厚硬顶板悬顶致灾机理及切顶控制技术研究

Study on disaster mechanism of thick and hard overhanging roof and top cutting control technology

  • 摘要: 针对侧向厚硬悬顶下临空巷道围岩变形大、失稳风险高的问题,以大同马脊梁煤矿3810工作面运输巷为工程背景,建立了厚硬侧向悬顶力学模型,确定合理切顶位置理论值为内错煤柱3.98 m。建立UDEC数值计算模型,分析了厚硬悬顶长度、断裂位置对煤柱应力分布及3810运输巷围岩变形的控制效果,结果表明:降低悬顶长度、在煤柱上方合理位置断裂,能够有效降低煤柱侧向应力集中程度,减少巷道围岩的破坏范围及变形。根据分析结果,确定煤柱采空区侧厚硬悬顶进行切顶卸压控制,促使厚硬顶板及时垮落,提高采空区顶板垮落带高度,从而降低煤柱承载的载荷并为煤柱提供侧向约束,提高煤柱承载性能。提出了厚硬侧向悬顶水压致裂切顶卸压控制方案并应用于现场,结果表明:3810运输巷采取水力压裂切顶措施后,巷道围岩变形得到显著改善;切顶后巷道两帮最大值移近量为600 mm,顶板最大下沉量为277 mm;相对于未采取切顶方案的区段,巷道变形量分别降低39.6%(两帮)、31.8%(顶板),巷道有效断面能够满足矿井安全高效生产的需要。

     

    Abstract: To address the challenges of significant deformation and high instability risks in the surrounding rock of unsupported roadways beneath a laterally thick and hard overhanging roof, this study focused on the 3810 working face transport roadway in Majiliang mine, Datong coalfield. A mechanical model of the laterally thick and hard overhanging roof was established, determining the theoretical values for the optimal top cutting position to be 3.98 m from the side of the external faulted coal pillar goaf. A UDEC numerical simulation model was developed to analyze the effects of roof length and fracture position on the stress distribution in the coal pillar and the deformation of the surrounding rock in the roadway. The findings revealed that reducing the overhanging roof length and fracturing at a reasonable position above the coal pillar effectively decreased the lateral stress concentration in the coal pillar, minimized surrounding rock failure, and reduced roadway deformation. Based on these results, a top cutting and pressure relief control strategy was proposed, targeting the thick and hard overhanging roof on the coal pillar's goaf side. This approach promoted timely collapse of the roof, increased the height of the roof fall zone, reduced the load on the coal pillar, and provided lateral confinement, thereby enhancing the bearing capacity of the coal pillar. A hydraulic fracturing-based top cutting and pressure relief plan was proposed and implemented in field practice. Post-application results indicated that the surrounding rock deformation of the 3810 transport roadway improved significantly. After top cutting, the maximum convergence of the roadway sides was reduced to 600 mm, and the maximum roof subsidence was 277 mm. Compared to sections without the top cutting measure, roadway deformation decreased by 39.6% (sides) and 31.8% (roof). The effective cross-sectional area of the roadway met the requirements for safe and efficient mining operations.

     

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