Undersea tunnels can face some particular maintenance challenges, such as ion erosion and water pressure, but frequent concrete condition surveys can help ensure problems are tackled quickly to ensure structures last for much longer.
Britain has been constructing large tunnels for transport purposes since the age of the canals, followed by pioneering work with the first railways, and then the inaugural underground.
Many of these tunnels were built to pass underwater, but while crossing under a river produces some strains, the challenges of undersea tunnels may be greater.
Having constructed the Channel Tunnel to France, the next big project of this kind could be to link the different islands of the Shetland archipelago, emulating the undersea road links in place in the Faroes.
Finding the funding, which a recent report estimated would require £402 million, is one challenge, but so too would be maintaining the tunnels.
How Do Ion Erosion And Water Pressure Affect Undersea Tunnels?
The issues of ion erosion and water pressure in undersea tunnels were highlighted in a 2024 article by the engineering journal EngiSphere. Problems it highlighted included:
· Ion erosion can decay tunnel linings, including concrete
· Water pressure increases pressure and accelerates deterioration
· The combination of these will shorten the life of tunnels unless the right action is taken
However, the article noted that a research study had highlighted some important factors and, as a result, some effective responses that could help optimise tunnel maintenance.
· The quality of concrete was a factor, with higher-quality material having greater resistance to ion erosion.
· Regular inspections and early interventions were crucial in preventing the first signs of stress and displacement from deteriorating at an accelerating rate
· Ion damage is greater at certain critical points, which means these need more attention
These findings led to the conclusion that higher-quality concrete, better coatings and the use of high-tech equipment to monitor tunnels are all key steps to help maintain them.
Concrete condition surveys can help ensure damage in any tunnel is spotted and can be addressed. But in undersea tunnels, the specific strains and pressures faced mean these may need to be much more frequent.