Explicit analysis for the ground-support interaction of a circular tunnel excavation in anisotropic stress fields

Abstract

ABSTRACTThe convergence-confinement method (CCM) applied to a circular tunnel drilled through the ground under, initially, an anisotropic stress condition is investigated in this paper by employing the explicit procedure for implementing the analytical solution for executable calculations that can be directly estimated using a simple computational spreadsheet. The solutions of ground-support interaction in the final equilibrium state are solved with, in the elastic state, the simultaneous equations between the support confining curve (SCC) and the ground reaction curve (GRC) and using the Newton recursion method for finding roots in the plastic state. The influence factor of ground reaction, the apparent shear modulus of the ground, the apparent stiffness of the support and the interaction curve (IC) were especially examined in this study to consider the influence of locations around the tunnel in anisotropic stress fields. The validity of the developed explicit procedure for analytical solution was verified by numerical analysis to study the effects of in-situ stress ratio on the stress path, SCC and GRC at the intrados of the tunnel. The comparison of results obtained between the proposed explicit analysis (EAM) and the numerical analysis (FEM) was found to be consistent in elastic and elastic-perfectly plastic media.