GROUND SUPPORTS FOR TUNNELS IN WEAK ROCKS

The various factors and how they influence the loading and deformation of supports needed in deep tunnels in weak rocks are presented. Broadly, these are the rock and water conditions and their response to excavation, the excavation and support timings and procedures, and the support details and their workmanship. Particular attention is drawn to the need to consider the truly three-dimensional influence of rock discontinuities on excavation collapse mechanisms with the aid of models and field observation as a guide to support and safety requirements; to consider during construction the positioning and timing of support placement in relation to the rate of advance of the face (another three dimensional effect); to allow a degree of rock yielding by means of yielding supports on the basis of concepts developed from simple yielding rock/support interaction theory combined with construction monitoring; and to consider quantitatively the real load-deformation properties of the structural supports and their interface with the rock. The effects of these variables are illustrated by observations from tunnel projects in hilly and high mountain areas. There is no such thing as the load on a support. Proper assessment and control of the many variables which combine to produce a satisfactory and efficient support system cannot be done at the design stage. It is strongly recommended that construction should be aided and guided by monitoring of tunnel performance carried out by engineers relieved of contractual responsibilities as the only positive means of taking sensible, economic and safe decisions during progress of the work. The technical superiority of the observant engineer can cause the rock to work for him. /Author/TRRL/

Language

  • English

Media Info

  • Features: Figures; Photos; References;
  • Pagination: p. 133-171
  • Serial:
    • GEOTECHNIQUE
    • Volume: 28
    • Issue Number: 2
    • Publisher: Thomas Telford Limited
    • ISSN: 0016-8505

Subject/Index Terms

Filing Info

  • Accession Number: 00182729
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Oct 31 1978 12:00AM