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基于流固耦合动态模型的煤层钻孔成拱特性研究

Research on characteristics of pressure arch around borehole in seambased on fluid-solid coupling dynamic model

  • 摘要: 为探讨煤层钻孔周围是否存在压力拱,构建了基于Hoek-Brown准则的含瓦斯煤流固耦合动态模型,并运用COMSOL软件进行解算,分析了钻孔施工前后孔周煤体主应力及应变能密度分布规律,研究了不同煤体结构煤层孔周煤体位移量及压力拱内边界、厚度的变化特征,并结合孔周煤体塑性区分布规律对煤层钻孔成拱特性进行了探讨。研究结果表明:煤层钻孔顶底部存在压力拱,其拱脚与拱座位于钻孔两侧;压力拱区域内孔周煤体水平位移量变化较为平缓;压力拱内边界及厚度可作为评判钻孔稳定性的指标,两者随地质强度指标GSI值的增大而逐渐减小,即煤体结构越完整、强度越高,压力拱范围越小;当GSI值非常大或非常小时,压力拱效应不明显,甚至趋于消失。

     

    Abstract: In order to investigate the existence of pressure arch around coalbed borehole,the fluid-solid coupling dynamic model of coal containing gas based on Hoek-Brown criterion was established and solved by COMSOL software.Then,the distribution law of principal stress and the strain energy density of coal body around borehole before and after drilling in coal seams was analyzed,the variation characteristics of horizontal displacement of coal body with different structure around borehole,the inner boundary and thickness of pressure arch were studied.Furthermore,the characteristics of pressure arch was discussed combined with the distribution law of plastic zone of coal body around borehole.Research results show that pressure arch exists at the top and bottom of coalbed borehole,the arch springing and abutments locate on both sides of borehole.The changing trend of horizontal displacement of coal body around borehole in pressure arch area is relatively gentle.The inner boundary and thickness of pressure arch can be used as two indexes to evaluate the stability of coalbed borehole,and they all decrease gradually with the increase of GSI value,that is,the more complete the coal structure is and the higher the strength is ,the smaller the pressure arch range is.When GSI value is

     

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