World's longest sea crossing opens to traffic

24.10.2018

The new Hong Kong-Zhuhai-Macao link includes the world's longest immersed tunnel for road traffic, which for Chinese contractors was designed using an innovative watertight concrete structure developed by COWI's tunnel experts.

The 55 km long Hong Kong-Zhuhai-Macao Bridge connecting Hong Kong with Macao and Zhuhai on the Chinese mainland across three cable-stayed bridges and an undersea tunnel between two artificial islands officially opened to traffic this week.

This mega-project is expected to reduce journeys from Hong Kong to Zhuhai and Macao by road from 4 hours to just 45 minutes, while strengthening trade, finance, logistics and tourism throughout the region.

The 5.6 km long immersed tunnel is the longest in the world for road traffic and includes two bores with three lanes in each direction and a service gallery in between.

The deepest foundation is located at a remarkable 44 m below sea level. Over 30 tunnel elements were built and installed, with each measuring up to 180 m x 38 m x 11 m and weighing 72,000 tons. 

The design approach was similar to what was implemented on the Øresund tunnel connecting Denmark and Sweden and the Busan-Geoje fixed link tunnel in South Korea.

Tommy Olsen, Project Director at COWI and Design Manager on the project commented:

"This project is key for the region to enhance economic development and improve connectivity, but it is also an important project for our immersed tunnel specialists. The project allowed us to develop new and improved methods for designing foundations, not only for the Hong Kong-Zhuhai-Macao tunnel, but also for future immersed tunnels.”

Given the constraints on construction cost, programme and the complex geotechnical conditions in the area, the design involved a watertight concrete structure concept (primarily used in Europe) to ensure a durable tunnel and long service life.

“We look forward to using our experience in this unique location and expertise in long immersed tunnels on some of the world's most complex underground projects in the coming years," said Tommy Olsen.