Abstract: In western China, many irrigation canals have been built to encourage the development of agriculture. At the same time, the failures of loess landslides are provoked by irrigation, and caused great loss and heavy casualties. Taking the failure of loess landslide caused by irrigation in Gaolou village channel as an example, the irrigation of the canal is proposed. The water infiltration produces a certain depth of water pressure in the sliding body, the loess cohesion decreases and the friction angle becomes smaller, which causes shear failure of the landslide body at a certain depth, and then the shearing damage occurs at the trailing edge of the sliding body, causing the trailing edge loess to be in the state of the post-destruction zone and generating unbalanced shear stress. The unbalanced shear stress drives the sliding body to move forward until only one point of the sliding surface is in a critical state, and then the entire landslide is destroyed, and the body is disintegrated to generate mudflow. This failure process can be summarized as follows: the landslide first produces shear failure, and then the trailing edge produces tensile shear failure. When the driven shear stress generated in the post-destruction zone is greater than the frictional resistance of the sliding body, it will push the landslide forward until the landslide occurs damage completely. The correctness of this failure mechanism is demonstrated by theory and experiment, and the rationality of a new shear stress constitutive model is verified.

Key words: shear failure, traction failure, new shear stress constitutive model, progressive failure process