陡倾结构金属矿山采空区围岩破坏机制研究

Failure mechanism of goaf surrounding rock with steeply dipping discontinuities in metal mine

在地下金属矿山开采中会造成采空区围岩变形破坏,影响地下采矿安全。采用现场调查、位移监测、微震监测,并结合理论分析等方法对金山店东区地下采空区的围岩破坏机制进行研究。考虑水平构造应力和崩落岩体的影响,基于极限平衡理论和能量法分别得到上下盘采空区围岩破坏机制,即倾倒滑移破坏和溃曲滑移破坏。上盘和下盘围岩在陡倾结构面的切割作用下,分别形成反倾结构和顺倾结构。在水平构造应力作用下,上盘陡倾结构岩体向采空区侧发生倾倒破坏,岩体变形破坏进而导致F4断层活化。随着采矿的深入,破坏的岩体数量和范围不断增加,形成一个深部滑动面,并穿过F4断层。下盘采空区围岩在水平构造应力作用下诱发了矿体边界处F1断层滑移,同时引起顺倾结构岩柱发生溃曲-滑移破坏,沿着节理面形成滑动面。

During underground mining of metal resources,the surrounding rock of the goaf is deformed and damaged,which will affect the safety of underground mining.The failure mechanism of surrounding rock in the underground goaf at Jinshandian East District is studied by means of field investigation,displacement monitoring,microseismic monitoring and theoretical analysis.Considering the influences of horizontal in situ stress and caving rock mass,the failure mechanisms of surrounding rock of the goafs in the hanging wall and footwall are obtained,i.e.toppling–slipping failure and buckling–slipping failure,based on limit equilibrium theory and energy method,respectively.Under the cutting action of the steeply dipping discontinuities,the surrounding rocks of the hanging wall and footwall form an anti-dip structure and a forward-dip structure,respectively.Under the action of horizontal in situ stress,the rock mass with steeply dipping discontinuities in the hanging wall topples to the side of the goaf,and the deformation and damage of the rock mass leads to the activation of the fault F4.As the mining deepens,the number and extent of the failure rock mass continues to increase,and a deep slip surface is formed and traversed the fault F4.Under the action of horizontal in situ stress,the surrounding rock of the goaf in the footwall induces the slip of the fault F1 at the boundary of the ore body,and simultaneously causes the buckling–slipping failure of the rock column with forward-dip discontinuities,and forms a slip plane along the discontinuity surface.