Critical Characteristics of Slip Zone Soil in Loess Landslide with Flow Failure Pattern

The loess landslide movement in the southern tableland of Jingyang County has the characteristics of flow state. Taking L5 loess and L9 loess in the west section of Jingyang Southern Tableland as the research object, the humidifying constant shear test has been carried out from the angle of unsaturated loess, which controlled different initial moisture content. The characteristics of soil and water boundary in the process of loess flow failure have been discussed on the basis of the curve of loess humidification deformation process. The relationship between pore difference and moisture content before and after the failure of loess flow state has been further revealed from the microcosmic point of view. The critical condition and mechanical mechanism of loess flow failure has been put forward. The results show that the loess has the characteristics of fluid deformation, and there exists critical moisture content in its humidification deformation curve. The concepts of "adaptive first stable field" and "adapted second stable field" have been proposed for the first time. The results of soil pore mutation before and after the critical point reveal the rationality of the deformation model. In addition, the basic condition of flow deformation is related to the distribution of soil pore and particle size. Under the condition of unsaturated high-water content, the small change of water content (suction stress) can cause larger strain increment of soil. Based on the closed equation of hydraulic characteristic curve model, the mechanical mechanism of fluid deformation has been put forward in order to provide the scientific basis and theoretical basis for the prevention and control of fluid failure loess landslide.