REVIEW ON THE MECHANISM AND THEORETICAL MODEL OF DESICCATION CRACKING IN CLAY SOIL

Desiccation cracking is a common phenomenon in clay soils, which have an important influence on the properties of soils, leading to all kinds of engineering and environmental problems. Therefore, studying the soils cracking phenomenon, finding out its mechanical mechanism and build theoretical model is of great importance. This paper introduces the mechanical mechanism and related theoretical models of soil cracking by collecting relevant data, analyzing the characteristics of each model, and introducing its classification based on the theoretical basis of the models. In general, the following main conclusions are obtained. Researchers think that the mechanism of the crack haven't been unified. The mainstream view thinks that cracks are a form of damage of soil. Tension stress and tensile strength are the two key mechanical indexes, but it can't explain all the cracking phenomenon. In general, the theoretical models related to soil cracking can be divided into four categories. (1)Based on the theory of fracture mechanics, representatives are the linear elastic fracture mechanics model, elastic-plastic fracture mechanics model and the finite element model based on linear elastic fracture mechanics. (2)Based on the theory of tension stress failure, representatives are the linear elastic model, the shear failure model, elastic mechanics model and the cohesive crack model. (3)Water content-volume change model based on the process of shrinkage deformation of soil. (4)The analysis of stress path model on the basis of the soil consolidation theory. On this basis, the shortcomings and applicable conditions of each model are evaluated. Finally, this paper also puts forward the key directions of the studies about the issues. They include soil microstructure change and micromechanics analysis during the process of evaporation, the migration process, distribution and occurrence of pore water in the process of evaporation, research on soil shrinkage, research on tensile strength of soil, prediction model about fracture width, depth and growth geometry characteristics of crack soil.