Abstract: Loess plateau is a typical topography in loess areas; high steep slopes at plateau edge cause frequent geologic hazards of collapses and landslides. One of them is the south Jingyang plateau which is located at the south of Jing river in Shaanxi province of China. From southeast to northwest, frequently collapses and landslides form a 30 kilometers landslide group. Dongfeng landslide which occurred in recent years is one of the major landslides of the landslide group. Process and mechanism of high steep landslides were analyzed by field trips, in-situ measurement and physical and mechanical laboratory tests which were carried out on soil samples taken from leading edge and trailing edge of the landslide mass of Dongfeng landslide. Through grain size analysis and collapsibility test obtained collapsibility and liquefaction of mass loess. The influence of water content on strength parameters was studied by direct shear tests and triaxial tests on leading edge and trailing edge of the landslide mass. The structural properties of loess were studied by comparison of undisturbed loess and remolded loess. The consistency between remolded saturated loess stress-strain curves, volumetric strain-axial strain curves and Duncan-Chang model were certified by triaxial consolidated drained tests. The results of shear strength and deformation parameters of the landslide mass loess will benefit the parameter choices in the stability analysis of high and steep loess slopes.

Key words: loess plateau, slope stability, landslide, triaxial test, strength parameters