老采空区条带煤柱失稳对地表建筑物的影响

Influence of Instability of Strip Coal Pillar in Old Goaf on Surface Buildings

摘要:

老采空区条带煤柱在长期地下水浸泡及高荷载状态下容易造成两侧煤壁屈服剥离，导致煤柱部分失稳，进而对地表建筑物产生影响。为分析条带煤柱失稳对地表建筑物的影响，本文以某矿区条带开采形成的老采空区为工程背景，基于AH威尔逊煤柱局部屈服理论计算得到煤柱屈服区，采用数值模拟的方法研究了条带煤柱失稳前后覆岩破坏、竖向应力分布及地表移动变形特征。研究表明：条带煤柱失稳后，覆岩仍以剪切破坏为主，煤层顶底板破坏加剧，承受拉伸破坏范围增大；条带煤柱承载应力增加，监测线5处的煤柱应力集中系数由1.57增加到1.96，距煤层越远，应力集中系数较条带煤柱失稳前差值越小，距煤层50 m以上岩层应力分布特征基本不变；地表下沉值增加，煤柱失稳引起的最大“活化”下沉为293 mm。最后结合数值模拟结果，反演得到煤柱剥离前后沉陷预测参数，预测得到地表建筑物最大“活化”下沉值为288 mm。研究成果为“三下”压煤开采设计及地表建筑物保护提供参考价值。

Abstract:

Under long-term groundwater immersion and high load conditions, strip coal pillars in the old goaf are easy to yield and peel off the coal walls on both sides. It will lead to partial instability of the coal pillars and affect surface buildings. Taking the old goaf formed by strip mining in a certain mining area as the engineering background, based on the AH Wilson coal pillar local yield theory, the yield zone of the coal pillar has been calculated. By using numerical simulation, characteristics of overlying rock damage, vertical stress distribution, and surface movement deformation before and after strip coal pillar instability. It is showed that after the instability of strip coal pillars, the overlying rock still experiences shear damage. The damage at the roof and floor of coal strata has been intensified,with an increased range of tensile failure. The bearing stress of the strip coal pillar increases, and the stress concentration factor of the coal pillar at monitoring line 5 increases is 1.57~1.96. The further away from the coal seam, the smaller the difference in stress concentration factor compared to before the instability of the strip coal pillar. The stress distribution characteristics of the rock layer above 50m from the coal seam remain basically unchanged. The increase in surface subsidence value resulted in a maximum "activated" subsidence of 293 mm caused by coal pillar instability. Finally, based on numerical simulation results, the predicted parameters for subsidence before and after coal pillar stripping were inverted, and the maximum "activated" subsidence value of surface buildings was predicted to be 288 mm. It will provide references for the design of "three underground" coal mining and the protection of surface buildings