Research On Reliability Design Method Of CFG Pile Composite Foundation

Based on the design theory of composite foundation,the reliability limit state theory of CFG pile composite foundation is studied in this paper.Firstly,the limit state equation is established by determining the random variables,and the reliability index?of CFG pile composite foundation is studied by JC method.Then the reliability index of CFG pile composite foundation is discussed,and the influence law of each random variable is analyzed.The partial coefficient of load and resistance is given by general separation method,and the partial coefficient of load and resistance is calibrated.In this paper,the reliability of CFG pile composite foundation is studied,and the result can be used as the reliability of composite foundation.The design method provides a certain reference.The main studies are as follows:?1?At present,the traditional safety factor design method is still used in composite foundation,which does not take into account the discrete degree and specific distribution of random variables.Based on the design theory of composite foundation and reliability theory,the limit state equation is determined in this paper.?2?According to the established limit state equation,the calculation program was compiled by Matlab,to solve the reliability index?.Under different conditions,the reliability index?of CFG pile composite foundation is about 3.57,3.59,3.62,and the sensitivity analysis of the related variables is carried out:The reliability index increases with the increase of pile side resistance,pile end resistance and replacement rate;The reliability index decreases with the increase of the coefficient of variation of the pile side resistance,and the reliability index decreases with the increase of the coefficient of variation of the pile end resistance,The reliability index decreases rapidly with the increase of the coefficient of variation of the pile side resistance;The reliability index decreases with the increase of the constant load coefficient of variation,and the reliability index decreases with the increase of the live load coefficient of variation,The reliability index decreases rapidly as the coefficient of variation of the live load increases.?3?The calculation results of resistance partial coefficient and load partial coefficient of CFG pile composite foundation are as follows:The item-coefficient of pile lateral resistance?₁ was 0.82,the item-coefficient of pile tip resistance?₂ was0.95,the item-coefficient of static load?₃ was 1.22,and the item-coefficient of dynamic load?₄ was 1.43,After calibration,all of them meet the requirements.?4?The partial coefficient of CFG pile composite foundation is calculated by MIDAS/GTS finite element numerical simulation,and the results meet the requirements.