Pretensioned partially encapsulated resin bolting with mesh systems (PPERBMSs) are commonly employed in underground mines, particularly for soft coal gateways requiring immediate support. However, the behavior of bolts and reinforced coals has not been explained, and supporting schemes are determined by engineering analogy and experience. Herein, two large-scale physical models of extremely soft coal gateway sidewalls, reinforced with traditional and improved PPERBMSs, were constructed to probe the performance of pretensioned bolts and the deformation evolution of reinforced coal during roadway driving and panel extraction. Results reveal the bolting effect distribution characteristics of traditional PPERBMS. The mechanism and mode of bolts-mesh-surrounding coal system (BMSCS) instability were analyzed. The control effects of the two supporting schemes were compared, and stability-controlling principles for extremely soft coal roadways were proposed. High bolt pretension force and mesh stiffness are found to be important for improving the bearing capability of BMSCS, especially for reducing the extent of squeezing deformation and severe failure zones in shallow coals. The control method of “high-pretension-force bolts + fine mesh steel–plastic or rhombic screen + high-stiffness welded wire mesh + long bolt/cable for compensating reinforcement at key parts” is proposed to promote the formation of a supporting force interaction zone within surface and shallow coals, reduce the weakly reinforced region causing BMSCS structural instability, and improve the stability and bearing capability of the interaction zone in the bolt anchorage section. These findings are helpful for understanding the bolting effect of PPERBMSs and could provide guidelines for bolting design in soft coal roadways.

中文翻译：

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预张紧部分包封树脂锚杆与网格系统对极软煤通道的控制效果：大规模实验研究

带有网状系统的预拉伸部分封装树脂螺栓 (PPERBMS) 通常用于地下矿井，特别是对于需要立即支撑的软煤通道。然而，锚杆和加筋煤的行为尚未得到解释，支护方案由工程类比和经验确定。在此，构建了两个采用传统和改进 PPERBMS 加固的极软煤通道侧壁的大型物理模型，以探讨预紧螺栓的性能以及在巷道掘进和面板提取过程中加固煤的变形演化。结果揭示了传统PPERBMS的锚固效应分布特征。分析了锚杆-网-围煤系统(BMSCS)失稳的机理和模式。对比了两种支护方案的控制效果，提出了极软煤巷道的稳定控制原则。研究发现高螺栓预紧力和网格刚度对于提高 BMSCS 的承载能力很重要，特别是对于减少浅层煤层的挤压变形和严重破坏区的程度。提出“高预紧力螺栓+细网钢-塑料或菱形筛网+高刚度电焊网+关键部位补强长螺栓/索”的控制方法，促进支撑力相互作用的形成表层及浅层煤层内带，减少造成BMSCS结构失稳的弱加强区，提高锚杆锚固段相互作用带的稳定性和承载能力。