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Abstract Using self-made “triaxial stress thermal-hydro-mechanical coal containing gas permeameter”，an experimental study was carried out to investigate how the unloading speed of confining pressure influences the mechanical properties and gas permeability of containing-gas coal rock，under cooperation of different initial confining pressures and various gas pressures. The research result showed that from an aspect of mechanics，the coal would first undergo a stage of stress flat roof，after the unloading process began，and then a break would happen due to destabilization. When the confining pressure was unloaded at a higher speed，the destabilizing breakage was easier to happen on the coal which also represented shorter time to maintain at the stage of stress flat roof. During the unloading process of confining pressures，the time of coal being in the stage of stress flat roof showed a power function with the unloading speed of confining pressures. From an aspect of gas permeation，the permeability of coal was tightly relevant with its deformation and the changing trend of its volume strain could well reflect the changing trend of its permeability. When the confining stress was being unloaded，the permeability of coal varied in an experience of four stages and it kept increasing. The permeability of coal increased at a faster rate when the unloading speed was larger. During the unloading process of confining pressures，the permeability of coal being in the stage of stress flat roof showed an exponential function with the corresponding time.
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Received: 19 July 2010
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2011, Vol. 30 
