This article describes the on going construction of the 35 M tunnel which will carry the northfleet southern bypass under the a226 London road. The chalk facings have been stabilized by sinking rockbolts into the face of the chalk at both ends of the tunnel. These form an anchor with the structure and are stressed accordingly. The faces have then been sprayed with concrete. The main roof sections of the tunnel are precast, bolted sections, but the portals are being cast in situ. The portals are temporarily supported with steel arch ribs, which will be cast into the concrete of the portals. The ribs themselves are supported by tubular struts and bolts to give lateral support. Timber soffits have been built to the shape of the arch of the tunnel and these slide along to facilitate the concrete pour. A 40 grade concrete mix has been specified. Once the pours have been completed the outer faces of the portals will be brick clad to the level of the buttresses.

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  • Corporate Authors:

    Reed Business Information, Limited

    Quadrant House, The Quadrant
    Brighton Road
    Sutton, Surrey  United Kingdom  SM2 5AS
  • Authors:
    • MASON, D
  • Publication Date: 1988-12-8


  • English

Media Info

  • Pagination: p. 18-9
  • Serial:
    • Volume: 170
    • Issue Number: 5024
    • Publisher: Hemming Group, Limited
    • ISSN: 0039-6303

Subject/Index Terms

Filing Info

  • Accession Number: 00487381
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Sep 30 1989 12:00AM