Coupled solid-fluid response of deep tunnels excavated in saturated rock masses with a time-dependent plastic behaviour

Abstract This article provides a general numerical approach for modelling the response of deep tunnels excavated in saturated time-dependent plastic rock masses, considering a coupled solid-fluid interaction and time-dependent plastic behaviour. In order to do that, a Burgers-viscoplastic strain-softening model has been developed and implemented into the finite element method software CODE_BRIGHT, and a coupled solid-fluid model is used to simulate the interaction between solid deformations and fluid flow. Parametric analyses are then performed to analyse the influence on the tunnelling response of different time-dependent models, different standstill times and different excavation rates. It has been observed that the time-dependent model selection is crucial to simulate the response of underground excavations. Additionally, the coupled solid-fluid results are significantly different from the purely mechanical ones. The liquid pressure build-up in the vicinity of the tunnel face and the overpressure dissipation with time due consolidation can be accounted for. Moreover, the higher the excavation rate, the larger build-up of liquid pressures occurs.