In the process of the gob-side roadway retaining by roof cutting, the retractable U-shaped steel (RUSS) has a broad application prospect in the stability control of gangue rib. In order to establish RUSS support design method, the working mechanism and mechanical properties of RUSS are studied by using theoretical analysis, numerical experiment and field test. The research results show that RUSS will be subjected to multiple loads of roof deformation, gangue impact and lateral pressure of gangue rib during service; The failure of RUSS is a gradual process, the lateral pressure of gangue rib is identified as the key factor leading to failure of RUSS; The mechanical properties of RUSS can be effectively improved by increasing the overlap ratio and section size. Under the same impact energy, the peak impact force of U36 steel is 17.9% and 29.9% higher compared to U29 and U25, respectively. When the overlap ratio increases from 0.45 to 0.6, the instability critical load of RUSS increases by 32.4% and the deformation decreases by 31.1%; Finally, according to the results of theoretical analysis and numerical experiments, a standardized design method of RUSS is proposed, and applied on the S1201 working face of the Ningtiaota Coal Mine. The field monitoring data show that the design scheme of RUSS is rational.

中文翻译：

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可伸缩U型钢脉石防护结构的工作机理及力学性能研究


在顶板切割对采空侧巷道进行支护过程中，可伸缩U型钢（RUSS）在脉石肋的稳定性控制中具有广阔的应用前景。为建立RUSS支撑设计方法，通过理论分析、数值实验和现场试验等方法，对RUSS的工作机理和力学性能进行了研究。研究结果表明：RUSS在服役过程中会承受顶板变形、脉石冲击和脉石肋侧向压力的多重载荷;RUSS 的破坏是一个渐进的过程，脉石肋的侧压被认为是导致 RUSS 失效的关键因素;通过增加重叠比和截面尺寸，可以有效改善 RUSS 的力学性能。在相同的冲击能量下，U36 钢的峰值冲击力分别比 U29 和 U25 高 17.9% 和 29.9%。当重叠比从 0.45 增加到 0.6 时，RUSS 的失稳临界载荷增加了 32.4%，变形减少了 31.1%;最后，根据理论分析和数值实验结果，提出了RUSS的标准化设计方法，并应用于宁条塔煤矿的S1201工作面。现场监测数据表明，RUSS 的设计方案是合理的。