Advanced fracture mechanics modelling to understand earth-environment interactions

该项目旨在开发新一代基于物理的岩石断裂模型，应用于采矿、开挖和地质灾害预测。土木和采矿工程行业有许多涉及岩石破碎的能源密集型过程。采矿占世界能源消耗的6%，其中岩石粉碎（研磨、破碎和切割）占这一巨大能源消耗的一半。岩石开挖，无论是通过机械钻孔还是爆破，都是从隧道到建筑物等广泛土木工程应用中最大的能源消耗来源。低能耗岩石压裂技术的出现可能对可持续性和全球变暖产生重大影响，并且由于经济竞争力，更严格的环境法规以及不断增长的全球能源需求，这是必要的。由于缺乏对微裂纹力学及其对外加载荷的整体响应的理解，阻碍了岩石粉碎程序的重大改进。由于涉及到大尺度，岩石工程中的变形和破坏传统上是通过经验方法建模的。然而，这些现象学模型需要广泛的校准，并且其适用性仅限于与校准方案相似的场景。预测建模需要与底层微观结构有明确的联系。开发将显著改变知识前沿的基于物理的模型所必需的基本要素现在已经具备。首先，最近高分辨率测量技术的重大进展——特别是微x射线计算机断层扫描和数字体积相关技术——提供了与微观结构的直接联系，并使裂纹模式表征成为可能。其次，由于更大的计算资源和可靠的数值方法的发展，可以将微观结构的相关特征纳入大规模模拟。该项目将结合理论、实验和数值方面的努力。在理论方面，将开发一个新的微观结构信息框架，能够从宏观和微观名义材料特性中提供预测，而不是经验参数。其目的是建立在“微力学革命”的成功基础上，这一革命大大提高了我们对金属和陶瓷的理解和建模。实验观察对于确定主导微裂纹扩展和合并的微观机制至关重要。在数值方面，该模型将在有限元设置中实现，并将与实验和离散元法（DEM）模拟进行比较。该模型将用于识别裂纹模式，这将允许设计低能量粉碎程序。不仅将建立最小摩擦的加载标准，而且裂缝分支将根据每个过程产生的矿物尺寸进行调整。通过深入了解起作用的机制，该项目将有利于理解和模拟其他地质应用，如水力压裂和地震破裂。

The project aims to develop a new generation of physically-based models for rock fracture, with applications in mining, excavation and prediction of geohazards. The civil and mining engineering industries have many energy-intensive processes that involve fragmenting rocks. Mining accounts for up to 6% of world energy consumption, with rock comminution (grinding, crushing and cutting) being responsible for half of this vast energy expenditure. Rock excavation, either through mechanical drilling or by blasting, constitutes the largest source of energy consumption in a wide range of civil engineering applications, from tunnels to buildings. The emergence of low-energy techniques for rock fracture could have a major impact on sustainability and global warming, and is necessary because of economic competitiveness, tougher environmental regulations, and continuously growing global energy demand. Major improvements in rock comminution procedures are hindered by the lack of understanding of the mechanics of micro-cracks and their overall response to applied loading. Because of the large scales involved, deformation and failure in rock engineering have been traditionally modelled through empirical approaches. However, these phenomenological models require extensive calibration and have a regime of applicability that is limited to scenarios resembling the calibration schemes. Predictive modelling requires an explicit connection with the underlying microstructure. The essential ingredients necessary to develop physically-based models that will significantly shift the knowledge frontier are now available. First, recent major advances in high resolution measuring techniques - particularly, micro X-ray computerised tomography and Digital Volume Correlation - provide a direct connection to the microstructure and enable cracking pattern characterisation. Secondly, relevant features of the microstructure can be incorporated into large-scale simulations as a result of larger computational resources and the development of robust numerical methods to capture crack fragmentation. The project will combine theoretical, experimental and numerical endeavours. On the theoretical side, a new microstructurally-informed framework will be developed, capable of delivering predictions from macro and micro nominal material properties, as opposed to empirical parameters. The aim is to build upon the success of the "micromechanics revolution" that has significantly enhanced our understanding and modelling of metals and ceramics. Experimental observations will be critical in identifying the micromechanisms dominating micro-crack growth and coalescence. On the numerical side, the model will be implemented in a finite element setting and comparisons will be conducted with experiments and discrete element method (DEM) simulations. The model will be employed to identify crack patterns that will allow designing low-energy comminution procedures. Not only will loading criteria be established for minimizing friction but also crack branching will tailor the mineral size as produced by each process. By giving insight into the mechanisms at play, the project will benefit the understanding and modelling of other geological applications, such as hydraulic fracture and earthquake rupture.