Desiccation cracking in clayey soils occurs when they lose moisture, leading to an increase in their compressibility and hydraulic conductivity and hence significant reduction of soil strength. The prediction of desiccation cracking in soils is challenging due to the lack of insights into the complex coupled hydro-mechanical process at the grain scale. In this paper, a new hybrid discrete-continuum numerical framework, capable of capturing hydro-mechanical behaviour of soil at both grain and macro scales, is proposed for predicting desiccation cracking in clayey soil. In this framework, a soil layer is represented by an assembly of DEM particles, each occupies an equivalent continuum space and carries physical properties governing unsaturated flow. These particles move freely in the computational space following the discrete element method (DEM), while their contact network and the continuum mixture theory are used to model the unsaturated flow. The dependence of particle-to-particle contact behaviour on water content is represented by a cohesive-frictional contact model, whose material properties are governed by the water content. In parallel with the theoretical development is a series of experiments on 3D soil desiccation cracking to determine essential properties and provide data for the validation of mechanical and physical behaviour. Very good agreement in both physical behaviour (e.g. evolution of water content) and mechanical behaviour (e.g. occurrence and development of cracks, and distribution of compressive and tensile strains) demonstrates that the proposed framework is capable of capturing the hydro-mechanical behaviour of soil during desiccation. The capability of the proposed framework facilitates numerical experiments for insights into the hydro-mechanical behaviour of unsaturated soils that have not been possible before.

中文翻译：

---

在干燥过程中模拟土壤水力学行为的混合离散连续体方法

黏性土壤失去水分时会发生干裂，导致其压缩性和导水率增加，从而显着降低土壤强度。由于缺乏对颗粒尺度上复杂的耦合水力机械过程的了解，对土壤中干燥开裂的预测具有挑战性。在本文中，提出了一种新的混合离散连续体数值框架，能够在颗粒和宏观尺度上捕捉土壤的水力学行为，用于预测粘土中的干裂。在这个框架中，土层由一组 DEM 粒子表示，每个粒子占据一个等效的连续空间，并带有控制非饱和流动的物理特性。这些粒子按照离散元法 (DEM) 在计算空间中自由移动，而他们的接触网络和连续混合理论被用来模拟不饱和流动。颗粒间接触行为对含水量的依赖性由内聚摩擦接触模型表示，其材料特性由含水量决定。与理论发展并行的是一系列关于 3D 土壤干燥开裂的实验，以确定基本特性并为验证机械和物理行为提供数据。在物理行为（例如含水量的演变）和机械行为（例如裂缝的发生和发展，以及压缩和拉伸应变的分布）方面的非常好的一致性表明，所提出的框架能够捕捉土壤的水力学行为干燥。