煤中瓦斯运移要经过脱附-扩散-渗流等贯序环节才能进入钻孔或巷道。大量有关残存瓦斯含量、煤的瓦斯吸附解吸残余变形及吸附解吸迟滞的研究显示，煤中瓦斯脱附扩散过程较吸附扩散过程存在不可忽略的附加阻力，其大小由扩散路径长度及复杂度所控制。脱附扩散附加阻力影响基质系统与裂隙系统间的质量交换，但当前被广泛的使用的双重孔隙煤体瓦斯运移模型并未考虑其影响，用于瓦斯抽采流场特性的理论分析时将使得瓦斯含量被低估。基质系统与裂隙系统间的质量交换也被称为窜流，窜流函数是计算基质系统与裂隙系统间质量交换量/速率的关键函数。为了修正煤层瓦斯运移模型，开展了以煤粒（煤柱）吸附解吸等温测试模拟裂隙压力恒定的窜流试验，提出了瓦斯脱附扩散迟滞压力用于定量评价附加阻力，修正了双重孔隙煤体窜流函数，并同试验结果进行了对比验证。获得如下成果：明确了瓦斯脱附扩散迟滞压力的概念与物理意义；当最大吸附平衡压力相同时，降压过程中瓦斯脱附扩散迟滞压力随粒径增大而增大，对于同一样品，瓦斯脱附扩散迟滞压力随压降值的增大而减小；使用修正模型模拟煤柱瓦斯解吸过程与实验获得的等温解吸数据匹配度较好，R2可达98.2%。随着开采深度增加，地应力增大，煤的基质尺度将大幅增大，脱附扩散迟滞压力对于煤层瓦斯运移的影响将更加显著，通过技术手段减小脱附扩散迟滞压力应成为深部煤层瓦斯治理或煤层气开发需深入研究的问题之一。

Gas desorption,diffusion and seepage make up the sequential gas migration pattern from coal seam to borehole or roadway. Plenty of studies on residual gas content,adsorption desorption residual deformation and sorption hysteresis on coal have revealed that there is non negligible additional resistance in the gas desorption process compared with the gas adsorption process,and the resistance is controlled by the length and complexity of the diffusion path. The additional resistance of desorption diffusion affects the mass exchange between the matrix system and the fracture system,but the widely used double pore coal gas migration model does not consider its effect,which will make the gas content underestimated when used in the theoretical analysis of gas drainage flow field. The mass exchange between the matrix system and the fracture system is also known as interflow,and the matrix fracture mass transfer function is the key function to calculate the mass exchange capacity/rate between the two systems. To modify the coal seam gas migration model,the coal particle (block) adsorption and desorption isotherm tests were used to simulate the interflow with constant fracture pressure,the gas desorption diffusion hysteresis pressure was proposed to quantitatively evaluate the additional resistance,and the matrix fracture mass function was modified and verified by comparing with the test results. The following results were obtained:the concept and physical meaning of gas desorption diffusion hysteresis pressure were clarified. When the maximum adsorption equilibrium pressure is the same,the gas desorption diffusion hysteresis pressure increases with the increase of particle size in the depressurization process. For the same sample,the gas desorption diffusion hysteresis pressure decreases with the increase of pressure drop. The simulation result of the gas desorption process of coal block based on the modified model can well match the isothermal desorption data,whose R2 value can reach 98.2%. As the in situ stress increases with the increase of mining depth,the matrix size of coal will be greatly increased,and the desorption diffusion hysteresis pressure of matrix fracture mass transfer will generate a more significant impact on gas migration in a coal seam. Reducing the hysteresis pressure of matrix fracture mass transfer by technical means should be one of the problems to be studied in the deep gas control or CBM development.

1 煤中瓦斯的脱附扩散的附加阻力

   1.1 煤中的瓦斯吸附与运移

   1.2 脱附扩散存在附加阻力的宏观表现

2 煤的瓦斯脱附扩散迟滞压力

   2.1 煤的吸附解吸迟滞测定试验

   3.2 瓦斯脱附扩散迟滞压力梯度

4 考虑瓦斯脱附扩散迟滞压力梯度的煤体瓦斯窜流函数

5 基于等温解吸数据的模型验证

   5.1 数值模型

   5.2 模拟结果

6 结论与展望