Coupled chemo-hydro-mechanical effects in one-dimensional accretion of cemented mine fills

Abstract Mine waste-cement mixtures have been extensively used for filling underground mined-out cavities worldwide as a sustainable solution to tailings disposal and for ground control. The pressure that a mine fill imposes on its retaining structures would dictate the stability of a subsurface backfill system. The pressure is influenced by the coupled consolidation and chemical shrinkage processes of a cemented mine fill. Various benchmark results have become available for understanding and predicting such coupled processes during the deposition of cemented mine fills in an ideal one-dimensional (1D) condition. Nevertheless, there has been a paucity of studies where the coupled chemo-hydro-mechanical effects in their entirety are rationally considered. In this paper, the coupled chemo-hydro-mechanical behaviour of fluid-saturated cemented mine fills during 1D accretion is investigated with a new chemo-poroelasticity framework. The present approach is conceptualized by extending Biot's poroelasticity to accommodate the water volume changes induced by cement hydration. The analyses performed in the study have brought new practical insights into the chemo-poromechanical behaviour of accreting cemented mine fills. In particular, the study has shown quantitatively for the first time how the consolidation of a hydrating mine fill is dictated by the specific evolution of its properties, rate of deposition, as well as backfill mix design during sedimentation. The study suggests that a case-specific analysis with coupled numerical tools, rather than the simple application of benchmark results, is mandatory for rationally assessing the nonlinear consolidation process.