沿空留巷长期扰动变形规律与卸压机理研究

The long-term and severe disturbance caused by overlying strata caving is the key factor of gob-side entry retaining’s structural instability. In this subject the methods of theoretical analysis, physical simulation and numerical calculation will be used to study the intermittent disturbance law of gob-side entry retaining due to sequential collapse of stope overlying strata, and to explore the compaction effect of rock blocks and the dynamic characteristics of the fractured roof during the increasing period of top pressure. And then the load application mechanism toward the gob-side entry retaining will be clarified combining the load transferring ability of roadway roof. On this basis the active control method with the core of lateral roof presplitting and pressure-relief will be proposed. The breakage position and breakage time are changed through the presplitting method to shorten the disturbance cycle and reduce the mining-induced stress. Contacting the rock’s bearing properties under the long slow pressurization, the coordination bearing mechanism of surrounding rock and anchorage support within the pressure-relief area will be further clarified. The results could provide theoretical guidance for space maintenance and control of gob-side entry retaining under complex conditions.

采场覆岩垮落形成的长时间剧烈扰动是沿空留巷围岩结构失稳的关键诱因。课题拟采用理论分析、物理模拟及数值计算等方法，深入研究采场覆岩分次垮落对沿空留巷的间歇性扰动规律，探索顶压渐增期间碎胀矸石的压实效应与断裂顶板的随动特性，结合巷道顶板传递载荷的能力，阐述顶板运动对沿空留巷的长期施载机理；提出以沿空留巷侧向顶板预裂卸压为核心的主动控制方法，通过岩层预裂手段改变顶板的断裂时机和断裂位置，从而缩短顶板的扰动周期并降低顶板的附加应力；揭示预裂孔两侧断裂块体的结构关系对沿空留巷卸压效果的影响规律，形成预裂卸压效果的评价方法；联系长时缓增压状态下岩体的承载性能，阐明卸压区围岩与锚固支护的协调承载机理。研究成果可为深部等复杂条件下的沿空留巷空间维控奠定基础。

采空区覆岩分次垮落扰动是沿空留巷围岩结构失稳的关键诱因。课题采用理论分析、物理模拟及数值计算等方法，研究了采空区顶板多关键层分次垮落对沿空留巷的长期扰动机理，探索了顶压渐增期间碎胀矸石的压实效应与断裂顶板的随动特性，阐述了关键层预裂卸压效应与沿空留巷围岩结构主动控制原理。两带内的关键层分次垮落对沿空留巷的扰动周期、充填墙体的承载大小和巷道变形具有显著影响。覆岩分次垮落期间在顶板主离层和巷道的隔离之下出现两次应力分流，经由采空区侧向楔形承载区向下传递，在巷道两侧形成“应力双峰”，沿空留巷呈现出波动性扰动变形。“两带”内主控关键层垮落后，老顶的变形基本达到最大值，得出了关键层断裂时机和扰动周期的判定方法。关键层的下沉量由垮落前的挠曲下沉、垮落期间的旋转下沉和垮落后的压缩下沉三部分组成，下沉量各占15%、55%和30%，矸石的压实效应延长了沿空留巷的扰动周期，但随着时间延续来压强度逐渐减弱。采空区侧向顶板预裂卸压能够加速坚硬老顶的破断运动并有效缓解留巷顶板的压力，卸压后侧向支承应力区向浅部转移，应力峰值有一定程度的降低，留巷围岩变形得到明显改善，提出了侧向顶板的卸压判据和悬臂长度的优化方法。提出了常规条件下的沿空留巷结构稳定性控制对策，包括“双层”主动锚固支护、强度动态匹配的巷旁充填以及扰动期间的辅助支护3项，以及特殊条件下的“卸压-锚固”双重主动控制技术，形成了沿空留巷“顶板结构可控、围岩应力可调、扰动周期缩短、巷道变形改善”的主动控制效果。在两个典型采煤工作面展开了沿空留巷工业性试验，从不同角度验证了研究结论。课题研究成果可为我国煤矿极其复杂多样的地质条件下展开无煤柱沿空留巷实践奠定基础。