Karavanke Tunnel work on Slovenian side on schedule

Photo: STA

Jesenice – Work on the second tube of the Karavanke Tunnel on the border with Austria is on schedule. Turkish Cengiz workers have already bored some 550 metres of what is a roughly 3.5-km tube on the Slovenian side. No major problems have been encountered since boring started last August and is expected to be completed in two years.

Supervisor Andrej Štimulak from Slovenian company DRI told the press on Tuesday that 6-9 metres of the tunnel is bored a day, depending on geological conditions.

Nevertheless, there are still some unknowns and the most difficult geotechnical conditions are yet to come.

Geotechnical conditions are much better on the Austrian side of the Karavanke mountain range, which is also a reason why 30 years ago, Austria used less time to bore the first tube than Slovenia.

Slovenia had a major problem with underground waters, but this is unlikely this time round, said Štimulak, explaining hydrostatic pressures are considerably lower due to the drainage effect of the first tube.

Workers nevertheless came across quite a big source of water with a flow rate of more than 20 litres per second some 300 metres into the tube.

“The situation was tackled by catching the water, directing it into a channel towards a purification facility and into the river Sava,” said construction site head Edvard Kastelic from Cengiz.

“We are on schedule or slightly behind, which is still manageable,” said Štimulak.

However, the initial delay which occurred due to complaints in the contracting procedure, could not be made up for.

The Austrians are expected to have bored their 4.5-km section of the tube in August, after launching it in September 2018.

They will have to wait for the Slovenian side to be completed before proceeding with construction work.

Since some of the needed equipment will be used in the entire tunnel, it will be purchased through common tenders.

Some 80 Cengiz workers from Turkey are currently working in the tube in three shifts, 24 hours a day year-round.

Slovenian subcontractors are meanwhile involved in some other works, including landfills for the excavated material.

The Jesenice one, which can take 85,000 cubic metres of material, will be full in two weeks’ time, so a new one, near Mojstrana, is being prepared.