A comparison of predicted and actual tunnel behaviour in the İstanbul Metro, Turkey

The empirical method proposed by Hoek and Brown is combined with rock mass classifications to predict the deformation behaviour of İstanbul Metro. The rock mass was assessed using both Bieniawskiʹs RMR89 and its strength was estimated from the formula of Hoek and Brown for the RMR89 system. The applicability and validity of the proposed procedure has been checked by comparing the predictions with actual observations. It is found that the predictions agree well with observations in the intact rock. Although there are some differences between predictions and observations in the faulted rock, these probably reflect the inevitable inaccuracies in empirical approaches, and differences in behaviour of the actual support system that is assumed in modelling. In addition, anisotropy features like faults which are not accounted properly in the Hoek et al. equation that assumes isotropic behaviour.