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，它提供了约10%的世界电力和20%的英国电力，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中发挥重要作用。然而，核能的一个主要缺点是其发电过程产生的放射性废物可能在数十万年内仍然是危险的。在过去60多年的核电使用中，英国和世界各地积累了许多放射性废物，其中大部分暂时储存在核电厂附近的仓库中。对我们来说，处理废物以保护人类健康和环境至关重要。在这一领域已达成全球共识，即将与地面处置不相容的放射性废物永久隔离在合适的地下岩层中（即，通过开发地质处置设施（GDF）来处理岩石。正如2014年白色文件中所述，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）领导开展这项工作。开发GDF依赖于稳定的岩层，以确保围岩的机械稳定性和屏障功能。因此，了解影响岩石完整性的因素至关重要。这是具有挑战性的，部分原因是在地球上地壳广泛存在的岩石裂缝的复杂性。虽然岩石力学行为的研究有很长的记录，试图了解岩石变形中的断裂的作用仍然有未解决的问题。例如，天然岩石裂缝经常被粗略地处理;几乎所有以前对这个问题的研究都假设岩石裂缝是连续的，具有可以忽略的零或非常小的内聚力。然而，它几乎是一个普遍存在的特点，在地下天然岩石裂缝是初期和异质的，具有相当大的抗拉强度和凝聚力。这是由于次生矿物重结晶，将断裂面粘合在一起，或者由于岩石桥。矿脉），经常在地下看到，但往往被忽视或较少研究到目前为止。INFORM的目的是通过开发一个基于力学的多尺度框架来了解裂缝非均匀性对岩石完整性和变形行为的影响，从而提高对GDF设计、施工和运营的信心。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）确定不同尺度下裂缝非均匀性的影响因素，（2）考虑天然裂缝几何形状和非均匀性，了解脉状岩石的剪切和三轴变形行为，（3）考虑裂缝非均匀性，为储存库结构开发现场尺度模型。与大多数以前的研究不同，这些研究主要集中在机械断裂对岩石行为的影响上，INFORM将首次调查天然脉的影响，并将在应用于GDF的脉岩行为建模中考虑和实施这些观察结果。INFORM将通过将微观尺度的观察与非均匀脉岩和裂隙岩的宏观尺度变形相关联，向广大受众提供新的见解。我们的学术和工业合作伙伴（英国RWM;英国Jacobs;中国东北大学;德国GFZ;美国斯坦福大学）的大力支持以及我们精心设计的推广和出版计划的帮助下，这将成为可能。INFORM将导致更准确和可靠的裂缝非均质性检查，这不仅将直接有利于GDF研发，而且还将扩大岩石工程应用（例如，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).