复杂应力路径下含瓦斯煤渗透性变化规律研究

INVESTIGATION ON CHANGE RULE OF PERMEABILITY OF COAL CONTAINING GAS UNDER COMPLEX STRESS PATHS

通过含瓦斯煤渗透特性试验研究,系统分析复杂应力路径下含瓦斯煤渗透性的变化规律,建立含瓦斯煤渗透率与轴向压力、围压、瓦斯压力、围压升降、全应力–应变过程等之间的定性与定量关系,深入探讨各种不同应力路径下含瓦斯煤渗透性的控制机制和变化规律。结果表明,应力路径对含瓦斯煤的渗透率有重要影响:(1)含瓦斯煤渗透率随着轴向压力和围压的增大而减小,随瓦斯压力的增大而增大。(2)含瓦斯煤渗透率与轴向压力、围压和瓦斯压力均呈指数关系变化。(3)围压升、降过程中,含瓦斯煤渗透率会受到一定程度的损害,其损害程度可以用最大渗透率损害率和渗透率损害率来表征。同时,三维压缩条件下含瓦斯煤会发生二次密实效应。(4)三轴压缩下全应力–应变试验过程中,含瓦斯煤的渗透率呈"V"字型变化趋势;渗透率随煤样的应变先减小后增大,然后达到最大值,并且渗透率的增幅小于其减幅。

According to experimental investigation on permeability property of coal containing gas,the change rule of permeability of coal containing gas is analyzed systematically under complex stress paths.Quantitative and qualitative relations of the permeability of coal containing gas with axial pressure,confining pressure,gas pressure,loading-unloading of confining pressure and complete stress-strain process are established respectively.The controlling mechanism and change law of permeability of coal containing gas under different stress paths are discussed.The results show that the stress path has an important impact on the permeability of coal containing gas：（1） The permeability of coal containing gas decreases with the increase of axial pressure and confining pressure,while increases with the increase of gas pressure.（2） The relationships of permeability of coal containing gas with axial pressure,confining pressure and gas pressure obey approximately an exponential law.（3） During the loading-unloading process of confining pressure,the permeability of coal containing gas is damaged to a certain extent and this damage can be represented by the maximal damage rate and damage rate of permeability.At the same time,the results show that the second-compacting effect of coal containing gas will happen under the condition of triaxial compression.（4） During the complete stress-strain a test process under triaxial compression,the change trend of permeability of coal containing gas versus strain curve is V-shaped approximately.The permeability of coal sample decreases first,then increases with strain,and reaches its maximum finally.The increasing amplitude is less than the decreasing amplitude.