Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof, making it imperative to identify the most suitable target stratum for effective control. Physical experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving (LTCC). A numerical model is established using the material point method (MPM) and the strain-softening damage constitutive model according to the structure of the physical model. Numerical simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic fracturing. The results show that ground hydraulic fracturing releases the energy and stress of the target stratum, resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing stratum. Ground hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures, dissipates the energy consumed by the fracture of the hard roof, and reduces the abutment stress. Therefore, it is advisable to prioritize the selection of the lower hard roof as the target stratum.

中文翻译：

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多重硬顶地面水力压裂目标层选择物理与数值研究


地面水力压裂对于远场硬顶的控制起着至关重要的作用，因此必须确定最合适的目标地层进行有效控制。根据工程特性进行物理实验，模拟长壁放顶煤放顶煤（LTCC）过程中顶板的逐渐塌陷。根据物理模型的结构，采用材料点法（MPM）和应变软化损伤本构模型建立数值模型。通过数值模拟分析了不同硬顶下地面水力压裂的LTCC过程。结果表明，地面水力压裂释放了目标地层的能量和应力，导致上覆岩层的压裂在水力压裂地层发生塌陷之前存在较大滞后。低硬顶地面水力压裂减少了水力裂缝的滞后效应，消散了硬顶破裂所消耗的能量，降低了邻台应力。因此，建议优先选择下部硬顶作为目标层。