Research On Underpinning Technology Of Pile Foundation In The Rear Wiring Section Of Xi'an Airport Intercity Rail

The Xi'an North Station to Airport Intercity Rail Project is the quick access to the two major transportation hubs of,Xianyang International Airport and Xi'an North Passenger Station.The airport station is the hub for airport and airport transportation and is located at the T3A terminal of Xi'an Xianyang International Airport.the station rear wiring,it is need to pierce the No.22 pier of the main line bridge of the existing T3A terminal.Based on the surrounding environment of the project and the actual situation of the existing mainline bridge,this paper stu,died the underpinning technology of the pile foundation of No.22 bridge pier of the existing mainline bridge by means of model tests,numerical simulations and engineering techniques.The main results are as follows:1.Design and make a local node model of the connection area between joist and existing pile caps,perform finite element analysis on the model forces,and perform progressive repeated loading static test on the pressure testing machine.Combine the finite element analysis and model test results,analyze the failure modes of the local node model,and obtain the cracking load,the average value of the ultimate load carrying capacity,and the shear strength of the node model and the joint.After converting the form of the "chiseling+drill anchorage+interface gel"joint to the actual underpinning project,the shear resistance of the four sides of the existing pile cap was determined.2.According to the principle of similarity,based on the principle of,symmetry and force equivalence,a 1:4 overall model of 1/2 toe-changing beam was designed and manufactured,and a progressive repeated loading static test was performed on the test bench.The flexural capacity,shear capacity and anti-sliding ability of beam-pier-turret-pile joints under underpinning loads were tested and analyzed.And analyze the strength,stiffness and crack resistance of the underpinning beams.Analyze the failure form,elastic ultimate load-carrying capacity and ultimate load-carrying capacity of the underpinning beam structure.3.finite element analysis software was used to establish a finite element analysis model for the complex bridge structure in the upper part of the pier.By calculate and analyze the combination of the most unfavorable load effects,the limit value of the bridge pier during underpinning of the bridge pile foundation was obtained.