Reliability Analysis Of Shallow Foundation In Unsaturated Soil Considering Spatial Variability

The spatial variability of soil and the suction of soil are the important factors which can influence the reliability analysis of unsaturated soil.A reliability analysis method with high efficiency and good accuracy is presented in this paper.The reliability analysis for shallow foundation of unsaturated soil is carried out which regarded foundation soil as random field on the basis of considering the spatial variability of soil parameters and simulating the seepage of rainfall,the main result are:The unsaturated soil of shallow foundation was regarded as a random field,and compared the commonly method that used to discrete random field,research has shown that the random variables acquired through center point method is associated with the model grid number,the result are usually disorder.The random variables of the Karhunen-Loeve series expansion method are mainly related to the number of truncation items,the result is gradual.The discrete random field is used for reliability analysis of unsaturated soil,and this paper contrasted the advantages and disadvantages of the MCSM and FORM: MCSM calculation accuracy is high,but usually requires a great amount of calculation,but FORM generally requires little number of iterations which during solution procedure of reliability index.The author finally found that it is an efficient method of the reliability analysis which discrete the random field though Karhunen-Loeve series expansion method,and then carrying out the reliability analysis of shallow foundation of unsaturated soil through FORM.The influence of rainfall intensity,initial suction,seepage time and self-correlation distance on the reliability analysis of shallow foundation of unsaturated soil was discussed.The results show that: with the increase of rainfall intensity,the reliability index of foundation decreases gradually;with the increase of initial suction,the reliability index of the foundation increases;with the increase of seepage time,the reliability index decreased first,and then tended to moderate;with the increase of autocorrelation distance,the base reliability index decreased.