金属矿急倾斜矿体开采地表移动范围理论分析初探

Preliminary study on theoretical analysis of surface movement range in mining steeply inclined ore body in metal mine

为揭示金属矿急倾斜矿体开采地表移动规律,有效预测地表移动范围,以弓长岭铁矿急倾斜矿体开采上盘地表移动为例,考虑地形、废石回填、采深3个因素,建立了用于计算地表主应力分布与易开裂范围的力学模型。基于力学模型,将移动角与地表易开裂范围建立了力学联系,并对移动角进行了补充定义:由最深部开采层边缘向地表作直线,位移为0且使地表开裂范围最大的直线即为移动边界线,移动边界线与水平方向的夹角即为移动角。提出了借助力学模型计算移动角的试算法:预设不同的移动角,由力学模型计算得到的地表最大易开裂范围所对应的预设移动角即为真实移动角。在得到真实移动角后,由力学模型可确定地表易开裂范围与深度。同时,借助极限平衡原理将地表易开裂范围与块体滑移建立了力学联系,提出了地表潜在陷落范围的计算方法:对地表易开裂区内不同开裂点对应的潜在滑移块体列极限平衡方程,依次判别块体是否会发生剪切滑移,可确定地表潜在陷落范围。经计算,弓长岭铁矿下盘含铁带地下开采对上盘地表的移动角为60°,上盘地表具有初次滑移风险的位置距离初采位置的水平距离为130 m,潜在滑移角为55°。根据弓长岭铁矿露天与地下联合开采的现场经验,利用废石及时对地下采空区进行密实回填,并通过优化联合开采时空顺序与开采强度可有效控制地表移动,实现露天与地下安全联合开采。

To reveal the law of surface movement in mining steeply inclined ore body of metal mines and effectively predict the range of surface movement,taking the surface movement of the hanging wall of steeply inclined orebody mining in Gongchangling Iron Mine as an example,a mechanical model for calculating surface principal stress distribution and surface prone-cracking range was established.The topography,waste rock back filling and mining depth were considered in the mechanical model.Based on the mechanical model,the mechanical relation between the subsidence angle and the surface prone-cracking range was established,and the definition of subsidence angle was supplemented:the subsidence angle is the angle measured from the horizontal of the moving boundary line,a straight line with a displacement of 0 from the edge of the deepest extraction level to the surface and the largest surface cracking range.A trial calculation method for calculating the subsidence angle was proposed:by presetting different subsidence angles,the subsidence angle corresponding to maximum surface prone-cracking range calculated by mechanical model is the real subsidence angle.After the real subsidence angle is obtained,the surface prone-cracking range and depth can be determined by the mechanical model.At the same time,based on the limit equilibrium principle,the mechanical relation between the surface prone-cracking range and the slip of block was established,and the calculation method of the surface potential collapse range was proposed:the range can be determined by setting up limit equilibrium equations for potential sliding blocks corresponding to different cracking points in the surface prone-cracking range,and determining whether the blocks will undergo shear slip in turn.The subsidence angle at hanging wall caused by underground mining of the footwall iron-bearing belt of Gongchangling Iron Mine is 60°,the horizontal distance from the location with initial slip risk to the initial mining location is 130m,and the potential slip angle is 55°.According to the field experience of combined open-pit and underground mining in Gongchangling Iron Mine,timely and compact backfill of underground goaf and optimization of mining space-time sequence and mining intensity can effectively control surface movement,and realize safe combined mining of open-pit and underground in metal mine.