AWirth double telescopic shield TBM is currently being assembled ready to start excavation in June 2000 on a 9.2km long, 5.6m i.d. service tunnel on the Florence-Bologna high-speed rail link, one of the largest tunnelling contracts in the world.
The service tunnel will run for 6.5km parallel to the 18km long Vaglia Tunnel, the longest and final tunnel approaching Florence on the 73km, 9 tunnel project. The remaining 2.7km will comprise the access adits.
Contractor CAVET will advance from the former Ginori Quarry, near the southern portal of the Vaglia Tunnel. The TBM is equipped with advanced geological surveying systems and is capable of adjusting the method of advance according to the different geomechanical conditions it encounters.
Lining will comprise 250mm thick prefabricated, reinforced, trapezoidal concrete segments. Design and construction management of the mechanised excavation will use the ADECO-RS approach. Both the service tunnel and the final 10.5km long section of the Vaglia Tunnel will be constructed mainly through the Monte Morello Formation, consisting of alternating marly limestones and lime marls with marly strata.
A decision on how to construct the end part of the Vaglia Tunnel (from chainage 71+500) was only reached in Dec ’99, although construction at this point had been reached in April ’99, leaving approximately 10.5km of the main tunnel and 9.2km of the service tunnel to go. This last section includes the connection into Florence.
Excavation from chainage 71+500 has now reached 72+500. The Vaglia Tunnel is scheduled for completion by 2005.
