基于围岩破断表达及力学响应研究的二次沿空留巷控制机理

The stability control of secondary gob-side entry retaining is a basic theory to resolve gas overrun at working face end and guarantee the gas efficient extraction in gob fracture zone. This project aims at the problem of weaker theoretical research in this aspect, takes the typical mining gateway as the research object, adopts the means of experimental research and mathematical mechanics theory, carries out the rock strength attenuation test and analyzes its attenuated characteristic parameters under the condition of multi-stage axial pressure and confining pressure loading and unloading in the laboratory for secondary gob-side entry retaining roof; moreover, utilizes the experiment with three-dimensional similar material model, field borehole imaging and laser stereoscopic imaging to research the fractured and caved structure characteristics of secondary gob-side entry retaining roof, and builds this roof caving structure physical model in the laboratory and uses load test to study its mechanical transmission and load-bearing characteristics; furthermore, combines with the field mine ground pressure automatic monitoring system and three-dimensional simulation test to analyze the evolution data of surrounding rock stress and deformation. Finally, it is expected to establish the failure and fracture expression model of roof rock mass strength attenuation model, and a three-dimensional roof fracture and caving structure mechanical model, and reveal the mechanical response law of secondary gob-side entry retaining surrounding rock. The research results of this project will further reveal the surrounding rock stability control mechanism of secondary gob-side entry retaining, improve the theoretical system of gob-side entry retaining, and lay a foundation for supporting design of engineering application.

二次沿空留巷稳定控制是解决采煤工作面端部瓦斯超限问题和保障采空区裂隙带瓦斯高效抽采的基础理论。本项目针对该方面理论研究较薄弱的问题，以典型矿井回采巷道为研究对象，采用试验与数学力学理论研究方法，开展二次沿空留巷顶板岩石室内多级轴压及围压加卸载作用下强度衰减试验并分析其表征参数；利用三维相似材料模型二次沿空留巷试验、现场钻孔成像及采空区激光立体成像技术，分析顶板断裂垮落结构特征，并在室内构建该垮落结构物理模型，利用载荷试验研究其力学传递及承载特性；结合现场矿压自动监测系统及三维模拟试验，综合分析空间围岩应力、变形演化数据，预期建立二次沿空留巷顶板岩体强度衰减模型，三维顶板断裂垮落结构力学模型等围岩破断表达模型，以及揭示全过程空间围岩力学响应规律。本项目的研究成果将进一步揭示二次沿空留巷围岩稳定控制机理，完善沿空留巷理论体系，为工程应用支护设计奠定基础。

二次沿空留巷稳定控制是解决采煤工作面端部瓦斯超限问题和保障采空区裂隙带瓦斯高效抽采的基础理论。利用巷道锚杆应力监测仪、离层仪、变形仪等监测设备，结合岩石力学理论、物理实验、数值模拟，对煤矿二次沿空留巷巷道围岩体变形及应力开展监测监控分析。主要结论如下：（1）发现沿空留巷过程运输巷的采动影响可分为影响微弱区、明显影响区、剧烈影响区和缓慢变化区等四个区，可确定工作面超前支护范围和滞后支护范围。（2）工作面超前一定范围内锚杆受采动影响大；工作面滞后一定范围内巷旁支护体外侧采空区顶板发生多次断裂破坏，说明巷旁锚固矸石袋加强支护体具有较大的刚度，对采空区顶板具有切顶作用。（3）相似材料模型试验发现，巷旁支护体仅仅承受其上部“倒梯形”体的荷载，荷载主要来自“大结构”下部的部分破碎岩体；7#煤层开采对于8#煤层相当于保护层开采，起到了一定卸压作用。（4）数值模拟试验表明，随着巷旁支护体强度和宽高比的增加，支护体内部应力也随之增大，二次留巷阶段增加速率较高；低宽高比易导致支护体本身失稳，最终留巷失败。