Ground reaction curves for tunnels excavated in different quality rock masses showing several types of post-failure behaviour

Rock mass behaviour model selection and, in particular, rock mass post-failure behaviour are key issues in analysing tunnel stability, in particular in terms of the correct application of design techniques such as the convergence–confinement method and also numerical modelling. Three different quality rock masses (good, average and poor) were defined in which simulated standard tunnels were excavated. Different behaviours – including elastic perfectly plastic, elastic brittle and three strain softening behaviours – were modelled for each type of rock mass and increasingly realistic parameters were calculated, along with the corresponding ground reaction curves. The results obtained demonstrate the importance of adequate post-failure behaviour model selection for tunnel analysis. Also assessed are the effects of the standard support and reinforcement.