开采厚度对沿空掘巷围岩稳定性的影响分析

目前大多煤矿根据平均开采厚度来确定煤柱宽度,进而指导沿空掘巷,然而煤层在形成过程中受各种因素影响,存在同一煤层厚度变化较大的情况。针对综放工作面煤层开采厚度变化大,导致沿空掘巷围岩变形差异大及破坏机理复杂等问题,采用FLAC 3D软件建立巷道模型,分析平均开采厚度下的围岩变形和破坏规律,并确定合理的煤柱宽度:平均开采厚度为18 m时,在实体煤帮侧,煤体内支承压力峰值与煤柱宽度呈正相关,且煤柱宽度大于8 m后,支承压力增长幅度变缓,因此合理的煤柱宽度应为8 m。在煤柱宽度确定的情况下,研究开采厚度对沿空掘巷围岩稳定性的影响,结果表明:煤柱宽度为8 m时,随着开采厚度的增加,顶板剪破坏面积增大,覆岩变形范围与顶板下沉量增大,但两帮剪破坏面积和两帮移近量减小;当煤层开采厚度小于18 m时,煤柱内支承压力峰值与煤层开采厚度呈负相关;当煤层开采厚度大于18 m时,煤柱内支承压力峰值与煤层开采厚度呈正相关,但增长幅度较小。根据数值模拟结果得出结论:开采厚度的增大对沿空巷道两帮的围岩控制有一定益处,但对顶板维护不利,对开采厚度较大的部位应及时补加锚杆进行强化支护。现场实际应用验证了本文研究的可靠性和有效性。

Analysis of the influence of mining thickness on the stability of surrounding rock of goaf-side roadway driving

At present,in most coal mines,the coal pillar width of goaf-side roadway driving is determined by the average mining thickness.However,the thickness of the same coal seam could be varied greatly by various factors during the formation process.The large variation of mining thickness in the fully mechanized working face leads to large difference of surrounding rock deformation and complex damage mechanism of the goaf-side roadway driving.In order to solve the above problems,FLAC 3D software is used to establish a roadway model so as to analyze the surrounding rock deformation and damage law under the average mining thickness,and determine the reasonable coal pillar width.When the average mining thickness is 18 m,on the side of the solid coal,the peak supporting pressure in the coal is positively correlated with the coal pillar width.Moreover,when the coal pillar width is greater than 8 m,the growth rate of the supporting pressure slows down.Therefore,the reasonable coal pillar width should be 8 m.This paper studies the influence of mining thickness on the stability of the surrounding rock of goaf-side roadway driving in the context of determined coal pillar width.The results show that when the coal pillar width is 8 m,with the increase of mining thickness,the shear damage area of roof increases,and the rock deformation range and the roof subsidence increase.However,the shear damage area of two sides and the distance between the two sides decrease.When the mining thickness is less than 18 m,the peak support pressure in the coal pillar is negatively correlated with the mining thickness.When the mining thickness is greater than 18 m,the peak support pressure in the coal pillar is positively correlated with the mining thickness,but the growth is small.According to the simulation analysis results,it is concluded that the increase of mining thickness is beneficial to the control of the surrounding rock along the two sides of the goaf roadway,but not beneficial to the roof maintenance.For areas with large mining thickness,anchor rods should be added to strengthen support in time.The actual application on site verifies the reliability and validity of the research in this paper.