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Karst caves slow construction progress

In the second longest tunnel on the Divača-Koper second track route, the Beka Tunnel (T2), contractors encountered karst caves that were more challenging to overcome than the caves that had been discovered so far. Currently, the rehabilitation of the karst phenomena is being carried out in both pipes (main and service) in accordance with the engineering design solutions. In the photos you can see the machine carrying out the karst rehabilitation operation.

Karst phenomena are heterogeneous and, as a consequence, the treatment of each one is unique. Cave 66 stopped excavation at the head of the Beka tunnel for a while, which affected the dynamics of the excavation work. Once the Beka Tunnel cave-in has been rehabilitated, the contractors will resume excavation work. The excavation of the tunnel tubes is currently at a standstill for two weeks and major karst phenomena may affect the completion date of the excavation works.

At present, 5,440 metres have been excavated in the main pipe of the Beka Tunnel, leaving approximately 550 metres to be excavated.

On 1 March, a karst cave was discovered in the main pipe of Lokev Tunnel (T1), which is of particular interest. Initially, a relatively small entrance on the right-hand side of the face of the calotte led into a large room.

Karst phenomena discovered during excavation work are studied and documented in detail, and solutions are always sought to preserve as much of the cave as possible. As a rule, therefore, caves are not filled in, but preserved as much as possible, and the measures necessary to ensure the long-term stability of the tunnel tubes are implemented.

11. 3. 2024

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