| The occurrence of coal in China is complex,especially the possibility of coal and gas outburst disaster in thick coal seam increases sharply.Some typical outburst accidents show that the outburst mainly occurs near the structural belt,and the area is mainly loose and fragile structural coal.The biggest change is to greatly increase the gas adsorption/desorption capacity.In this paper,using the method of combining laboratory experiment and theoretical calculation,under the guidance of pore measurement theory,coal adsorption/desorption kinetics and gas energy theory,the relationship between pore structure and adsorption desorption characteristics of coking coal is analyzed,the influence of tectonic movement on pore characteristics of coking coal is clarified,and the promoting effect of rapid desorption characteristics of structural coal on outburst process is determined.Tectonic movement has caused great changes in the pore structure and shape of coking coal.Among them,the pore volume and specific surface area of structural coal are 1.23～2.97times and 2.08～6.93 times that of primary coal,indicating that structural movement will promote the evolution and development of pores;The pores in structural coal mainly exist in the form of micropores,with pore volume of 6.141～12.434 cm~3/g,accounting for28.90%～40.94%of the total pore volume,and specific surface area of 5.011～9.194 cm~2/g,accounting for 72.16%～78.46%of the total specific surface area;The pulverization process of coking coal will increase the complexity of pore structure,but the increase of micropore of structural coal is smaller than that of primary coal,which is reflected in the decrease of micropore proportion,which indicates that the formation of structural coal will change the pore structure of coal,and then improve the adsorption capacity and gas fluidity of coal.By changing the pore structure that affects the adsorption capacity of coking coal,the tectonic movement increases the limit gas adsorption capacity by 23.67%～125.54%compared with primary coal,and the limit gas adsorption capacity of tectonic coal and primary coal increased by 1.06～1.93 times with the decrease of particle size,respectively.The fractal dimension of the pore structure of tectonic coal has decreased,indicating that geological tectonic action has damaged the matrix of tectonic coal sample pores,making the pore structure simple and single,and is affected by the degree of coal pulverization.In addition,the evolution of pore structure of coking coal caused by tectonic movement also affects its gas desorption capacity;from the perspective of initial gas desorption amount,the gas desorption amount of tectonic coal before 60 s is 3.61～9.13 mL/g,which is 1.45～5.75 mL/g of primary coal(1.45～5.75 mL/g).The tectonic coal with the same particle size has a stronger desorption capacity than the primary coal.The initial gas desorption rate of the tectonic coal is5.5829～16.41 mL/g·min,which is 1.28～1.92 times that of the primary coal(4.3645～8.5324mL/g·min);coking coal pore size and pore shape development characteristics affect desorption characteristics,tectonic movement makes coking coal pulverized and promotes pore development,and simplifies pore structure,thereby enhancing gas flow in coal,improve the desorption capacity.Tectonic coal is one of the necessary conditions for coal and gas outburst.First,in the initial stage of desorption,the gas adsorbed by tectonic coal is more likely to move from the interior to the surface;secondly,the gas desorption rate characteristic of pulverized tectonic coal is extremely fast.The power of the rock is greater.Specifically,the gas expansion energy of the Shaqu tectonic coal sample is between 0.808～3.683 J,which is 1.86～3.97 times that of the primary coal(0.41～1.616 J).The estimated critical outburst particle size of tectonic coal is2.761,which is 3.93 times that of primary coal(0.702),which also indicates that the risk of tectonic coal outburst increases. |
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