The Bauma is a construction trade fair that's held in Munich every couple of years. This year it was held in April and somehow I landed a ticket for an evening's visit with a good friend of mine. Some beers later we were around the Herrenknecht stand; a company that makes massive Tunnel Boring Machines ( TBM's ) and who are based in Germany. The evening progressed as it normally does and somehow we all ended up in a cocktail bar in the city ( it's called "networking", right? ) and I got chatting to the project manager for a project beside Stuttgart called the Filder Tunnel. Norbert Hörlein is the site project manager andI take sports photos so after about the 3rd Mojito we both thought it would be cool to use the empty tunnel as a location for some sports shooting. Some months later (after the hangover had worn off) Norbert contacted me again to ask what was happening with the photo project. I had no idea what it really looked like down there underground so I decided to pack my camera, take an ICE train to Stuttgart for a day and check out the location.
After arriving at Suttgart Hbf I took the U6 to the end of the line at Fasanenhof and, from there, the site is only a short walk away. I met Michael on-site and he was my tour and safety guide for visiting the first tunnel. PUCH cars seemed to be all around the site, they're Austrian cars and most of these seemed to be ex-army. The old PUCH took a little while to start but as soon as it did we were rolling down into the first tunnel.
The first tunnel was referred to by Michael as the traditional Austrian tunnel. "Why is it it called traditional Austrian?" to which Michael replied "Have you not seen how many mountains we have in Austria? We have a lot of experience blasting through them with dynamite", so that answered the question: "traditional Austrian" means dynamite blasting through mountains. We parked the car in what appeared to be, in terms of dust, the start of a war zone. The products of blasting do not make for a clean environment and everything was covered by a thick layer of dust, which would make the photography challenging.
We stepped out the PUCH and Michael explained to me that we weren't far from the tunnel head and the heavy construction work currently in progress.
In particular we had to be extremely careful not to get in the way of any of the trucks, due to the darkness and dust it's extremely difficult for the drivers to see anybody.
We walked past a bunker, used for breaks and for shelter when the dynamite goes off. On the wall is the trigger box for the dynamite.
The further we walked down the tunnel and the closer we got to the excavation work, the more the dust got thicker and we had to place a filter mask over our noses.
At the tunnel head, the dust was really thick, and, despite the air getting pumped in through the overhead tubing it still felt really close and slightly suffocating. In the darkness the power of the work getting done felt slightly intimidating and we had to be very careful where we walked.
At this point in the tunnel they were building a connection to the parallel TBM tunnel. Some weeks in the future the TBM will bore through and make the connection here. Michael informed me he had to go and catch a flight, so after guiding me safely away from the construction he drove me out of tunnel number 1 and handed me over for a visit to the 2nd tunnel - the one with the TBM.
The TBM tunnel entrance is rail way accessed using a small service train that has a pay load platform and a cabin to take the shift workers in and out. The cabin is a small box with about ten seats and offers a dark ten minute rail ride into the tunnel head.
Outside, close to the entrance of the tunnel the ring sections are stacked up ready to get transported in by the train and fed to the TBM. For every 2m advancement of tunnel a new reinforced concrete ring is inserted. For this tunnel's circumference there are six sections plus a smaller key stone and, depending on the curve of the tunnel, the sections are twisted millimetres at a time to guide direction. The outer shell is soft plastic and rubber, holes in the face exist to pump in concrete and waterproofing agents. Construction of the reinforced concrete tunnel is not only integral to the tunnel's structure but also to the TBMs advancement since the whole rig which, being about 100m long, runs on wheels over the rings which have previously been laid.
When the train stopped I was greeted by the foreman who showed me around the very confined, noisy and slightly claustrophobic space close to the head of the TBM. In this tunnel noise was more of an issue compared to the darkness and dust levels in the first "traditional Austrian" one. I was taken underneath the main platform and shown exactly how the TBM works. The whole drilling head is pushed forward using a ring of pistons that act off the leading edge of the last reinforced concrete ring that was placed. The pistons push the drilling head into the rock and debris falls to the bottom of the drill housing and is carried away by conveyor belts. In the 4th picture below the pressure pistons can be seen - when these reach 2m extension the bore machine is stopped, pistons are retracted, and a new reinforced concrete ring is laid.
Turning around and looking away from the tunnel head to the back of the TBM we can see how the concrete rings are placed. Each segment is "suctioned off" the train's pay load and carried along the under belly of the TBM before it's rotated 90° and laid ready for collection and placement by a rotating arm. Once a complete ring is placed the pistons from the bore head begin their 2m push forwards again off the leading edge of the freshly placed ring and the whole TBM itself rolls forward, advancing on it's wheels.
The end of my visit came at about 1730, which marked the end of a 12hr day shift for the workers and the night shift was coming in. Working in such a small and noisy environment for 12hrs at a time must be very difficult. The ten spaces in the train cabin leaving the tunnel seemed to be cramped and one space short, which, I guess was the photographers' fault that day. The men all appeared tired but still smiling and in good spirits.