远距离下保护层开采对上覆煤岩层卸压效果的影响

为探究晋城矿区下保护层开采对上覆岩层卸压效果，综合运用数值模拟和现场实测等手段，并以该矿区开采9号煤层作为3号煤层下保护层为工程背景开展研究。采用数值模拟手段研究下保护层开采上覆煤岩体卸压效果及被保护层煤体膨胀变形规律，并确定有效保护范围。研究结果表明:保护层回采后，上覆煤岩体出现分区卸压效应，卸压效果随与工作面垂直距离增加而降低；被保护层倾向卸压角为63°，走向卸压角为60°；采空区中部被保护层膨胀变形率保持在4‰左右，为稳定卸压区域。现场工业试验后，通过钻孔电视发现被保护层煤体受采动影响产生离层裂隙。煤层瓦斯参数测定发现，被保护层煤体瓦斯含量、瓦斯压力分别降低至开采前50%和60%，表明开采9号煤层作为保护层对上覆3号煤层卸压消突效果显著。

Influence of long distance lower protective seam mining on pressure relief effect of overlying coal and strata

In order to explore the pressure relief effect of Jincheng mining area’s lower protective layer mining on the overlying strata，the numerical simulation and field measurement are comprehensively used，and the mining of No.9 coal seam as the lower protective layer of No.3 coal seam in the mining area is taken as the engineering background to carry out the research.Numerical simulation is used to study the pressure relief effect of overlying coal and rock mass and the expansion and deformation law of coal in the protected seam，and to determine the effective protection range.The results show that:after the protective layer is mined，the pressure relief effect appears in the overlying coal and rock mass，and the pressure relief effect decreases with the increase of the vertical distance from the working face.The pressure relief angle of the protected layer is 63°.The strike relief angle is 60°.The expansion deformation rate of the protected layer in the middle of the goaf is about 4‰，which is a stable pressure relief area.After the field industrial test，through the borehole TV，it is found that the coal body in the protected layer is affected by the mining，resulting in bed separation cracks.The measurement of coal seam gas parameters shows that the gas content and gas pressure of the protected seam are reduced to 50% and 60% before mining，respectively，which indicates that the effect of pressure relief and outburst elimination of overlying No.3 seam is remarkable by mining No.9 seam as the protective seam.