考虑蠕变效应的复合煤层定向水力冲孔工艺参数研究

    Research on process parameters of directional hydraulic punching considering creep effect in composite coal seam

    • 摘要: 随着我国煤矿开采深度和瓦斯治理难度的增加,复合煤层定向水力冲孔强化瓦斯抽采技术得到了一定的推广和应用。为了进一步提高复合煤层定向水力冲孔的效率和效果,开展了煤岩蠕变效应对定向冲孔卸压时间、冲孔间距、冲孔直径等参数的影响研究;根据蠕变效应理论和现场实际条件,提出了考虑蠕变效应的定向冲孔工艺参数模拟方案;通过数值模拟对比分析蠕变效应对定向水力冲孔的影响,设计了考虑蠕变效应的定向冲孔工艺参数,并通过现场试验进行验证。结果表明:相对于摩尔−库伦模型,考虑蠕变效应的模拟结果更符合现场实际情况;考虑蠕变效应后,复合煤层定向水力冲孔孔洞周边煤岩卸压区、塑性区、蠕变位移范围随着蠕变时间和冲孔直径增加而增加,钻孔之间煤岩蠕变卸压所需时间随着钻孔间距增大而增长;结合现场情况和考虑蠕变效应的复合煤层定向冲孔参数模拟结果,设计的冲孔压力为26 MPa、冲孔间距为6 m;复合煤层定向冲孔30 d内蠕变范围已覆盖钻孔之间煤岩,蠕变范围内均出现不同程度卸压,大幅缩短了卸压增透和抽采达标周期,同时提高了水力冲孔效率。

       

      Abstract: With the increasing depth of coal mining and the difficulty of gas control in China, the technology of directional hydraulic punching to enhance gas extraction in composite coal seam has been widely promoted and applied. In order to further improve the efficiency and effectiveness of directional hydraulic punching in composite coal seam, we carry out the study on the influence of coal rock creep effect on parameters such as directional punching pressure relief time, punching spacing, and punching diameter; based on the theory of creep effect and actual on-site conditions, a simulation scheme for directional punching process parameters considering creep effect is proposed, the influence of creep effect on directional hydraulic punching is compared and analyzed by numerical simulation, the process parameters of directional punching considering creep effect is designed and verified through on-site experiments. The results indicate that, compared to the Mohr Coulomb model, the simulation results of considering creep effect are more in line with the actual situation on site; when the creep effect is considered, the pressure relief zone, plastic zone, and creep displacement range around the directional hydraulic punching hole in the composite coal seam increase with the increase of creep time and punching diameter, and the time required for coal rock creep and pressure relief between boreholes increases with the increase of borehole spacing; based on the on-site situation and the simulation results of composite coal seam directional punching parameters considering creep effect, the designed punching pressure is 26 MPa and the spacing between holes is 6 m; the creep range has covered the coal and rock between the boreholes within 30 days of directional punching in the composite coal seams, and different degrees of pressure relief have appeared the creep range, which has greatly shortened the period of pressure relief and gas extraction, and at the same time, it has improved the efficiency of hydraulic punching. The research on process parameters of the directional hydraulic punching technology considering creep effect in composite coal seam is expected to further improve the efficiency of pressure relief and gas extraction.

       

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