Numerical investigation of drying-induced cracking in layered geomaterials under humidity variations

Drying-induced cracking is a common phenomenon in near-surface geomaterials subjected to environmental humidity fluctuations, significantly affecting their hydraulic, mechanical, and durability properties. This study develops a coupled humidity diffusion–shrinkage stress–damage framework (RFPA-Humid) for simulating drying-induced cracking in layered hygroscopic geomaterials by integrating moisture diffusion, material heterogeneity, and progressive damage. Parametric analyses revealed that thinner surface layers produced higher crack densities and smaller polygonal units, higher moisture diffusion coefficients accelerated damage accumulation and crack propagation, and greater material homogeneity promoted the formation of more regular polygonal crack networks. A critical moisture diffusion threshold marking the onset of sustained micro-damage and macroscopic cracking was identified. Quantitative validation against published experimental data demonstrated that the model accurately reproduced the dependence of crack characteristics on surface layer thickness and the evolution of both vertical surface cracks and horizontal interfacial damage. Applicable to humidity-driven shrinkage cracking in layered hygroscopic materials under isothermal drying conditions, the proposed framework provides a quantitative tool for investigating drying-induced damage in earthen structures, surface soils, slopes, and cultural heritage materials.