Numerical modelling of stress analysis around rectangular tunnels with large discontinuities (fault) by a hybridized indirect BEM

Abstract

Tunnels are one of the major transportation routes to pass mountains and difficult geological conditions. The behavior of these structures is significantly influenced by rock mass and discontinuities. Orientation of discontinuities is one of the most important geometrical parameters affecting discontinuities behavior. The effect of large discontinuities (faults) behavior on a jointed medium around rectangular tunnels is studied. A hybridized indirect boundary element code named TFSDDM (fictitious stress displacement discontinuity method) is used to study the stress distribution around the tunnels excavated in jointed rock masses. The code uses advantages of both fictitious stress and displacement discontinuity methods to analyze discontinuity effects more accurately. Results show that the dip angle of discontinuities has significant effect on stress distribution around the tunnel. It is also shown that increase in the discontinuities dip angle located in the roof will result in decrease in tensile stress of the roof. Stresses reaches to 8 MPa in the roof while due to dilation effect they reach up to 13 MPa.

Keywords

displacement discontinuity method / fictitious stress method / discontinuity / orientation

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