Hard roof is the primary concern of strata control in underground mining. Various techniques have been utilized to fracture the hard roof and control the failure of strata. Understanding the impact of cracks on strata behaviour is vital for optimizing strata control strategies. In this study, the hard roof was regarded as a beam structure with different loading, support, and boundary conditions. The equivalent spring model was adopted to represent the edge-cracked section of the hard roof, which allows additional rotation at the crack location. A piecewise-defined function was developed for solving equations of hard roof in the vicinity of the crack section. By combining the hard roof beam model and the equivalent spring model, the impact of a crack on the hard roof can be measured. A case study was carried out to explore the impacts of crack location and crack depth on the mechanical state of the hard roof. Results showcase the failure of the hard roof controlled by the crack depth and greatly influenced by the crack location. From the perspective of coal burst prevention, roof fracturing should be implemented at the high-stress area of strata, whereas it has been challenging in practice to determine such a location precisely. To address this challenge, it was suggested that hard roof fracturing should be carried out before coal seam de-stressing, increasing the likelihood of a crack occurring in a high-stress area. By adopting the proposed method, the mechanical state of the edge-cracked hard roof can be quantified.

中文翻译：

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地下采矿中边缘开裂硬顶板的失效：分析研究


硬顶板是地下采矿中地层控制的主要关注点。已经使用了各种技术来破坏硬屋顶并控制地层的破坏。了解裂缝对地层行为的影响对于优化地层控制策略至关重要。在本研究中，硬屋顶被视为具有不同载荷、支撑和边界条件的梁结构。采用等效弹簧模型来表示硬屋顶的边缘裂纹部分，这允许在裂纹位置进行额外旋转。开发了一个分段定义函数，用于求解裂缝截面附近的硬屋顶方程。通过结合硬屋面梁模型和等效弹簧模型，可以测量裂缝对硬屋面的影响。通过案例研究，探讨了裂缝位置和裂缝深度对硬屋顶力学状态的影响。结果表明，硬屋顶的破坏受裂缝深度控制，并受裂缝位置的影响很大。从防煤冲的角度来看，顶板压裂应在地层的高应力区域实施，而在实践中如何精确确定该位置一直具有挑战性。为了应对这一挑战，建议在煤层减压之前进行硬顶板压裂，这增加了高应力区域发生裂缝的可能性。通过采用所提出的方法，可以量化边缘开裂硬屋顶的力学状态。