含瓦斯煤渗透率动态演化模型

Dynamic permeability model for coal containing gas

瓦斯排采过程中煤层渗透率会随着瓦斯压力的变化而动态变化,渗透率的动态演化主要是由有效应力改变及煤体基质收缩两种因素共同作用的结果。基于裂隙平板模型,理论推导了瓦斯解吸、扩散及渗流过程中煤体渗透率的变化关系。利用表面化学与有效应力理论,构建了该过程中基质收缩和有效应力增大等因素影响下的渗透率动态演化模型。根据矿井煤层实测参数,对模型进行了求解。计算结果显示:渗透率与瓦斯压力的关系呈现一种非对称"U"字型变化规律。最后通过渗透率计算结果与实验室实测结果的对比分析,两者吻合度较高,进而验证了理论模型的正确性。

With the changes of gas pressure during the gas drainage process,the dynamic evolution of seam permeability occurs. The dynamic evolution of coal permeability was the result of interaction of matrix contraction and effective stress. In the paper,the change relationship of coal seam permeability during the gas desorption,diffusion and percolation process was theoretically deduced based on the fractured plate model. A dynamic evolution model on permeability was established based on surface chemistry theory and effective stress principle. The model was validated according to the measured parameters in coal mines. The results show that the relationship between permeability and gas pressure is asymmetric U-shaped variation law. It closely matches the experimental results in the laboratory. Therefore,the correctness of this model is verified.