1.School of Safety Engineering, China University of Mining and Technology, Xuzhou , China; 2.National Engineering Research Center of Mine Gas Control, Xuzhou , China

为探究煤在低温冻结石门揭煤过程中煤体未冻水含量的变化，采用低场核磁共振技术对褐煤、烟煤和无烟煤共3种类型的饱和试样进行测试，同时结合T2谱图从微观角度分析了冻融过程中未冻水在煤孔隙内的赋存分布情况和变化特征。试验结果表明：3种煤样在冻融过程中，其未冻水含量随温度变化呈现出相似的特征：在冻结过程中，可划分为3个阶段，波动段、急剧下降段和稳定段；在融化过程中，可划分为2个阶段，稳定增加段和急剧增加段，并且有明显的滞后现象；在冻结时，大孔隙内的水先开始相变成冰，然后是中孔，最后微、小孔内的水才开始明显下降；在融化时，微、小孔内的冰先开始融化；在同样的冻结温度区间内，烟煤和无烟煤中未冻水含量的降低程度要小于褐煤。

In order to discover the unfrozen water content variation of the coal from the low temperature frozen cross-cut passed through seam, a low-field nuclear magnetic resonance technology was applied to the test on three type saturated coal samples of the lignite, bituminous coal and anthracite coal. Meanwhile,in combination with the T2 spectrogram, from a microcosmic view, the paper had an analysis on the unfrozen water distribution and variation in coal pores in the freezing-thawing process. The experimental result showed that in the freezing-thawing process of the three different type coal samples, with the temperature varied, the unfrozen water would appear similar characteristics. In the freezing process, the process could be divided into three stages and they were a fluctuating stage, steeply reduced stage and stable stage. In the thawing process, the process could be divided into two stages and they were a stable increased stage and steep increased stage with an obvious lagging phenomenon. During the freezing period, the water in the big pores would firstly have a phase transition and then be in ice. Late the water in the medium pores, micro pores and small pores would finally be reduced obviously. In the thawing period, the ices in the micro and small pores would firstly be thaw. Within the same freezing temperature zone, the unfrozen water contents in the bituminous coal and anthracite coal would reduce less than the lignite.