Shengte Engineering Case: Replacement Foundation Project for Ten Bridges on Chengdu-Chengdu-Lele Railway

The Airport Road Tunnel spans from DK165+530 to DK170+920, with a total length of 5,390 meters. Located in the city of Chengdu, the tunnel employs excavation methods for the section along the Third Ring Road, while the rest is constructed using the open cut method. Starting from the Chengdu South Railway Station, the tunnel descends at DK165+530, proceeding along the left side of the Airport Highway. It passes beneath ten bridges, including the West Ring Link Railway Bridge, the Third Ring Blue Sky Interchange Bridge, the Third Ring Blue Sky Ramp Bridge, and the Chengdu-Ya'an Expressway Interchange Bridge, with a significant number of underpasses.

The project employed the patented technology "New Construction Tunnel Crossing Existing Buildings Replacement System." Construction began in May 2014, and all underpinning lifting work was completed by early 2015.

Key Technologies: Active Transfer, Loading Lifting, Displacement Deformation Control, Prestress

The new construction technique of this project presents a challenge, as does the pre-topping and system conversion. Tunneling work inevitably disturbs the soil around the new replacement piles, increasing lateral movement. The excavation and support of the tunnel also alters the load-bearing system of the replacement structure, making it a second challenge to minimize the impact of tunneling on the piles. The bridge with the replacement foundation piles continues to be used during the foundation replacement process, and the high traffic volume is sure to affect the system conversion and the safety of cutting the piles, which is the third challenge. The upper structure's ability to adapt to uneven settlement between new and old piles is quite limited. The settlement and deformation of the old piles should be considered largely stable in the absence of new influencing factors. However, the new replacement piles will inevitably settle and deform under load, thus controlling the settlement and deformation of the replacement structure is a core issue in pile foundation replacement.