Analysis and Research on the Inhibitory Effect of Pipe Shed on the Settlement of Top Push Underpass Bridge Pavement
To study the restraining effect of pipe sheds on road surface settlement during the entire process of jacking bridge construction,a case study was conducted on a municipal secondary road underpass project beneath an airport expressway.A three-dimensional finite element numerical simulation model was established,both without a pipe shed and with a Φ 402 pipe shed.The"layered block excavation method"and"birth and death element method"were employed to simulate the settlement patterns of the existing pavement during the jacking process,as well as the stress and deformation characteristics of the pipe shed itself.The results indicated that the established 3D numerical simulation model effectively simulated the pavement settlement under the advanced support of the pipe shed,with the calculated results closely matching the field monitoring data.During the jacking construction,using aΦ 402 pipe shed effectively restrained road surface settlement,especially near the entrance,with the maximum settlement generally meeting the requirement of being less than 20 mm.The deformation of the pipe shed exhibited four distinct segments,with lower stiffness on the left side and higher stiffness on the right side of the bridge structure,causing the pipe shed to display a noticeable spatial torsion.To better control surface displacement,the spacing between pipe sheds on the left side can be appropriately reduced,while on the right side it can be increased.After jacking is completed,grouting treatment at the top of the tunnel should be carried out promptly to reduce the total amount of pavement settlement.The research results provide a reference for the jacking construction of bridge-type shield tunnels under advanced support of pipe sheds.
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