| With the deep development of coal mining, coal mine disasters are increasing andcoal and gas outburst has seriously affected the safe and efficient mining of the mine.Exploiting protective layer is used as one of the most effective regional measures forpreventing of coal and gas outburst, and the key problem is to locate the protectionscope exactly. As a result of the traditional protection range is located on the basis ofreference values of <Coal and Gas Outburst Prevention Regulation>, there may bedeviation in particular cases such as exploiting steep-incline layer with a bowpseudo-incline technique. And combined with the influencing of the factors such as thedepth of coal seam, spacing of coal seam, ground stress and physical and mechanicalproperties of coal and rock, it makes harder to locate the protection scope. As aconsequence, this paper takes Yanshitai coal mine of Nantong mining co., LTD as anengineering example and according to combining methods of numerical simulationanalysis and field investigation research, the locating of protection scope for exploitingsteep-incline upper-protective layer was taken into study. Through the establishment ofsolid and gas coupled mathematical model of coal&rock deformation and gas flowunder mining effecting and its application in numerical calculation for protection scopeof exploiting steep-incline upper-protective layer, at the same time according to theresults of field investigation, the numerical simulation method was verified to be properand reliable. In the last, by the contrast analysis, method to locating the protection scopefor exploiting steep-incline upper-protective layer of Yanshitai coal mine wasdetermined. The main conclusion and results of this paper can be drawn that:①Aim at the research objects, coal&rock deformation control equation and gasseepage control equation were established on the base of assumptions. By importingsolid and gas coupling variables, solid and gas coupled mathematical model of coal&rock deformation and gas flow under mining effecting was established. And throughverifying, this mathematical model was proved to be corrected.②According to numerical calculation for protection scope of exploitingsteep-incline6#upper-protective layer of Yanshitai coal mine with a bow pseudo inclinetechnique, the law of stress and deformation in4#protected layer was gained after6#upper-protective layer was mined as well as gas pressure distribution in4#protectedlayer. The numerical calculation results show that the pressure-relief angles of6# upper-protective layer located by the discrimination criterion of residual gas pressureare81.7°and78.9°along inclined upper and lower boundary respectively and55.6°along strike and the pressure-relief angles located by the discrimination criterion ofcoalbed deformation are80.4°and77.6°along inclined upper and lower boundaryrespectively and53.2°along strike. As a consequence, the results of the two methodsare basically the same between values and distribution.③According to the results of field investigation of protection scope for exploiting6#steep-incline upper-protective layer of Yanshitai coal mine, the change law for4#protected layer of coalbed gas pressure, gas flow from borehole and permeabilitycoefficient was obtained. And the four distribution range of gas dynamic parametersvariation was also drawn out. The field investigation results show that thepressure-relief angles of6#upper-protective layer are47.1°～74.1°along strike and85.7°and79.5°along inclined upper and lower boundary. And besides, the reasonableahead distance for work face of6#upper-protective layer is114m.④By the contrast analysis of the results of field investigation and numericalcalculation, the pressure-relief angles from two methods are basically the same so that itis reasonable and achievable to use numerical calculation method to locate the effectivepressure relief range of4#protected layer. Through comprehensive analysis, thepressure-relief angles can be gained according to the results of both field investigationand numerical calculation, which are53.2°～59.8°along strike and80.4°～85.7°along inclined upper boundary and77.6°～79.5°along inclined lower boundary. |
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