Numerical Simulation And Analysis Of Gas Outburst Tendency Under Fluid Solid Coupling

Coal is the main energy source in China,and coal and gas outburst accident is one of the factors limiting its safe and efficient exploitation.In recent years,the increasing demand for coal mine safety has put forward higher requirements on research of the mechanism of coal and gas outburst and disaster prevention and control.Fluid solid coupling mechanism is one of the basic problems in the research of gas outburst mechanism and gas disaster prevention and control.Therefore,it is of great significance to study the interaction between coal seam and gas.In this paper,based on the damage field,the fluid solid coupling model is established.The model is solved by COMSOL software.Then this paper analyzes the law of gas migration and the tendency of gas outburst in the process of coal mining,and studies the law of gas migration in the process of drilling and drainage.Conclusions are as follows:(1)With the advancing of working face,the gas pressure decreases and the distribution of damage field increases in the front of the working face.(2)Considering the influence of mining on desorption of adsorbed gas,the principal stress direction of the coal seam in front of the working face is analyzed which indicating the third principal stress is the main cause of gas outburst.The area of gas outburst is determined according to direction of the third principal stress and damage field.The influence of overburden pressure and initial gas pressure on the gas outburst danger area is analyzed which indicating that when the overburden pressure and the initial gas pressure is greater,the tendency area of gas outburst is larger.(3)The gas migration rules were studied by means of numerical simulation in the borehole extraction process.In the initial stage of drainage,borehole flow is larger.With drainage,the gas flow rate decreases,and tends to be stable.The gas pressure decreases gradually with the extraction.(4)The influence of mining pumping negative pressure on drainage effect was analysised.It is found that when the suction pressure is lower,the borehole flow rate is larger and the extraction effect is better.In the initial stage of drainage,the negative pressure has little contribution to the flow rate.With the extraction,the effect of negative pressure is gradually increased.(5)The influence of the diameter of the borehole on drainage effect was analysised.When the diameter of borehole is larger,the flow rate is the greater and the extraction effect is better.In the initial stage of drainage,the diameter of borehole has large contribution to extraction effect.With the extraction,the effect of diameter of borehole is gradually discreased.(6)In the porous gas extraction process,the flow rate of outermost borehole is obviously larger than that of the inner borehole.The flow rate of inside boreholes has little difference.With the increase of the distance between boreholes,the flow rate increases,and the extraction efficiency is higher.