Europipe Landfall Tunnel, Dornumersiel

The Europipe natural gas pipeline crosses the Lower Saxony "Wattenmeer" national park en route from the gas fields in the North Sea off Norway to the German coast. For ecological reasons, a 2535 m long 3.8 m diameter landfall tunnel was thrust underneath the tidal flat to reach a target shaft 2 km off from the mainland between the islands of Baltrum and Langeoog. Pipes with an external diameter of 3,800 mm and a nominal width of 3,000 mm. weighing 43 t were thrust. To save time, 2 pipes each 4.000 mm in length were installed and jacked in a single cycle. The special feature about this Mixshield is that the cutting wheel is designed as a cone crusher, as larger stones were expected at the end of the section. As a result, stones up to 60 cm in size presented no problem whatsoever. The cutter bits, which protruded some 200 mm above the cutting wheel arms produced an extremely even cutting pattern. In order to overcome the pipe frictional forces, there were 25 auxiliary stations set along the total length of 2.535 m and it was intended to lubricate the entire column of pipes. In practice, the maximum frictional resistance only amounted to 10% of what had been calculated. As a consequence, the auxiliary stations were gradually set 150 m apart and not 100 m as initially had been the case. In actual fact, the entire pipe column up to a length of 2.200 m was moved solely via the main jacking station with the exception of the first few metres following the weekend break. The principal of central operation and monitoring was realised in a very effective manner. All the machine's functions were controlled from the container in the starting shaft. When it entered the Tie-in-Chamber, the shield had covered 2.531 m in 100 days of tunnelling between Feb. 1st. and June 6th, 1994. Peak advance rates were achieved with 58.50 m per day. 223.40 m during one week and 707 m in May 94.The originally planned construction time was thus reduced by some 40 %.

• Country: Germany
• Region: Niedersachsen
• Tunnel utilization: Utilities
• Type of utilization: Landfall Tunnel for Gaspipeline
• Client: Statoil
• Main construction method: Trenchless
• Type of excavation: Pipe jacking
• No. of tubes: 1
• Tunnel total length: 2535 m
• Cross-section: Inner diameter 3 m / Outer diameter 3.8 m
• Construction start/end: Oct 1993 till June 1994
• Opening: 1994