Immersed tunnel for the Hong Kong-Zhuhai-Macao fixed link

Photo: COWI-HZM
Work is under way to build the fixed link Hong Kong-Zhuhai-Macao between Hong Kong and mainland China. The structure is considered China’s most important infrastructure project technically and politically and will include the world’s longest immersed tunnel for road traffic.
 

When the Hong Kong-Zhuhai-Macau fixed link opens, motorists will be guided out of western Hong Kong on a 5 km long bridge. From there, an immersed  tunnel will take them underwater some 6 km before they ascend a 23 km bridge that takes them to Macau and on to Zhuhai on China’s mainland. COWI is participating in the design of the immersed tunnel.

New immersed tunnel record holder

With approximately 32 elements submerged at depths of more than 40 metres below the water, the project pushes the boundaries for what is technically possible.

The tunnel will, for example, exceed the length of the current record holder – the Oresund fixed link’s immersed tunnel between Denmark and Sweden – by about 40 per cent.

Familiar challenges

The tunnel will be constructed on a soft seabed requiring soil improvement to prevent the elements from settling, and in rough, open waters under deep navigation channels trafficked by the world's largest ships.

The geographical area bears a lot of similarities to the Busan-Geoje fixed link.

Extra precautions

Sediment accumulation is another challenge to consider. The tunnel is placed in a deep excavated trench and after it has been in use for a few decades, layers of sediment up to 20 metres thick will accumulate above it. The sediment combined with water pressure from above will impose enormous forces on the tunnel’s central sections.

The design also has to address the risk of earthquakes in the area. In particular, the joints between the tunnel elements must stay watertight when exposed to seismic ground movements.

LAST UPDATED: 07.01.2017