| With the deepening development of China’s economy,the impact of human engineering activities on the geological disturbance of mountainous areas is becoming more and more serious.In addition,extreme weather phenomena are frequent,and landslides occur from time to time,posing a great threat to the safety of people’s lives and property.Among them,rainfall is one of the important factors that induce landslides.Accurately assessing the infiltration of rainwater in the strata is a key point for preventing and controlling slope instability.At present,although many scholars have studied and analyzed rainfall-induced landslides,the theoretical research on the dynamic change of soil moisture profile shape in soil slopes and its influence on slope stability still needs to be further improved.Based on summarizing the previous infiltration theory in homogeneous and layered soils and the analysis of rainfall-induced landslide mechanism,this paper comprehensively considers the influence of slope angle and the change of soil moisture profile shape during rainfall process,derives an improved infiltration model,proposes a corresponding slope stability analysis method,and extends the model to double-layer soil slopes.A three-dimensional slope model is established by geographic information system(GIS),and the proposed infiltration model and slope failure criterion are coupled to analyze the stability of three-dimensional slope.The main work content and corresponding results of this paper are as follows:(1)Using the shape curve with modified shape coefficient to describe the change of soil moisture profile during rainfall infiltration;combining the shape curve with the hydraulic characteristics of unsaturated soil,the equivalent permeability coefficient is calculated;considering the slope angle effect,combined with Darcy’s law,an improved infiltration model suitable for homogeneous soil slope is derived.The model is verified by numerical solution of Richards equation and experimental values.The results show that the model is applicable to different types of soils and has high accuracy under different rainfall conditions.Through sensitivity analysis of model parameters,it is found that saturated volumetric water content has the greatest influence on wetting front infiltration depth,followed by initial volumetric water content,saturated permeability coefficient and slope angle.(2)Based on the improved infiltration model,a slope stability analysis method suitable for homogeneous infinite soil slopes is proposed.According to the change of rainwater distribution in the soil slope with time,the safety factor of the slope at different depths is calculated.The calculation results show that: in the early stage of rainfall,the potential sliding surface is mostly located at the bedrock surface;in the middle and late stage of rainfall,the soil above the wetting front tends to be saturated.Considering the change of soil moisture profile shape,the potential sliding surface appears above the wetting front,rather than at the wetting front.(3)Considering the boundary conditions and water balance equation in the double-layer soil,the improved infiltration model is extended and a rainfall infiltration model suitable for double-layer soil slope is proposed and applied to the infinite slope stability analysis of doublelayer soil slope considering rainfall influence.The theoretical solution is compared with the numerical solution.The results show that the proposed infiltration model can predict the volumetric water content at the soil surface and the interlayer interface and the cumulative infiltration amount with time more accurately;the infiltration process in the double-layer soil is mainly affected by the hydraulic characteristics of the fine-grained soil layer.(4)Using GRASS GIS and Python to build raster structure data,perform spatial interpolation,and build a three-dimensional slope model.Select an ellipsoid as the threedimensional sliding surface,determine its geometric parameters according to the elevation values of the sliding surface in the raster column,select the ellipsoid neutral surface based on the slope change,and simulate the ellipsoid surface parameters by Monte Carlo method to determine the trial sliding surface.(5)Combining the infiltration model in this paper,using Hovland three-dimensional limit equilibrium method to calculate the three-dimensional slope safety factor considering the influence of rainfall infiltration.According to the different relative position relationships of wetting front,interlayer interface and potential sliding surface,the grid unit column is divided into five cases.Through example analysis,the feasibility of the proposed three-dimensional slope stability analysis method under rainfall condition is verified.The results show that: the optimal value of Monte Carlo simulation trial sample number can be set as 2500 times,and the simulation trial results show a distribution of high in the middle and low on both sides;the minimum three-dimensional slope safety factor decreases with the increase of rainfall duration. |
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