The world's longest tunnel will take shape deep beneath the Swiss Alps on Friday when a giant drillingmachine clears a path for a key high speed railway through the heart of Europe.
After 15 years of construction work, the 9.5-meter (31-foot) wide drillingmachine will bore through the remaining 1.5 meters of rock to join two ends of the tunnel some 2,000 meters under a mountain.
The functions of the driving mechanism directly affect drilling efficiency, borehole quality and other technological performances of the drillingmachine.