厚层砂岩顶板沿空切顶成巷及围岩结构变形机理研究

Many engineering practice about gob-side entry formed by cutting roof slipped indicated that the thick sand rock have appreciable impact on the deformation control of gob-side entry. It is important to discover the expansion and abjunction mechanism of gob-side entry thick sandstone roof by adopt and move pressure. It has great theoretical significance and practical value to surrounding rock structure formation and deformation control of gob-side entry. The capital account item will do model experiments and FDEM experiments about thick sandstone joint-cutting lateral roof of gob-side entry. The experiment will discover the mechanism of action about joint-cutting expansion influenced by the factors such as the mining height、supporter resistance、joint-cutting parameters、sandstone strength、soft rock strata. And it will also give the process of the joint-cutting expansion and the mechanical sate of the thick sandstone breakage and abjunction. And then basis on the optimal abjunction and breakage state of lateral roof after joint-cutting expansion stopped, the plane stress similar material model experiment and UDEC simulation will be made up to research the interaction rule between cover rock movement and gob-side entry surrounding rock with the fault structure evolutionary process with the different support force and different joint cutting parameters. And then the deformation mechanism of gob-side entry retained by cutting roof down automatically. Basis on the orthogonal numerical simulation experiment, the stable mechanism model of gob-side entry will be established to show primary and secondary influencing factors of the surrounding rock stability and macrostructure stability. By this way the key parameters could be chosen rationally. The research could provide the theory and calculation method to design and analyze effectively the surrounding rock deformation and stability control of gob-side entry with joint-cutting advance face.

在多个沿空切顶成巷无煤柱开采实践探索中，发现厚层砂岩顶板可对切顶成巷围岩的最终变形量产生显著影响，正确揭示沿空巷道厚层砂岩预切缝顶板在采动压力作用下的切缝扩展、切落、围岩断裂结构形成及变形机理具有十分重要的理论与工程意义。本项目拟通过沿空巷道侧向厚层砂岩切缝顶板模型加载实验和FDEM数值实验，研究采高、支护阻力、水平挤压力、切缝参数、砂岩强度、软弱层切割等因素对厚层砂岩顶板切缝扩展的作用机理，分析厚层砂岩顶板沿预切缝扩展断裂过程及切落状态,得出合理切顶参数；采用相似材料模型实验和UDEC模型，研究厚层砂岩顶板合理切顶参数下，沿空巷道侧向覆岩移动与沿空巷道围岩结构变形间相互作用规律，揭示切顶成巷围岩结构变形机理；采用正交参数数值实验，分析合理切顶参数下沿空巷道大结构与围岩小结构间稳定的主次影响因素及作用规律，建立基于主要影响因素的切顶成巷围岩结构变形分析力学模型。

本项目以厚层砂岩顶板沿空切顶成巷及围岩结构变形机理为研究中心，通过相似模拟、数值模拟、理论分析、现场试验及测试等方法展开研究工作，项目取得了如下创新性成果：.（1）通过相似模型试验、理论分析、数值计算研究了沿空侧厚层砂岩顶板切顶断裂影响因素、作用规律、作用机理：通过预制切缝岩板来压荷载仅为常规无切缝岩板来压荷载的61.8%，下降38.2%，卸压作用明显。基于板理论解析解，推导了切顶条件下沿空巷道悬板破断距离计算公式，分析了切顶对沿空巷道悬板破断的影响力学机理。采用岩石破裂软件，分析了厚层砂岩悬顶长度、切顶参数、切顶支护阻力、水平挤压力、砂岩硬度等关键参数对沿空侧向厚层砂岩顶板断裂扩展、断裂特征及断裂结构失稳的影响及作用机理。采用砌体梁理论，研究了有利于围岩结构稳定的切落、结构断裂状态下的合理切顶参数确定方法。.（2）采用相似材料模拟实验，研究厚层砂岩顶板切缝扩展完成后，含扩展后切缝的沿空侧顶板与上覆岩围岩的移动变形破坏规律，以及厚层砂岩顶板沿空侧向顶板断裂成巷力学机理。采用三维数值软件，研究了含切缝扩展后断裂结构面条件下，沿空侧向上覆岩移动与沿空巷道切顶顶板变形间相互作用时空加卸载规律，揭示切顶成巷顶板变形机理。.（3）通过正交参数数值模拟实验，研究最佳切缝断裂状态下沿空侧顶板大结构与巷道围岩小结构稳定的主次影响因素作用规律，揭示切顶成巷变形机理。采用理论力学，建立厚层砂岩沿空切顶顶板结构力学模型，推导了其平衡力学条件和防止二次断裂的力学条件。建立切顶短臂梁结构力学模型，采用势能原理，推导了顶板悬臂长度产生的变形量计算方法提出了沿空侧厚层砂岩顶板围岩加卸载变形规律分区及对应变形机理，并根据分区变形机理提出了分区控制对策，现场应用后取得良好效果。