浅埋缓倾斜煤层开采覆岩及地表裂缝发育规律与形成机理

Development law and formation mechanism of overburden and surface cracks induced by inclined coal seam mining in shallow buried area

为掌握浅埋缓倾斜煤层开采覆岩及地表裂缝发育规律和形成机理,采用野外实地调查、模拟实验和理论分析等方法,以羊场湾煤矿110207综采工作面为工程背景开展研究。研究表明:浅埋缓倾斜煤层开采诱发的地表裂缝发育特征明显。垂直回采方向裂缝呈弧形和直线形,平行间隔展布;平行回采方向裂缝展布于工作面两侧顺槽外侧,且工作面机巷侧裂缝发育范围大于工作面回风巷道侧。工作面顶板初次垮落步距60 m,周期性垮落步距平均为21.6 m,顶板以悬臂梁和铰接岩梁的形式重复破断活动;覆岩离层裂隙具有“产生—增大—减小—闭合”的演化规律,与竖向裂隙贯通后,导致导水裂隙带发育高度增大。地表裂缝具有动态发育和宽度动态变化2种动态规律,前者与覆岩周期性破断引起的地表动态下沉有关,后者则有“只开不合”、“先开后合再开”和“先开后合”3种活动类型,与地表岩土体复杂运移特征密切相关。倾向上工作面机巷侧(下山方向)裂缝发育范围大是煤层倾斜地表移动变形非对称偏移造成的。

In order to master the development law and formation mechanism of cracks induced by gently-inclined coal seam mining in shallow buried area,a comprehensive method was used to explore 110207 working face in Yangchangwan Coal Mine:field investigation,indoor simulation experiment and theoretical analysis.The research results show that:the development characteristics of surface cracks induced by mining of gently-inclined coal seam in shallow-buried area were obvious.The cracks perpendicular to the mining direction were arc-shaped and linear,and distributed at parallel intervals.The fractures parallel to the mining direction are distributed on the outer side of the working face grooves,and the development range of the fractures in the downhill grooves is larger than that in the uphill grooves.The initial caving distance of the working face roof is 60 m,the average periodic caving distance is 21.6 m,and the repeated breaking activities occurred as the form of cantilever beam and articulated rock beam.The strata separation cracks in overburden rock evolve in the process of“generation-increase-decrease-closure”,which will lead to the increase of the height of the water-conducting fracture zone after it connects with the vertical fractures.There are two dynamic development laws of surface fractures:dynamic expansion and dynamic development in width.The former is related to the dynamic subsidence caused by periodic overburden fractures,while the latter involves three kinds of activity types:“only open and not closed”,“open and then close again”and“open and then close first”,which is closely related to the complex migration characteristics of surface rock and soil mass.The large development range of the fractures in the upward and downhill channels is caused by the deformation and migration of the inclined surface of the coal seam.