Spatial And Temporal Distribution Of Gravity Erosion On Loess Gully Sidewall

This paper studies the influence of rainfall and geomorphic conditions on the spatial distribution characteristics of gravity erosion,and analyzes the influence of rainfall duration and rainfall frequency on gravity erosion in time,which can provide the basis for monitoring and controlling the gravity erosion disaster in the Loess Plateau.Based on the rainfall simulation experiment of gravity erosion on loess gully sidewall,this paper analyzes the spatial and temporal distribution characteristics of gravity erosion,and uses the sensitivity analysis method based on variable growth rate to analyze the sensitivity of different types of gravity erosion near the gully edge to rainfall and geomorphic factors.The main research results are as follows.(1)The spatial distribution of gravity erosion under the influence of rainfall and underlying surface was analyzed.The results show that.1)The top of the gully sidewall is the erosion prone area,followed by the middle part of the gully sidewall,and the erosion at the foot of the sidewall is the weakest.2)The rainfall increased from 24 mm to 48 mm,and the gravity erosion of the gully slope moved up,which intensified the erosion development in the middle and upper part of the gully slope.3)Slope is an important limiting factor of gravity erosion.When the slope changes from 70°increase to 80°,the severe gravity erosion section of gully sidewall gradually moves down,which intensifies the development degree of slope toe erosion.4)Slope height is an important factor of gravity erosion,and the increase of slope height has the greatest impact on collapse.When the slope height increases from 1.0 m to 1.5 m,the severe gravity erosion section of gully sidewall gradually moves down,which intensifies the development degree of slope toe erosion.(2)The time distribution characteristics of gravity erosion under the influence of different rainfall periods and rainfall times are analyzed.The results show that.1)In the process of rainfall,collapse is easy to occur between 20-60 min of rainfall,landslide is easy to occur between 40-60 min of rainfall,and mud flow occurs less frequently,mostly between 40-60 min of rainfall.2)When the rainfall duration is 60 min,the collapse mostly occurs in the first and second rainfall.When the rainfall lasted for 30 min,the collapse began from the third rainfall.When the rainfall duration is 60 min,landslides mostly occur in the second and fourth rainfall.Mud flow mostly occurs in the fourth rainfall.(3)The sensitivity of different gravity erosion types to rainfall and geomorphic factors near the gully edge line was analyzed.The results show that.1)For the total amount of landslide erosion near the gully edge line,the rainfall has the greatest impact on it,and the sensitivity coefficient is 34.2,which is a promoting effect,while the slope height has less impact on it,and the sensitivity coefficient is-1.6,which is a restraining effect.2)For the total amount of soil erosion near the gully edge line,the rainfall has the greatest impact on it,with the sensitivity coefficient of 9.1,followed by the slope,and the slope height is the smallest,with the sensitivity coefficients of-2.5 and-1.7 respectively.3)For the total amount of collapse erosion near the gully edge line,the sensitivity to rainfall,slope and slope height is not much different,and the sensitivity coefficients are 0.6,-0.4,-0.3,respectively.(4)The reliability and practicability of loess gully sidewall model test results are analyzed.The results show that: 1)Comparing the results of gravity erosion model test of loess gully sidewall and field observation of gravity erosion of loess plateau gully sidewall,it is found that the gravity erosion of the upper part of gully sidewall,that is,near the gully edge line,is the most serious,so there is a good similarity between prototype and model.2)It is suggested that effective engineering measures should be taken near the gully edge line to effectively prevent the gravity erosion of gully sidewall.