The Long Dig28 May 2019 14:24
There is much of interest in the 2008 New Yorker article 'The Long Dig - getting through the Swiss Alps the hard way' by Burkhard Bilger
https://www.newyorker.com/magazine/2008/09/15/the-long-dig (3-free-articles-a-month scheme)
but note the geology of the Gotthard base tunnel is vastly more challenging than North Yorkshire.
'When completed, in 2017, it will be the longest traffic tunnel in the world; it is also one of the most geologically challenging ... The Gotthard crosses nine geological zones, none of them fully understood. It cuts through granite and quartz, along fault lines and beneath a sugarlike layer of dolomitic marble - a sand trap to anything going through it.'
... 'The roar of the machinery, muffled inside the cabin, now seemed to redouble. As we shuffled down the catwalk, it began to tremble underfoot, then lurch and shake as if trying to buck us off. An acrid taste of burning oil filled my mouth, and the walls seemed to flex and heave around us. Herrenknecht grabbed my arm and pointed to the pistons thrust into the walls on either side, wedging the worm into the tunnel. "Bilger! Feel the power!" he shouted. "More than three hundred and fifty bars of pressure to the Gripper!" The entire site consumed about as much energy as a city of thirty thousand. But the rock here was soft enough that the machine was operating at only quarter power.
Herrenknecht stepped onto a platform at the front of the machine and stood with his fists on his hips. "It is excellent work!" he shouted. He pointed to another set of pistons, angled forward from the Gripper, that were driving the cutting head into the rock. The head was fitted with blunt disks, seventeen inches wide, made of an obdurate alloy of manganese, steel, and chromium. As the cutting head turned, the crushed stone fell into spokelike dividers inside it, was funnelled onto a conveyor belt along its axis, and carried to dump trucks waiting outside. By the time the cutting head pulled back and the engines cut off, the teeth were red hot. "You can put an egg on them," Herrenknecht said. "Sunshine up."
The tunnel was suddenly silent. With a low rumble, the back half of the worm ratcheted forward two metres and planted its legs. The Gripper slid forward an equal distance and braced itself against the wall. Then the engines ignited for the next attack.'