煤铝共采岩层运动与裂隙发育规律的颗粒离散元研究

Study on the law of overburden rock movement and fissure development in coal and aluminum co⁃mining based on particle discrete element method

通过建立“上煤下铝”资源共采颗粒离散元力学模型,研究了煤层长壁式与铝土矿房柱式共采下覆岩应力叠加规律,揭示了煤层顶板压力拱、煤铝层间压力拱及底板压力拱的成拱机制及叠加传递特征,提出了铝土矿柱稳定、部分矿柱失稳及整体性失稳下对应的覆岩运动模式,得到了煤铝共采叠加扰动下岩层运移破坏规律。结果表明:采空区两端铝土矿柱受组合应力拱叠加影响易承压过大而发生失效破坏,继而引发邻近矿柱的联动效应,导致铝土矿上覆岩层大范围切落滑移,覆岩矿压显现剧烈。通过分形几何方法对煤铝共采下覆岩裂隙发育规律进行定量表征,发现当铝土矿柱尺寸较小时,铝土矿房覆岩在采空区两端分形盒维数明显大于岩层未受扰动区,表明铝土矿房覆岩裂隙具有向煤层采空区发育贯通演化的特征。

In this study,the Lyuliang mining area was taken as the research object.A discrete element numerical calculation model of upper coal and lower aluminum coal measure resources co⁃mining was es⁃tablished.The stress superposition law of overlying strata under long⁃wall coal seam and room⁃and⁃pillar bauxite seam co⁃mining was studied.The arching mechanism and superposition transfer characteristics of coal seam roof pressure arch,coal⁃aluminum interlayer pressure arch and floor pressure arch were re⁃vealed.The corresponding overburden movement modes under the stability of bauxite pillar,partial pillar instability and overall instability were proposed.The law of strata migration and failure under the super⁃imposed disturbance of coal and aluminum co⁃mining was analyzed.The results showed that the bauxite pillars at both ends of the goaf were prone to failure and damage due to the superposition of the com⁃bined stress arches.Then,it caused the linkage instability of the adjacent pillars,where the bauxite layer has occurred a large scale cut and slip of the overlying strata and a violent phenomenon of mine pressure appearances.The fracture development law of overlying strata under coal and aluminum co⁃mining was quantitatively characterized by using fractal geometry theory.When the pillar size was small,the fractal box dimension of the bauxite room overburden was significantly larger than that of the undisturbed area of the rock stratum,that the overburden fissures of the mine room have developed through to the coal seam at both ends of the goaf.