To study the deformation and failure characteristics of drainage borehole in soft coal seam with deep mining,the whole process of deformation and failure of drainage borehole in soft coal seam with deep mining was simulated based on the finite element theory and the statistical damage theory. The stress and deformation distribution,the evolution of pressure re-lief zone and the permeability characteristics of the coal body around the borehole were analyzed. The results showed that the damage form of borehole was upper collapse and side damage,with the formation of the collapse zone and fracture zone re-spectively. All the coal body around the borehole moved to the borehole,and the displacement of coal was larger near the borehole and relatively smaller in the distance. The shape of borehole changed from the initial circle to a 'rugby like' shape gradually,and then the 'rugby like' shape section of borehole reduced gradually until the collapse. In the process of borehole failure,the permeability of coal body around the borehole increased gradually,and both the variation quantity and variation range of coal body around the borehole increased gradually. The permeability distribution of surrounding coal body substan-tially presented the 'V' shape variation law,namely the permeability of coal body presented the trend of first decrease,then increase,and tend to be stable with the increase of distance away from the borehole. The research results can provide the theoretical support for the gas control and gas drainage in soft coal seam with deep mining in China,with a guiding signifi-cance.%为了研究深部开采松软煤层抽采钻孔变形失稳特性,基于有限元理论和统计损伤理论数值模拟了深部开采松软煤层抽采钻孔变形失稳整个过程,分析了钻孔周围煤体应力及形变分布、卸压区演化和渗透特性.研究表明:钻孔破坏形式为上方发生垮塌,形成垮塌区;左右侧发生破坏,形成破碎区;钻孔周围煤体均向钻孔移动,钻孔附近煤体位移量较大,远处煤体位移量相对较小;钻孔形状由开始的圆形逐渐变成"类橄榄球形",然后钻孔"类橄榄球形"断面逐渐减小至坍塌.钻孔失稳过程中,钻孔附近煤体渗透率逐渐增大,钻孔周围煤体渗透率变化量及变化范围均不断增加;周围煤体渗透率分布均大致呈"V"字型变化规律,即煤体渗透率呈随着距钻孔距离的增加先减小后增加然后趋于稳定的趋势.研究结果可以为我国煤矿深部开采松软煤层瓦斯治理和煤层瓦斯抽采提供理论支撑,具有指导性意义.
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