Bringing submerged floating tunnels into reality

Opening up new crossings with innovative solutions

Designing crossings for long, large or deep bodies of water has long been a challenge for engineers. Weighing costs against environmental impact and practical design and installation considerations for very deep or wide crossing points demands innovative solutions and deep domain expertise.

One solution is the submerged floating tunnel. With a performance which is unaffected by length, submerged floating tunnels have significant advantages over bridges or more conventional tunnel designs. Additionally, they are less affected by weather conditions or seismic activity making them especially suitable for certain regions around the globe.

China is one such area with large bodies of water and some regions frequently threatened by typhoons. The China Communications Construction Company commissioned TEC as part of a research team along with TU Delft and the Tian Research Institute for Water Transport Engineering to investigate the concept and bring theory into reality.

Joint technical research project

Instigated in 2018, the joint technical project is made up of 11 areas for research and assessment. TEC is taking the lead in seven of these:

• Assessment and comparison of structural design options, defining motion criteria and a Vortex Induced Vibration study.
• Hydrodynamic and structural model analysis including experiments using TU-Delft water lab and China wave basin.
• Development of a methodology to identify and analyse risk and explore mitigation.
• Numerical model development to simulate the behaviour of the SFT in wave and current conditions. Validate results with physical model tests.
• Assessment of theoretical and practical application of mooring concepts.
• Research regarding joints between submerged elements and at the transition between the shore and water.
• Creation of a design and construction manual and guidelines.

Spearheading submerged floating tunnel innovation

The technical research project has provided detailed analysis that will contribute to the design and success of submerged floating tunnel technology. This type of tunnel could have a significant economic and social impact, enabling connections across bodies of water that are otherwise unsuitable for tunnels or difficult to bridge. This could improve trade transit or employment opportunities through easier and faster transit between areas.