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The construction of a new incineration plant in Hamburg-Waltershof at the same time required a new remote-steam connection line below the Köhlbrandt, a side arm of the Elbe. In the original Elbe valley, each age left its mark. In warm periods, sediments were deposited, the ice ages which followed pressed them together to form a compact mica clay complex. This over consolidated clay is admittedly similar to rock but it can develop swelling pressures of up to 350 kN/m² in conjunction with inflowing water. The mica clay is overlain by alternating layers of gravels and sands with interbedded glacial marl layers. Granite erratic blocks are to be found especially in the transition zone between the sands and the glacial marl. The drive was begun in the form of a shield heading from a 33 m deep and 10 m diameter starting shaft. The decision to choose a hydro-shield and segmental lining resulted in the smallest underwater tunnel of its kind being constructed. The problems associated with swelling clay were solved by choosing this mode of construction. After taking all requirements into consideration, a hydro-shield with 4 follow-up machine pipes and 4 trailers with a total length of 41 m was devised and built. The cutting wheel was equipped with roller bits, stripping knives and reamers in view of the ground conditions which had to be penetrated. In this way, all conceivable operations in the extraction chamber could be reduced to a minimum given maximum pressures in the event of high tide of 3.5 bar. The complicated starting up procedure was first completed after an eighth of the total section had been negotiated. After the orientation phase, the best rates of advance could be attained in gravel/sand with 13 m. The depth amounted to roughly 29 m related to mean high tide level. After 382 m of tunnelling and 5 months, the target shaft on the other side of the Köhlbrand was reached. The shield machine was driven into a pressure unit installed in the target shaft section-by-section and recovered from there. 2 activated hose seals and a lip seal prevented soil and groundwater from entering the pressure unit, the shield tail and the brush seal remained in the ground. With a clear diameter of 2.37 m, a ring with 5 segments and a key-stone was devised. Given a wall thickness of only 25 cm only one sealing level could be installed, which was required to withstand a dimensioned water pressure of 4.0 bar. The segments were transported by a tracked battery-driven locomotive. A separating plant with 2 cyclone stages was used to separate hydraulically transported muck. The trial run for the distance-heating connection line began in February 1999.


  • Country: Germany
  • Region: Hamburg
  • Tunnel utilization: Utilities
  • Type of utilization: district heating
  • Client: HEW-Fernwärme (Hamburgische Elektrizitätswerke AG)
  • Consulting Engineer: Ed. Züblin AG, Philipp Holzmann AG
  • Contractor: Philipp Holzmann AG
  • Main construction method: Trenchless
  • Type of excavation: Shield machine (SM)
  • Lining: Reinforced concrete segments
  • No. of tubes: 1
  • Tunnel total length: 382 m
  • Cross-section: outer diameter 2.87 m, inner diameter 2.37 m
  • Contract Volume: approx. 15 mill. DM
  • Construction start/end: 1996 till 1998
  • Opening: 1999