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Belgian Seminar on Immersed & Floating Tunnels - CONGRESS REPORT

On the 26th of March ABTUS-BVOTS hosted, in the magnificent building of Tour & Taxis, a seminar on immersed & floating tunnels. The audience consisted of approx. 70 participants with a good mixture of engineering companies, general contractors, manufacturers and owners. ABTUS-BVOTS managed (assisted by mr. Hans Mortier) to compile a high-level program about the challenging subject of immersed & floating tunnels. The program was composed with wide variety, in order to create insights on al the aspects of immersed & floating tunnels always featured by an academic bottom-line. Again, we like to thank the participants and off course the lecturers to share their knowledge with us. For those who weren’t able to attend the seminar, the abstracts of the presentations are shown underneath.

Pictures of the event you can find HERE


Projects pushing the boundaries of the Immersed Tunnel Technology - Hans de Wit

(Tunnel Engineering Consultants, The Netherlands)

Until the nineties of last century most of the immersed tunnels were applied for river crossings with lengths for the immersed sections general less than 1.0km and with sometimes reaching 1.5-2.0km There were some exceptions such as the 5.8km BART (Bay Area Rapid Transport) tunnel in San Francisco and an immersed tunnel under a runway at Schiphol airport in Amsterdam. The last two decades the immersed tunnel technology is rapidly developing, becoming more advanced and successfully entering new areas such as the crossing of sea straits or even using the technique under existing buildings. As a result, innovative concepts were introduced that increased the possibilities and pushing the boundaries of the technology. The presentation is discussing projects that have contributed to the expansion of possibilities of immersed tunnels in the last two decades. Most of them will focus on the crossing of sea straits, the associated challenges and the innovative solutions that were developed to overcome these challenges. The Øresund Link between Denmark and Sweden, Busan Geoje Link in South Korea and the HZMB link will be briefly discussed as successful realized projects. The Femernbelt Link and the Shenzong Link will be described as ongoing projects in the same field. Finally, a very special way of using the immersed tunnel technology under the historic railway station building for the North/South Metro Line will be illustrated.

The Söderströmstunnel - Stephen Slot Odgaard


The presentation will describe the complexities of constructing an immersed tunnel in a protected lake

in the middle of Stockholm.

The project required a great deal of ingenious solutions on the part of the designer and the contactor to respect the environmental requirements set out by the owner. Key features include:

Continuous 300 m immersed tube structure built of 3 elements (110, 110, 85 m length) functioning as an “Underwater bridge”; Installation on 4 underwater pile groups semi embedded in soil; Steel formwork transported on barges across the Baltic limited by dimensions of a navigational lock to the lake; 2-stage Floating casting to avoid excessive work in Stockholm Historical center and passing threshold with only 6 m water depth ; One sided Joint House with low friction bearing where all movements are taken (temperature and tectonic); Underwater connection to Rock Tunnels at both ends.

Floating Tunnels - Dirk Jan Peters

(TEC / Technical University Delft)

The submerged floating tunnel is ‘old’ innovative concept, which has been an inspiration for planning of challenging subsea crossings. In the past 20 years serious research efforts and technical feasibility studies have been carried out in Italy, Japan, Norway, Korea and China.

At present TEC, the Netherland and the Technical University Delft are partners in a joint research project lead by Chinese contractors. The objective is to further develop the concept of an SFT as a safe and economically affordable alternative to bridges and sub-seabed tunnels for strait, estuary and fjord crossings. The development of the concept shall be aimed at the level of finding solutions for all scenarios and failure mechanisms, enabling contractors and designers to make safe and economical preliminary designs of SFT’s for a potential location of a major fjord crossing in Norway, and/or links to islands near the Chinese mainland.

The submerged floating tunnel design concepts include solutions for 500 to 1000 m deep water

crossings with tether supports tunnels. Like cable stayed bridges and suspension bridges the tunnel tube should be a monolith structure. This is a solution that differs from an articulated tube structure with flexible joints able to follow geotechnical deformation.

Innovative IMT Concepts to mitigate hindrance to navigational channels

Eelco van Putten

(DIMCO (DEME Infra Marine Contractors))

The growing urbanization in coastal areas creates an ongoing need for waterway crossings. Immersed tunnels may have benefits over bored tunnels and high level bridges for water crossings at certain locations since they lie in a pre-dredged trench only a short distance below the river or seabed.

Compared with high level bridges or bored tunnels, the overall length of crossing including the approaches will be shorter.

These waterways often act as a piece of infrastructure itself in the form of a navigational channel and growing global economies creates more and larger ships travelling these waters. Although integrating an immersed tunnel into the landscape can be benefit, the downside is that the construction activities can come into conflict with the shipping activities in these channels. By providing a few example projects insight is provided how technical innovations have helped mitigating the hindrance to shipping during the construction of immersed tunnels.

Immersed tunnel Scheldt, Oosterweel-link - Ron van Beek

(Technical Manager BAM – Scheldetunnel)

In order to solve the bottlenecks and mobility problems and improve the quality of life in the Antwerp region, the Oosterweel-link is of vital importance. It will improve the city and the port’s accessibility, reduce congestion, increase traffic safety and provide a good transit route for freight traffic.

The Scheldt tunnel, as part of the Oosterweel-link, dives under the River Scheldt on the Left Bank between the nature conservation areas Blokkersdijk and Sint-Annabos and resurfaces at the Right Bank.

The 1,8 km long tunnel will have two tubes for motorway traffic and a separate tube for cyclists.

The immersed part counts eight elements which are built in the Port of Zeebrugge and towed to Antwerp via the North Sea and River Scheldt. Technical challenges of the tunnel design lie in the amount of sediment present in the tidal river, minimizing hindrance to shipping activities and the longitudinal behaviour due to differential loadings and foundation stiffnesses.

Innovative design of an immersed tunnel in the Golden Horn - Coen van der Vliet

(Senior specialist civil structures at Arcadis, The Netherlands)

The presentation covers the reference design of the Unkapanı Highway Crossing under the Golden Horn in Istanbul. The complex site conditions and the expected seismic activity imposed high demands on the design. The designed solution is a submerged tube bridge, crossing the Golden Horn halfway river bed and water level. In order to accommodate the expected dynamic response to seismic loads, flexible joints and supports have been designed.

Conservation of immersion joints and deformations existing tunnels – status within the COB tunnel program - Hans Mortier

(DIMCO (DEME Infra Marine Contractors))

Within the DBFM contract of the 2nd Coentunnel in Amsterdam, also the refurbishment of the 1st Coentunnel was comprised. As two immersion joints showed leakage problems, an analysis was made to detect the causes that led to these leakages and the appropriate mitigating measures that should be implied. As the outcome was to only take care of the evacuation of the leakage water after an elaborate decision process, Rijkswaterstaat (RWS) together with the contractor’s joint venture and the Dutch Center for Underground Constriction (COB) decided to set up a commission to investigate whether similar problems could arise with the other existing tunnels in the Netherlands. At the date this ‘Immersion Joint Commission’ delivered its final report it became clear that, facing the huge renovation program of RWS whereby 22 of the 73 tunnels need to be renovated in the coming 10 years, there was an urgent need to extend the scope of the ‘joint’ commission to all kind of joints (immersion, segmental and closure joints) and to all kind of tunnels (immersed, cut&cover and bored tunnels). Moreover, parallel commissions were installed focusing on degradation of materials, deformations and structural health reporting. All four (sub)commissions reside under the umbrella of the ‘Structural failure’ commissions, on its turn being part of the COB tunnel program. The presentation of today will enlighten how things evolved from out of the immersion joint commission into the sub-commission deformations.

The today’s status and the strategy for the upcoming years will be clarified. New monitoring techniques like Multichannel Analysis of Surface Waves (MASW) and Glass Fiber Monitoring will be shown as well.

Renovation of immersed tunnels – Keeping the tunnel watertight - Joel van Stee

(Trelleborg Ridderkerk B.V.)

Although we have been building immersed tunnels for over a century now the real incline in number of tunnels have been from the 60’s onwards. Now that slowly many tunnels reach their 50th birthday we also start to see that the tooth of time has taken its toll.

We have limited knowledge of our tunnels and their current status. We have found that within the tunnel each joint behaves differently and may have different complications to be solved. An integral systematic approach is needed.

0. Collect all as built data. Know your tunnel

1. Find out the requirements for each joint

2. Examine the current condition of the joint against what is required

3. Judge act and react by doing what is necessary and possible taking often complex operational conditions in mind.

There is a great need to combine and find the right expertise within the market to find solutions together for very demanding and sometimes urgent problems. We will need new innovative and creative solutions to tackle the problems and a different mentality to deal with problems in an efficient matter.

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