DESIGN AND CONSTRUCTION OF REPAIRS TO SECONDARY LINING AT CONISBROUGH TUNNEL, CADEBY, SOUTH YORKSHIRE

Conisbrough Tunnel, in South Yorkshire, was opened to passenger traffic in 1849. Subsequent to construction of the tunnel two sections of the brick and masonry-lined tunnel were supported by the installation of wrought iron ribs infilled with brick. This resulted in a reduction of clearances and the application of a Permanent Speed Restriction (PSR). Studies carried out by the lead authors on behalf of Railtrack LNE concluded that the lining of the tunnel in its current state was stable, but that the wrought iron arches were not contributing to the support provided by the secondary lining. These wrought iron ribs were extremely corroded and therefore their full removal was recommended. The studies also concluded that the failure mechanism (resulting in the original installation of the secondary lining) was geomechanical. This paper describes the detailed design studies carried out to provide a solution comprising installation of 8m to 12m long rock dowels on a regular pattern, followed by removal of the secondary lining and installation of stainless steel mesh. It was concluded that removal of the whole of the secondary lining, which would improve clearances in the tunnel and permit the lifting of the PSR, could be carried out provided the stability of the primary lining could be maintained. The critical stability of the primary lining was achieved by prior installation of the rock dowels, sleeved off through the secondary lining. Grouting of the voids above the crown using lightweight aggregates was the recommended method for reducing the risk from upwards movements in the crown leading to further sidewall movement. Construction of these repairs commenced in March 2000 within a series of restricted night-time possessions. To date, all planned rock dowel installation is complete and removal of the secondary lining is well underway. The paper describes the installation of the rock dowels, removal of secondary lining and installation of the mesh. The paper further describes the careful sequencing required at the temporary works stage to ensure the stability of the primary lining and guarantee the safety of workers in the tunnel, and also the careful programming carried out to minimise disruption to the railway. For the covering abstract see ITRD E123713.

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  • Corporate Authors:

    ENGINEERING TECHNICS PRESS

    46 CLUNY GARDENS
    EDINBURGH,   United Kingdom  EH10 6BN
  • Authors:
    • HILLS, R L
    • YATES, PGJ
    • INSTONE, R R
  • Publication Date: 2001

Language

  • English

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Filing Info

  • Accession Number: 00985531
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-947644-45-8
  • Files: ITRD
  • Created Date: Feb 4 2005 12:00AM