The fracturing of hard roofs in different layers would result in complex ground pressure on the working face, such as supports collapsed and severe roadway deformation. However, the mechanism of the ground pressure induced by hard roof fracturing in different layers is still unclear. In the paper, a physical model of a 20 m extrathick coal seam mined with hard roofs existing was established based on the physical simulation similarity criterion. The overburden fracturing structure, abutment stress distribution, and failure characteristics of the coal body were monitored by a noncontact strain measurement system and resistance strain gauges, to reveal the mechanism of ground pressure induced by hard roof fracturing. Furthermore, on-site measurement was used to monitor and analyze the ground pressure affected by hard roofs in different levels. The results provide a theoretical basis for the control of ground pressure in extrathick coal seam mining with hard roofs.

中文翻译：

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特厚煤层开采不同层数硬顶板压裂地压研究

不同层数的硬顶板的破裂会导致工作面的复杂地压，如支座倒塌和巷道严重变形。然而，不同层位硬顶板压裂诱发地压的机理尚不清楚。本文基于物理模拟相似性判据建立了硬顶板开采的20 m特厚煤层的物理模型。通过非接触式应变测量系统和电阻应变仪监测煤体上覆压裂结构、台肩应力分布及破坏特征，揭示硬顶板压裂诱发地压的机理。此外，还通过现场测量来监测和分析不同层次硬屋顶对地压的影响。