Abstract The low gas extraction concentration is one of the main factors that affect the prevention and control effect of coal and gas outburst. Based on this, the factors of air leakage around the roadway and borehole are analyzed. The effect of extraction time, seal length and air leakage on the gas concentration is discussed by the fluid-solid coupling model, which is proved by the borehole environmental parameter instrument.The research findings show :(1) Influenced by roadway excavation and drilling, a large number of cracks are created inside the coal around the roadway and the boreholes, which are the main air leakage channels for the air to flow from roadway into borehole; (2) Inside the borehole, the closer it is to the bottom of the borehole, the fewer the cracks in the coal seam, the higher the gas concentration. The critical point of air leakage in which the gas concentration is 100 % moves continuously to the bottom of the borehole with extraction time, until it is stable. The effective sealing length must exceed the position of critical point of air leakage; (3) The gas concentration is related to the sealing length and the amount of air leakage. Increasing the sealing length, and reducing the air leakage can greatly improve the extraction efficiency. Based on the above results, combined bag-type segmented grouting technique, which is to inject different sealing materials into different regions divided by the stress, is proposed to block the air leakage channel by comparing the crack characteristics of the coal surface in the abnormal stress zone and the normal stress zone by SEM technology. According to the field test results, the application of the new sealing technology blocks the crack channel, improves gas concentration and reduces the risk of coal and gas outburst. The results have important guiding significance for improving gas utilization rate, reducing greenhouse gas emission and enhancing safety in production.

中文翻译：

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基于气-气混流耦合模型的煤层预抽瓦斯钻孔密封效果研究

摘要 瓦斯抽采浓度低是影响煤与瓦斯突出防治效果的主要因素之一。在此基础上，分析了巷道和钻孔周围漏风的因素。采用流固耦合模型讨论了抽取时间、密封长度和漏气量对瓦斯浓度的影响，并通过钻孔环境参数仪进行了验证。研究结果表明：（1）受巷道开挖和钻探的影响，巷道及钻孔周围煤体内部产生大量裂缝，是空气从巷道流入钻孔的主要漏风通道；(2)钻孔内部，越靠近钻孔底部，煤层裂缝越少，瓦斯浓度越高。气体浓度为100%的漏气临界点随着抽采时间不断向井底移动，直至稳定。有效密封长度必须超过漏气临界点位置；(3)气体浓度与密封长度和漏气量有关。增加密封长度，减少漏气，可大大提高抽气效率。基于以上研究结果，通过对比异常应力下煤面的裂纹特征，提出将不同密封材料注入受应力划分的不同区域的组合袋式分段注浆技术封堵漏风通道。区和正应力区通过 SEM 技术。根据现场测试结果，新封堵技术的应用封堵裂缝通道，提高瓦斯浓度，降低煤、瓦斯突出风险。研究结果对提高气体利用率、减少温室气体排放、加强安全生产具有重要指导意义。