液氮对含水煤样裂隙疲劳增扩作用的试验研究

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。

Experimental Study of the Fatigue Crack Extension Influence of Liquid Nitrogen on Water Cut Coal Sample

In order to analyze the influence of liquid nitrogen immersion on the fatigue crack extension in water cut coal seam, dry coal samples, 50% water saturated coal samples and 100% water saturated coal samples were collected respectively, and a cyclic fatigue liquid nitrogen immersion experiment was carried out in laboratory. The changes of crack structure on coal sample surface before and after liquid nitrogen immersion was observed by laser microscope and the crack extension velocity was measured by sound wave tester. Results show that 1)liquid nitrogen immersion has no obvious effect on the dry coal samples, which were still intact after 10 immersion cycles; 2)the crack extension is mainly along the vertical direction to joint;3)the higher the water saturated degree is, the more obvious the crack extension of coal sample; 4) the higher the water saturated degree is, the shorter the immersion period required by liquid nitrogen immersion. The water saturation percentage of coal specimen has remarkable effect on the coal crack growth due to liquid nitrogen immersion.