Numerical modeling of an instrumented shallow gallery excavated in Toulouse’s molasses by a conventional method

The excavation of a shallow tunnel induces deformations of the soil volume in the vicinity and above the tunnel and consequently on the nearby buildings. The range of these deformations depends among other on the geological conditions, the geometry of the tunnel, and the excavation method. In this context, this research focuses on the 3D numerical modeling with a finite difference code of a shallow tunnel instrumented during its construction, located on the Toulouse (France) subway line B for which the excavation has been carried out in a conventional manner in an overconsolidated molassic geological context. The results of this 3D model are confronted with the in-situ measurements in order to validate the geotechnical characteristics of the molasses and consequently have useful basis for the back-analysis of the different monitoring sections implemented in areas where the tunnel excavation is made by TBM with pressurized front. © 2014 Taylor & Francis Group, London.