Design Method And Test Study Of Bridge Foundation In Cross Steep Slope Based On Finite Bar Element Method

In the western of China,the construction of expressways have to be located at mountainous due to complex geological environments.In that cases,not only demands of the safety could be necessarily ensured,and the economy of planning should also be seriously considered.On account of this,the pile foundation of bridges that locates at steep slopes,termed steep-slopes-piles,can be essential to across the valleys.It is clear that the mechanical responses and performances of the so-called steep-slopes-piles could be more sophisticated than that of the conventional piles.In addition to the loads of the superstructure,the designer should take the earth pressure produced by the slopes into account;however,there is no specific design method in the current code.For this reason,details of the design method,including bearing capacity and load-settlement responses for the steep-slopes-piles,were carried out on aspects of theoretical analysis,model test as well as numerical simulation.This study is a part of the work carried out by grants from Western Transportation Construction Project of Transportation Ministry“Design and Construction Technology for Bridge Pile-column Foundation in High and Steep Cross Slope".In this study,the current situation of the design and calculation of pile foundation design in high and steep slope section is summarized in this paper,and the bearing capacity of pile foundation in steep slope section under complex load is analyzed,which could be utilized to establish the pile foundation force analysis model.Based on the traditional finite element,an improved finite element analysis method with uniform form is proposed,which could the "P-?" effect,pile-soil interaction and two-parameter foundation model.The internal force and displacement of the bridge pile are obtained certainly.On this basis,the influencing factors were analyzed.The results show that the influence of the horizontal load on the internal force and displacement of the pile foundation in the steep slope section is more significant than that of the earth pressure,but the effect of the earth pressure cannot be neglected.With the increase of the vertical load,the internal force and displacement of the pile increase obviously and the "P-?" effect is very apparent,which mean that small deformation superposition principle is no longer applicable.On the other hand,based on the characteristics of double pile structure and load characteristics,the whole force analysis model of bridge pile foundation in high and steep slope sections is established,which could consider the sliding wedge and earth pressure transmission.Based on the improved finite element,the reinforcement and deformation analysis of the double pile are obtained.On the basis of this,the influence of earth pressure,horizontal load on column top,beam stiffness and foundation soil resistance ratio coefficient on internal force and displacement of double pile foundation are analyzed emphatically.Then,the design and calculation flow of bridge pile foundation in high and steep slope could be put forward.In addition,relying on the actual engineering,the pile stress data of a pile foundation in high and steep slope in the whole process of bridge construction and bridge test are collected.On this basis,the axial force,pile side friction and pile bending moment distribution of pile are analyzed.Then,the distribution law of pile side earth pressure is fitted by inverse calculation.On the basis of the similarity principle,the indoor model test of double pile foundation under high and steep slope condition is designed,which could discuss the failure mode and internal force and displacement law of double pile foundation under different slope and pier height.Finally,based on the actual engineering,ABAQUS finite element analysis software is used to establish the double pile foundation model about piles in high and steep slope sections.The effect of slope deformation on pile foundation is discussed.In addition,the influence of some parameters including slope rock mass and elastic modulus on the development of internal force and horizontal displacement of double pile foundation are analyzed emphatically.