The Study On Nonhomogeneous Of Soil Parameters And Reliability Of Soil Slope

Reliability evaluation of slope stability is a very important research content in geotechnical engineering,and the uncertainty of soil parameters in geotechnical engineering is an important factor affecting slope stability.Due to the difference of geological,chemical and environmental effects,the soil parameters show the fluctuation and trend along depth.The common mathematical models describing the uncertainty of soil parameters are divided into two categories: random variable models and random field models.The random variable model neglects the spatial variability of soil parameters.Random field model can effectively simulate the spatial variability of soil parameters,which is often used in slope stability reliability analysis.In the homogeneous random field model,it is usually assumed that the fluctuation scale of the soil parameters are constants.However,the existing non-homogeneous random field models,although considering the non-homogeneous characteristics of soil parameters,are all derived from the evolution of the homogeneous random field model,and lack of in-situ test data support.For the slopes with different soil types,especially those with local weak layer,the homogeneous and non-homogeneous model can not effectively simulate the influence on the slop stability by the weak layers.Therefore,this paper studies the non-uniform characteristics of statistical characteristic parameters of different soil parameters of clay,based on the multi-element soil property database established by TC-304 website,and the clay in Norway,Sweden,Finland and other regions is screened out,and the soil parameters with depth parameters are extracted.On this basis,a layered non-homogeneous random field model of soil parameters with multi fluctuation scales along the depth direction is present.Furthermore,a simplified layered non-homogeneous random field model is proposed for engineering application.According to the stratification characteristics of soil slope,the mean value and the variance of soil parameters are assumed as the functions that are varied with depth of different soil layers.The covariance matrix of the present non-homogeneous random field is constructed by exponential correlation function.By the combination of the non-homogeneous random field model of soil parameters with the plastic limit analysis method,the reliability of slope stability is analyzed for a practical engineering,and the difference of critical slip surface and stability reliability between different random field models is compared.The influence of non-uniform fluctuation of shear strength parameters such as cohesion and internal friction angle of the soil on the shape and position of critical slip surface and the reliability of slope stability is studied.The main conclusions of this paper are as follows:(1)Compared with the homogeneous random field model and the linear continuous non-homogeneous random field model,the layered non-homogeneous random field model can effectively consider the discontinuous change of the statistical characteristic parameters of the soil parameters with depth,which provides an effective way to reasonably characterize the non-uniform characteristics of the soil parameters.(2)The spatial variability of soil parameters leads to a variety of failure modes,and different random field models lead to significant differences of the shape and location of the critical slip surface.For the layered slope,the slip mode of the linear continuous non-homogeneous random field model is the shallow slip mode at the top of the slope,which is inconsistent with the engineering experience;the slip mode of the layered non-homogeneous random field model is the deep slip mode through the weak soil layer or weak interlayer,which is more consistent with the engineering experience.(3)For layered slope composed of many kinds of soil,in the homogeneous random field model,the spatial variability of the mean and variance of soil parameters is ignored,and the slope stability will be overestimated;Compared with the linear continuous non-homogeneous random field model,the calculation results of layered non-homogeneous random field model considering the discontinuous change of the statistical characteristic parameters of soil parameters along the depth are more reasonable.