Multi-scale modeling of coupled multiphysics processes in geomaterials: Theoretical and experimental study

在岩土工程和环境工程以及能源生产的各个方面，例如废物处理（包括核废料）和土壤污染问题中，已经观察到多物理场过程和不同程度的相互耦合，其中热效应增加了多相耦合的复杂性。油气工业中页岩等致密岩水力破裂过程中的水-力学相互作用与水入渗引起的边坡破坏。对于这些复杂的工程问题，仅仅对各个物理过程单独进行分析是不够的。相反，在分析中考虑它们的相互耦合是至关重要的。这些过程涵盖了不同的尺度，从颗粒大小到更大的工程尺度。因此，需要在多尺度上考虑各种耦合的多物理场过程来研究相关基础设施的性能。***本研究的主要目的是了解不同物理过程（特别是流体流动和应力引起的变形）对岩土材料不稳定和退化的潜在机制的耦合效应。此后，将开发跨尺度的数学框架来描述材料行为，适当考虑土壤行为的微观力学方面。研究包括理论分析、实验室试验和涉及机械、水力和环境过程的土壤行为的数值模拟。实验研究包括利用x射线微ct数字图像分析在颗粒水平上表征内部结构，并对工程土的性质进行室内测试，以了解应力诱导变形、内部结构变化和水流等不同过程对工程土的影响。这项数学工作将发展出一种新的多尺度、多相的配方，这种配方可以深入到颗粒尺度上的颗粒活性细节，并通过微观力学分析和均质化回到宏观尺度。该数学框架在实现为计算机建模代码并针对基准问题进行验证后，将用于分析岩石水力破裂等各种实际问题。***提出的研究的独特之处在于它解释了耦合的水-机械-环境过程对岩土材料行为的影响。所开发的多尺度建模方法利用颗粒级信息进行更大规模的模拟，如公路路面的季节性恶化、岩石的水力破裂以及气候变化对岩土基础设施的影响。六名研究生将接受拟议研究的培训。显然，在项目结束时，每个人都会成为训练有素的研究人员。********

Multiphysics processes and different levels of mutual coupling have been observed in various aspects of geotechnical and environmental engineering and of energy production, such as waste disposal (including nuclear waste) and soil pollution problems where heat effects add to the complexity of multi-phase couplings, hydro-mechanical interactions during hydraulic fracture of shale or other tight rocks in oil and gas industry and slope failure induced by infiltration of water into the ground surface. It is not sufficient to solely carry out analysis on each physical process separately for these complicated engineering problems. Instead, it is crucial to consider their mutual coupling in the analysis. These processes cover different scales, from particle size to much larger engineering scales. Therefore, it is required to study the performance of relevant infrastructures by considering various coupled multiphysics processes on multi-scales.*** The main objectives of the research are to understand the coupled effects of different physics processes (particularly fluid flow and stress-induced deformation) on underlying mechanisms of instability and degradation in geomaterials. Thereafter, a mathematical framework will be developed across scales to describe material behavior, with micromechanical aspects of soil behaviour being properly taken into account.*** The research consists of theoretical analysis, laboratory tests and numerical modelling of soil behaviour involving mechanical, hydraulic and environmental processes. The experimental study includes the characterization of internal structure on particle level using X-ray micro-CT digital image analysis and laboratory tests on engineering soil properties to understand the effect of different processes, such as stress-induced deformation, internal structure change and water flow. The mathematical work will develop a new multi-scale, multi-phase formulation that penetrates down to details of grain activity at the particle-scale, and back to the macro-scale through a micromechanical analysis and homogenization. The mathematical framework, after being implemented into a computer modelling code and validated against benchmark problems, will be used to analyze a variety of practical problems such hydraulic fracture of rock. *** The proposed research is unique in that it accounts for the effect of coupled hydro-mechanical-environmental processes on the behaviour of geomaterials. The developed multi-scale modeling methods employ information at the grain level for larger scale simulations for difficult problems, such as seasonal deterioration of highway pavements, hydraulic fracture of rock, as well as for the impact of climate change on geotechnical infrastructures. Six graduate students will be trained in the proposed research. Clearly, each would become a highly trained researcher at the end of the project.********