Abstract: 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.

Key words: metal mine, steeply dipping discontinuities, underground mining, surrounding rock failure of goaf