软岩近距离煤层采动覆岩破坏特征模拟研究

Study on simulation of overburden failure characteristics of soft rock in close distance coal seam mining

为了研究软岩煤层组开采过程中围岩及地表的破坏移动规律,基于采动覆岩移动、裂隙分布规律及破坏机理,采用相似模拟研究方法,以依兰煤矿首采区工作面为工程原型,建立了地质力学模拟模型,分析研究了软岩煤层组的采动力学演化特性、顶板裂隙破断发展轨迹、地表移动变形规律和围岩塑性区分布范围。研究得出:依兰煤矿首采区上煤层采后覆岩破坏最大裂采比为7.5,多煤层覆岩综合裂采比为9.3,地表下沉系数为0.76,地表移动变形值达到Ⅳ级变形;揭示了覆岩纵向裂隙呈梯形分布于采空区两端,横向裂隙分布于顶板应力卸压区的特征;指出采空区围岩应力与空间位置有关,顶板应力变化幅度大于煤柱应力变化;分析得到“三软”覆岩移动变形速度较大,同时软岩煤岩层对采动围岩变形起到了缓冲作用,覆岩裂隙破坏范围在围岩中受到限制。

In order to study the damage movement law of the surrounding rock and the ground surface during the mining of the soft rock coal seam group,based on the mining overburden movement,the fissure distribution law and the failure mechanism,using the similar simulation research methods,taking the first mining area of Yilan Coal Mine as the engineering prototype,the geomechanics simulation model was established,and the mining dynamics evolution characteristics of the soft rock coal seam group,the development trajectory of the roof fissure,the law of the surface movement and deformation,and the distribution range of the plastic zone of the surrounding rock were analyzed and studied.Research concluded that the maximum crack-production ratio of the overburden failure after the mining of the upper coal seam in the first mining area was 7.5 in Yilan Coal Mine,the comprehensive crack-production ratio of the overburden of the multiple coal seam was 9.3,the surface subsidence coefficient was 0.76,and the deformation value of the ground movement reached gradeⅣ.It revealed the characteristic that the longitudinal fissures of the overburden were distributed trapezoidally at both ends of the goaf,and the transverse fissures were distributed in the stress relief zone of the roof.It was pointed out that the surrounding rock stress of the goaf was related to the spatial position,and the variation of the roof stress was greater than that of the coal pillar.Analysis showed that the movement and deformation speed of the"three soft"overburden was higher,at the same time,the soft rock coal rock layer had the buffer effect on the deformation of the surrounding rock caused by mining,and the damage range of the overburden fissure was limited in the surrounding rock.