Analysis of convergence data and 3D numerical modelling of tunnels excavated in fine-grained soils

This paper focuses on the convergence measurements of twin motorway tunnels under excavation in a Pliocene formation in the South of Italy. The tunnels are driven full face, with a cross-section of 120 m2, by means of a conventional excavation method, up to a maximum depth of 120 m. The primary lining is an open arch made up of shotcrete and steel sets; the definitive lining consists of concrete cast in three different stages. Convergence measurements were analyzed on the basis of the curve-fitting technique proposed by Sulem et al. (1987). Then, the influence on tunnel deformation of overburden and lining construction se-quence is investigated. Finally, the role of the primary and final linings in reducing tunnel convergence is in-vestigated by means of a three-dimensional stress-strain analysis, performed with FLAC3D code.