Study On The Construction And Numerical Simulation Of The Coupling Model Of The Thermal Fluid Solid Multi Physical Field Of The Gas Bearing Coal Rock Mass

With the increase of coal mining depth,the temperature and ground stress of coal seam also increase,which makes the environment of gas seepage more complicated.This brings many technical problems to gas drainage and prevention.Studying the patterns of gas migration under the coupled field of "heat flow solid" can provide theoretical basis for gas drainage and prevention in coal mines.In this paper,mercury porosimetry is used to study the porosity characteristics of gas bearing coal rock mass with different buried depth.Moreover,the adsorption characteristics of gas bearing coal rock mass are considered by gas adsorption constant tester.Finally,based on Shaqu mine,a gas drainage model is built to study the characteristics of pressure,permeability,porosity and temperature around the borehole in the process of gas drainage to analyze the gas migration and distribution law under the coupling effect of "heat flow solid" three fields.The main conclusions are as follows:(1)The pore connectivity and pore volume of coal rock mass are affected by the burial depth.For the deep coal storage,the pore volume of macropore,mesopore and transition pore increased obviously.(2)At 30 ?,gas pressure increased from 0.775 mpa to 6.027 mpa,and gas adsorption content increased from 8.239 ml to 16.124 ml,increased by 195.7%.Under other temperature conditions,the gas adsorption content significantly increases with the promotion of gas pressure.At 40 ?,50 ?,60 ?,70 ?,the gas adsorption content has increased 208.7%,210.7%,222.3%,223.1%,which shows the pressure has a promoting effect on gas adsorption.(3)At a constant pressure of 0.775 mpa,the temperature increases from30 ? to 70 ?,and the adsorption content gradually decreases from 8.239 ml to 6.892 ml,down by 16.4%.With the increase of temperature,the values of adsorption constant a and b gradually decreased.The temperature increased from 30 ? to 70 ?,the values of a and b decreased by 10.6% and 42.8%,respectively.(4)Based on Shaqu mine,a gas drainage model is built to study the pressure,permeability porosity and temperature around the gas drainage borehole.It shows that the gas decreases with the increase of extraction time,most of the gas near the borehole is extracted,and the gas pressure far away from the borehole is also reduced,from 1.7mpa to 1.0MPa at the beginning,and the gas pressure is reduced by 42.2%.The curve of each time point decreases at the same speed,and the gas pressure reaches a certain value with the increase of extraction time.The permeability distribution has a great change.The farther away from the borehole,the greater the permeability is,and the farthest permeability is the largest.The porosity of coal decreases with the increase in extraction time.At the same time,the porosity of coal increases with the increase of drilling distance.With the increase of gas extraction time,the gas pressure,gas content and temperature of coal body descrease.In addition,in this process,there is also heat conduction between gas and coal and rock mass.