Abstract: This paper aims to investigate the evolution law of soil cracks in the rainfall-evaporation process. Based on a full-scale slope model test, the surface moisture content of soil was measured, and the crack ratio was extracted by image vectorization technology. The critical water content during the repeated cracking process was studied by dividing the cracked soil into soil matrix and crack domains, respectively. The critical cracking matric suction and water content of the soil matrix domain were deduced and calculated according to the horizontal strain increment constitutive model of unsaturated soil. The results show that the soil cracking during the rainfall-evaporation process has repeatable characteristics, and the crack rate generally increases with the increase of rainfall-evaporation times; the cracking water content in the crack domains increases with the increase of rainfall-evaporation cycles, while the matrix domain has the opposite result. The matrix suction can both inhibit or promote the generation and propagation of the cracks. In the soil matrix domain, the cracking water content range calculated based on the constitutive model of the homogeneous isotropic unsaturated soil strain increment is close to the measured value, and the model can explain the variation law of cracking water content in soil matrix and crack domains.

Key words: rainfall-evaporation, full-scale model test, crack domain, matrix domain, cracking water content, strain increment constitutive model