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低透气性坚硬煤层联合卸压增透关键技术研究

Study on key technology of combined pressure relief and permeability enhancement in low permeability hard coal seam

  • 摘要: 基于焦作某矿煤层呈现高瓦斯含量、低渗透性、硬度高及复合煤层等特点,且矿区不具备开采保护层条件的情况,为提高冲孔效果及瓦斯抽采效果,提出“松动爆破‒机械造穴‒水力冲孔”联合增透技术;运用ANSYS/LS-DYNA有限元分析软件对不同的钻孔间距下的裂隙扩展状态进行模拟;对装药密度、装药结构与装药量等爆破参数进行了现场考察;利用PFC2D数值模拟软件对不同造穴钻孔直径下的裂隙发育范围进行模拟;对刀具开闭程度与水压的关系进行了调试。结果表明:在辅助孔的导向作用下,在2孔之间生成贯通裂隙面,且模拟出爆破孔与辅助孔最佳间距为4 m;最佳的装药结构为使用联合增透技术后“改造药仓3卷并排装药”,合理的装药密度为1.02 kg/m;通过PFC2D进行模拟确定合理的扩孔直径为500 mm;现场进行水压与刀臂张开度测试,显示当水压达到6 MPa时,造穴刀臂能完全打开;现场工业性试验实施后,与矿井常规的水力冲孔措施相对比,冲孔速度提高1.21倍;冲孔效率提高1.23倍,钻孔冲煤量提高1.09倍;抽采浓度初始值、60 d值、120 d值分别增加20%、14%、16%。数值模拟与现场工业性试验结果均证明:提出的联合增透技术在低透气性硬煤中能够提高冲孔效果及抽采浓度,为其他低透气性坚硬煤层的瓦斯治理提供了参考。

     

    Abstract: Based on the characteristics of high gas content, low permeability, high hardness and composite coal seam in a coal mine in Jiaozuo, and the lack of mining protective layer conditions, in order to improve the punching effect and gas drainage effect; the combined anti-reflection technology of “ loose blasting-mechanical cavitation-hydraulic punching” is innovatively proposed. The ANSYS/LS-DYNA finite element analysis software is used to simulate the crack propagation state under different borehole spacing. The blasting parameters such as charge density, charge structure and charge amount were investigated on site. PFC2D numerical simulation software was used to simulate the fracture development range under different hole diameter. The relationship between the degree of tool opening and closing and water pressure was debugged. The results show that under the guidance of the auxiliary hole, a penetrating fracture surface is generated between the two holes, and the optimal distance between the simulated blasting hole and the auxiliary hole is 4 m; the best charge structure is to use the combined anti-reflection technology to transform the three-volume parallel charge of the drug warehouse, and the reasonable charge density is 1.02 kg/m. The reasonable reaming diameter was determined to be 500 mm by PFC2D simulation. The field test of water pressure and knife arm opening shows that when the water pressure reaches 6 MPa, the hole-making knife arm can be fully opened. After the implementation of the on-site industrial test, Compared with the conventional hydraulic punching measures in the mine, the punching speed is increased by 1.21 times. The punching efficiency is increased by 1.23 times, and the amount of coal flushing per meter of borehole is increased by 1.09 times. The initial value, 60 d value and 120 d value of the extraction concentration increased by 20%, 14% and 16% respectively. Combined with numerical simulation and field industrial test results, it is proved that the proposed combined antireflection technology can improve the unching effect and extraction concentration in low permeability hard coal, which provides a reference for gas control in other low permeability hard coal seams.

     

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