Busan-Geoje immersed tunnel and bridges, South Korea

Photo: COWI
The Busan-Geoje fixed link including the deepest immersed tunnel to be built in open waters is now open to traffic in South Korea. The immersed tunnel represents a major leap forward in immersed tunnel technology

The fixed link between South Korea's coastal city Busan and Geoje Island was officially inaugurated in December 2010. The opening of the Busan-Geoje fixed link marked the conclusion of seven years' work on the world's deepest immersed tunnel and two major cable-stayed bridges.

COWI lead consultant on tunnel and bridges

 

The fixed link reduces travel times between Busan and Geoje Island from 3.5 hours to 40 minutes. Construction work was carried out by South Korean contractor Daewoo Engineering & Construction Company. COWI served as lead consultant on the detailed design of both the immersed tunnel and bridge segments of the project.

World's deepest immersed tunnel open for traffic

With its lowest foundation point at 48 metres below sealevel, the immersed tunnel is the deepest immersed tunnel open for traffic in the world. The depth together with long swell waves made installation particularly challenging.

Extreme design conditions

The location of the fixed link on the Korean south coast with direct access to the open sea exposes it to extreme weather conditions such as typhoons and huge swell waves. These waves create a fluctuating pressure around the immersed tunnel during passage, leading to a maximum hydrostatic design pressure of 65 metres water depth. In addition, the area is prone to seismic activity with a fault zone in close vicinity, resulting in a challenging design of the tunnel element joints.

Advanced soil improvement techniques

COWI extended the use of advanced techniques for soil improvement below the immersed tunnel to new depths. A mixture of replacement, sand compaction piles and cement deep mixing was used to stabilise the soil down to 65 metres below sealevel.

LAST UPDATED: 21.12.2016