DSI Ground Support Products Secure Second Tube of Karavanke Tunnel

Since its opening on June 01, 1991, the Karavanke Tunnel has been a critical transport link between Western and Southern Europe. The 7,864-meter tunnel connects the Karavanke Highway A11 on the Austrian side with the A2 in Slovenia. It has shortened the journey to the south by about 1 hour for thousands of motorists each year. To tackle increased traffic and match modern safety standards ASFINAG (Autobahnen- und Schnellstraßen-Finanzierungs-Aktiengesellschaft) and DARS (Družba za avtoceste v Republiki Sloveniji - Motorway Operating Company of the Republic of Slovenia) decided to build a second tube in 2015.

In Austria, work began in 2018, breaking through at the Slovenian border on September 23, 2021. After a delay, excavation of the 3,546-meter tunnel section on the Slovenian side began in August 2020. The construction includes twelve cross-passages and four emergency bays.

The Karavanke is part of the Southern Limestone Alps. Located south of the Periadriatic seam, where African and Eurasian tectonic plates meet, the mountain range is prone to earthquakes. To counteract these problematic conditions and secure the excavation, the Slovenian contractor Cengiz relies on DSI’s ground support products.

DSI supplied the AT – Casing Drainage System, Ø 76mm, to drain the surrounding ground. Its simultaneous drilling and casing saves time and simplifies installation. DSI also provided its Hollow Bar Anchors R32-360 and R38-550, ideal for difficult ground conditions.

The AT – Pipe Umbrella System 114 with conventional thread was installed with a range of 9 meters. Standard threaded connections ensure a constant internal pipe diameter, reducing the section modulus. DSI Underground also produced and supplied passive support elements for this project. The LSC^™ Elements type 4N and 3N were created for use near fault lines, increased worker safety, and limited displacement. Additionally, Cengiz received technical support and training on the proper application and installation of the compression elements from DSI application engineers.

As of February 2022, about 50% of the tunnel on the Slovenian side has been excavated. Breakthrough at the border is scheduled for fall 2023. The tube is expected to be completed in June 2025, while the entire project, including updating the old tunnel, highway extensions, and bridges, is scheduled for completion in 2027.

DSI Underground is proud to contribute to the safety of future motorists in the second tube of the Karavanke Tunnel.