综采面切眼坚硬直接顶板静态致裂放顶技术研究

Research on Static Fracturing and Roof Caving Technology for Hard Immediate Roof in Fully Mechanized Mining Face Crossheading

  • 摘要: 针对综采工作面初采悬顶问题,传统水力压裂与火工品爆破等技术存在效果不稳定、安全风险高、施工复杂等问题。因此,提出一种基于静态致裂剂(C−SCA)的绿色、高效放顶技术。通过实验研究发现,C−SCA与浆液式致裂剂同样具有高膨胀特性,其膨胀率达170%~200%,膨胀力达57.9 MPa。从工程实际出发,构建了C−SCA自由膨胀比率的概念,得到了C−SCA自由膨胀比率越大、最终作用于孔壁的膨胀力越小的演化规律。利用混凝土加围压的方式,模拟了大型岩体致裂工况,得到了孔间距为300 mm时,其所需应力和裂隙贯通时间较为适宜工程应用。利用CDEM数值模拟方法,针对切顶弱化措施条件下的坚硬岩层控顶效果开展模拟仿真评估,分析了弱化模式与未弱化模式两种条件下的顶板垮落规律。进行弱化的15221工作面在回采10 m内,基本顶出现破坏垮落,未进行弱化的15220工作面则在50 m时才出现垮落。通过分析工作面端头支架监测数据可以发现,采用静态致裂后,端头支架工作阻力稳定在25~35 MPa范围内,且架间阻力同步性好,整体波动幅度低。同时,对比了15221与15220工作面支架最大阻值、支架工作状态、单架超限时长等数据,使用C−SCA静态致裂的工作面优于不使用静态致裂的工作面。为进一步验证C−SCA的静态致裂效果,对两工作面现场监测数据也进行了对比分析,采用静态致裂技术的15221工作面初采期间漏风量显著低于15220工作面。15221工作面生产时粉尘浓度对比未致裂的15220工作面也有明显下降。研究结果表明,C−SCA对初采悬顶治理具有明显效果,C−SCA静态致裂技术为初采工作面坚硬悬顶治理提供了一种新的解决方案。

     

    Abstract: Regarding the issue of initial mining roof hanging in fully mechanized mining faces, traditional technologies such as hydraulic fracturing and explosive blasting suffer from unstable effectiveness, high safety risks, and complex construction. Therefore, a green and efficient roof−caving technology based on a static cracking agent (C−SCA) is proposed. Experimental studies show that C−SCA exhibits high expansion characteristics similar to slurry−type cracking agents, with an expansion rate of 170−200% and an expansion pressure of 57.9 MPa. From an engineering perspective, the concept of the free expansion ratio of C−SCA was established, revealing that a larger free expansion ratio results in a lower final expansion pressure acting on the borehole wall. By applying confining pressure to concrete to simulate large−scale rock mass cracking conditions, it was found that a borehole spacing of 300 mm provides suitable stress conditions and crack propagation time for engineering applications. Using the CDEM numerical simulation method, the effect of roof−cutting and weakening measures on controlling hard roof strata was simulated and evaluated, comparing the roof collapse patterns under weakened and non−weakened conditions. In the weakened 15221 working face, the main roof fractured and collapsed within 10 m of mining, whereas in the non−weakened 15220 working face, collapse occurred only after 50 m. Analysis of monitoring data from the face−end supports shows that after static cracking, the working resistance of the face−end supports stabilized within the range of 25–35 MPa, with good synchronization between supports and low overall fluctuation amplitude. Moreover, comparisons of maximum support resistance, support working conditions, and duration of excessive resistance per support between the 15221 and 15220 working faces indicate that the face using C−SCA static cracking outperformed the face without static cracking. To further verify the effectiveness of C−SCA static cracking, on−site monitoring data from the two working faces were compared and analyzed. The air leakage volume during initial mining in the 15221 working face using static cracking technology was significantly lower than that in the 15220 working face. Dust concentration during production in the 15221 working face was also notably reduced compared to the non−cracked 15220 working face. The research results demonstrate that C−SCA has a significant effect on managing initial mining roof hanging, and the C−SCA static cracking technology provides a novel solution for treating hard roof hanging in initial mining faces.

     

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