There are three core elements to an efficient tunnel construction project, with efficient excavation, support of the new tunnel shape and careful conveyor rollers to manage the mass amounts of debris that are the inevitable result of boring a gigantic hole into the side of a mountain all vital elements to success.

All three parts are integrated into the tunnel boring machine (TBM), which are huge, often custom-built machines designed for the sole purpose of building out a tunnel as rapidly as possible.

Because of this, TBMs continually get bigger, faster and more effective at moving earth, and as recently as late April 2024, the world’s largest hard rock TBM completed its inaugural project in Georgia.

Gudauri Tunnel

First suggested in 2019 with an Asian Development Bank report produced not long afterwards, the Gudauri Tunnel was part of a vital road infrastructure intended to provide greater capacity and reduced travel times on the North-South Corridor which links Georgia to neighbouring Armenia and Russia.

It is a two-lane 23km highway with five bridges and five tunnels along the way, but by far the largest and the one that necessitated the creation of a TBM was nine kilometres in length and 15 km wide, part of a section that passes along the Tetri Aragvi riverbed.

This section did not have any road network close to it, causing 11 villages in the Gudauri area to have no connection to the rest of Georgia in winter, a particularly treacherous prospect given the lack of medical infrastructure in the area.

Beyond this benefit, the original road was barely fit for purpose. The 33km route took over an hour. 

By comparison, a similar length distance between Bolton and Stockport takes less than half of this time and according to Prime Minister Irakli Kobakhidze, the path from Kvesheti to Kobi would cut travel times by as much as 45 minutes.

This is not only through featuring a much safer route but also by cutting 11km from the existing route by virtue of not having to go around the Gudauri area.

However, this is the least of the issues with the current route, which is often congested and sometimes closed entirely during winter due to the threat of avalanches. The Kvesheti-Kobi road project as a whole but especially the Gudauri Tunnel would be usable throughout the year.

The TBM in question is 182 metres in length, weighs 3900 tons and at a diameter of just over 15m is the largest single-shield hard rock TBM ever made.

The machine is known as Caucasus, named after the region that includes not only Georgia but also Russia, Armenia and Azerbaijan.

Mr Kobakhidze made a point of describing the tunnel as a “project of the future” and one that he credits to the innovations in the TBM drilling rig, which due to its ability to advance as much as 426m per month, over 100m faster than any other TBM of a comparable size.

This is thanks to innovations in the machine that allow for excavation and construction of the tunnel to take place at the same time.