Assessment Of Spatial Variability Of Mechanical Parameters Of Ningbo Soft Clay

soil is the most basic and important objects in geotechnical study,the mechanical properties of soil are the base of design construction theoretical calculation of geotechnical engineering and other engineering characteristics researches.Meanwhile,affected by complicated geological processes,soil with significant uncertainty.Both extensive experimental data and rich engineering practice indicate that heterogeneity is an inherent characteristic of soil,which show obvious spatial randomness and spatial correlation of parameters of rock and soil,and called as spatial variability.How to objectively demonstrate and model the spatial variability of soil of mechanical parameters is the premise and key to geotechnical engineering practice.In this dissertation,Based on project of Ningbo rail transit,according to the random field theory,the Spatial Variability of mechanical parameters of Ningbo soft clay have been studied.1)Described the basic concept of random field theory and its digital characteristic,its stationarity and ergodicity.Introduced the concept of variance reduction function and the correlation distance,the existing calculating methods of correlation distance are introduced.2)Based on engineering geological investigation data of Ningbo rail transit line 1 project,the general situation of engineering geology in this area is summarized,though on the above analysis,the statistical analysis of the mechanical parameters of soft soil in Ningbo was carried out,and the feature statistics of the mechanical parameters of soft soil were obtained.to characterize the spatial randomness of the mechanical parameters of soft soil in Ningbo.3)Through testing the stationarity and ergodicity of the soil property parameters of soft soil in Ningbo,it is shown that the random field model is applicable to the soil profiles of Ningbo.And by CPT data,vertical scale of fluctuation of each layer of Ningbo soft was calculated;though mechanical parameters,lateral scale of fluctuation of each layer of Ningbo soft was calculated,the confidence interval of average value by Bootstrap method,the representative value of the scale of fluctuation of each soft clay layer in Ningbo soft soil is obtained,to characterize the spatial correlation of the mechanical parameters of soft soil in Ningbo.The vertical scale of fluctuation of soft soil in Ningbo is further discussed,the vertical scale of fluctuation for goodness-of-fit test,the test results show that the optimal probability distribution is Beta distribution,and the probability distribution model of the scale of fluctuation of each soil layer is established.The CPT test data were taken as samples,the problems encountered in the determination of scale of fluctuation by recursive subspace method are studied,results show that,the first peak point should be taken as the scale of fluctuation.The influence of sampling spacing on the correlation distance soft clay in Ningbo is analyzed,and the principle for determining the correlation distance of Ningbo soft clay with the varied sample spacings is presented.Introduces the random field modeling method,and applies the covariance matrix decomposition method to build the random field model of compression modulus based on the actual engineering survey data.