Experimental Study On Coal And Gas Outburst Based On Leading Geo-Stress

Coal and gas outburst is serious disaster in China.With the mining deepening,the geo-stress gas pressure and temperature increase.The gas-stress-physical mechanics coupling is complicated,and many dangers threaten mining safety.Under the condition that the gas extraction reaches the standard,the coal and gas outburst accidents dominated by stress still happen from time to time,which has seriously restricted the coal mining safety.Based on the high stiffness coal and gas outburst test system in deep coal mines developed by Chongqing research institute of China coal science & engineering group,the main control factors of coal and gas outburst were analyzed and physical simulation similarity design is carried out to provide theoretical support for physical simulation test of coal and gas outburst.The stress-gas pressure-temperature evolution rule around the outburst hole and the distribution characteristics of coal outburst roadway during the whole process were analyzed.A multi-physical field parameter analysis model for the whole process of coal and gas outburst is established and the response law of multi-physical field parameters during coal and gas outburst is discussed.The main research results obtained in this paper are as follows:(1)Based on the PCA-Morris screening method,the main controlling factors affecting the strength of coal and gas outburst were discussed.Based on the PCA-Morris screening method,the main controlling factors affecting the strength of coal and gas outburst were discussed.According to the principal component selection criteria,the main controlling factors affecting the strength of coal and gas outburst were selected as gas pressure,geo-stress,firmness coefficient of coal,initial velocity of gas emission and porosity.The sensitivity analysis shows that the gas pressure and ground stress are sensitive parameters,the firmness coefficient and the initial velocity of gas emission are medium sensitive parameters,and the porosity is insensitive parameter.(2)The influence of raw materials and process environment on similar materials was studied,and the physical reconstruction method of similar materials with prominent coal was established.Through 25 groups tests with 3 factors and 5 levels,the similar materials ratio model based on the overall similarity of mechanical properties,adsorption and desorption characteristics and seepage characteristics under the fixed process was obtained.The uniaxial compressive strength error is less than 20%,and the elastic modulus,initial gas release velocity and porosity error are less than 10%.(3)Taking the "4·19" outburst accident in Dingji as the prototype,the physical simulation test of coal and gas outburst was carried out.The outburst coal in the test under the stress of 16 MPa and gas pressure of 0.5 MPa was 18.09 kg.In the process of coal and gas outburst,the gas internal energy is greater than the elastic potential of coal and rock mass.The gas internal energy accounts for 75% of the total energy.The gas internal energy is still the most important energy source of coal and gas outburst and plays a leading role in the process of outburst.However,it can be found that the elastic potential of coal and gas outburst,which is dominated by stress,can account for 22%.With the increasing mining depth,the elastic potential becomes more and more important.(4)The physical simulation test reveals the evolution law of stress-gas pressure-temperature in coal and rock mass around outburst holes.The stress variation decreases with the increase of the distance from the outburst.On the other hand,the gas pressure in the coal body changes violently and oscillates several times in the process of falling,with the maximum rebound range of 0.05 MPa.The drop rate of gas pressure was the fastest near the outburst,close to 0.05 MPa /s.The drop rate of gas pressure gradually decreased with the increase of distance from the outburst.(5)Analyzes the whole process of coal and gas outburst in the hot-flow-solid coupling,and build a whole process coal and gas outburst model.Comsol software is used to study physical parameters response of the whole process under high geo-stress condition,to reveal the highlight of coal and rock stress field around the hole-gas pressure field,temperature field,seepage field in different area in different time node response law.(6)The influence of stress on the energy condition of coal and gas outburst was discussed by using the energy model of coal and gas outburst and combining the coal and gas outburst of "4·19" in Dingji mine.The results show that the critical gas pressure under the energy condition of coal and gas outburst decreases with the increase of stress,and under the high stress condition,the smaller gas pressure can also meet the energy condition of coal and gas outburst,which also has the risk of coal and gas outburst.