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

水泥膏体充填(CPB)是一种脱水尾矿、粘结剂和水的工程混合物，正在全球采矿业中日益广泛地使用，以确保地下挖掘区的稳定性，提高矿石回收率，并减少矿山废物的地面处置。地下岩石开挖后，在静、动态荷载作用下，围岩与围岩之间发生界面相互作用。因此，发生在薄界面过渡带尺度上的CPB-岩石界面(C-RI)行为在宏观上影响CPB结构中内应力的大小和空间分布，从而显著影响其力学稳定性，以及采矿周期和充填成本。此外，C-RI相互作用涉及耦合的多物理过程(热、水力、机械和化学)。然而，对界面行为的多尺度和耦合热-水-力-化学(THMC)机制的了解仍然有限。为了准确和可靠地评估和预测C-RI行为及其对CPB性能的影响，有必要将多尺度/多物理耦合集成到先进测试和模拟工具的开发中。因此，通过将先进的数学建模和实验技术相结合，本研究计划旨在实现以下目标：(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。这将使有可能模拟岩石表面的随机轮廓，从而在微观和实验室尺度上调查各种THMC加载条件下岩石与CPB之间的真实相互作用；(2)设计大型多物理柱模型以实验研究C-RI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/多物理模型，以预测界面裂纹的萌生、扩展和合并，以及在广泛的时空尺度上各种THMC加载条件下对CPB质量性能的影响。这项研究将改善CPB块体的性能，提高矿山生产率，降低充填作业成本。该研究项目还将为两名博士生、三名硕士生和五名本科生提供高质量的学术培训机会。高素质人员(HQP)将获得坚实的理论和实践基础，以及极其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。这一研究项目的结果也将立即惠及加拿大研究界和采矿业。

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.