TRANSPORT | IMMERSED TUBE TUNNELS


NEXT STEPS TO RESILIENCE


Ageing immersed tube tunnels are informing a shift in how the industry thinks about performance, from component durability to system performance, or resilience, says Jurriaan van den Berg, design engineering manager at Trelleborg Marine & Infrastructure.


operation, the cumulative effects of ground settlement and thermal movement, and the quality of installation and maintenance applied thereafter. What operational evidence from tunnels in service since


the 1960s consistently shows is that correctly specified and maintained sealing systems can outlast other structural components. The risks to long-term watertightness more often originate in concrete and steel degradation, elsewhere in the structure, presenting significant implications for where inspection and maintenance investment should be directed across the full asset life cycle.


Proactive inspection and maintenance programmes are becoming increasingly important as immersed tunnel owners move away from reactive interventions and towards data-led, long-term asset stewardship.


The immersed tube tunnel industry has spent decades refining what it means to build a watertight, safe and durable structure in extreme conditions. This accumulated expertise has produced some of the most technically ambitious infrastructure ever constructed. As the industry progresses, we are seeing an emerging


convergence of three drivers: design life requirements pushing towards 120 years and beyond; operational environments of growing complexity; and, an era of heightened scrutiny over how long-term performance is actually validated. Meeting all three drivers requires a shift in how the industry thinks about immersed tube tunnel performance, from component durability to system performance.


DISTINCTION BETWEEN DURABILITY AND PERFORMANCE Durability and resilience are related but distinct: durability asks whether a material or component will survive its specified service life; resilience asks whether a system will continue to perform as intended across its full life cycle, in its actual operating environment, as conditions change around it. For immersed tube tunnels, that distinction has practical consequences. A sealing system that passes every certification requirement at the point of installation does not automatically deliver watertight performance across 120 years of operation. Performance over time is shaped by the behaviour of the tunnel segments under continuous


18 | July 2026


VALIDATION MATCH TO OPERATIONAL COMPLEXITY Testing and qualification for immersed tube tunnel sealing systems have evolved considerably in response to increasingly demanding project requirements. Tunnels are frequently built in seismically active zones, at greater depths, with larger structural elements and higher movement tolerances than any that preceded them. For example, the Coatzacoalcos tunnel in Mexico


required Gina seal cross-sections larger than any previously produced, designed to accommodate seismic ground accelerations and joint openings of up to 86mm. Furthermore, the Hong Kong-Zhuhai-Macao Bridge Tunnel Link required a closure joint combining an active hydraulic system with M-Seals that can accommodate movements of up to 400mm, a solution with no direct precedent. The Marieholm tunnel in Gothenburg, Sweden,


illustrates a different category of operational challenge. Gothenburg’s position on soft alluvial soil creates conditions of higher ground settlement and extreme movement tolerances that place sustained demands on the immersion joint across the full-service life of the structure. The 500m-long tunnel, which opened in 2020 as an additional crossing of the Göta Älv and serving the Nordic region’s largest port, required Gina gaskets and Omega seals engineered to maintain watertightness under these conditions at a depth of 20m. Marieholm is an instructive example of how site-specific operational conditions must be translated into precise engineering requirements from the outset. Delivering sealing systems for projects of this


complexity has required a corresponding evolution in how performance is validated. This shift in validating performance is reflected in several testing approaches now gaining wider acceptance across the industry.


All Images courtesy of Trelleborg Marine & Infrastructure.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45