Mining with backfill: predicting backfill strength requirements, long-term behaviour, and placement

Abstract

The main challenge in mining with backfill is to design a flowable backfill capable of ensuring good stability of the backfilled stopes after placement and hardening. This would require, among other things, a good understanding of the physics (particle size distribution curve) and the mineralogy (presence of sulphides and/or clay minerals) of the mine waste, the correct determination of the required strength (based on the factor of safety), the correct definition of the rheological parameters (slump S, critical solids mass concentration %Cw-cr, adequate shear yield stress τY and viscosity µ), the proper selection of the backfill mix recipe (formulation taking into account the physico-chemical properties of the mixture ingredients), the correct design of the backfill retaining barricades (horizontal pressure), the good understanding of the hydromechanical properties (self-weight consolidation), the better control of the filling sequences (dissipation of the pore water pressure), the long-term compressive and shear strengths of the backfill, the reduction of the backfilling operation costs (possibility of reducing the amount of binder used), the prediction of the cemented rockfill and paste backfill strength.