ABSTRACT
The project consists in the construction of 5 Km single-carriage way, including viaducts, embankments and tunnels, excavated with a single shield hard rock TBM, with 13.72m excavation diameter. The geological and geotechnical setting mainly consists in biotite-muscovite gneiss and amphibolites. The weak rock conditions did not allow the application of sufficient thrust force to steer the shield by means of the advance cylinders. Among the different countermeasures applied, the application of the strand jack system has solved the TBM steering difficulties and, in order to allow an easier installation of the equipments, a new technical solution has been designed, self retaining system, permitting the installation close to the shield and reducing the operative costs. During the tunnels excavation, both systems were together applied on the machine, with excellent results leading to the complete restoration of standard TBM steering conditions.
