Study On Horizontal Bearing Characteristics Of Pre-deformation Plus Carrier Behind The Foundation Of Arch Bridge On Mountain Based On Anchor-cable And Frame Beam

The geological conditions in the mountainous areas of southwest China are complex,and in order to meet the line spreading requirements,it is inevitable to build the bridge structure on slopes.The current design of the foundation of the arch bridge in mountainous areas often adopts the composite arch seat foundation with arch seat pile foundation,but under the geological conditions of thick overburden in mountainous areas,the foundation form cannot meet the horizontal displacement limit requirement under the horizontal thrust of the arch bridge.In order to solve this problem,a new composite foundation form of vertical pile + arch seat pre-deformation plus carrier is innovatively proposed,and the pre-deformation plus carrier in its foundation form is composed of prestressed anchor frame beam structure and geotechnical body behind the arch seat.Therefore,in this study,based on the arch of the north bank of a large bridge in the southwest Mountain area as the prototype,the horizontal bearing characteristics and influencing factors of pre-deformed plus carrier were studied and analyzed by model test and numerical simulation.The main contents and conclusions of this paper are as follows:(1)The reinforcement mechanism and force-deformation characteristics of the anchor cable frame beam structure are summarized and analyzed.Based on the characteristic that anchor frame beam structure has significant advantages in reinforcing the geotechnical body of slope,it is innovatively applied to the geotechnical body behind the foundation of arch bridge under thick overburden in mountainous areas to meet the horizontal displacement requirements of the arch base of the bridge.(2)By means of indoor model tests and finite element numerical analysis,two kinds of soils are selected to study the difference of horizontal bearing capacity of pre-deformed plus carrier and the original soil.The results show that the pre-deformed plus carrier has significant horizontal bearing characteristics compared with the original foundation soil,and reveal the deformation coordination mechanism of mutual offset between anchor cable prestress and horizontal load of frame beam,resulting in the reduction of horizontal displacement of predeformed stiffener by about 50.9% and 21.4% for coarse sand and fine gravel foundation soil,respectively.(3)The influence of anchor frame beam design parameters on the bearing characteristics of pre-deformed plus carrier structure was analyzed.The results showed that the size of anchor pre-stress has a small influence on the bearing characteristics of its structure;within a certain anchor cable inclination range,the horizontal bearing capacity of pre-deformed plus carrier increases significantly with the decrease of anchor cable inclination;the horizontal bearing capacity of pre-deformed plus carrier can be enhanced significantly by changing the spatial arrangement of anchor cable vertical spacing and transverse spacing reasonably.(4)By comparing the horizontal bearing capacity of the pre-deformed plus carrier structure of the two soils,the analysis shows that the anchor cable frame beam structure has a more significant reinforcement effect on the coarse sand soil prototype,while the reinforcement effect on the fine gravel soil prototype is not obvious.The research results of this paper are helpful to fully understand the bearing mechanism of anchor frame beam and geotechnical body together forming pre-deformed plus carrier,and promote the wide application of this new structure of pre-deformed plus carrier in strengthening the bearing capacity of geotechnical body.