The Soft Soil Roadbed Abutment Pile Design And Calculation Of Key Issues

Usually the joint segment of embankment and bridge is heightened and broadened, if there is thick auger ground under the embankment of bridgehead, the embankment loads on the soft soil and make it lateral distortion and consolidation , three primary aspects influence on nearby piled bridge abutment and superstructure are in existence: (1) Subgrade earthfill of bridgehead makes the auger ground lateral distortion, accordingly the distorted soft soil extrudes the pile body, which makes the piles deflection even fracture (2) Subgrade earthfill of bridgehead induces the foundation soil consolidation, accordingly negative friction makes the pile foundation settlement even differential settlement.(3)The influence is the disadvantage to the abutment and superstructure, specially movement of abutment, great movement of abutment can make the bearing ,expansion device, back wall and beam local pressure distortion even fracture. When the earth is filled in advance, movement of abutment induces the contraction of span and cannot install the precast beam. Although the earth fill is cleared, the displacement cannot recover.The interaction of soil and piled bridge abutment on the soft soil foundation has the important engineering background and research significance. The paper mostly researches the lateral interaction.(1) Systematically summarize and discourse all sorts of the existing calculation theory and analysis method of the interaction of soil and piled bridged abutment on the soft soil foundation, including experiential method, earth pressure method, displacement method and finite element method.(2) The embankment on the back of bridge abutment and the conical slope produce the additional vertical stress in the abutment foundation.The stress is the key parameter to calculate the differential settlement and the lateral movement of the abutment, the lateral pressure and flexibility of the piled bridged abutment. The paper, based on the elastic theory formula and the superposition principle, deduces the calculation formulas of the stress, and solves the problem of the existing code only applicable to single-track roadbed and error due to looking up table with interpolation. In addition, the formula is apt to make the compute program. (3)The present computational methods of lateral earth pressure on piled bridge abutment are analyzed and compared. Based on the application of the limited earth pressure,the paper uses the mobilization factor of lateral force a_m to solve the method of earth pressure of the pile body in liquid and plastic zone(4) Mechanics model of bridge abutment- bearing platform -pile interaction is built, which can take multilayer soil, the parameters of the soil and piles, and lateral earth pressure into account, and the computation expression is deduced. Based on the foundational differential equation of the strength bar, the new method of applying the transfer matrix method to analyze bridge abutment and pile's internal force and displacement is brought forward. It can not only analyze single pile but also pile group.(5) The method of judging the abutment movement is comprehensively analyzed and the additional horizontal force, stability, horizontal displacement of abutment on the thick soft soil foundation in the Wen-FU railway are systematically calculated. For the reasons given, the effective technical measures, which are applied to control the lateral displacement of abutment, are preliminarily brought forward. It elaborate the necessity and important significance of field monitoring and examining...