承压煤体瓦斯解吸-扩散特性实验研究

为了研究承压条件下含瓦斯煤的解吸-扩散特性,建立了受载煤体瓦斯扩散系数的动态演化模型,并采用单孔模型和双孔模型计算了粒度0.25~0.5,0.5~1和1~2 mm煤样在0~12 MPa轴向压力条件下的瓦斯扩散系数。实验结果表明:双孔模型计算结果与实验数据相关性系数均稳定在99.5%以上,拟合效果优于单孔模型,其中,宏观有效扩散系数在10~(-4)s~(-1)数量级上,高出微观有效扩散系数1~2个数量级;瓦斯解吸量、宏观/微观有效扩散系数随轴压升高呈先下降后波动上升的趋势,与受载煤体扩散动态理论模型相符;煤样粒度越大,宏观/微观有效扩散系数对应力越敏感,并且宏观有效扩散系数对应力的敏感性高于微观有效扩散系数;瓦斯解吸量、宏观/微观有效扩散系数随煤样粒度减小而增大。研究结果能为井下构造煤瓦斯扩散规律提供借鉴。

Experimental study on gas diffusion in coal under stress

In order to study the gas diffusion in coal underground,the gas desorbing process was recorded when coal particles within 0.25-0.5,0.5-1 and 1-2 mm were applied to axial stresses of 0-12 MPa,respectively.Then,the experimental data was fitted for the diffusion coefficient using the unipore model and the bidisperse model.According to the relationship between the diffusion coefficient and the porosity,the dynamic evolution model of the gas diffusion coefficient was established,which is in accordance with the experimental results.Results show that the bidisperse model can match the experimental data more perfectly than the unipore model.The diffusion coefficients of macro-pores were on the order of 10-4 s-1,which were 1-2 order higher than that of micro-pores.Both the desorbed gas and diffusion coefficients increased with the increasing stresses.The desorbed gas and diffusion coefficients increased with the decreasing size of coal particle.Coal samples with larger size were more sensitive to the stress,and the macro-pores showed more sensitive to stresses than the micro-pores.This study would provide some reference to understand gas diffusion in deformed coal underground.