Abstract: Based on the in-situ stress state and field stress path of soil slopes,a series of triaxial tests,composed of isotropically and anisotropically consolidated undrained(ICU/ACU) compression tests and constant-shear-drained(CQD) triaxial tests,were carried out on undisturbed saturated loess.The stress-strain behaviour of a saturated loess were studied,and the steady state line and the state boundary surface were obtained.According to the test results,the mechanism of irrigation-induced landslides of loess was discussed.