Direct Current Electric Method Response Of Regional Coal And Gas Outburst Danger And Its Application

Coal and gas outburst is a serious dynamic disaster in mine which has the characteristic of obvious regional distribution. It is emphasis and difficulty of regional outburst prevention that how to carry out accurate and effective prediction and division of region of coal and gas outburst. It requires to enhance the level of technology and equipment yet. Based on this point, this thesis puts forward a method of geophysical exploration known as active DC method to predict the danger region of coal and gas outburst, revealing the law and mechanism of role of element of outburst danger for coal electrical characteristic, studying DC response pattern during the evolution process of coal and gas outburst, putting forward technical approach and identifying method of exploring outburst danger region with DC method, and carried out on-site preliminary application.(1) Real-time test and analysis the change rule of different coal resistivity during the process of uniaxial compression, cyclic loading and hierarchical load. It shows that resistivity along with the change trend of load pressure is consistent for the coal of the same electrical conductivity. For the coal of different electrical conductivity, resistivity presents different change rule before outburst and is on the rise after outburst. Through studying change rule of coal resistivity on different stages of uniaxial compression whole stress-strain process, dilatancy that volumetric strain as a symbol has an important influence on coal resistivity were found, mainly embody resistivity appeared catastrophic phenomenon at dilatancy point.(2) Based on gas adsorption and desorption characteristics, real-time test and analysis variation regularities of coal resistivity during gas adsorption/desorption process and study the response characteristic of the coal resistivity according to different coal, different gas pressure and different gas species. The results show that variation characteristics of resistivity of different coal are different. Because of difference of coal conductive properties, resistivity presents two trends of rise and fall during gas adsorption phase. Coal resistivity presents the opposite trend during gas adsorption phase and desorption phase, and with gas pressure become bigger, the adsorption capacity become larger, the change range of coal resistivity also become bigger.(3) Analyzed conductive mechanism and conductive characteristics of coal from microcosmic angle, putting forward conductive mechanism of weak bound ion, revealing the evolution of conductive characteristics of coal and pore and fissure structure is main factor for change characteristics of coal resistivity. Based on theprinciple of mechanical properties of coal containing gas, mechanism of gas for coalresistivity was studied, The mechanical properties of coal containing gas has essentialinfluence to the coal resistivity was found. From the essence, the change ofmechanical properties of coal containing gas is the mechanism of stress and gas forcoal resistivity.(4) Established coal and gas outburst simulation experiment system and parallelelectrical method testing system，studying DC response pattern in the evolutionprocess of outburst. The result shows parallel electrical method has a good responsefor the role of stress and gas and difference during outburst process.It suggests thatparallel electrical method can reflect time-space evolution process of coal and gasoutburst. Apparent resistivity value, spontaneous potential and a field current ascharacteristic parameters of parallel electrical method to analyze and characteristicparameters have own change rule during evolution process of coal and gas outburstwas found. Comparison and analysis characteristics of apparent resistivity of hardcoal and soft coal were carried out. Apparent resistivity of soft coal is lower and softcoal has the characteristics of strong heterogeneity.(5) Put forward the technical approache and identifying method of exploringoutburst danger region with DC method. Combined with gas geology analysis, wecarried out field test of detection of working surface by network parallel electricalmethod and regional outburst of drivage roadway, the case of working surface anddrivage roadway also verified the detection results.The research results provide a new technical means for coal and gas outburstregional prevention, and have an important significance to promote the applicationand development of coalfield geophysical prospecting technology. Also, it has animportant reference role for prevention of other rock or coal dynamical disasters.