Concrete for the final closure joint of the Hong Kong-Zhuhai-Macao Bridge (HZMB) immersed tunnel began to be cast by 232 workers at the Guishan Island Immersed Tube Prefabrication Factory on March 13. This will clear the way for the undersea tunnel to be fully connected after submergence of the unit next month.

Workers ready to pour concrete 

The 2,400-ton steel shell was shipped from Nantong in Jiangsu Province on stone-laying and compacting barge Zhenbo 28 on Feb 27. It docked at Guishan Island in Zhuhai on March 7.

Casting of concrete with high fluidity began at 10:30 am using trailer pumps. Yang Zhen, head of the project's quality inspection department, said the concrete would be cast in five installments depending on force bearing and structural features. The first pouring of 394 cubic meters will take 10 hours and the second of 263 cubic meters seven hours. Casting of next three segments will take three hours for 82 cubic meters, seven hours for 268 cubic meters, and eight hours for 321 cubic meters.

Workers cast concrete [Photos by Zhong Fan / Zhuhai Daily]

Zhang Hong, deputy project manager of the Sanyi Work Zone of the Island & Tunnel Project, explained that the final closure joint adopts an elastic steel structure with an upper base of 12 m and lower base of 9.6 m. This type is the first to be used in a domestic undersea tunnel. After about 15 days of casting and accessory structure installation, the 5,500-ton final closure joint will be delivered and sunk for installation to achieve full connection of the world's longest undersea tunnel.