Impact of a constitutive model on inverse analysis of a NATM tunnel in stiff clays

The paper demonstrates the influence of soil constitutive model on predictions of a NATM tunnel in overconsolidated clays (Dobrovského tunnel, Brno, Czech Republic). Two constitutive models are compared: standard Mohr-Coulomb model and advanced hypoplastic model. The models have been calibrated using laboratory experimental data. Their parameters have subsequently been optimised by means of inverse analysis using monitoring data from exploratory adit, excavated inside the future tunnel. The hypoplastic model gives reasonable predictions of the adit behaviour even with parameter set calibrated using experiments. The Mohr-Coulomb model requires unrealistic parameters to predict the adit behaviour correctly. The optimised parameters are used for calculation of settlements due to the tunnel. Although both the models with optimised parameter sets give comparable predictions of settlements due to the adit, predictions of the behaviour of the whole tunnel differ substantially. Predictions by the hypoplastic model appear to be more reasonable, but detailed conclusions cannot be drawn yet. They will be available after excavation of the whole tunnel in 2009. 1