Reliability Analysis Of Foundation Engineering Considering Soil’s Spatial Variability

Due to various geological effects in nature,the properties of soil have spatial variability.Within a certain scale of spatial fluctuations,the soil parameters between various points affect each other.Urban buildings and various infrastructures are located on the soil,so the spatial variability of the soil will affect the reliability of the foundation project.At the same time,due to the tight land use of urban buildings,the distance between the two buildings is very close,so it is necessary to analyze the influence of the foundation distance on the reliability of the foundation project.This paper takes the shallow foundation in the spatially variable soil as an example to study the reliability of foundation engineering.The main results are as follows:1)In order to study the spatial variability of soil parameters,a large number of basic property tests,shear tests and consolidation tests are carried out on cohesive soil samples in a certain area of Hefei city,and the physical property parameters,strength parameters and deformation parameters of the soil are measured.Probabilistic statistical analysis is carried out on the soil parameters obtained from the experiment,and the mean value,mean square error,coefficient of variation and probability distribution type of the parameters are obtained;the scale of fluctuation of the soil parameters is calculated by the autocorrelation function method.The calculation results show that the variability of the strength and deformation parameters is much greater than the variability of the basic soil parameters of the soil.Therefore,the spatial variability of the cohesion c,the angle of internal friction φ and the elastic modulus E need to be considered in the subsequent calculation of the reliability of the foundation engineering.All soil parameters satisfie the normal distribution or log-normal distribution;the horizontal scale of fluctuation of the cohesive soil samples in Hefei city is about 6.8 m,and the vertical scale of fluctuation is about 0.7 m.2)In order to study the influence of soil spatial variability on the reliability of foundation engineering,a single-foundation model and a dual-foundation model are established respectively.For the single-foundation model,the cohesion c,the angle of internal friction φ and the elastic modulus E are regarded as log-normally distributed random fields.The Karhunen-Loeve series expansion method is used to carry out the random field discretization,and the fluctuation of the scale of fluctuation and coefficient of variation of the geotechnical parameters on single-foundation reliability indexes are analyzed.For the dual-foundation model,the distribution type of the settlement difference between two adjacent foundations and the influence of foundation spacing on the reliability of the dual-foundations were analyzed.Research shows that with the increase of the scale of fluctuation of the geotechnical parameters and the coefficient of variation,the reliability index of foundation settlement difference decreases;the differential settlement between two adjacent foundations obeys the normal distribution,and the settlement of the single foundation obeys the logarithmic normal distribution;The larger the distance between the two foundations,the larger the reliability index of differential settlement between two adjacent foundations,and the smaller the mutual influence between the two foundations.