Failure Mechanism And Reliability Updating Of Soil Slopes Under Rainfall Infiltration Considering Spatial Variability Of Multiple Soil Parameters

Landslides are the most common geological disaster in the world,which could cause a large number of casualties and property damage.Among them,rainfall infiltration is the most important factor.Rainfall infiltration will lead to the increase of soil unit weight,weaken the shear strength parameters of slope,and reduce the matrix suction inside slope,which will seriously affect the stability of the slope.Therefore,it's of great practical significance and economic benefits to carry out research on the failure mechanism and reliability of rainfall-induced slope.However,there are some shortcomings in the current research on rainfall-induced slope instability:(1)Neglect of the influence of spatial variability of soil hydraulic model parameters;(2)Lack of the research on failure mechanism of slope under rainfall infiltration with multi-parameter spatial variability of soil;(3)Lack of the effective use of slope site information.For these reasons,this paper aims at the research work in slope reliability analysis methods,soil multi-parameter spatial variability simulation,and the failure mechanism of rainfall-induced slope and so on.The major research studies are as follows:(1)In this paper,the literatures on slope reliability considering the spatial variability of parameters are investigated.The current researchs about spatial variability characterization of slope parameters and reliability analysis of slope under rainfall infiltration are reviewed,and the shortcomings of the current studies on failure mechanism and reliability analysis of rainfall-induced slope are summarized.(2)A non-intrusive stochastic analysis method for evaluation of slope reliability,which can consider the spatial variability of hydraulic model parameters and shear strength parameters is proposed.The interface implementation procedure between the seepage finite element analysis of GEOSTUDIO and reliability analysis of MATLAB is constructed,which can realize the mutual uncoupling between the deterministic analysis and reliability analysis.The proposed method has much higher computational efficiency in comparison with the direct Monte-Carlo simulation method,which can provide an effective way to calculate the slope reliability problem of low probability level(10^-4?10^-3).(3)The sensitivity analysis is carried out to explores the influence of spatial variability of hydraulic parameters(saturated permeability coefficient k_s,hydraulic model parameters a and n)and shear strength parameters(cohesion c and internal friction angle?)on slope reliability.The failure probability of slope is positively correlated with the COVs of c,?and k_s.The cohesion affects the slope reliability the most,while the saturated hydraulic conductivity has the least effect on the slope reliability.In addition,the failure probability of slope almost keeps unchanged as the COV of hydraulic model parameter a varies,while the failure probability of slope decreases as the COV of hydraulic model parameter n increases.(4)A modified Green-Ampt model which can determine the distribution of soil moisture content and the wetting front depth within the slope under different rainfall durations is developed.Failure mechanism of the infinite slope considering the interaction of the spatial variabilities of multiple soil parameters and the rainfall infiltration is investigated.The results indicate that the weak zones induced by the spatial variability of shear strength parameters is the crucial factor that affects the slope stability during the initial period of rainfall,and the advance of the wet front is the crucial factor that affects the slope stability during the late period of rainfall.(5)The BUS method is adopted to update the soil parameters using the real field observation information in this paper.The safety fctor of slope calculated based on parametric posterior statistics is basically greater than 1.0,and the probability of slope maintaining stability reaches more than 90%,which indicate that the slope based on the posterior statistics of shear strength parameters will keep stable under natural condition,which is consistent with the engineering practice.Then,the failure mechanism and reliability analyses of slope are carried out on the basis of post-test statistics of shear strength parameters,and the failure mechanisms of slope under four different rainfall stages are revealed.