Multiscale/Multiphysics Testing and Modelling of Cemented Paste Backfill-Rock Interface Behaviour and Application to the Design of Cemented Paste Backfill Structures

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Cemented paste backfill (CPB) - an engineered mixture of dewatered tailings, binder and water - is becoming increasingly and intensively utilized within the mining industry worldwide to ensure the stability of underground excavated areas, enhance ore recovery rates and reduce the surface disposal of mine waste. After placement into underground rock excavations, the interface interaction between rock and CPB occurs under both static and dynamic loading conditions. Consequently, the CPB-rock interface (C-RI) behaviours that occur at the thin interfacial transition zone scale affect the magnitude and spatial distribution of internal stresses in the CPB structure at the macroscale, and thus significantly influence its mechanical stability, as well as the mining cycle and backfilling cost. Moreover, the C-RI interaction involves coupled multiphysics processes (thermal, hydraulic, mechanical and chemical). However, knowledge of the multiscale and coupled thermo-hydro-mechanical-chemical (THMC) mechanisms responsible for interface behaviours remains limited. To accurately and reliably assess and predict C-RI behaviours and their effects on CPB performance, it is necessary to integrate multiscale/multiphysics couplings into the development of advanced testing and simulation tools. Therefore, through a combination of advanced mathematical modelling and experimental techniques, this research program aims to achieve the following objectives: (1) develop an advanced interface profile control and observation approach through 3-dimensional (3D) printing technology and scanning electron microscopy (SEM). This will make it possible to simulate random profiles of rock surfaces, and thus investigate the realistic interaction between rock and CPB under various THMC loading conditions at the micro- and laboratory scales; (2) design a large-scale multiphysics column model to experimentally investigate the behaviour of the C-RI and its influence on the performance of CPB mass; (3) formulate and validate advanced multiscale/multiphysics models to predict interfacial crack initiation, propagation and coalescence, as well as the effect on material properties and the performance of CPB mass under various THMC loading conditions over a wide range of spatiotemporal scales. This proposed research will improve the performance of CPB mass, enhance mine productivity and diminish backfilling operational costs. This research program will also provide high-quality academic training opportunities to two Ph.D. students, three master's students and five undergraduate research students. The highly qualified personnel (HQP) will gain a strong theoretical and practical foundation, as well as exceptionally valuable hands-on experience and experimental and mathematical modelling skills which will aid them in their future careers. The outcomes of this research program will also immediately benefit the Canadian research community and the mining industry.