Predicting the long-term behaviour of rock masses in tunnelling

Being able to predict how the rocks will behave and deform in underground environment over time using practical tools and applied methodologies can lead to design optimization preventing projects delivery delays and cost overruns. Especially in the case of underground nuclear waste repositories where their lifetime is estimated to be over one million years. However, in tunnelling engineering and design practitioners and engineers tend to pseudo-simulate the long-term behaviour by reducing the Young’s modulus of the rock usually be a factor of 0.3 to 0.5. The latter can lead to erroneous estimates as various rocks and rock masses behave differently over time, consequently, a general rule cannot be applied. This paper shows a new approach on how to use laboratory data from static loading data to in numerical analysis to simulate the time-dependent strength degradation of the rock mass around underground openings and tunnels.