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Abstract Internal and external pore characteristics of raw coal sample of medium and high degrees of metamorphism which were obtained from Liupanshui mining area were studied by using TESCAN VEGA II scanning electron microscope(SEM)-energy-dispersive X-ray(EDX) and ASAP2020 specific surface microanalyzer. Triaxial seepage experiments of constant different gas pressures were carried out by independently developed traixial seepage device. The results show that：(1) There is positive correlation between metamorphic grade of coal and interior and external pore characteristics. The higher the metamorphic grade is，the higher the fractal dimension is and the greater the raw coal adsorption capacity and pore volume are. (2) There is also positive correlation between internal and external pore characteristics of raw coal and permeability. The more developed the internal and external pore，the greater the permeability is. (3) Under the conditions of constant mean effective stress and temperature，with the increasing gas pressure，at first the permeability sharply decreases and then tends to decrease gradually；and the relationship between permeability and gas pressure obeys exponential distribution. The research results have some theoretical significance to gas disaster prevention and development and utilization of coalbed methane of Liupanshui mining area.
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Received: 15 September 2011
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2012, Vol. 31 
