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，为全球零排放做出了巨大贡献。在全球向低碳经济转型的过程中，核电将继续发挥重要作用。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，这些废物可能会在数十万年内保持危险。在过去60多年里，英国和世界各地都在利用核能，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，处理废物对于保护人类健康和环境至关重要。在这一领域达成了一项全球共识，即通过开发地质处置设施，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(即寄主岩石)中。正如2014年白皮书所述，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)牵头开展这方面的工作。发展GDF依赖于稳定的岩层，以确保围岩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。这在一定程度上是具有挑战性的，部分原因是地球上地壳中广泛存在的岩石裂隙的复杂性。尽管岩石力学行为有很长的研究记录，但试图了解裂隙对岩石变形的作用仍然是悬而未决的问题。例如，天然岩石裂缝通常被粗略地处理；几乎所有以前关于这个问题的研究都假设岩石裂缝是连续的，没有或非常小的内聚力可以忽略不计。然而，地下天然岩石裂隙具有启发性和非均质性，具有相当大的抗拉强度和粘聚力，这几乎是一个普遍存在的特征。这要么是由于次生矿物重结晶，将断裂面粘合在一起，要么是由于岩桥。这一INFO项目将专注于充填矿物的裂缝(即矿脉)，这些裂缝经常出现在地下，但到目前为止往往被忽视或研究得较少。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隙非均质性对岩石在不同尺度上的完整性和变形行为的影响，从而增加对GDF的设计、施工和操作的信心。该框架将综合成像分析、实验室实验、数值模拟和现场观察，以(1)确定导致裂缝跨尺度非均质性的因素，(2)了解考虑天然裂缝几何形状和非均质性的脉状岩石的剪切和三轴变形行为，以及(3)开发考虑裂缝非均质性的储集库结构的现场尺度模型。与大多数以前侧重于机械破裂对岩石行为影响的研究不同，INFORM将首次调查天然矿脉的影响，并将在应用于GDF的脉状岩石行为建模中考虑和实施这些观察结果。INFO将通过将不均匀脉状和裂隙岩石的微观观察和宏观变形相互关联，向广泛的受众提供新的见解。在我们学术和工业合作伙伴(英国理工学院；英国雅各布斯大学；东北大学，中国；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外联和出版计划的帮助下，这将是可能的。INFORM将导致对裂缝非均质性进行更准确和可靠的检查，这不仅将直接有利于GDF的研发，而且还将有助于更广泛的岩石工程应用(例如隧道施工、洞穴施工)。

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).