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为分析液氮注入对含水煤层裂隙疲劳增扩的影响,分别取干燥煤样、50%水饱和煤样和100%水饱和煤样,在室内开展了周期疲劳液氮浸泡试验,利用激光显微镜和声波测试仪测试液氮作用前后煤样表面裂隙结构和波速的变化。结果表明:1)经过液氮浸泡后,干燥煤样裂隙扩展效果不明显,10个浸泡周期后煤样仍完整;2)含水煤样的裂隙主要在垂直节理方向发生扩展;3)饱水程度越高,煤样裂隙扩展越显著;4)饱水程度越高,煤样液氮浸泡破坏所需的浸泡周期越短。煤样的饱水程度对液氮致裂效果影响显著。
In order to analyze the effect of liquid nitrogen injection on the fatigue crack growth of water-bearing coal seam, dry-type coal, 50% water-saturated coal and 100% water-saturated coal were taken respectively to carry out periodic fatigue liquid nitrogen immersion test in laboratory. Changes of Structure and Velocity of Fissure on Coal Sample Surface before and after Liquid Nitrogen Test with Sonic Tester. The results show that: 1) after the soaking of liquid nitrogen, the effect of fissure expansion of dry coal is not obvious, and the coal samples are still intact after 10 soaking cycles; 2) the fissures of water-bearing coal mainly expand in the direction of vertical joints; 3) The higher the degree of fracture, the more obvious the crack propagation is; 4) The higher the degree of water saturation, the shorter the immersion period required for liquid nitrogen immersion destruction. The degree of saturation of coal sample has a significant effect on the cracking effect of liquid nitrogen.