The Use of a Robotized Inclinometer System to Measure Deep-Seated Ground Deformation in a Monumental Area During TBM Tunnel Excavations. The Case of Rome Subway, New Line C

The new section T3 of Rome Metro network (line C) stretches in an important World Heritage area (Colosseo, Fori imperiali etc.). In order to monitor and assure the safety of this heritage, a very complex monitoring network has been installed to provide information on monuments status, on the effectiveness of the designer's hypothesis and on the evolution of the TBM tunnel excavation. In cooperation with METROC S.c.p.A, General Contractor for planning and construction of the project, a robotized inclinometer system was experimentally installed with the aim of measuring the deep-seated ground deformations in three sections with different inclinometer tubes length. This equipment allows the measurement of deep horizontal displacements using a single inclinometer probe and a robotic system that automatically manage the probe for the entire length of the borehole with 50 cm step and double reading (0/180°). The experimental activity was carried out before, during and after the TBM excavation and allowed the monitoring of three sections at the Basilica of Santo Stefano Rotondo al Celio (62 m), Fori Imperiali (43 m and 33 m) with a frequency of measurement up to 6 measurements/day. The results showed interesting relations between TBM progress and horizontal deep deformations induced by tunnel excavation. These deformations, although very small, highlighted the potential of this instrumentation in terms of accuracy, vertical spatial resolution and very high frequency of measurements. This type of results can be useful to a more complete interpretation of the subsoil deformations and interaction between excavation and the surrounding built environment.