Abstract:

We describe the method to explore the Carlin-type deposits with low grade,tilt,and middle thick orebody located in Nalin gold mine.It is proved that sublevel caving mining method can only be applied in this mine.Different problems have been encountered in testing and production such as stability of rock,possible deformation of the tunnel in the orebody during excavation soon after the tunnel is completed.Its stability can not last more than 3 ~ 4 month even with puffanchor.Large-scale falling may happen when gob doesn’t exist longer enough or exposure space is not large enough although depth of exploitation is less than 150 m due to the introduction of adit development. But it is sufficient to prove greater mine residual stress from geological structure causes poor stability of tunnel during the formation of deposits.It is advised that tunnel be excavated at the foot of the edge of the orebody and to improve stability by technogy of hole to hole blowing method.We analyze and discuss the above-mentioned issues in order to grasp the nature of residual stress and stability of tunnel which will serve mine production, change from passive to active,nature to freedom to achieve safe,efficient and economical development of mineral resources purposes.

Key words: Sublevel Caving Method, Residual stress, Tunnel stability, Covered rock, Analysis and discussion