From micro- to macro-scale characterization of geomaterials: the role of heterogeneities and scale in geomechanics

岩石在颗粒（微）尺度上的力学和几何性质决定了所有尺度上的岩体行为。 近年来，我的研究小组，除其他外，已经开发并成功地使用微机械混合有限元/离散元建模技术（FDEM）模拟隧道和其他地下工程活动。这些结果支持以下假设：基于物理的校准微观力学模型可以固有地捕获在所有地质材料中观察到的异质性和尺度效应，并作为涌现行为再现与岩石中复杂破坏机制相关的那些潜在物理过程（即，剥落、压裂、渐进斜坡不稳定性）。然而，到目前为止，还没有公认的程序存在如何将微观输入参数与特定的实验室测量值相关联;因此，研究人员在合理校准和验证他们的模型时遇到了困难。 我的研究计划的长期目标： 为了理解非均质性在所有尺度上对工程和地质结构的行为的作用（即，隧道，矿山，水库）受到不同的多物理（热-水力-机械-化学）条件，并将其转化为数值解。 短期目标 目标1了解非均质的空间、体积和尺度分布如何影响变形和破坏过程的定位和进展。 目标2：发展一种用于微机械数值代码定量验证和校准的通用方法。 目标3：开发一种可重复的、可靠的策略，用于扩大微力学数值代码的使用，以研究从实验室到隧道/矿山/水库规模的各种空间分辨率下的岩石行为。验证过程将评价在数字代码中实现的微观尺度物理学及其再现能力，作为模型的一个新兴特性，在实验室和实地观察到的宏观尺度行为。 该研究项目的新奇在于将先进的微机械实验室研究、经验和机器学习分析以及微机械FDEM建模独特地结合在一起，以解决地质力学中一个非常古老但仍未解决的问题：尺度效应。 这项研究的预期成果将大大有助于减少大多数地质力学工程项目所固有的与规模有关的不确定性（例如，此外，还可以为核废料深地质储存库、隧道、矿山、页岩油气藏的能源开采活动提供技术支持，并提高对岩石工程设计的信心。该研究计划为HQP在实验和数值地质力学方面的培训提供了一个独特的机会，这是整个加拿大自然资源行业非常感兴趣的主题。

Mechanical and geometrical properties of rock at grain (micro-) scale govern the behaviour of rock-masses at all scales. In recent years, my research group, among others, has developed and successfully used micro-mechanical hybrid finite/discrete element modeling techniques (FDEM) to simulate tunneling and other underground engineering activities. These results support the hypothesis that physically-based calibrated micro-mechanical models can inherently capture the heterogeneity and the scale effect observed in all geomaterials, and reproduce, as emergent behaviours, those underlying physical processes associated with complex failure mechanisms in rock (i.e., spalling, fracking, progressive slope instabilities). However, to date, no accepted procedure exists on how to relate micro-scale input parameters to specific lab measured values; thus, researchers have difficulties when it comes to soundly calibrating and verifying their models. Long-term goal of my research program: to understand the role that heterogeneities have, at all scales, on the behaviour of engineering and geological structures (i.e., tunnels, mines, reservoirs) subjected to varying multi-physics (Thermo-Hydro-Mechanical-Chemical) conditions, and to translate it into numerical solutions. Short-term objectives Obj.1 Understanding how spatial, volumetric, and scale distributions of heterogeneities influence localization and progression of deformational and failure processes. Obj.2 Development of a general methodology for the quantitative validation and calibration of micromechanical numerical codes. Obj.3 Development of a reproducible and reliable strategy for upscaling the use of micromechanical numerical codes to study rock behaviour at various spatial resolutions, from laboratory to tunnel/mine/reservoir scale. The validation process will evaluate the micro-scale physics implemented in the numerical codes and their ability to reproduce, as an emergent property of the model, macro-scale behaviours observed both in the laboratory and in the field. The novelty of this research program is the unique combination of advanced micromechanical laboratory investigations, empirical and machine learning analysis, and micromechanical FDEM modeling, to address a very old, but still unsolved problem in geomechanics: the scale effect. The anticipated outcome of this research will greatly contribute to reduce the scale-related uncertainties inherent to most geomechanical engineering projects (e.g., excavation of deep geological nuclear waste repositories, tunnels, mines, energy exploitation activities for shale oil and gas reservoirs), as well as increase confidence in rock engineering design. The research program offers a unique opportunity for HQP training in experimental and numerical geomechanics, a subject of great interest to the whole Canadian natural resource industry.