Calculation And Settlement Prediction Of Pile Foundation Bearing Capacity Of Intercity Railway Viaduct In Deep Soft Soil Area

The bearing capacity of pile side soil in coastal soft soil area is low.In order to meet the requirements of bearing capacity,pile foundation is usually set as super long pile.At present,there is no clear definition of super long pile in the code,and there is no special provision and distinction for the calculation and design of its bearing capacity.In engineering,the design of super long pile is still based on the common pile foundation design theory,which is easy to lead to a certain deviation between the design value and the actual value of the super long pile.Although it can meet the safety requirements of the project,it is easy to lead to the excess bearing capacity of the pile and cause waste.Therefore,it is necessary to study the bearing behavior of super long pile in deep soft soil area.According to the bearing behavior of super long pile in deep soft soil area,a series of researches have been carried out on the sensitivity of pile foundation and soil parameters on pile foundation bearing capacity and soil mechanical properties inversion of pile side soil.Based on numerical analysis,theoretical analysis and measured data,use psosvr,which has the advantages of small sample,good stability and strong extensibility,to study The elastic modulus and Poisson’s ratio of the soft soil around the pile.Finally,combined with the engineering practice of Ningbo Fenghua intercity railway,the analysis model of deep soft soil pile foundation is established by numerical method,and the parameters affecting the bearing capacity and settlement of pile foundation are analyzed.The main contents and conclusions are as follows(1)This paper analyzes the loading characteristics of pile foundation engineering in deep soft soil area,the mechanism of pile side bearing capacity exertion,and the important influence factors of pile side resistance exertion,and puts forward the calculation method of pile foundation bearing capacity considering the factors of softening of pile side soil and depth effect.Through comparison,the error between the calculated pile foundation bearing capacity calculated by this method and the measured pile foundation bearing capacity is8.88%.The fruit is safe.(2)In this paper,the bearing capacity of pile foundation in practical engineering is analyzed by using numerical analysis method.By modifying the parameters of pile foundation and pile side soil one by one,the influence of different parameters on the bearing capacity of pile foundation is analyzed.The order of sensitivity of each parameter to the load displacement relationship of pile foundation is obtained as follows: pile length,Poisson’s ratio of pile side soil,elastic modulus of pile side soil,pile diameter,the stiffness of the pile body,the internal friction angle of the pile side soil and the cohesive force of the pile side soil are analyzed.(3)The particle swarm optimization(PSO)algorithm is used to optimize the parameters of support vector regression(SVR)kernel function with its advantages of strong grid searching ability and high efficiency.It is applied to the regression inversion of elastic modulus and Poisson’s ratio of soft soil around piles in deep soft soil area.The pile-soil interaction model is established by using the finite element method to check the inversion parameters.The results show that the error between the predicted value and the actual value is3.6%,that is to say,the psosvr inversion results have high accuracy and meet the requirements of engineering application accuracy.