Abstract
This paper studies the accuracy of the three-dimensional finite-element predictions of a displacement field induced by tunneling using new Austrian tunneling method NATM in stiff clays with high K0 conditions. The studies are applied to the Heathrow express trial tunnel.
Two different constitutive models are used to represent London Clay, namely a hypoplastic model for clays and the modified Cam-clay MCC model. Good quality laboratory data are used for parameter calibration and accurate field measurements are used to initialize K0 and void ratio.
The hypoplastic model gives better predictions than the MCC model with satisfactory estimate for the displacement magnitude and slightly overestimated width of the surface settlement trough. Parametric studies demonstrate the influence of variation of the predicted soil behavior in the very-small-strain to large-strain range and the influence of the time dependency of the shotcrete lining behavior.