Efficient Uplift Control using GEWI® Piles at the Sluiskil Tunnel
The existing swing bridge near Sluiskil in Southwestern Netherlands is one of the biggest bottlenecks along the channel from Ghent to Terneuzen. The bridge has to be opened frequently to passing ship traffic, leaving it useable to road traffic for just five hours per day.
In order to allow road traffic to move freely, work on the new Sluiskil Tunnel began in October 2011. The double tube tunnel runs underneath the channel, thereby creating a bypass to the swing bridge. The 1,330m long (including access ramps) double tube tunnel is being driven using a Tunnel Boring Machine (TBM). The two approx. 1,150m long, 11m diameter tunnels will accommodate two lanes each after their completion. At their lowest point, the tubes are more than 30m below sea level.
The entry and exit ramps for the tunnels are built in excavations that are up to 15m deep. These excavations also serve as a starting and reception shaft for the TBM. A bottom seal had to be installed for the waterproof excavations.
The underwater concrete slabs had to be additionally secured against uplift due to the high prevailing water pressure. For this purpose, DSI produced and supplied a total of 999 x 63.5mm GEWI® Piles with anchor plates in average lengths of 25.3m. The installation was executed by a subcontractor joint venture of BAM Speciale Technieken and Voorbij Funderingstechniek, both the foundation specialists of BAM Civiel and TBI Mobilis respectively.
Due to a layer of clay underneath the excavations that exhibited swelling both during and after the excavation work, the GEWI® Piles were fitted with special casings to minimize the influence of the swelling loads. The special casings were designed to prevent the clay from adhering to the GEWI® Piles so that the access and exit ramps for the Sluiskil Tunnel could be built in a way that was both economical and time efficient.
In addition, DSI also supplied 279 temporary DYWIDAG Strand Anchors in lengths of 36m and 29 removable 47 WR DYWIDAG Bar Anchors in lengths of 56m for tying back the sheet pile walls.