Study On The Characteristics Of Pile Foundation During The Construction Of Viaduct And The Road Under Bridge In Deep Soft Soil Area

As one of the oldest forms of foundation,pile foundation has been widely used for its simple construction,small settlement deformation and high bearing capacity.Especially in deep silt soft soil area,pile foundation has become a major foundation form.The engineering practice has proved that the external load has a great influence on skin friction of pile,in which the negative friction not only can not bear the load of the upper structure,but also has a pull down effect on the pile,which affects the normal use of the building.Therefore,it is of great practical significance to study the load transfer characteristics of negative skin friction of pile foundation,and to study the force characteristic of bridgepile foundation.The main work of this paper is as follows:(1)Based on the analysis of the load transfer law of pile foundation,this paper analyzes the mechanism of negative skin friction under the pile-soil interaction,and the distribution of the neutral point is studied;calculation method of negative skin friction of single pile and pile group.(2)The working characteristics of single pile and pile group under different conditions are analyzed,and the influence of different parameters on the negative skin friction of pile,the axial force of pile,the displacement of pile top and the settlement of soil around pile are studied,comparative analysis of theoretical calculation,measured data and numerical simulation results to prove the reliability of finite element analysis.(3)Based on the engineering background of NO.9 piers in the fourth contract section of Yongtaiwen Expressway,the test piles were selected for field test,designing the sensors embedded scheme according to the engineering situation and test piles,collecting test data,and the influence of different construction stages on the axial force and negative skin friction of pile is analyzed.(4)Aiming at the field test of NO.9 bridge pier,the 3D whole model was established established by using the finite element software of PLAXIS 3D,and the variation law of the axial force of pile,the negative skin friction of pile side and the displacement of pile top in different construction stages are analyzed;changing the construction process,establishing the numerical model,comparing the working characteristics of the pile under different construction processes,and studying the difference of the influence degree of the road construction process on the pile foundation,and providing the basis for the reasonable choice of road construction.