This article describes the work being carried out on Britain's first immersed tube road tunnel at Conwy in North Wales. The 700 m tunnel is due to open in 1991 and has a design life of 125 years; its cost is about 50 million. The remaining road works will consist of 6.5 km of dual carriageway, including 14 bridges and many other substantial retaining structures. Sections of the immersed tube are being built in a giant dry dock, excavated beside the Conwy river estuary. The immersed tube will be laid in a trench dredged across the river bed; twin pontoons will carry each tunnel section and lower it into position; a concrete slab supports the free end of each newly placed tunnel section. Steel bulwarks will keep the tunnel sections dry and buoyant during construction, and shear pins in one unit will locate into matching sockets in the adjacent tunnel section. The bulwarks will be removed in the final stages of construction, after all sections have been sealed against entry of the river water. Other operations required include the special procedures being carried out to fit the ends of the under-water tunnel properly into the adjacent cut and cover tunnels, miscellaneous strengthening operations, the relieving of all the stresses locked in the joints between adjacent units, and the backfilling of the trench. Finally, the road surface will be laid within the tube. (TRRL)

  • Availability:
  • Corporate Authors:

    Thomas Telford Limited

    London,   United Kingdom 
  • Authors:
    • JONES, H
  • Publication Date: 1988-3-24

Media Info

  • Pagination: p. 26-27
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00493275
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: May 31 1990 12:00AM