Ground response curves for rock masses exhibiting strain-softening behaviour

In this paper, a one-dimensional numerical solution to obtain the ground reaction curve (GRC) for circular tunnels excavated in strain-softening materials is presented.The problem is formulated in a very general form and leads to a system of ordinary differential equations. By adequately defining a fictitious lsquotimersquo variable and re-scaling some variables the problem is converted into an initial value one, which can be solved numerically by a Runge-Kutta-Fehlberg method, which is implemented in MATLAB environment.The method has been developed for various common particular behaviour models including Tresca, Mohr-Coulomb and Hoek-Brown failure criteria, in all cases with non-associative flow rules and two-segment piecewise linear functions related to a principal strain-dependent plastic parameter to model the transition between peak and residual failure criteria.