An experimental study on permeability characteristics of coal with slippage and temperature effects

Abstract

Ground temperature rises with the increase of mining depth. In this study, in order to investigate the seepage properties of coal with slippage and temperature effects, a thermo-fluid-solid coupling experiment on the methane-bearing coal was performed via the triaxial servo-controlled seepage equipment. Then, the permeability of coal in the gas loading-unloading processes was measured under different temperatures. Finally, a fractal slippage effect model with the temperature effect was developed to study the influences of pore pressure and temperature on permeability characteristics. The results indicate that as pore pressure rises, the axial strain of coal increases, while the radial strain decreases in the loading process. On the contrary, the axial and radial strains exhibit opposite trends with the rise of pore pressure in the unloading process. With the rise of temperature, the axial strain grows firstly and then falls, while the radial strain keeps decreasing. The permeability of coal decreases firstly and then levels off with the rise of pore pressure in both loading and unloading processes. Moreover, the slippage effect gradually weakens and flattens out with the rise of pore pressure. As the temperature rises, the slippage-induced permeability variation grows in the loading process, whereas it increases firstly and then goes down in the unloading process. The present work can provide a theoretical basis for coal seam gas extraction.