The most outstanding feature of the A485 Newbridge Bypass in Clwyd, North Wales is the 57.3 m high 5 span River Dee viaduct. Difficult access, the local landscape and Site of Special Scientific Interest (SSSI) had to be taken into account in the design. A viaduct with a variable depth, continuous post-tensioned reinforced concrete deck mounted on four slender reinforced concrete columns was chosen as the most economical, durable and aesthetic solution. A detailed geological investigation was carried out which dictated the location of the foundations. The geology of the area consisted of an upper layer of glacial deposits of silty sands, gravels and clays, and lower layers of siltstones and mudstones, of the Upper Middle Coal Measures. Significant landslipping and valley cambering were evident, and potential instability problems were indicated by the presence of major faulting including the Aquaduct fault. Piezometers and inclinometers were installed at an early stage. The south abutment was piled and the other foundations excavated down to competent bedrock in the Upper Coal Measures. Further details are given of the foundations including the use of mass concrete, reinforced shotcreting, rock-bolting and plastic netting to support excavations. Hollow reinforced concrete pier columns were cast in 4 m high lifts using a purpose made Doka climbing shutter. The two central columns are integral with the deck and act as a portal frame. The other columns are surmounted by 2000 tonne capacity free sliding bearings. Deck construction was by the balanced cantilever method in 3.5 m long segments. (TRRL) (Author/TRRL)

  • Availability:
  • Corporate Authors:

    British Cement Association

    Wexham Springs
    Slough,   England 
  • Authors:
    • PRICE, D
  • Publication Date: 1990


  • English

Media Info

  • Pagination: p. 5-7
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00623738
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Jul 31 1992 12:00AM