Fire hazard-risk area in small coal pits can be found in the southern part of the Shigetai Coal Mine, a close-distance coal seam mining sector in the Shendong mining area, which is susceptible to the risk of harmful toxic gas intrusion, seriously threatening the safety of mining around the working surface. Aiming at this problem, a numerical model representing the mining activity on the close-distance coal seams was established to simulate the movement pattern of overlying strata and the development process of fractures based on the horizontal stress “normalization” technology. Also, the principal air-leak passageways were detected with the SF6 tracer analysis. On this basis, the influencing pattern of harmful toxic gas intruding into the working surface can be comprehensively analyzed, providing a basis for effectively preventing and controlling gas intrusion disasters. The research findings show that, after a lower coal seam has been mined, the caving zone ranges from 73 m to 94 m in height, and the fractured zone tends to develop all the way to the surface. Furthermore, shear fractures are the major passageways for air leakage, and the occurrence of gas intrusion disasters is basically taking place at the same time frame as the occurrence of roof weighting. Meanwhile, the harmful toxic gas intrudes the working surface through the fractures on the security coal pillars and shear fractures on the overlying strata. To prevent intrusion disasters from occurring, the applications of inorganic foaming and curing materials for filling were studied in combination with the actual engineering conditions. The construction grounds in sections where the fire hazard-risk area in small coal pits have not been stripped were drilled, and filling materials were poured into the goaf to create an isolation belt. As can be observed from the applied areas, constructing isolation belts to block the major air-leak passageways can effectively prevent the harmful toxic gases from intruding into the working surface, ensuring the safety of mining on the working surface.

中文翻译：

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近距离煤层火灾高危区有害有毒气体侵入防治技术

神东矿区近距煤层开采区石格台煤矿南部存在小煤坑火灾危险区，易受有害毒气侵入风险，严重威胁工作面周围的采矿安全。针对这一问题，基于水平应力“归一化”技术，建立了近距离煤层开采活动的数值模型，模拟了上覆地层的运动模式和裂缝的发育过程。此外，主要的漏气通道也通过 SF6 示踪分析检测到。在此基础上，可以综合分析有害有毒气体侵入工作面的影响规律，为有效防治瓦斯入侵灾害提供依据。研究结果表明，下层煤层开采后，崩落带高度为73 m～94 m，裂缝带一直发育至地表。此外，剪切裂缝是漏风的主要通道，瓦斯侵入灾害的发生基本与顶板加重发生在同一时间段。同时，有害有毒气体通过安全煤柱上的裂缝和上覆地层的剪切裂缝侵入工作面。为防止入侵灾害的发生，结合工程实际情况，对无机发泡固化材料在填料中的应用进行了研究。对小煤坑火灾危险区未剥离的地段进行施工场地钻孔，并在采空区注入充填材料，形成隔离带。从应用领域可以看出，在主要漏风通道上设置隔离带，可以有效防止有害有毒气体侵入工作面，确保工作面采矿安全。