CALCULATION OF ROCK PRESSURES ON TUNNEL SUPPORTS

Formulae are derived for the magnitude of rock pressures on roadway supports, making use of flamant's and melan's principle of "the propagation of forces from a loaded point". Flamant's principle was adopted to derive formulae for pressures in loose rocks, while the formulae for pressures in cohesive rocks were based on melan's principle. It was assumed that the supports are subjected to loading from the section of rock body contained between two vertical limiting planes. Vertical pressures were determined as the sums of the effects of elementary volume forces over the section defined by the limiting planes and the roof of the workings, assuming that the rock body exhibits isotropic properties, that hooke's law is true in this medium, and that the rocks and supports have the same elastic constants. The value of vertical pressures is expressed by the equations (4) and (8). Next formulae were derived for pressure values, treating the rock body as a rheological kelvin medium and assuming an elastic model for the supports. A semi-plane was considered as being in a state of primary stress due to the weight of the overlying strata. The pressure values may be expressed by the equation (27). From the analysis of the formulae derived it may be concluded that the pressure value depends on the width of the workings, poisson's number, the shear modulus of the rock body, the rigidity of the supports, and the depth at which the workings are excavated. The relation between rock pressure and depth is not linear because as the depth increases the pressure decreases. /TRRL/

  • Corporate Authors:

    Warsaw University of Technology

    Institute of Structural Mechanics
    Armii Ludowej 16
    Warsaw,   Poland  00-637
  • Authors:
    • Chudek, M
    • Swist, E
  • Publication Date: 1973

Media Info

  • Features: Figures; References;
  • Pagination: p. 3-11
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00125608
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Feb 19 1976 12:00AM