坚硬煤层水射流切缝卸压效应研究

    Research on the unloading effect of hydraulic jet cutting in hard coal seam

    • 摘要: 煤矿冲击地压灾害防治的关键是实现煤层快速卸压,高压水射流切缝技术是煤层卸压防冲的有效手段。通过开展煤层水射流切缝钻孔卸压效应研究,可确定安全高效的切缝钻孔解危卸压合理参数。本文分析了水射流破煤过程及煤体破坏类型,将破煤过程划分为水锤压力和滞止压力两个阶段。基于水射流动量定理和Boussinesq-Flamant模型,建立了水射流最大切缝深度理论公式,以济宁三号煤矿3煤层为研究对象,开展地面切缝深度试验验证了射流压力与切缝深度的对应关系。测试结果表明,80 MPa、90 MPa、100 MPa压力下对应的切缝深度分别为1.24 m、1.46 m、1.52 m。理论分析了静载卸压机理,建立顶板沉降高度同割缝区域煤体支承压力对应关系。分析了切缝缝槽的动载阻隔作用,阐述了切缝卸压防冲机制。在济宁三号煤矿12306回采工作面辅顺开展超高压水射流切缝卸压试验,分别考察切缝半径、径向应力与轴向应力卸压效果。通过现场试验表明:在3煤层条件下,当切缝压力为100 MPa时切缝半径达1.55 m。钻孔径向卸压影响范围2~3 m,在钻孔轴向方向上孔深10 m处卸压效果显著。在孔口5 m处受切缝缝槽应力转移影响,煤体内部应力呈现小幅度上升,切缝缝槽在钻孔轴向方向上应力影响范围3 m,为冲击地压煤层大区域卸压提供合理的参数指导。

       

      Abstract: The key to preventing and controlling rock burst disasters in coal mines lies in achieving rapid pressure relief within coal seams. High-pressure hydraulic jet cutting is an effective technique for coal seam destressing and burst prevention. By investigating the pressure relief effect of hydraulic jet cutting boreholes, reasonable and efficient parameters for hazard mitigation can be determined. This study analyzes the coal breaking process and failure types induced by hydraulic jets, dividing the breaking process into two stages: the hydraulic hammer pressure stage and the stagnation pressure stage. Based on the hydraulic jet momentum theorem and the Boussinesq-Flamant model, a theoretical formula for the maximum cutting depth is established. Taking the 3lower coal seam of Jining No.3 Coal Mine as the research object, surface cutting depth tests are conducted to verify the relationship between jet pressure and cutting depth. Test results show that the cutting depths at pressures of 80 MPa, 90 MPa, and 100 MPa are 1.24 m, 1.46 m, and 1.52 m, respectively. The mechanism of static load relief is analyzed theoretically, and the relationship between roof subsidence and the abutment pressure of the coal in the slotted zone is established. The dynamic load blocking effect of the slot is analyzed, and the pressure relief and burst prevention mechanism of cutting is elaborated. Ultra-high pressure water jet cutting and pressure relief tests are carried out in the auxiliary transport roadway of the 123 lower 06 longwall face in Jining No.3 Coal Mine, and the cutting radius as well as radial and axial stress relief effects are investigated. Field tests demonstrate that, under the conditions of the 3 lower coal seam, the cutting radius reaches 1.55 m at a jet pressure of 100 MPa. The radial pressure relief influence range of the borehole is 2-3 m, and a significant pressure relief effect is observed at a borehole depth of 10 m in the axial direction. At a distance of 5 m from the borehole collar, the internal stress of the coal increases slightly due to stress transfer from the slot, and the stress influence range of the slot along the borehole axis is 3 m. These findings provide reasonable parameter guidance for large-scale pressure relief in rock burst-prone coal seams.

       

    /

    返回文章
    返回