Building the Second track

Since 75% of the second track runs through seven tunnels, only a small portion of the track is visible on the surface, specifically in the areas where the track crosses three major valleys—viaducts and the open sections of the track. The entire track has only 5.4 kilometers of railway on the open section. Although the open section does not feature grand structures like tunnels or viaducts, constructing the open track from Divača to Koper is still a major challenge. This is because numerous support structures, embankments, cuts, and culverts need to be built. Special attention is given to the quality of embankment construction and the foundation soil, as settlement is unacceptable due to the rigid base that the track will be laid on in the open section. The construction of just over 5 km of the open track of the second line also represents a unique engineering challenge, as numerous new structures must be built to overcome geological and topographical characteristics, which will connect tunnels to the new railway line along with the viaducts.

The deviation of the track in Divača, carried out as part of the second track project of the railway connection between Divača and Koper, involves key adjustments to the existing railway infrastructure to facilitate the construction process. The relocation (deviation) of the railway track in Divača was completed in August 2023. A 900-meter-long track was constructed, rails and switches were installed, and an electric traction system along with signaling, safety, and communication devices were put in place.

The route of the second track intersects with the existing railway route, so the existing track had to be moved to a new path.

In planning the deviation, the highest standards of safety, efficiency, and environmental sustainability were considered.

It is the second-longest tunnel on the route, measuring 6,017 meters. The main and service tunnels are connected by 13 cross-passages. The tunnel mainly runs through carbonate rocks (about ¾ of the length), with a smaller part running through transitional layers at both ends of the tunnel and also in intermediate layers of carbonate rock. The construction uses the NATM (New Austrian Tunneling Method) technology, which involves digging and blasting, rather than boring.

This is the third-longest twin-tube tunnel, measuring 3,808 meters. The main and service tunnels are connected by 7 cross-passages. Excavation technology in the flysch foundation was performed mechanically with tunnel excavators, hydraulic hammers, and drilling and blasting. In the area of low overburden in the Škofijica Stream valley, preliminary measures were necessary to remove poor soil above the tunnel and replace it with cement stabilization, followed by the construction of a reinforced concrete arch cover.

The Vinjan railway viaduct is the longest on the second track, at 620 meters. The viaduct is designed as a valley viaduct, spanning the Vinjan valley with piers up to 60 meters high and spans of 100 meters. Technologically and organizationally, it is the most complex of the three viaducts on the route of the second track.

The Gabrovica viaduct runs beneath the Črni Kal highway viaduct, both designed by the renowned engineer Marjan Pipenbaher, which is why their style is quite similar. The railway viaduct runs

The method used to construct the Gabrovica viaduct with incremental launching represents an innovative technique. Pre-stressed reinforced concrete segments are fabricated in a workshop and then pushed forward over supporting piers. This advanced technology allows builders to construct the viaduct gradually, without traditional formwork supports, contributing to a faster and safer project execution.

The construction of the Glinščica viaduct was a prerequisite for the start of tunnel construction at Lokev (T1) and Beka (T2) from both sides. It is designed as a closed box-shaped reinforced concrete structure. Its innovative design allows proper ventilation for tunnels Lokev (T1) and Beka (T2), and provides protection against derailments, wind, noise, and emissions in the protected Beka Landscape Park. The Glinščica viaduct will connect the first tunnel, Lokev, the longest at 6.7 kilometers, with the second Beka tunnel, which is 6 kilometers long, forming a continuous tunnel of nearly 13 kilometers.

Tunnel T7, or Mlinarji Tunnel, is named after the settlement of Mlinarji nearby. At 1,154 meters in length, it is one of the medium-length tunnels on the second track. It is constructed as a single-tube tunnel, with a cross-side service or escape tunnel 165 meters long at its center. There are no residential buildings within the area affected by the tunnel construction.

Initially, two tunnels were planned in the area of the Osp tunnel, but in later phases, the two tunnels were merged into a single tunnel of 505 meters.

Its uniqueness lies in its steep location and two areas of low overburden, where pre-excavation measures were needed on the surface to remove poor soil and rock above the tunnel and replace it with cement stabilization.

The Tinjan Tunnel is a single-tube tunnel and, at 1,949 meters, is the fourth-longest on the second track. It also has two exit tunnels. Excavation work in the tunnel began in June 2022 and finished in February 2024. No residential buildings are within the area affected by the tunnel construction.

This is the shortest tunnel on the second track, at 335 meters, and is the first tunnel coming from Divača, under the Karst edge. Together with the Osp Tunnel (T5-6), it is considered one of the short tunnels, which do not require forced ventilation and escape routes that are needed in medium and long tunnels, provided through side exit tunnels or cross-passages in a parallel service tube. No residential buildings are within the area affected by the tunnel construction.

At 6,714 meters, it is the longest tunnel on the new track. Together with the Beka (T2) and Škofije (T8) tunnels, it is a twin-tube tunnel, meaning that a service tunnel runs parallel to the main tunnel, with the same cross-section. In the Lokev Tunnel (T1), at intervals of up to 500 meters, the two tunnels are connected by 13 cross-passages, which provide safe evacuation in case of an emergency via escape and intervention routes, allow for effective maintenance, and provide space for the installation of electrical and mechanical equipment, signaling and safety devices, and firefighting water systems.