Based on the combined finite–discrete element method (FDEM), this paper presents a moisture diffusion–fracture coupling model to simulate soil desiccation cracking. The coupling model, firstly, analyzes moisture content distribution within the soil according to a moisture diffusion model. Then, the shrinkage stress caused by the change of moisture content is calculated and applied to the system equation of FDEM. Finally, if a new crack is generated, the node sharing relationship and mesh of adjacent solid elements are updated for moisture diffusion calculation in the next time step. In this paper, examples of 1D moisture migration in the soil trip, shrinkage stress and deformation caused by the moisture reduce in the rectangular soil are studied. The simulation results agree well with analytical solutions, which verifies the correctness of the proposed model. Then, the model is used to simulate soil desiccation cracking process, and the crack evolution pattern in the numerical results is consistent with experimental results. Besides, several main factors affecting soil desiccation cracking are also investigated, including the elastic modulus, the moisture shrinkage coefficient, and the soil thickness. The moisture diffusion–fracture coupling model provides a new research tool for studying the mechanical mechanism of soil desiccation cracking.

基于组合有限离散元法（FDEM），本文提出了水分扩散-裂缝耦合模型来模拟土壤干燥开裂。耦合模型首先根据水分扩散模型分析土壤中的水分含量分布。然后，计算由含水量变化引起的收缩应力，并将其应用于FDEM的系统方程。最后，如果产生新的裂纹，则更新相邻实体单元的节点共享关系和网格，用于下一时间步的水分扩散计算。本文以矩形土体中水分减少引起的一维水分迁移、收缩应力和变形为例进行了研究。仿真结果与解析解吻合良好，这验证了所提出模型的正确性。然后，利用该模型对土壤干燥开裂过程进行模拟，数值结果中的裂纹演化模式与实验结果一致。此外，还研究了影响土壤干燥开裂的几个主要因素，包括弹性模量、水分收缩系数和土壤厚度。水分扩散-断裂耦合模型为研究土壤干燥开裂的力学机制提供了新的研究工具。水分收缩系数和土壤厚度。水分扩散-断裂耦合模型为研究土壤干燥开裂的力学机制提供了新的研究工具。水分收缩系数和土壤厚度。水分扩散-断裂耦合模型为研究土壤干燥开裂的力学机制提供了新的研究工具。