Analysis On Mechanical Characteristics Of Pile Foundation Of Viaduct In Deep Soft Soil Area

There is a large range of soft soil in the southeastern coastal areas of China,whose thickness can reach tens of meters.Soft soil has high water content,low bearing capacity,large compression,slow consolidation and poor engineering properties,so large diameter and super-long pile group foundation is the main type of bridge foundation in this area.Negative skin friction of bridge pile foundation in soft soil area can not be neglected.The negative skin friction of pile foundation will be caused by the surface soil surcharge adjacent to pile foundation,the consolidation settlement of the soil around pile during the preloading period and operation period of the road under the bridge,which will have a great influence on the mechanical characteristics of the pile foundation.In this paper,based on Wengyan Viaduct of Zhejiang Coastal Expressway and the road under the bridge as the engineering background,the mechanical characteristics of viaduct pile foundation in deep soft soil area were studied.The main research contents are as follows.(1)Understanded the research status of negative friction of pile foundation at home and abroad;summarized the theoretical study of pile-soil interaction,the analysis method of negative skin friction of single pile and pile group and the calculation theory of pile group settlement.(2)Taking the pile group foundation of 21# pier of Wengyan Viaduct as the research object,combined with soil surcharge of field,the Midas/GTS NX finite element numerical model was established to analyze the influence of adjacent soil surcharge on the mechanical characteristics and settlement of pile foundation of viaduct under different working conditions.(3)By using the sensors embedded in the pile foundation of 30# pier of Wengyan viaduct during construction,the field axial force monitoring test was carried out.The monitoring data of pile foundation axial force during the preloading period of the road under the bridge were sorted out,and the changes of the mechanical characteristics of the viaduct pile foundation during the preloading period of the road under the bridge were analyzed.(4)Aiming at the axial force monitoring test of 30# pier pile foundation,the Midas/GTS NX three-dimensional finite element model was established to analyze the variation of the mechanical characteristics and settlement deformation of the viaduct pile foundation with time during the preloading period of the road under bridge,and compared with the field monitoring data.The influence of the road under bridge on the mechanical characteristics of the viaduct pile foundation with the consolidation time was explored in operation period,and the mechanics and settlement deformation of the pile foundation were predicted.