Mechanised Tunnel Excavation Through an Instrumented Site in Rome: Class A Predictions and Monitoring Data

Contract T3 of Line C of Rome underground is currently under construction. The running tunnels, excavated using two EPB shields, cross the historical centre of the city, potentially interacting with the existing monuments of great historic value. For this reason, two fully instrumented control sections were established at the beginning of this contract, in representative ground conditions. In addition to a greenfield section, an embedded barrier of bored piles running parallel to the tunnel axis was monitored, to study its effectiveness for settlement mitigation. Class A predictions of the passage of the tunnels through the control sections were carried out using a recently developed advanced numerical procedure, modelling in detail the main physical processes occurring around the shield, including cutter-head overcut, shield tapering and tail void grouting. Hypoplastic laws, calibrated with all the available data from the geotechnical investigation, were employed to model the behaviour of the soil. In this paper, the numerical results are compared with preliminary data gathered during the passage of the TBMs, showing a good qualitative agreement and suggesting strategies to improve the predictions.