Feature Of Slope Gravity Erosion Based On 3D Laser Scanning Technology

The secondary earthquake disaster triggered by the Wenchuan earthquake resulted in a large number of loose deposits on both sides of the Minjiang River and the channel after the earthquake.The identification of loose deposits on the slope after the earthquake is the basis of scientific judgment and calculation of the scale,characteristics and effects of sediment yield and the degree of harm of slope body force erosion.The traditional ground survey and optical remote sensing technology are difficult to identify in the southwest mountainous area with complex terrain and dense vegetation,which leads to insufficient research on the characteristics of slope erosion after the earthquake and has not yet formed an effective method for quantifying the characteristics of slope erosion.In this paper,the thorough Guan area as the research background,based on high-precision,rich three-dimensional laser point cloud information,combined with high-resolution images and field survey data,using improved red stereo map data processing method,overlaying terrain parameters and mountain shadow,the identification method of loose deposits on the slope after the earthquake is proposed.On this basis,slope units were extracted and classified by DEM hydrological analysis,and the slope weight force erosion was studied.The sediment yield characteristics and influencing factors of slope erosion after earthquake were quantitatively analyzed.The main work and results of this paper are as follows:1)In order to solve the problem of difficult identification and information extraction of dangerous rock mass on high and steep slopes with complex terrain,this paper establishes a fast identification interpretation sign of dangerous rock mass based on field investigation data and the covariance characteristics of rock point cloud.The information extraction of structural plane is completed by using the HSV color reconstruction technology based on point cloud normal vector and the DBSCAN clustering algorithm.With the help of point cloud characteristics,the minimum path method is used to extract the information of cracks and dangerous rock edge.Finally,the stability evaluation of dangerous rock mass is analyzed.2)Aiming at the problem that the geometric characteristics of rock mass are greatly affected by the search radius of spherical field,the experimental analysis of different scales of the same eigenvalue and the same scale of different eigenvalues is carried out.The comparative analysis shows that when the r value is 5 m,the flatness and verticality characteristics of dangerous rock mass are obvious,and the operation efficiency is fast.When r=15m,the total variance characteristics of dangerous rock point cloud are obvious,and the boundary effect diffusion is greater than 15m,and the operation time is greatly doubled.3)In order to solve the problem that it is difficult to effectively identify the loose deposits of the slope after the earthquake with complex terrain,based on digital terrain analysis technology and improved RRIM image data processing method,this paper superimposed the raster data of mountain shadow,ridge index and terrain position index,combined with high-resolution image and field investigation data,and comprehensively established the interpretation and identification marks of the loose deposits after the earthquake from the aspects of the shape,texture and color of the loose deposits.A total of 39 loose deposits of the slope after the earthquake were identified,with a total area of about 0.881 km~2.4)High-precision DEM was generated based on three-dimensional laser point cloud.Hydrological analysis,difference method and superposition analysis were used to obtain slope weight force erosion parameters in the study area.The erosion and sediment yield effects of different slope types were calculated,and the relationship between gravity erosion characteristics and influencing factors was analyzed.The overall erosion amount,accumulation amount,sediment yield and sediment yield of Chediguan steep slope area were 339.27×10~4 m~3,123.98×10~4 m~3,215.29×10~4m~3 and 60.46%,respectively.The sediment yield capacity of different slope types was also different.The contribution rates of convex,concave and mixed slope in the study area were 42.74%,32.43%and 14.59%,respectively.In the range of 35°–55°,the slope erosion contributes the most,accounting for about 95%of the total erosion.The study area is mainly dominated by collapse and landslide geological disasters,which indirectly indicates that the slopes of the two types of disasters are greater than 35°.The sediment yield of slope erosion is positively correlated with the slope area,which is in a certain exponential function relationship;relative height difference within200-500m,slope erosion sediment yield and height difference was proportional;overall,the sediment yield characteristics of slope are not only determined by one factor,but also influenced by many factors.The research results can provide certain reference for disaster prevention and mitigation of slope weight force erosion disaster and sediment regulation in the basin after the earthquake.Figure 39,table 9,reference 91.