Abstract:

In order to enhance mine safety management, a ultra-large refined three-dimensional numerical model for an oversea ultra-large-scale block caving mine was established. The spatiotemporal evolution patterns of underground cave bodies and surface rock movement throughout the mining were simulated using FLAC^3D, and the safety of surface infrastructures was evaluated according to composite surface subsidence criteria. Results demonstrate that caving morphology development exhibits discontinuous, intermittent and leapfrogging characteristics. A definitive transition threshold exists in propagation modes - vertical caving dominates prior to surface breakthrough, shifting to lateral propagation afterwards. Caving crater expansion follows bimodal evolutionary patterns: initial rapid large-scale caving due to weak superficial strata, transitioning to velocity attenuation in mid-late stages through debris infill, ultimately forming cave zones with high spatial correlation to undercut areas and location. Evaluations based on composite subsidence criteria confirm that critical surface infrastructures remain outside the subsidence limit throughout the mining. Furthermore, the "priority exceedance" characteristic of curvature parameters proves effective as an early warning indicator for surface breakthrough.

Key words: ultra-large-scale, block caving, surface subsidence criteria, nonlinear evolution, cave zone, subsidence limit