A Chinese-led engineering consortium is constructing a subsea tunnel in Abu Dhabi using an unconventional cut-and-cover method supported by a steel cofferdam, a technique that has drawn attention for its scale and execution.

The Abu Dhabi 1B tunnel, linking Saadiyat Island with Umm Yifenah Island, is being built by a consortium led by China Railway International Group, with construction having begun in October 2024. Unlike traditional shield tunnelling or immersed-tube approaches, the project involves enclosing a section of the seabed with a single-row steel pipe pile cofferdam, allowing work to be carried out in a dry environment after seawater is pumped out.

According to project officials, excavation work has been completed and the cofferdam has been successfully sealed, with the structure remaining stable. The project has now moved into the main structural construction phase.

Engineering challenge below sea level

Project manager Liu Kun said the tunnel’s lowest point lies 27 metres below sea level, requiring the cofferdam to withstand significant water pressure while maintaining stability and watertightness.

He described the use of a single-row steel pipe pile cofferdam at this depth as unprecedented in terms of scale, noting that the approach required extensive structural testing and monitoring.

International design collaboration

Dorukhan Kellecioglu, head of the design team at Swiss-based engineering consultancy PINI Group, said the outcome exceeded initial expectations.

“We initially had doubts about whether a single-row steel pipe pile cofferdam could perform under such conditions,” he said. “Its successful application here represents a notable engineering achievement.”

Project management and regional impact

Hu Peng, project lead from China Railway International Group, said the tunnel reflects coordinated management across international partners, with a focus on risk control, construction sequencing and resource integration.

Once completed, the tunnel is expected to improve connectivity between the two islands and support Abu Dhabi’s wider transport network. Wu Lebin, deputy general manager of the international business department at China Railway Tunnel Group, said the project would contribute to regional mobility and economic activity.

Construction is scheduled for completion by the end of 2026.