DEFORMATION AND DAMAGE MECHANISM OF|A SHAFT DUE TO UNDERGROUND MINING IN JINCHUAN NO. 2 MINE AREA

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 F207 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 F207 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 F16 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.