Hangzhou Bay Cross-Sea Railway Bridge

First Main Tower Pier Pile Foundation Construction Completed

At 16:18 on October 22, on the sea surface of Hangzhou Bay—one of the world's three major strong-tide bays—as the last truckload of concrete was poured into Pile Hole No. 6 of Main Tower No. 8 of the North Channel Bridge of the Hangzhou Bay Cross-Sea Railway Bridge, it marked the completion of pile foundation construction for the first main tower pier of the world's longest cross-sea high-speed railway bridge—the Hangzhou Bay Cross-Sea Railway Bridge on the Nantong-Ningbo High-Speed Railway.

The Hangzhou Bay Cross-Sea Railway Bridge is a key controlling project of the Nantong-Ningbo High-Speed Railway. It adopts ballastless track, has a design speed of 350 km/h and a total length of 29.2 km, and comprises three channel bridges—north, middle and south—as well as approach bridges crossing the embankment, in the sea and in the shallow shoal area, making it an ultra-long, large-scale high-speed railway bridge cluster project. Among them, the North Channel Bridge has a main span of 450 m and is the world's largest-span ballastless-track cable-stayed bridge with twin towers, twin cable planes and a steel box-steel truss composite girder; the Middle Channel Bridge has a main span of 2×448 m and is the world's largest-span ballastless-track three-tower cable-stayed bridge; and the South Channel Bridge has a main span of 364 m.

The North Channel Bridge of the Hangzhou Bay Cross-Sea Railway Bridge is 932.7 m long in total and has two main towers—Main Tower No. 8 at the north end and Main Tower No. 9 at the south end—both of curved H-shaped reinforced concrete structure. Main Tower No. 8 is 200 m high and has 52 bored cast-in-place pile foundations with a diameter of 2.5 m, arranged in a plum-blossom pattern, with a maximum pile length of 129.5 m and a drilling depth of about 151 m, making them large-diameter ultra-long bored piles.

It is reported that the sea area where Pier No. 8 is located has complex geological conditions, mostly flowing-plastic or soft-plastic layers, making hole formation and pile formation difficult. To ensure the progress of bored pile construction and the quality of hole formation, China Railway Major Bridge Engineering Group developed the SWDM800 large rotary drilling rig, with a maximum drilling diameter of 4.5 m and a drilling depth of up to 155 m. This equipment was used in relay drilling with the XR580 rotary drilling rig to form the holes, and was equipped with corresponding hole-forming equipment. At the same time, the construction process was optimized, and methods such as pre-assembling the main cage and tremie pipe in place in advance at adjacent holes were adopted, saving the time for lowering and splicing the reinforcement cage and tremie pipe and greatly improving construction efficiency.

The Nantong-Ningbo High-Speed Railway line starts from Nantong West Station of the Yancheng-Nantong High-Speed Railway, runs south through Suzhou City of Jiangsu Province and Jiaxing City and Ningbo City of Zhejiang Province, and leads into Ningbo Station of the Ningbo hub. The newly built line is 301 km long, with a design speed of 350 km/h and a construction period of 5 years.