Influence of Fracture Heterogeneity on Rock Deformation and Failure (INFORM): A Mechanics-based Multi-scale Framework for Radioactive Waste Disposal

核电是低碳绿色能源。目前，它提供了全球约10%的电力和英国20%的电力，为全球净零排放做出了巨大贡献。核电将继续在全球向低碳经济转型的过程中发挥重要作用。然而，核能的一个主要缺点是，它的发电过程会产生放射性废物，这些废物在数十万年的时间里都是有害的。在英国和世界范围内过去60多年的核电利用中，积累了许多放射性废物，其中大部分被临时储存在核电站附近的仓库中。对我们来说，处理废物对保护人类健康和环境至关重要。在这一领域已达成一项全球共识，即通过发展地质处置设施，将无法进行地面处置的放射性废物永久隔离在适当的地下岩层（即寄主岩石）中。正如2014年白皮书中所述，英国政府致力于实施地质处置，并由放射性废物管理有限公司（RWM）牵头开展这项工作。开发GDF依赖于稳定的岩层，以确保宿主岩石的力学稳定性和屏障功能。因此，了解影响岩石完整性的因素是至关重要的。这是具有挑战性的，部分原因是地球上地壳中广泛存在的岩石裂缝的复杂性。尽管岩石力学行为的研究已经有了很长的记录，但试图理解裂缝对岩石变形的作用仍然存在未解决的问题。例如，天然岩石裂缝通常处理得很粗糙；之前几乎所有关于这一问题的研究都假定岩石裂缝是连续的，可以忽略的内聚力为零或很小。然而，地下天然岩石裂缝的初始性和非均质性几乎是一个普遍的特征，具有相当的抗拉强度和内聚性。这要么是由于次生矿物的再结晶，将断裂表面粘合在一起，要么是由于岩石桥。INFORM项目将重点关注在地下经常看到的富含矿物质的裂缝（即矿脉），但到目前为止，这些裂缝往往被忽视或研究较少。INFORM的目的是通过开发基于力学的多尺度框架来了解裂缝非均质性对岩石完整性和变形行为的影响，从而提高对GDFs设计、建造和运行的信心。该框架将整合成像分析、实验室实验、数值模拟和现场观察，以：(1)确定影响裂缝非均质性的因素，(2)考虑天然裂缝几何形状和非均质性，了解脉状岩石的剪切和三轴变形行为，以及(3)考虑裂缝非均质性，为储存库结构建立现场尺度模型。与以往大多数关注机械裂缝对岩石行为影响的研究不同，INFORM将首次研究天然矿脉的影响，并将这些观察结果考虑并应用于GDF的矿脉岩石行为建模中。INFORM将通过将非均质脉状和断裂岩石的微观尺度观测与宏观尺度变形相关联，为广大受众提供新的见解。在我们的学术和行业合作伙伴（英国RWM、英国Jacobs、中国东北大学、德国GFZ、美国斯坦福大学）的大力支持下，以及我们精心设计的宣传和出版计划的帮助下，这一切将成为可能。INFORM将带来更准确、更可靠的裂缝非均质性检测，这不仅将直接有利于GDF的研发，而且将更广泛地应用于岩石工程（如隧道、洞穴建设）。

Nuclear power is low-carbon and green energy. It presently provides about 10% of the world's electricity and 20% of the UK's electricity, contributing enormously to global Net Zero emissions. Nuclear power will continue to play an important role in the global transition to a low carbon economy. However, one major disadvantage of nuclear power is that its generation process produces radioactive waste that can remain hazardous for hundreds of thousands of years. Over the past more than 60 years' utilisation of nuclear power in the UK and worldwide, many radioactive wastes have accumulated, most of which are stored temporarily in storage near nuclear power plants. It is vital for us to deal with the waste to protect human health and the environment. A global consensus has been reached in this area, that is to isolate radioactive waste that is incompatible with surface disposal permanently in suitable underground rock formations (i.e., host rocks) by developing a geological disposal facility (GDF). As also set out in the 2014 White Paper, the UK Government is committed to implementing geological disposal, with work on developing this led by Radioactive Waste Management Ltd (RWM). Developing a GDF relies on a stable rock formation to ensure mechanical stability and barrier function of host rocks. It is therefore essential to understand factors that influence the integrity of rocks. This is challenging partially because of the complexity of rock fractures that are widespread in the Earth upper crust. Although rock mechanical behaviour has a long record of study, attempts to understand the role of fractures on rock deformation still has unresolved issues. For example, natural rock fractures are often dealt with crudely; almost all previous studies of this problem assume rock fractures to be continuous, with zero or very small cohesion that can be neglected. However, it is almost a ubiquitous feature that natural rock fractures in the subsurface are incipient and heterogeneous, with considerable tensile strength and cohesion. This is either due to secondary minerals having recrystallised, bonding fracture surfaces together, or due to rock bridges.This INFORM project will focus on mineral-filled fractures (i.e., veins) that are frequently seen in the subsurface but often ignored or less researched so far. The aim of INFORM is to increase confidence in the design, construction, and operation of GDFs, by developing a mechanics-based multi-scale framework to understand the influence of fracture heterogeneity on the integrity and deformation behaviour of rocks across scales. The framework will integrate imaging analysis, laboratory experiments, numerical modelling, and field observations, to (1) determine factors contributing to fracture heterogeneity across scales, (2) understand the shear and triaxial deformational behaviour of veined rocks considering natural fracture geometry and heterogeneity, and (3) develop a field-scale model for repository structures considering fracture heterogeneity. Unlike most previous studies, which have focused on the influence of mechanical fractures on rock behaviour, INFORM will for the first time investigate the influence of natural veins, and will consider and implement these observations in the modelling of veined rock behaviour applied to a GDF. INFORM will "inform" a wide range of audiences with new insights through correlating micro-scale observations and macro-scale deformation of heterogenous veined and fractured rocks. This will be possible with the strong support of our academic and industrial partners (RWM, UK; Jacobs, UK; Northeastern University, China; GFZ, Germany; Stanford University, USA) and the help of our well-designed outreach and publication plans. INFORM will lead to a more accurate and reliable examination of fracture heterogeneity, which will not only directly benefit GDF R&D, but also broader rock engineering applications (e.g., tunnelling, cavern construction).