Tremors!.. They're getting louder... OMG, it's getting out - and it's HUGE!!
What dwells beneath, does not dwell so quietly - these enormous machines are notorious for producing shaking and loud noise, but they do the job - excavating tunnels wide enough to fit two trains inside (maximum tunnel diameter 19 meters). They produce a smooth tunnel wall, but woe to any creature that stands in its way (obviously).
Here is how Herrenknecht company describes it: "With two 57km-long tunnels, the Gotthard Base Tunnels will be the world's longest railway tunnel. Four Herrenknecht Gripper machines are excavating a total of 75km through the Alps. The identical S-210 and S-211 (diameter of 8.830m each) have been cutting their way through the rock from the south since November 2002 and February 2003 respectively."
These machines easily capture the imagination of movie makers. The whole pulp-style scientific romance "Core" is built around exploring the Earth's innards, and in "Oceans 13" the guys smuggle a 600-ton tunnel boring machine under Vegas.
Here is TBM cabin control center - and the driver:
There were special conditions with the Arrowhead Project, that Herrenknecht AG has been commissioned to undertake - very close proximity to major earthquake fault:
"Nobody has ever excavated so close to the site of earthquakes before. The route of the S-233 and S-234 through the South Californian mountains above San Bernardino is only a few hundred meters away from San Andreas Fault."
"Providing drinking water for the population of Los Angeles, California, is without doubt one of the greatest challenges facing the municipal authorities and local government. The mountain overlooking San Bernardino, through which a tunnel is to be drilled to pipe the water, presents quite unique challenges of its own: the aqueous rock has been heavily fissured by the San Andreas fault, which is located very close to the mountain."
Here is a good animation of how these machines work:
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