Looking forward

25 May 2016

This time last year I wrote about the impressive amount of tunnelling required to solve the unanswered questions of the scientific community. In recent years, the Large Hadron Collider (LHC) has been the highest profile of these projects.

Nestled in the Geneva area of Switzerland, it has expanded humanity’s knowledge of the subatomic world by smashing particles together at extremely high energies. For engineers too it is an impressive project. At 3.8m-diameter, the 27km-long circular tunnel was constructed in the early 1980s at depths of 50 to 175m. All in, the entire project required 32.6km of tunnels, 19 shafts and 37 caverns to accommodate the equipment necessary to scoop Nobel Prizes.

But bigger is better, and scientists are looking to the tunnelling industry to help with a new project they have been mulling over. As the subatomic particle ‘zoo’ gets populated, higher magnetic energies (and bigger colliders) are needed to find new species. So in the next issue of Tunnels and Tunnelling, we will be reporting on plans for the Future Circular Collider (FCC).

This really will be a big one if it goes ahead. The circumference range being examined is 80-100km, and as expected the physicists are pushing for the 100km option. There is also a cadre arguing that this should be a double ring installation, which would see the project dwarf the Gotthard base tunnel (152km total tunnelling) or the Delaware aqueduct (137km) to become the largest tunnelling project in history.

Mega colliders require smaller colliders to preaccelerate particles before they enter the main structure. It is much like going through the gears in a car, starting at a low gear first. So locating the FCC near the LHC is desirable to make use of the older collider for this purpose.

However, the sheer size of the FCC makes locating it dif_ cult during feasibility studies. Staying in good rock is challenging, and whatever the depths tunnelling will take place at, the shafts required for this project will be very impressive. The concept currently calls for 16 shafts, of which access shafts will be 12m in diameter. However, other shafts need to be up to 31m in diameter and up to 400m deep. This is because the scientific equipment is so precisely machined it has to be monolithic, and cannot be broken up into sections for lowering.

Construction methodology for the shafts and tunnels varies due to the wildly differing conditions across the project. Read the article for more