Cutting-edge technology

Work on the Variante di Valico is taking place in one of Europe's most geologically and morphologically complex regions in terms of underground gas and unstable geological formations.

In excavating the Sparvo Tunnel, one of the most complex works in terms of the characteristics of the terrain, Autostrade per l'Italia opted to use the most innovative technology available in the field of mechanised excavations: the Tunnel Boring Machine (TBM-EPB). Designed in collaboration with the Florence Local Health Authority and the University of Bologna, the TBM was built by Herrenknecht in Germany and is the largest shield TBM ever made,. The TMB has an excavation diameter of 15.70 m, an overall length of 110 m and cost around €50 million to make (said cost being borne by TOTO, the company contracted to perform the works on the highway stretch).
This machine will allow works to progress at a rate of about 10 m per day (compared to less than one metre per day using traditional boring methods), thus allowing the tunnel to be completed by 2013.

The use of the new TBM means that the work will have:

  • reduced environmental impact due to the lesser degree of disruption to land and rock masses with the use of the TBM as compared to traditional excavation in terms of noise and vibration.
  • reduced hydrogeological system impact.
  • greater guarantees as to the quality of the work (quality control: prefabricated lining ashlars of prefabricated coating, sophisticated TBM equipment) a high degree of safety for tunnel workers (the basic function of a TBM shield is to temporarily support the unstable rock thus keeping the excavation intact and protecting workers).

In particular, as regards safety, TBM checks are performed by a specialist operator located inside the cabin who is able to monitor and guide the excavation with millimetric precision thanks to a series of monitors and computer systems. The boring head acts within a closed, sealed chamber and is equipped with teeth and disks that break the rock bringing the extracted material into the chamber for subsequent removal. The process is automated and takes place with the use of a conveyor belt.
The tunnel lining is placed by a radio-controlled robot that is able to withstand both water and gas. The conveyor chain of material is encapsulated as a further safety measure, so as to prevent gas from infiltrating areas frequented by man. The atmosphere is also constantly monitored in both the encapsulated area and in all TBM areas. This will allow timely intervention (with suitable safety and/or emergency procedures) if gas is detected and warning alarm thresholds are exceeded.


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