| Coal and gas outburst is an extremely complex dynamic type of disasters during coal mining. The four stages of its occurrence: preparation phase, excitation stage, development stage and end stage all relate gas migration law in coal seam. Permeability is the difficult degree indicator as gas migration in coal seam, and it has great significance on researching on coal and gas outburst mechanism, prediction and prevention. In this paper, taking the briquette coal samples got from Sanhui No.1Mine Tianfu Coal CO.,LTD K1 outburst seam and Chongqing Energy Investment Group Songzao C&E CO.,LTD Datong 1Mine 7# coal seam as the research object, using the self-developed fluid-solid-heat coupling with axis servo seepage system of coal, research on permeability of two coal samples in triaxial compression flow, cyclic loading and unloading confining pressure before the peak were carried on. Through the above research work, the main achieved results of this dissertation are as follow:1) The deformation law of coal sample was studied, and the influence that confining pressure and gas pressure exerting on peak strength, elastic modulus and deformation of coal sample was analyzed. The results show that the peak strength, elastic modulus and deformation of coal increase with the increasing of confining pressure, and decrease with the increasing of gas pressure. Besides, there is a linear relationship between peak strength and confining pressure,and a second nonlinear relationship between elastic modulus and confining pressure and gas pressure. The influence that confining pressure exerting on peak strength, elastic modulus and deformation of coal was significantly greater than that on the gas pressure. Furthermore, taking the confining pressure valued 4MPa as the boundary, two sub-type constitutive equation of coal sample were established under conventional triaxial compression.2) Considering stress-strain conditions, analyzed that confining pressure and gas pressure impacted on the permeability of coal sample, the relationship between them and permeability was power function; analyzed that deformation of coal sample influenced on permeability, similar results were got; The changes process of permeability under complete stress-strain was divided into five stages: compression stage, linear elastic stage, plastic harden stage, strain soften stage, plastic flow stage3) Under the cyclic loading conditions, stress-strain curves of coal sample generated the corresponding hysteretic loop and change of hysteretic loop closely is related to the number of cyclic loading: with the increase of the cycle number changes of hysteretic loop keep basically stable; Deformation and permeability of coal sample has the same trend with the increase of the number of cycle, permeability and number of cycles has power function relationship.4)Destruction process of briquette coal sample shows the characteristics of plastic creep under unloading confining pressure before the peak; Deformation of coal sample could be divided into uniform increase phase, strain accelerate increase phase and after the destruction stage; And compared to seepage under complete stress-strain, permeability characteristics under unloading confining pressure before the peak was divided into three stages: axial stress loading phase, constant phase and falling phase. Permeability and gas pressure, confining pressure has the opposite dynamic trend under unloading confining pressure; analyzed that gas pressure and confining pressure had been impact on them, two important parameters were the maximum permeability damage rate and permeability damage rate of coal.
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