Important Preparatory Work for the Second Gotthard Tube at the South Access Gallery
Important Preparatory Work for the Second Gotthard Tube at the South Access Gallery

The second Gotthard road tube will be con­structed over the next few years. Since the be­ginning of 2021, the Marti Group has been hard at work on access tunnel 343, the Gotthard South access gallery at the South Portal in Airolo. The tunnel boring machine reached 2,000 m in February 2023, and tunneling operations will have reached 5,000 m by the summer.

Since 1980, the Gotthard Road Tunnel bet­ween Göschenen and Airolo has been operating as a national road link and is in need of exten­sive reha­bilitation. A second tunnel tube is to be built for this pur­pose over the next few years. In the fall of 2022, the Marti Group received the definitive contract for lot 341, the con­struction of the south main tunnel. This batch of work in­cludes ex­cavation of the new road tunnel over a length of appro­ximately 7.8 km as well as additional ex­cavation of a southern fault zone. Marti has also been awarded lot 111, which in­cludes materials manage­ment and logistics for North and South. Preliminary work has already begun on both batches of work.

Lot 343, the Gotthard South access gallery on which Marti has been working since 2021, is also part of the over­all Second Gotthard Tube project. In this case, a tunnel boring machine (with a diameter of 7.42 m) has been working its way north­ward to the geo­logical fault zone mentioned above, known as the “Guspis zone,” since the summer of 2022. This zone is located in the mount­ains about 5 km from the South Portal in Airolo and will sub­sequently be crossed and secured as part of main batch of work 341. This makes it possible for the large tunnel boring machine (with a diameter of 12.26 m) of the main lot to sub­sequently cross the zone with­out any complications. After completion and commissioning of the road tunnel, the access gallery will be used as a ventilation and drainage gallery.

Status as of mid-December 2022

At this point in time, the tunnel boring machine (TBM) is engaged in tunneling ope­rations at around 1,250 m. It al­ready crossed the existing tube of the Gotthard Tunnel, putting it in a slightly sloping section (approx. 0.5%) until it is at the level of the future road tunnel. The tunnel is lined from end to end with concrete ring components, known as seg­mental rings, in single-shell con­struction. These rings will remain visible upon com­pletion of the project. The Marti Tunnel crew uses an erector to position the seg­mental rings in the rear part of the shield of the ingeniously engineered TBM. After each tunneling stroke of 1.8 m in length, the crew members insert a complete tunnel ring con­sisting of six seg­mental ring components. Each day, the ex­perienced team is in­stalling an average of 60 of these compo­nents, corres­ponding to tunneling operations of 18 m. In parallel with the tunneling operations, the miners are installing a floor in the tunnel behind the TBM. A Marti Technik traversing bridge is used here to ensure that there is no interruption to the logistics of the machine, which is continuously supplied with segmental rings.

This con­struction site is particu­larly fasci­na­ting because you get to expe­rience a wide range of tunneling work in a very brief period of time
Nicole Kölbener,
Production Manager for Driving Operations , Marti Tunnel AG

Segmental ring production in in-house plant

The segmental rings for the Gotthard access gallery are currently being manu­factured as quickly as possible at the Marti seg­mental ring plant at Klus near Balsthal. Some 7,000 of a total of 16,500 compo­nents have been com­pleted as of the be­ginning of December 2022. “At the moment we are working in three shifts and pro­ducing bet­ween 27 and 30 compo­nents per shift,” explains Oskar Gisler, the Seg­mental Ring Production Manager. The segmental rings are trans­ported by rail. Twice a week, a 13-car train de­livers 26 complete tunnel rings directly from Klus to Airolo. These two trips make it possible to trans­port a total of 336 compo­nents to Ticino per week. A third trip per week will be added in early 2023.

Back in the South access gallery

“We are dealing with widely variable and challenging geo­logical con­ditions here,” reports Nicole Kölbener, Production Manager for Driving Operations at the con­struction site. Weak rock and the resulting insta­bility of the working face made steering the TBM difficult at times. Various work steps are carried out simultane­ously, a circum­stance that re­quires complex planning. Starting in January, in addition to the on­going TBM tunneling operations and the con­crete con­struction of the floor behind it, the logistics niches are to be con­structed using blasting.