Herrenknecht TBM Tackles Gotthard Base Tunnel from NorthThe AGN JV between Murer and Strabag started excavation of the Gotthard base tunnel from the north side at the Amsteg jobsite on 27th May, 2003. Herrenknecht's Gripper TBM S-229, 9.58 m in diameter, will excavate the 11.4 km east tube to Sedrun. This represents 20% of the whole Gotthard base tunnel. Completion is expected in 2008. The second TBM (S-230) for the north alignment will start up tunnelling of the west tube in August 2003.The 441 m-long TBM S-229 is the world's longest tunnel boring mechanism. The machine weighs 3,200 t and its cutterhead supplies a power of 3,500 kW at a rated speed of 5.3 rev/min. The contact pressure of the cutterhead is 16,267 kN. The TBM will reach its actual high speed excavation in October 2003. The average daily advance is expected to be around 10.4 m while the maximum daily progress may reach 35 to 40 m in optimal conditions.Altogether, 50 of the 57 km of the Gotthard base tunnel will be excavated by Herrenknecht TBMs. Two other machines (S-210 and S-211) are currently driving and securing the tunnel from the south portal in Bodio to Faido. At week 21, TBM S-210 had already excavated 305 m on the east tunnel whereas TBM S-211 had burrowed 736 m on the west tunnel. The fourth Herrenknecht TBM (machine S-230) is in the assembly process in the west tube in Amsteg. Click ch/19. Visit www.herrenknecht.com and www.alptransit.ch 24/03.