Abstract: A series of geological disasters are observed in metal mines by sublevel caving method. In order to ensure safe production in mining areas, it is of great significance to carry out research on time-dependent strata movement behavior caused by sublevel caving method. The footwall of western area in the Chengchao Iron Mine was taken as the research case and more than 10 years of GPS monitoring data on the surface were collated and analyzed. By combining the monitoring data with in situ failure investigation and engineering geology, the time-dependent behaviour of strata movement under different zones was studied. The research results indicate that the time-dependent behaviour of strata movement is determined by deformation failure process, and its time-dependent behaviours are different in different zones. It can be further characterized by initial deformation, progressive deformation, accelerated deformation and residual deformation stages. The four time-dependent behaviours correspond to stable state, critical state, unstable state and post-mining creep state. The initial deformation stage corresponds to the initial creep process of the rock mass, and the progressive deformation stage reflects the process of resisting deformation. The accelerated deformation stage is related to the formation of through-going failure surface and the strong stress release. There is no space for the caved waste rock mass to flow after the mining activity is stopped, the strata movement is weakened due to the caved waste rock mass is compacted by surrounding rock mass. The residual deformation time is controlled by the creep characteristics of the rock mass and the compaction process of caved waste rock mass. A longer residual deformation time is observed in in the toppling-slipping zone due to an additional compaction process of caved waste rock mass.

Key words: metal mine, caving method, mining disturbance, strata movement, time-dependent behaviour