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

胶结膏体充填体（CPB）是一种由脱水尾矿、粘结剂和水组成的工程混合物，在世界范围内的采矿业中得到越来越多和集中的应用，以确保地下采掘区的稳定性，提高矿石回收率和减少矿山废物的地表处置。地下岩石开挖后，岩石与CPB在静、动载荷条件下均发生界面相互作用。因此，发生在薄界面过渡带尺度上的CPB-岩石界面（C-RI）行为在宏观尺度上影响CPB结构内应力的大小和空间分布，从而显著影响CPB结构的力学稳定性、回采周期和回填成本。此外，C-RI相互作用涉及耦合的多物理场过程（热、水力、机械和化学）。然而，对界面行为的多尺度和耦合热-水-机械-化学（THMC）机制的了解仍然有限。为了准确、可靠地评估和预测C-RI行为及其对CPB性能的影响，有必要将多尺度/多物理场耦合集成到先进测试和仿真工具的开发中。因此，通过先进的数学建模和实验技术的结合，本研究项目旨在实现以下目标：(1)通过三维（3D）打印技术和扫描电子显微镜（SEM）开发先进的界面轮廓控制和观察方法。这将使模拟岩石表面的随机剖面成为可能，从而在微观和实验室尺度上研究不同THMC加载条件下岩石与CPB之间的真实相互作用；(2)设计大尺度多物理场柱模型，实验研究C-RI的行为及其对CPB质量性能的影响；(3)建立并验证先进的多尺度/多物理场模型，以预测大范围时空尺度下不同THMC加载条件下界面裂纹的萌生、扩展和聚并，以及对材料性能和CPB质量性能的影响。该研究将改善CPB体的性能，提高矿山产能，降低充填作业成本。本研究项目还将为2名博士生、3名硕士生和5名本科生提供高质量的学术培训机会。高素质人才（HQP）将获得强大的理论和实践基础，以及非常宝贵的实践经验和实验和数学建模技能，这将有助于他们未来的职业生涯。该研究项目的成果也将立即使加拿大研究界和采矿业受益。

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.