Research On The Synergistic Mechanism Of Existing Counterweight Retaining Wall And Newly-built Pile-slab Wall

With the rapid development of the national economy,the current railway transportation system is gradually unable to meet the increasing social needs,and the transformation and expansion of existing lines has become a key direction in the current railway construction.The Zhongwei-Lanzhou Railway(Gansu Section)was introduced into the Lanzhou hub project.The newly-built railway line is adjacent to the existing Lanzhou-Xinjiang Railway.Due to the limitation of the roadbed site,the existing slope supporting structure(pile foundation supporting beam counterweight retaining wall)was retained in the design.),build a new pile-slab retaining wall within the retaining range,and implement the widening of the existing roadbed and the construction of new third and fourth lines.The existing counterweight retaining wall and the newly-built pile-slab wall work together to form a new-old combined retaining structure and jointly bear the load of the railway subgrade.This paper conducts an in-depth study on the synergistic mechanism of this type of combined retaining structure.At present,there are few researches on the composite retaining structure at home and abroad,and few people have carried out the research on the composite retaining structure of the existing counterweight retaining wall and the newly built pile-slab wall,and there are few project materials that can be referred to.In order to further clarify the synergistic mechanism of the existing counterweight retaining wall and the newly built pile-slab wall,this paper is based on the calculation of earth pressure and the theory of retaining wall design,through field measurement and numerical simulation calculations,aiming at the width of the roadbed and the newly built three-fourth The impact of line construction on the existing subgrade and the existing counterweight retaining wall,the force and deformation characteristics of the pile-slab wall during the construction process,the load sharing ratio of the new-old retaining structure and other key issues are deeply analyzed,and numerical simulations are used The software discusses the influence of the pile size,pile spacing,and the layout of the composite retaining structure on the force and deformation of the structure in the new-old combined retaining structure,and has obtained rich research results,which can be used for the design and construction of such projects.Provide guidance and reference.The main research results obtained in this paper are as follows:(1)Conduct field test based on actual project.In the actual project on site,a typical section is selected,an earth pressure box is buried behind the pile-sheet wall piles to measure the earth pressure on the back of the wall,a rebar meter is installed symmetrically on the main reinforcement of the steel cage to measure and calculate the bending moment of the pile body,and the pile body is buried.An oblique tube is installed to measure the displacement of the pile body,and a large amount of actual measurement data is obtained to analyze the distribution law of the earth pressure behind the pile-slab wall and the force and deformation characteristics of the pile-slab wall.(2)Use Midas GTS NX numerical simulation software to simulate the actual project.Combined with site survey report and design data,3D modeling of typical road sections was carried out,and the influence of the construction process on the existing subgrade and counterweight retaining wall,the force and deformation characteristics of the newly-built pileslab wall were analyzed,and a theory based on earth pressure was proposed.To calculate the new-old supporting structure load sharing ratio calculation method.(3)Use Midas GTS NX numerical simulation software to study the influence of design parameters in the combined supporting structure.Establish a three-dimensional solid model of different pile body sizes(pile length,pile section size),different pile spacing and different newold retaining structure spacing,calculate the model and analyze the earth pressure behind the pile-sheet wall pile,the horizontal displacement of the anchored pile,The internal force of the anchor pile itself,the displacement and internal force of the existing counterweight retaining wall,and the calculation results of the load sharing ratio of the new-old retaining structure.Through comparative analysis,the effect of different factors is studied,and the most reasonable pile length and pile section are proposed.The value of size,pile spacing and spacing between new and old retaining structures.