Clayey rocks have a complex microstructure with multiple characteristic lengths. Deformation under mechanical loading generally induces damage by microcracking, which essentially concerns the scale of mineral inclusions embedded in the clay matrix. The modelling of these materials is considered within the framework of a double scale approach, by numerical homogenisation, of the squared finite element method type. This allows a heterogeneous microstructure of the material to be taken into account and a distribution of morphological properties to be introduced. Emphasis is placed on the generation of microstructures satisfying experimental observations, and keeping a certain simplicity to fit into the framework of double scale modelling. The material characteristics and behaviour are defined at the grain scale: the mineralogical properties include the mineral phase proportions and the grain morphology, while the material constituents are represented by elastic grains separated by damageable cohesive crack models. Then, the overall microscale behaviour of the material under solicitation is derived from equilibrated elementary area (EA) configuration and computational homogenisation. The variability of the material response is studied with regard to small-scale aspects as microstructure variability, microstructure size, grain angularity, and properties of grain contacts. Deformation analyses at grain contacts emphasise a dominant shear deformation mode and the development of decohesion between grains. The latter induces microfaulting processes across the entire EA and strain softening of the overall response. Moreover, the improvement of microscale behaviour modelling opens new possibilities for more realistic multi-scale modelling and upscaled behaviour of heterogeneous rocks.

中文翻译：

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在均质化数值微机械响应和微裂纹中解释粘土岩的小尺度非均质性和变异性

粘土岩具有复杂的微观结构，具有多种特征长度。机械载荷下的变形通常会导致微裂纹损坏，这主要涉及嵌入粘土基质中的矿物包裹体的规模。这些材料的建模被考虑在双尺度方法的框架内，通过数值均匀化，平方有限元方法类型。这允许考虑材料的异质微观结构并引入形态特性的分布。重点放在满足实验观察的微观结构的生成上，并保持一定的简单性以适应双尺度建模的框架。材料特性和行为在颗粒尺度上定义：矿物学特性包括矿物相比例和晶粒形态，而材料成分由可破坏的内聚裂纹模型分隔的弹性晶粒表示。然后，征求下材料的整体微观行为来自平衡的基本区域 (EA) 配置和计算均质化。材料响应的可变性在小尺度方面进行研究，如微观结构可变性、微观结构尺寸、晶粒棱角和晶粒接触的特性。晶粒接触处的变形分析强调了主要的剪切变形模式和晶粒之间脱聚的发展。后者导致整个 EA 的微故障过程和整体响应的应变软化。而且，