After the No.14 shaft was repaired in Jinchuan No.2 mine,two big cracks were formed in the new shaft well.Therefore,further reinforcement program was put forward on the repaired shaft.Based on GPS monitoring data of ground surface movement,this paper evaluated the feasibility of the reinforcement program of No.14 shaft by numerical simulation.The results show that the shallow reinforcement measure did not change the extent of mining impact on the shaft,and the reinforcement method did not achieve the desired effect.Then,the prestressed cable reinforcement was used for inspecting the adaptability of this strengthening program.It was further found the level and distribution of shaft wall displacement and stress did not change significantly before and after the reinforcement.This shows that only shallow reinforcement program was not effective for the shaft which located in the severely affected region of rock movement induced by underground mining.It was a useful guide for engineering design and had practical significance in mining production.Finally,further reinforcement program was suggested after considering damage reasons of No.14 shaft,problems in the former inforcement program,as well as trends of rock movement.

As the access tunnel of underground mining,the mine shaft plays an important role in safety production. This paper examines the No.14 shaft that located on the support of ore body in Jinchang No.2 mine area. Its depth if 715.5 m. It intersected with the F207 fault. The surrounding rocks included ultramafic rock,granite,marble and dolerite. The shaft excavation was commenced in October 1999 and completed for using in 2002. It collapsed in March 2005. Based on the spot investigated data and numerical simulation method,this paper presents the deformation characteristics and damage mechanism of the No.14 shaft. The results show that there were such several damaged modes such as displacement and crack of shaft wall,fall,and breakage of shaft wall caused by impacting of falling substance. The convergence deformation of its surrounding rock was characterized by large deformation,rapid and long duration. Furthermore,the damage mechanism of the No.14 shaft was analyzed by numerical simulation. The result stated that the failures appeared possibly on the following positions of the shaft influenced by underground mining:(1)the upper part (0 to 200 m apart from the shaft head),where tension failure and shearing slide might happen. (2) the F207 fault zone (200 to 220 m apart from the shaft head),where the fault displacement might happen to induce shearing failure of the shaft. (3) the middle part (360 to 460 m apart from the shaft head),where the bulging damage might appear because of strong mining effect. (4) the influencing zone of the F16 fault (0 to 50 m apart from the shaft bottom),where the rock would loose due to the influence of the underground mining,which might induce the appearance of falling at the position of discontinuity plane traversing the shaft.