Modification of the Supported Longitudinal Displacement Profile for Tunnel Face Convergence in Weak Rock

The employment of convergence-confinement analysis as a preliminary support design aid is an industry standard. The Longitudinal Displacement Profile (LDP), a component of the convergence confinement method [1-4], relates the normalized profile displacement to a normalized location along the tunnel’s axis with respect to the tunnel’s face location. However, current versions of the LDP do not take into consideration the interaction of the support with the other convergence-confinement components (i.e. the Ground Reaction Curve and the Support Reaction Curve). The authors investigated the support interaction influence on the LDP, and this resulting paper proposes a modification of the calculation of the displacement at the tunnel face to current LDP approaches. This modification is a function of the plastic radius or the final tunnel convergence. Furthermore, this modification will lead to a more accurate approximation of the LDP in front of the tunnel face (within the rock mass). This increase in accuracy will result in a better estimate of the stresses acting on pre-support structural support members.