Steel Caisson Installation Site, Photo by Shen Qiongyun

On December 3, with the completion of the successful placement of the steel caisson at Pier Q6 of Qinglongmen Bridge, the final steel caisson for the Ningbo Zhoushan Port Liuheng Highway Bridge was successfully lowered, marking the official transition of the entire project into the offshore construction stage.

A steel caisson is a cofferdam structure used for the construction of bridge pier caps. It also serves as the formwork for concrete pouring and plays the role of protection against collisions. The steel caissons installed this time measure approximately 45 meters in length, 26 meters in width, and 9.5 meters in height, with a total weight of about 516 tons. To ensure the smooth installation of the caissons, the Ningbo Meishan Maritime Safety Administration Department organized multiple evaluations of the project's steel caisson design, sinking and lowering procedures. These evaluations focused on reviewing and optimizing the construction technical plans to ensure the structural safety and stability of the steel caissons.

The maritime department continuously monitored weather conditions such as wind strength and wave data in the construction area and decided to begin the lifting operation on the afternoon of December 3. Additionally, the maritime department conducted patrols in the construction waters to ensure the safe escort of the steel caisson installation. Using an 800-ton crane vessel, the caisson was lifted, moved, positioned, and sunk. The caisson passed through 22 drilled pile foundations like a “needle threading through fabric”, gradually sinking into place and successfully completing the installation.

“The steel caisson adopted for No. 6 pier is reconstructed from the original No. 5 main pier steel caisson, which greatly improves the recycling efficiency of materials and effectively reduces the construction cost of the project." said Li Zhibo, manager of the project department of the Phase II Section 5 of Liuheng Bridge.

Ningbo Zhoushan Port Liuheng Highway Bridge is 31.4 kilometers long, including Qinglongmen Bridge and Shuangyumen Bridge, two world-class sea-crossing bridges. Qinglongmen Bridge, as the core control project of the entire project, is the largest three-tower steel box girder cable-stayed bridge in the world. Once the bridge is completed and opened to traffic, it will vigorously promote the development of the two core port areas of Meishan and Liuheng of Ningbo Zhoushan Port and the industry adjacent to the ports, which is of great significance to the construction of Ningbo Zhoushan Port into a world-class and powerful port. (Reporter: Weng Tianyu; Correspondents: Song Zuming, Shen Qiongyun)