Stability Analysis Of High Loess Slopes Under Rainfall Conditions Based On Improved Green-Ampt Seepage Theory

With the continuous advancement of china’s western development strategy,the construction of the loess mountainous area in northwestern China has continued to expand,and the disturbance to the geological environment has become more and more severe,forming various loess cut slopes and fill slopes.Once encountered extreme weather conditions,such as heavy rains,Earthquakes,etc.,slope instability is very prone to occur,causing loss of life and property to local residents.Therefore,it is necessary to accurately evaluate the slope stability in the loess area and conduct real-time monitoring and early warning of slope instability.This paper takes the Fanzhuang slope in Yan’an area as the research object,uses electronic inclinometers and laser rangefinders to monitor the deep displacement and surface displacement of the slope in real time,and establishes a slope displacement prediction model based on the monitoring data.In the indoor test,the Q₂ loess’s strength and soil-water characteristics under different dry and wet cycle conditions were studied.Through theoretical deduction,the applicability of the Green-Ampt infiltration model in loess was further optimized and improved.Finally,through numerical simulation,A comparative analysis was carried out with on-site monitoring data and the applicability of the improved Green-Ampt model in this paper was verified.The main research contents and conclusions are as follows:（1）The slope stability during the construction period was evaluated according to the cumulative displacement-depth curve and slip belt displacement-time curve.Based on the field monitoring data,a dynamic gray model of the Fanzhuang slope displacement was established,and the next stage of the slope The displacement value was predicted,and the early warning status of the slope in the next stage was given an early warning based on the established early warning criterion.（2）Using filter paper method and direct shear test to study the strength and soil-water characteristics of Fanzhuang slope Q₂ loess,analyze the change law of soil-water characteristic curve and shear strength under different numbers of dry and wet cycles,and obtain the soil The fitting formula of water characteristic parameters and shear strength parameters with the number of wet and dry cycles.（3）Based on the BC model,the improved Green-Ampt infiltration model is derived,and the change function of the wet layer redistribution ratio with the rainfall time is obtained through numerical simulation,based on the seepage theory of this paper and the Fredlund unsaturated shear strength theory,Deduced the analytical formula of the slope safety factor considering the redistribution of the wet layer during the rainfall process,and compared with the solution results of other Green-Ampt models to verify the applicability of the model in this paper.（4）The thermal-fluid-solid coupling numerical analysis was carried out on the Fanzhuang loess high slope,compared with the field monitoring data,and the parameter analysis was carried out.The results showed that the monitoring data were close to the numerical calculation results.