Brenner Base Aica-Mules pilot bore breaks throughOn 03.11.2010, a 6.3 m-diameter double shield TBM completed excavation of the 10.5 km-long exploratory tunnel between Aica and Mules as part of the 62.7 km-long Brenner Base railway project. The drive, started in April, 2008, was completed on schedule. It will be used to minimize risks and budget costs by investigating geology, rock characteristics and behaviour, and providing data for design and construction of the running tunnels.The Brenner Base line will connect Austria with Italy underground, reducing travel time by 70 minutes.In 2007, BBT-SE awarded the EUR101 million contract for the exploratory tunnel to the Austrian-Italian ATB consortium headed by Pizzarotti with Condotte d'Acqua Spa, SELI Spa, Collini Spa, Bilfinger Berger, Alpine Bemo Tunneling and Jaeger Bau. The JV was in charge of all construction, with the exception of tunnelling operations, subcontracted for EUR54 million to SELI. The TBM averaged 16 m/d boring through generally very hard and abrasive Brixen granite with a compressive strength ranging from 15 to 220 Mpa. The tunnel is lined with 20 cm-thick and 1.5 m-long precast concrete five-segment rings. A base invert cast inside the ring carries the track. The lining is designed to cope with asymmetric thrusts, sudden and violent projection of rock blocks, wide faults running parallel to the tunnel axis, and pressurized groundwater. Special steel reinforcement was utilized along the area characterised by strong asymmetric thrusts. For more click here, at/16 and it/103. 46/10