孤岛煤柱巷道围岩损伤演化规律及锚杆锚索协同稳定控制机理研究

Because coal has been mined intensely by many mines for many years, recoverable reserves of coal resource go down so sharply that many mines has progressively gone into residual mining period. All kinds of island pillar are recovered that is of great significance for improving coal resource recovery rate and extending mine life. However, some theoretical problems on crack propagation law, surrounding rock damage of island coal pillar, roadway instability and stability control mechanism on bolt in coordination with cable, etc. remain to be solved. The project studies such scientific issues as surrounding rock crack propagation mechanism and bolt and cable cooperative stability control mechanism by combining rock mechanics test, physical modeling technique, computer numerical simulation and field tests, and by adopting the theoretical methods including rock mass mechanics of underground engineering and damage mechanics. Surrounding rock crack propagation model and stress criterion of roadway is established to reveal crack propagation mechanism. Surrounding rock damage mechanics model in the course of crack propagation is established in use of damage mechanics theory and method. The mechanical model of surrounding rock structures for gob-side entry driving in narrow coal pillar of island coalface is built. Key block balance condition is calculated and then instability criterion of island mining pillar roadway is put forward. The crack propagation inhibition mechanism of bolt or cable is revealed by anchored rock mass modeling experiment. Finally bolt and cable cooperative stability control method is put forward. The research provides the theoretical basis for supporting design of island pillar roadway and stable control of surrounding rock.

许多矿井由于多年高强度开采，煤炭资源可采储量急剧衰减而逐步进入残采阶段，进行各类孤岛煤柱的回收，对于提高煤炭资源回收率，延长矿井寿命具有重要意义。但对孤岛煤柱裂隙扩展规律、围岩损伤以致失稳机理与锚杆锚索协同稳定控制机理等深层次理论问题亟待解决，本项目采用地下工程岩体力学理论、损伤力学理论相结合的方法，借助实验室岩石力学试验、物理模拟、计算机数值模拟与现场实测相结合的综合手段，对孤岛煤柱巷道围岩裂隙扩展机理与与锚杆锚索协同稳定控制机理等关键科学问题展开研究。建立巷道围岩的裂纹扩展模型及应力判据，揭示裂隙扩展机理；建立裂隙扩展过程中围岩损伤力学模型；构建孤岛面窄煤柱沿空掘巷围岩结构力学模型，计算关键块体力学平衡条件，提出孤岛面窄煤柱沿空掘巷失稳判据；揭示锚杆（索）裂隙扩展抑制机理，提出锚杆锚索协同作用巷道稳定控制方法，为孤岛煤柱巷道支护设计并实现巷道围岩稳定控制奠定理论基础。

许多矿井由于多年高强度开采，逐步进入残采阶段，进行各类孤岛煤柱的回收，对于提高煤炭资源回收率，延长矿井寿命具有重要意义。但对孤岛煤柱裂隙扩展规律、围岩损伤以致失稳机理与锚杆锚索协同稳定控制机理等深层次理论问题亟待解决，本项目采用地下工程岩体力学理论方法，借助物理模拟、计算机数值模拟与现场实测相结合的综合手段，对孤岛煤柱巷道围岩裂隙扩展机理与与锚杆锚索协同稳定控制机理等关键科学问题展开研究。数值模拟研究了相邻上下工作面回采，孤岛煤柱巷道掘进及孤岛工作面回采全过程巷道围岩变形与裂隙发育规律，孤岛煤柱巷道开挖后，沿空小煤柱会出现整体下沉，沿空巷道采空区侧变形大于实体煤侧，沿空巷道小煤柱左侧（第一临空面）经历二次扰动及两次扩容，导致煤柱左侧胶结基本完全破坏，裂隙发育向煤柱中部延伸，呈现弧形的裂隙分布特征。受本工作面回采超前动压影响时，煤柱内部裂隙发育充分，基本贯通，导致煤柱完全损伤破坏，承载能力较弱。揭示了孤岛煤柱工作面巷道围岩失稳机理为：孤岛沿空巷道围岩所在区域由于存在高偏应力场，使巷道围岩具备形成蝶形塑性区的条件，同时由于侧向支承压力常发生主应力旋转，使得塑性区沿巷帮即煤层方向充分的发展，该情况下巷道将表现为大面积破坏、难支护等特征。构建了孤岛面窄煤柱沿空掘巷小结构应力拱力学模型，拱脚分别位于巷道一侧的实体煤和另一侧煤柱。分析表明水平摩擦力、拱跨距、容重、埋深和侧压系数是小结构稳定主要影响因素，并揭示了各因素的影响规律。数值模拟研究了锚杆锚索协同巷道稳定控制机理，高预应力增大锚杆作用范围岩体内压应力，合理锚杆间排距使压应力区部分重叠而连续。锚杆使浅部围岩形成具有一定自稳与承载能力整体，锚索可充分调动深部围岩的承载能力，两者协调共同作用维持巷道稳定。工程实践表明进行孤岛煤柱巷道采用锚杆-锚索协同支护后，保证了工作面安全高效回采。项目研究成果为孤岛煤柱巷道支护设计并实现巷道围岩稳定控制奠定理论基础。