DSI Reinforces new Tunnel Pekel on Southern Railway in Slovenia

The old Počehovo railway tunnel between Šentilj and Maribor has been used since 1846. However, the tunnel’s geometrical curvature doesn’t allow trains to go faster than 70 km/h, and it has only one track, even though the tunnel was built for a double-track line. Because of this limitation and various security concerns, the Slovenian Government decided to build a new tunnel, the Tunnel Pekel. DSI Underground produced and supplied different ground support products and services.

The railroad connection between Vienna and the Adriatic port of Trieste, also known as the Southern Railway line, was completed in 1857. Part of this railway from Austria to Italy is the connection from Šentilj to Maribor in Slovenia, which goes over a viaduct in the Pascina valley and through the Počehovo tunnel. At the time of construction, the tunnel was one of the most demanding constructions because of the geological structure of the hills it goes through. Though the tunnel was built for two tracks, only one was laid, and the steep curves limit the trains’ speed to 70 km/h. Due to the amount of work needed to achieve modern safety standards, the Slovenian Directorate for Infrastructure decided to build a new tunnel.

The double-tracked tunnel through the Pekel hills will be about 1,530 m long and outfitted with different safety systems. In addition, the new tunnel will shorten travel times considerably and increase the capacity for tourist and freight transportation. The tunnel system will include a drive station, an emergency shaft connecting the tube with the surface, and a fire alarm system.

Preparations for the construction began in September 2020. In 2021 the contractor started excavating the north and south portals. To support drilling and blasting, Avesco AG provided a Sandvik DT922i, an advanced control system based, electro-hydraulic two boom jumbo, equipped with DSI’s AT – Pipe Umbrella Automation Unit with squeeze connection. The forepoling system was installed with a range of 15 m and 18 m.

To stabilize the slopes, DSI supplied SN Anchors with Ø28mm. DSI also provided the AT – Casing System 114 with squeeze connection to strengthen the crown and improve load-bearing capacity, and the self-drilling DSI Hollow Bar Anchors R32-250Ø, allowing simultaneous drilling and grouting. Other ground support products produced and supplied by DSI included lattice girders, drill steel, and pumps.

The construction of the Pekel Tunnel is part of a larger project to update the railroad between Šentilj and Maribor, funded by the EU’s Cohesion Fund with €101m. It is being built east of the existing railway tunnel Počehovo, which will be converted into a pedestrian and bike tunnel. The project also includes a new viaduct, the expansion of several train stations, and the entire transportation network. The tunnel Pekel is scheduled for completion in 2023.

Owner:            Government of Croatia

Contractor:     BINA Istra public-private partnership

DSI Unit:         DSI Underground Austria GmbH

DSI Scope:     Production, supply

DSI Products: DSI Hollow Bar Anchor System ØR32-280, DSI OMEGA-BOLT®, DSI MAI® Pump


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