COUPLING MODEL OF STRESS-DAMAGE-FLOW AND ITS APPLICATION TO THE INVESTIGATION OF INSTANTANEOUS SEEPAGE MECHANISM FOR GAS DURING UNLOADING IN COAL SEAM WITH DEPTH
Abstract：On the basis of basic theories of gas flow and coal deformation，the coupled gas-rock model for investigating the failure process of coal-rock is established by introducing the related equations governing the evolution of stress，damage and gas permeability along with the deformation of coal and rock. Implemented with rock failure and process analysis code (RFPA)，this model can be used to capture the evolution of gas permeability in coal seam at great depth and the distribution of gas pressure around the drilling hole，and explore the instantaneous seepage mechanism of gas flow. From the simulated results，it can be found that the coal seam，located around 67 m above the excavated seam，is under unloading state and its gas permeability dramatically increases about 2 000 times as that excavated in underlying coal seam，and the size of the unloading region is around 70 m in diameter. The simulated results are in good accordance with the in-situ results. Therefore，it is safe to say that this numerical tool is of significance in both theory and practice to investigate the evolved mechanisms of gas permeability and gas drainage.
