The paper mainly studies the mechanical behaviors of the surrounding rock of underground group caverns in open stopping afterwards back-filling mining at Yongping copper mine. The mechanical state of the surrounding rock will change because each stage in the process of open stopping afterwards back-filling mining will affect it. The analysis is done with FLAC30 software considering the actual geological conditions and rock material parameters. The dangerous zone will be found after comparison between the each stage in mining of displacement and stress. Also the displacement and stress of dangerous zone should be monitored during the simulation. It is shown that the intersect zones are the dangerous zones and it is very sensitive to the mining behavior. The surrounding rock would develop to the most unstable state when the tunnel is dug at the bottom of filling body.
With the development of mineral resources exploitation, most of the metal mines have already turned to the underground mining. The underground mining is accompanied by collapse and rock burst frequently. So it seriously threatens the efficient exploitation of mines and personal safety (Cai 2006). In recent years, filling mining develops rapidly for its excellent plasticity, mechanical property and high residual strength (Han et al. 2006). Besides, filing body will force to the surrounding rock initiatively, support the stope structure and control the deformation of surrounding rock effectively. Based on its excellent properties, filling body prevent much trouble that may occur (Yu & Dong 2013, Wang & Zhu 2012).
Study is based on the engineering background of Yongping copper mine. A new way of filling mining is adopted in Yongping copper mine, and the entire mining steps can be divided into three steps, first, excavating haulage tunnel and stopping tunnels in ore room and stopping the ore pillar; second, cemented filling the pillar; third, excavating haulage tunnel and stopping tunnel in filling body and stopping the ore room. This method is different from traditional filling mining method. This method can maximize the ore mining, and create huge economic benefits. But, excavating tunnel in filling body will influence existing group caverns, and that the new group caverns in filling body and the existing group caverns get together to form a large through group caverns. The stability of surrounding rock will be influenced by excavation, so it's necessary to do the analysis and put forward a optimization design.