Research On Coal And Gas Outburst Occurrence Mechanism And Joint Prevention Method Of Short-Distance Multi Coal Seams

There are lots of short-distance multiple coal seams in Chinese mines.The proportion of gas outburst accidents increases as these mines develop to deep.The main reason is the particularity of the geological conditions of gas in closed coal seams.Meanwhile,the mechanism of the outburst is more complicated because of the existence of multiple outburst hazards.It not only brings great losses to the mine itself in terms of personnel,financial resources and material resources,but also seriously restricts the safe and efficient production of the mine,and even causes the shutdown and closure of some mines.In the implementation of comprehensive prevention measures,the joint prevention is not considered,or the method of prevention is not perfect,even the corresponding prevention method is not established.Combining with the concrete conditions of the mining conditions of the close seam group in the test mining area,the distribution law of the stope stress field in the upper adjacent seam and the lower adjacent seam is analyzed by means of numerical simulation,and the reason why the combined outburst prevention is necessary for the close seam group is explained.In this paper,the typical near-overhanging multi-outburst coal seam in Wulan Coal Mine of Hulusitai Mining Area in the western margin of Ordos basin were studied.Theoretical research,numerical simulation,technical research and field test were applied.In this paper,a new method and device for simultaneous determination of gas adsorption capacity,porosity and deformation of coal is developed,which can ensure the absorption of gas.Accurate determination of accessory parameters and porosity provides support for improving the accuracy of gas content in coal seams.Based on accurate determination of gas content,a method for judging regional outburst danger and classifying and zoning of close coal seams is developed.In view of the situation that most of the coal seams with short-distance outburst are easy to be exposed and penetrated by mistake when the upper adjacent seams are first mined,an on-line prediction system of outburst risk in the upper adjacent seams with short-distance outburst is developed.Based on the systematic analysis of the energy mechanism of the multi-outburst danger source in the closed multi-coal seams and the distribution law of the mining stress field,from outburst prevention and "four-in-one"comprehensive outburst prevention measures,combined with four key technologies:prediction and detection of regional outburst risk faced by close multi-seam joint outburst prevention,regional joint outburst risk prevention,joint inspection and verification,and continuous analysis of outburst risk in working face,the method of joint outburst prevention for closed distance multi-coal seams was proposed,and experiments were carried out in the field.The main research results are as follows:(1)Put forward the concept of multi-outburst danger sources and create the energy equation of coal and gas outburst danger sources in closed distance coal seams.(2)Aiming at the problem that high pressure volumetric method can not accurately measure the change of volume and porosity of coal adsorbed gas,combining industrial CT technology with high pressure volumetric method,a method and equipment for simultaneous determination of coal sample deformation-porosity-adsorption capacity is proposed.The result of traditional high pressure volumetric method for determining coal adsorbed gas constant is revised to 11%,which supports coal bed gas.Based on the above results,a modified method for direct determination of gas content in coal seam is proposed,and a method for judging and classifying the regional outburst risk of coal seam based on gas content precise measurement is established.(3)Invented joint outburst prevention method in closed distance coal seams combined with the pre-control measures(pre-judgment of coal seam outburst risk,layer control),joint control measures(joint anti-burst,simultaneous elimination)and enhanced detection(deep-hole rapid fixed-point continuous detection,continuous analysis,online monitoring and management).(4)A new index A2 is proposed to predict the outburst risk of outburst sources in the closed distance upper neighbouring seams mining face.And online monitoring and forecasting experiments were carried out in Wulan Coal Mine to form a forecasting system.Figure[49]table[15]reference[147].