Research On Bearing Characteristics Of Rectangular Pile Group Foundation Of Long Span Arch Bridge With Thrust

Rectangular pile is a new type of pile foundation with rectangular cross section.When the cross-sectional area of the pile is constant,the cross-sectional circumference of the rectangular cross-sectional pile is greater than that of the circular cross-sectional pile.So under the condition of using the same amount of concrete,the lateral area of the rectangular cross-sectional pile is larger.The moment of inertia and stiffness of the rectangular cross-sectional pile are both larger than that of the circular cross-sectional pile,and the bending resistance is stronger.Therefore,the horizontal bearing capacity and vertical bearing capacity of rectangular section pile are both superior.However,rectangular piles are more often used as anti-slide piles in deep foundation pit and high slope support engineering of subgrade.It is very rare for rectangular piles to be directly used as the foundation of bridges.There are gaps in theoretical research and practical application.Some empirical formulas and understanding of regularity obtained in the study of circular piles need to be further verified by practical engineering for rectangular piles.The rectangular pile group foundation is used as the abutment foundation for the first time in the Hetonghuang G3 high-speed large-span arch bridge of the Yangtze River to Jihuai River Diversion Project.The research on this project can provide theoretical support for the application of rectangular pile group foundation in bridge foundation.Based on the Hetonghuang G3 high-speed large-span arch bridge of the Yangtze River to Jihuai River Diversion Project,this paper uses the method of combining field test,finite element calculation and theoretical analysis to carry out in-depth research on the bearing characteristics of rectangular pile group foundation,and gets some useful results,which lays a foundation for further research.The main work contents are as follows:(1)A total of 10 piles of the arch abutment foundation of the Hetonghuang G3high-speed large-span arch bridge of the Yangtze River to Jihuai River Diversion Project are subjected to on-site monitoring tests for the whole period of construction.The change law of the moment,the horizontal displacement of the pile body and the pile side soil pressure under the combined action of horizontal and vertical loads is obtained.The long-term monitoring results show that the rectangular pile group foundation has good mechanical properties,the internal force and horizontal displacement of the structure are within the prescribed allowable values during the whole construction process,the existing rectangular pile group foundation is safe and reliable,and the structural design and site monitoring scheme of the rectangular pile group foundation are feasible.(2)The finite element software ABAQUS is used to conduct in-depth research on the bearing characteristics of the rectangular pile group foundation under horizontal and vertical loads.The rectangular section single pile foundation and rectangular section pile group foundation of the Hetonghuang G3 high-speed large-span arch bridge are established.The comparative analysis of the same circular cross-section pile foundation and rectangular cross-section group pile foundation models highlights the superiority of the rectangular pile foundation’s bearing performance from the aspects of pile internal force and displacement,pile foundation horizontal bearing capacity,and pile group effect.(3)The theoretical calculation method for the horizontal bearing performance of pile foundation is introduced.Relying on the Hetonghuang G3 high-speed large-span arch bridge project,the theoretical calculation method m method and p-y curve method are used to calculate the internal force and displacement of the rectangular section pile group foundation,and the theoretical calculation is carried out.The results at the stage of cap construction,arch abutment construction and superstructure construction are compared and analyzed with field test data.The variation law of internal force and deformation of rectangular pile obtained by the theoretical calculation method is consistent with the field measured data,and the calculation error is between 1% and 15%.Compared with the measured values,the internal forces calculated by API standard method and M method are slightly larger,the deviation is less than 5%,and the applicability is good.The results show that the rectangular pile equivalent to the circular pile of the same width,the same area and the same circumference is the most close to the field measured value,and the method can be given priority in the calculation.