Mathematical modelling and simulation for hydrating backfill body under cemented paste backfill/rock interface loading

ABSTRACT Cemented paste backfill (CPB)/rock interface shear resistance results in a spatiotemporal stress reduction in CPB and thus affects the mechanical stability of CPB structure in underground excavations. To study the stress distribution in CPB structure, an integrated model consisting of a cohesive zone model for CPB/rock interface behavior and a multiphysics model for hydrating CPB behavior is developed. The predictability of the proposed model is validated against measurements from laboratory tests and field studies. Thereafter, the validated model is used to investigate the influence of curing time, stope geometry, and field backfilling operation on the spatiotemporal stress development in CPB structure. It has been found that the CPB/rock interface loading is able to reduce the stress levels in CPB by up to 75%, and taking advantage of this phenomenon can significantly reduce the operation cost. Moreover, there exists a critical stope width that governs the extent of stress reduction in CPB. In addition, continuous mining activity in the secondary stope exerts limited impact on the stress redistribution in the primary backfill body. These findings provide practical guidance for the safe design of a CPB structure as well as a more strategic mining plan for the adjacent ore body.