高位关键层整层预裂下岩层结构随块度演化模式及防冲卸压效果

Structural evolution model and pressure relief effect of whole-layer pre-fracture in high-level key strata

  • 摘要: 针对坚硬顶板型冲击地压突发性强、破坏力大、影响范围广的特点,主动卸压防冲成为煤矿坚硬顶板型冲击地压区域解危的重要措施。在地质条件复杂的多关键层工作面中进行低位卸压时,易面临卸压范围有限导致的卸压效果差等问题,为此创新性地提出高位关键层整层预裂卸压技术,应用已有理论分析了不同预裂块度下的顶板关键层结构模型和演化过程,提出了随着预裂块度的变化,高位预裂层存在“砌体梁”—“短砌体梁”—“失稳结构”—“碎裂层”的结构演化模式,给出了合理预裂间距的确定方法。针对某矿2412工作面复杂的地质条件,结合预裂块度演化理论,选择了合适的预裂爆破层位与预裂间距,进行了高位关键层整层预裂爆破。通过工作面在常规开采区域和高位整层预裂卸压区域的支架压力、微震与巷道应力对比分析,验证了高位关键层整层预裂爆破的卸压效果。研究结果表明:高位关键层整层超前预裂爆破对高位厚硬岩层起到了显著的弱化作用,在工作面推进过程中降低了巷道应力,支架动载系数、 来压时长占比都有不同幅度的减小,且显著减少了2 kJ以上的微震事件数量和能量,有效降低了巷道和工作面的冲击风险,为类似地质条件下的冲击地压主动防控提供了可借鉴的理论依据和实践经验,对于推动我国煤矿安全生产技术的进步和发展具有重要意义。

     

    Abstract: Given the characteristics of strong suddenness, great destructive power, and wide impact range of hard roof-type coal bursts, proactive pressure relief has become a crucial mitigation measure for coal mines in such areas. In complex multi-key stratum working faces, low-level coal-rock pressure relief is often limited in range, leading to poor effectiveness. To address these issues, an innovative technique of whole-layer pre-fracture for pressure relief in high-level key strata is introduced. The structural model and evolution process of the key strata under different pre-fracture blocks are analyzed, and the structural change mode of the high key strata from “voussoir beam” to “short voussoir beam” to “unstable structure” to “fracture layer” is proposed, and the method for determining the optimal pre-fracture spacing has been provided. In light of the complex geological conditions of the 2412 working face at a Coal Mine, and based on the theory of pre-fracture block size variation, appropriate pre-fracture blasting layers and spacing are selected to conduct whole-layer pre-fracture blasting in high-level key strata. Subsequently, a comparative analysis of support pressure, microseism, and roadway stress between the conventional mining area and the high-level whole-layer pressure relief area is conducted, verifying the pressure relief effect of the whole-layer pre-fracture blasting in high-level key strata. The research results show that pre-fracture blasting has a weakening effect on the high thick and hard rock layer. During the advancing of the working face, roadway stresses are effectively reduced, and both the dynamic load coefficient of the hydraulic supports and the proportion of weighting duration are decreased. This decreases the number of microseismic events above 2000 J in the high-position rock strata, and effectively reduces the impact risk of the roadway and working face. This study provides a valuable theoretical and practical foundation for proactive coal burst prevention under similar geological conditions, contributing significantly to the advancement of coal mine safety technology in China.

     

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