Elevated Flyover With Large Span And Large Tonnage Pile Underpinning Experimental Research And Application

With the rapid development of China’s economy,the traffic volume of each big city is increasing day by day.In order to solve the problem of traffic congestion,the rapid rail transit system represented by the subway tunnel has become the inevitable trend of historical development.Because most of the city in the early planning without considering the subway,so it is inevitable to cross the bridge,the pile foundation of the building.The most economical and effective way to solve this problem is pile foundation underpinning technology.For pile base for structure and underpinning beam joint connection properties,especially the underpinning structure internal system by force mechanism and so on is still less,all of which need further study.Based on Xi’an Xianyang International Airport pile base project,the pile foundation underpinning beam physical model experiment,and using large-scale finite element software modeling,simulation analysis and study of large span large tonnage pile underpinning beam by mechanical properties,bearing capacity,deformation capacity and failure form.The main content of this paper is:(1)To explore the pile base for technology research status and existing problems,analysis of the subway tunnel crossing the bridge foundation,large span large tonnage pile base for the characteristics and difficulties of the structural system,a clear research direction.(2)Discusses the pile foundation underpinning theory and method,relying on Xi’an Xianyang International Airport pier pile base engineering,analyzes the typical project and combined with the characteristics of the project,put forward reasonable and feasible bridge pile base for architecture scheme,key technology and work flow.(3)Using similar theory designed and made the underpinning beam(beampier-cushion cap-Pile joint)1:6 overall test model and 1/2 support for beam(beampier-cushion cap-Pile joint)1:4 overall test model,conducted static loading test.(4)analysis of the strain test results,mainly research the test of bearing capacity,destruction form,main reinforcement,anchorage force and the plane section assumption and other properties,and numerical analysis of underpinning beam displacement and deflection.Analysis of the actual load for supporting the original bridge underpinning system mechanical performance,and provide experimental basis for strong practical engineering.(5)Using the finite element software to establish the underpinning structure refined finite element model,in-depth study of pile foundation underpinning the load transfer mechanism and prestress underpinning beam underpinning structure internal force characteristics,and to validate and complement the accuracy of test results.In this paper,to verify the selected support for structural system scheme is successful,as future pile base for engineering especially large tonnage,large span pile base for provide the technical and theoretical support.