常规三轴压力下含瓦斯煤蠕变–渗流演化规律

The creep of coal rock has an effect on the gas permeability during methane extraction, coal bed gas exploitation and coal and gas outburst in mines. It is important to study the evolution of gas-filled coal creep-seepage and to obtain the coupling relationship between creep and seepage. In this paper, the evolution of gas-filled coal creep-seepage at different gas pressures was tested under conventional triaxial compression. The results showed that the axial strain grew by degrees as the stress increased step by step, until the destruction of coal samples. On the other hand, the gas permeability of coal was declined first and then raised, which can be concluded that micropores and microcraks within the coal body went through two changes. When the stress was less than the long-term strength of coal, the micropores and microcraks were closed; the gas seepage channels were blocked and then the gas permeability was on the decline. While the stress was greater than the long-term strength or the strain was greater than the strain-threshold of coal, the gas seepage was raised. The micropores and microcraks were adjoined and the gas seepage channels were expanded. Therefore, it is suggested that the stress exceeding long-term strength and the strain reaching a threshold are the prerequisites for the instability of coal and rock, which indicates a new way to study coal rock failure. Based on Kozeny-Carman formula, reasonable hypothesis and deduction, the coupling formula between strain and permeability was obtained. Moreover, this coupling formula was validated by the test data. The above findings would play an important role in the development of the stress field, fracture field and seepage field coupling theory.