A key link in constructing the Zhuhai Bridge Tunnel – a concrete slab floor of a huge shield launch shaft -- was poured Dec 21 in preparation for 15.01-m (49.25-ft) diameter machines to begin boring 35 m (115 ft) below the riverbed next year.

The shield machine is called the "big power weapon" of tunnel construction. Two of them will be rolled off the assembly line early next year, and excavation will commence from both banks after on-site commissioning is completed. They will excavate 2,930 m (1.8 miles) through soft geology beneath the Modaomen Waterway.

Rendering of Zhuhai Tunnel project [Photo by Li Jianshu / Zhuhai Daily]

The 5-km (3-mile) tunnel will connect to Zhuhai Avenue on both ends of the heavily traveled east-west Zhuhai Bridge. It will have three lanes each way with a designated speed limit of 80 kmph (50 mph).

Zhuhai Avenue is now being widened with temporary roads on each side, leaving a working surface for tunnel excavation in the middle. Motorists will take middle lanes for the tunnel or side lanes to the bridge when the tunnel opens in 2024. 

China Railway Tunnel Bureau, the contractor, has extensive experience in dealing with soft and protuberant underlying bedrock. Among its benchmark projects is the Shantou Bay undersea tunnel in Guangdong Province on which shield tunneling with an excavation diameter of 14.57 m began last spring through complicated strata. 

A specialized technical committee was established in Zhuhai to conduct comprehensive technical research and address technical problems during construction.