Analysis Of Three-dimensional Slope Stability Based On GIS Under Rainfall Conditions

Recent years,with the frequent occurrence of rainstorms and floods in China,the proportion of landslide hazards in the total geological hazards in China is getting higher and higher.In the study of slope stability after rainfall,how to judge whether landslides will occur and how to predict the time has become the most concerned issue of the land department,and also the most urgent problem that scholars need to solve.However,most of the current studies focus on the two-dimensional slope and neglect the three-dimensional(3D)effect of slope.Based on the characteristics of slope model,this paper establishes a complete set of 3D slope modeling scheme by GIS.In this model,3D limit equilibrium method and rainwater infiltration model in rainfall and redistribution stages are considered.Then,combined with the algorithm of searching the most dangerous slip surface,the influence of rainwater infiltration on 3D slope is analyzed in depth.The main work and achievements of this paper are as follows:(1)Based on the characteristics of slope,a 3D slope modeling scheme with strong applicability and complete theory is established.This scheme uses GRASS GIS and Python as main tools,chooses interpolation theory to fit different geological body models,and uses unified model management method.By studying the composition of data transmission between different platforms,the coupling between the slope model and the numerical simulation software can be accomplished by using self-compiled program.(2)Based on Green-Ampt infiltration model,Moore double-layer infiltration model and infiltration-redistribution model,a 3D rainwater infiltration model of slope at rainfall and redistribution stages is established.After the infiltration model is programmed,the wetting front position of slope at any time point can be calculated,and the calculation efficiency can be guaranteed.The results show that the infiltration rate of rainwater is faster in the process of rainfall,and after stopping raining,rainwater will continue to infiltrate under the dual effects of gravity and suction of soil matrix,but after stopping rainwater for four days,the process will basically stabilize(3)Based on the principle of rainwater infiltration and 3D limit equilibrium method,the influence of rainwater infiltration is considered in Hovland model and three-dimensional Janbu model.The results show that the influence of rainwater infiltration on slope stability at specific time can be expressed by the relative relations of potential sliding surface,soil interface and wetting front,and can also be reflected in the calculation of anti-sliding force and sliding force in 3D limit equilibrium analysis.(4)According to the characteristics of the 3D slope model,the sliding surface is assumed to be the lower surface of the ellipsoid,and the manifestation and geometric relationship of the sliding surface in GIS are determined-The method of calculating the geometric parameters needed in the calculation of the three-dimensional safety factor is deduced.(5)By means of Monte Carlo method,the potential sliding surface in the site is searched to obtain the minimum safety factor of the 3D slope,and the most dangerous sliding surface is determined by the parameters of the ellipsoid.The results show that this method can be used to analyze the stability of irregular 3D slope including rainwater infiltration,and has good adaptability.(5)A series of plug-ins and programs are written by Python.For example,plug-in for data transfer between different platforms can realize fast conversion between common formats such as xml,dwg,dxf,csv,slope,etc.Based on the basic theory of interpolation method,a plug-in for RST radial basis function method is developed and used in the modeling of 3D slope.The 3D limit equilibrium considering rainwater infiltration is programmed to form the sliding surface.On the premise of determining the formula,the safety factors at different time points under specific rainfall intensity can be obtained according to different 3D limit equilibrium method.According to the sliding surface form of 3D slope,a set of searching algorithm for the most dangerous sliding surface of 3D slope is compiled.