Micro-macro mechanisms, theoretical models, and evaluation techniques of loess collapsibility

Loess, widely distributed across northwestern China, is a Quaternary aeolian deposit characterized by its pronounced collapsibility. Owing to its naturally metastable structure, loess exhibits high strength under low-moisture conditions but may experience significant deformation when subjected to loading/wetting, thereby triggering serious geohazards such as landslides and subsidence. Based on the authors’ long-term research, this paper presents a comprehensive review of the micro-macro mechanisms, theoretical models, and evaluation methods of loess collapsibility. By comparing the microstructures, water retention properties, and compression and shear behavior of intact, compacted, and reconstituted loess, the coupled effects of soil structure and suction on collapse properties are elucidated. Furthermore, an elastoplastic constitutive model incorporating coupled structure-suction effects, and a simplified method for evaluating loess collapsibility, are developed. Combining the proposed simplified method with machine learning techniques and time domain reflectometry (TDR), an approach for in-situ rapid evaluation of loess collapsibility is proposed. These studies provide both theoretical and technical support for the assessment and mitigation of loess-related geohazards and engineering issues.