Reliability Analysis Of Slopes In Normally Consolidated Clays Considering Spatial Variation Of Parameters

Slope stability research is an important subject in the field of geotechnical engineering,which is of great significance to the excavation of urban underground foundation pits,water resources and hydropower,highway subgrade and other engineering constructions.The deterministic analysis methods such as traditional limit equilibrium method and numerical method cannot be used for the risk assessment of slope stability,and the random stochastic finite element analysis of slope reliability is mainly based on the assumption of stationary random field,and the non-stationary characteristics of soil parameters are rarely considered.This study aims at the shortcomings of existing slope reliability analysis methods,based on the random finite element method,and establishs a method to study the reliability of normally consolidated clay slopes considering the spatial variability of parameters.The main contents are as follows:(1)This study introduces the random finite element analysis method of slope reliability briefly.Based on probability and statistical theory,a non-stationary random field model suitable for normally consolidated clay slopes is proposed.Based on this model,a random finite element analysis method for normal consolidated clay slopes considering the spatial variability of parameters is established.Through comparison with existing research,it is found that when the slope safety factor is low,the assumption of normal distribution of strength parameters will underestimate the failure probability of the slope and give unconservative results.In this case,the assumption of the lognormal distribution of the intensity parameters must be used;(2)Based on the random finite element method,considering the anisotropy of the undrained strength of the soil,the reliability analysis method of normally consolidated clay slope under anisotropic conditions is established,and the reliability of the anisotropy of the undrained strength to the slope is explored degree of influence.It is found that if the effect of undrained strength anisotropy is ignored,the failure probability of the slope will be underestimated,and unconservative results will be obtained.The lower the coefficient of variation of undrained strength,the more the effect of anisotropy cannot be ignored;(3)Based on the random finite element method,this study researched the worst-case spatial correlation length of normally consolidated clay slopes.Through the relationship curve between slope probability of failure and related distance,the influence law of the average slope factor of safety and the coefficient of variation of undrained strength on the worst-case spatial correlation length of normally consolidated clay slope is obtained.When the mean value of the slope safety factor is low and the undrained strength variation coefficient is high,the location where the worst-case spatial correlation length occurs is the most obvious.The worst-case spatial correlation length can be used for conservative design for reliability analysis of normally consolidated clay slopes;(4)For the failure mechanism of normally consolidated clay slopes,random finite element method program can automatically search for the most dangerous sliding surface,and finds that when the coefficient of variation of undrained strength is high,the sliding surface ratio of normally consolidated clay slopes The sliding surface obtained by deterministic analysis is deeper.When considering the anisotropy of undrained strength,the shape of the sliding surface will appear partially "linear".