Based on artificial freezing engineering practice, the comprehensive technology is suggested to realize safe and fast rock cross-cut coal uncovering, which mainly includes four steps of drilling, water injection wetting coal, gas drainage, and injection liquid nitrogen into coal seam. Freezing test of liquid nitrogen injection into coal is carried out to obtain the cooling curves, and comparing the test results, the numerical inverse method is applied to determine the thermal conductivity of coal seam. Then, the model of injecting liquid nitrogen into coal seam is established to simulate and analyze the aging characteristic of effective freezing radius. The results show that the thermal conductivity of wetting coal increases linearly with temperature decreasing. The periodic method with 8h intervals can be adopted to inject liquid nitrogen into coal seam, and the freezing wall is formed around the injection hole. With the increase of freezing time, the effective freezing radius (below 273.15 K) increases by power exponent, and the freezing speed in coal seam decreases gradually. This result will provide a theoretical basis for layout optimization of injection holes in rock cross-cut coal uncovering.

中文翻译：

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岩石横切开煤冻结法：煤层注入液氮有效冻结距离的时效特性

结合人工冻结工程实践，建议采用综合技术实现安全、快速的岩石横切揭煤，主要包括钻孔、注水润湿煤、瓦斯抽放、向煤层注入液氮四个步骤。对煤中注入液氮进行冷冻试验，得到冷却曲线，对比试验结果，采用数值反演法确定煤层的导热系数。在此基础上，建立了向煤层注入液氮的模型，对有效冻结半径的老化特性进行了模拟分析。结果表明，润湿煤的导热系数随温度的降低呈线性增加。可采用间隔8h的周期方法向煤层注入液氮，在注入孔周围形成冻结壁。随着冻结时间的增加，有效冻结半径（273.15 K以下）以幂指数增加，煤层冻结速度逐渐减小。该结果将为岩石横切煤层揭砂喷孔布局优化提供理论依据。