ABSTRACT
In the convergence-confinement method, the analysis of three-dimensional response of the ground around the tunnel is reduced to a problem of plane strain. A point-symmetrical growth curve is generally adopted as stress release curve to determine the magnitude of deformations, such as surface settlement, displacement at the tunnel crown or the convergence, in the method. For the urban-NATM excavated in soft ground at shallow depth, however, it has been often pointed out that the point-symmetrical growth curve was not fitted to in-situ measured values very well. In this study, the stress release curve is modeled as a non-point symmetrical growth curve, Gompertz’s curve, to validate the predicting method of surface settlement above and ahead of the tunnel face under such conditions. We also discuss the method enabling practical application for urban-NATM at shallow depth based on Jeffery elastic solution.
