This article described the geotechnical methods used to assess the geological setting of the Du Toitskloof (Huguenot) Tunnel. This included drilling a pilot tunnel along the line of the second main tunnel. The detailed geological mapping and surface geology of the area through which the tunnel was to be excavated were provided, as were brief descriptions of the methods used to measure in situ stresses under various overburdens, with the data obtained from them. Rock displacements around a full sized test chamber under a maximum overburden of foam was measured using extensometers, a deflectometer and convergence stations, which allowed contours of displacement around excavation to be calculated. The strength and behaviour criteria of the various rock types over the tunnel were also determined. The geotechnical aspects affecting construction were described, and a brief summary of the support required over the various geological zones of the main tunnel were presented. Movement of the excavated rock surface was monitored by measuring convergence. In the Du Toitskloof fault zone this was supplemented by installing multipoint extensometers. Methods used to arrest any movements thus recorded were also described. Gloetzl pressure cells were installed between the concrete lining and the excavated rock surface to monitor rock/concrete interface pressure and within the concrete lining to monitor radial pressure. (TRRL)

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  • Corporate Authors:

    South African Institute of Civil Engineers

    9 St Davids Place, Parktown, P.O. Box 62129
    Marshalltown,   South Africa 
  • Authors:
    • Loudon, P A
    • McLea, R K
    • Wigginton, R L
  • Publication Date: 1988-4

Media Info

  • Features: References;
  • Pagination: p. 175-178
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00493080
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS, ATRI
  • Created Date: May 31 1990 12:00AM