Abstract: In order to obtain influence of matric suction on relaxation properties of unsaturated soil, we conduct stress relaxation tests of unsaturated soil of a landslide in Three Gorges Reservoir area by using GDS triaxial apparatus. Exponential function, logarithmic function and power function are selected for curve fitting. Through comparative analysis, power function is selected as the relaxation model as it has maximum fitting accuracy, and the model parameters under different matric suctions are obtained. The correlations between matric suctions and model parameters are analyzed, and function relationships are built. The function relationships are substituted into the relaxation model equation and a relaxation model that can reflect the effect of matric suction of unsaturated soil is obtained.

Key words: landslide, unsaturated soil, matric suction, relaxation model, relaxation properties