zone of surrounding rock under different coal pillar widths during the excavation of double roadways and the mining of fully mechanized mining faces. Finally, based on the results of numerical simulation and theoretical analysis, it is concluded that when the width of section coal pillar is 8.5 m, it is the best scheme for narrow coal pillar retention.

(4) Based on the design concept of " strong support-strong unloading, " high-strength pallets, high-strength supporting materials and high-prestressed anchor rod and cable are used to strongly support the surrounding rock of the crossheading. According to the limit equilibrium theory, the support parameter design of glue transport crossheading and auxiliary transport crossheading in 15217 fully mechanized mining face was completed. FLAC is used to evaluate the rationality of support parameters. The results show that the stress and deformation of coal pillars during the excavation of double roadways and the mining of fully mechanized mining face are small, and the stress and deformation of surrounding rock, plastic zone of surrounding rock and anchor rod and cable are all within the allowable range of safety.

(5) Based on the design concept of ' strong support-strong unloading ', the pressure relief scheme design of directional long borehole staged hydraulic fracturing in 15217 fully mechanized mining face and its on-site pressure relief effect monitoring and analysis were completed. There are four drilling fields in the fully mechanized mining face. Each drilling field contains three fracturing boreholes. The target fracturing horizon is siltstone, and the fracturing horizon heights are 18 m, 43 m and 62 m respectively. The microseismic monitoring of the pressure relief effect of hydraulic fracturing shows that the hydraulic fracturing effectively weakens the integrity of the hard roof, and the roof in the fracturing affected area can basically fall in time with the advance of the working face, which reduces the influence of the lateral abutment pressure on the coal pillar and cuts off the stress transfer path, thus optimizing the stress environment of the coal pillar.

(6) The monitoring scheme design and field measurement of 15217 fully mechanized mining face are completed. The results show that the first weighting step distance of 15217 fully mechanized mining face is 47.4 m, the periodic weighting step distance is 17.5 m, and the dynamic load coefficient is 1.27. The mining of 15217 fully-mechanized mining face began on June 13,2022 and ended on March 10,2023. The engineering practice shows that the deformation of surrounding rock in the crossheading during the mining of fully-mechanized mining face is within the allowable range, and the surrounding rock is not damaged. The safe mining of fully-mechanized mining face shows that the proposed support and pressure relief scheme is reasonable and effective.

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