Tunnel Rail Route 10: from Design to Construction

GCF's Works on Kosovo's Railway

From design to rehabilitation. The railway rehabilitation works in Kosovo continue along the terminal section of Lot 1 of Rail Route 10 – the Fushë Kosovë - Hani i Elezit segment – where GCF SpA is particularly engaged in the renovation works of the numerous and challenging tunnels, given the complex and fragile geomorphology of the border area with Macedonia.

A total of seven tunnels are located in the terminal section of Lot 1, spanning approximately 11 kilometers between the cities of Kaçanik and Hani i Elezit, with a total length of 1024 meters. For six of them, GCF SpA, through its Structural and Geotechnical Engineering Department, has taken full responsibility for the design, from concept definition to detailed design for construction.

"The geomechanical complexity of the locations affected by the widening works," explains engineer Alessio Bianchini, coordinator of GCF's Structural and Geotechnical Engineering Department, "and the disturbance induced in the rock masses during the construction of the existing tunnels required significant investigations during the survey phase. During this phase, topographical surveys were conducted to verify the current state, geological inspections were carried out to study the structural characteristics of the outcrops, and geognostic investigations were performed for stratigraphic reconstruction and piezometric level detection."

Core drilling and laboratory tests on samples allowed the determination of the mechanical properties of the rock mass. Accurate geophysical surveys were conducted to precisely identify the extent of the disturbed zone around the existing tunnels, while inside the tunnels, georadar tests and additional core drillings were used to reconstruct the thickness of the existing final lining and define the geomechanical properties of the surrounding rock mass.

"The analysis of this data," continues engineer Bianchini, "along with a careful assessment of the technologies available in the country, made it possible to define the necessary pre-consolidation interventions required before the widening excavation works. Numerical analyses have been used to design the primary lining, characterized by steel ribs and shotcrete, and the final lining made of reinforced concrete."

The technical solutions adopted for portals construction were defined after a detailed evaluation of the geomechanical conditions. Where poor or very poor rock mass conditions were foreseen, temporary retaining systems have been designed to provide the required support and confinement to the rock mass disturbed by the widening works with low cover.

"While work progresses on various sites for the reconstruction of the entire railway line," explains Raffaele Forcella, GCF Project Manager, "we are particularly focusing on adapting the existing tunnels in the area. The goal is to wide them according to European standards, reconstructing them with techniques ensuring complete waterproofing and absolute structural solidity. Once completed, the entire line should allow for an increase in speed from the current modest 70 km/h to the foreseen 120 km/h."

For tunnels 1, 2, 6, and 7, natural widening is planned. The final lining of tunnel 6 ("Valan," the longest at 270.5 meters) was recently completed, and work is now progressing section by section on tunnel 7 ("I shtati," 131.87 meters), an operation that, as illustrated by project manager Francesco Binotto, through excavation advancements characterized by tronco-conical sections due to the presence of the “forepoling” which is required to eliminate the risk of instability phenomena of the surrounding rock mass during the excavation. This system constitute a sort of protective "umbrella" for the workers - the installation of the horseshoe-shaped steel ribs, the wire mesh and the shotcrete complete the primary lining. Before proceeding with the construction of the reinforced concrete final lining, “full-round” waterproofing was carried out. The final lining was cast using a mobile formwork operating on temporary rails.

For tunnel 3 ("Guri i shpuar," now 50% completed), the decision was made to demolish the old tunnel and construct a new cut-and-cover tunnel using the bottom-up system. Meanwhile, for tunnel 5 ("Galeria"), originally located on a slope at high risk of rockfalls, GCF developed an ad hoc top-down design solution involving the demolition of the existing tunnel under the protection of a reinforced concrete roof slab, fixed at the head top of two double rows of micropiles, each of those running along the side walls of the existing tunnel, followed by the reconstruction of the final lining.
"This technical solution," explains engineer Bianchini, "was developed to minimize disturbance in the rock mass during the demolition of the existing tunnel and to protect workers at every operational stage from the risk of falling rocks. The installation of micropiles and the construction of the reinforced concrete roof slab take place only after eliminating the risk of rockfalls from the adjacent slope through the installation of a fixed drapery system consisting of a metal mesh anchored to the slope through a system of crossed galvanized cables and anchoring bolts."

The anchoring and excavation geometries were sized through finite difference numerical analyses, modeling the identified discontinuity joint sets responsible for potential rock mass instability, along with all construction phases responsible for changes in the original stress-strain state. An additional complexity addressed by the adopted design solution was managing the interference of permanent anchors from an existing retaining wall located downstream of the tunnel.

All Works in Lot 1 Fushë Kosovë - Hani i Elezit

Beyond the seven tunnels under construction, the inventory of civil works included in the 67-kilometer rehabilitation project of Lot 1 Fushë Kosovë - Hani i Elezit is notable, as outlined by Roberto Accinelli, GCF Project Manager: 14 reinforced concrete bridges to be rebuilt, 14 steel bridges to be reinforced, 6 additional bridges requiring minor repairs; 36 level crossings on dirt or asphalt roads to be replaced, covering a total of approximately 10 kilometers of new road pavements. Additionally, permanent protective measures include approximately 14 km of retaining walls and 3.2 km of gabion walls on both sides of the railway line, as well as drainage works involving underground pipelines, around thirty channels, and about eighty box culverts.

Finally, civil works to be modernized include 8 railway stations and their platforms, along with platforms at an additional 5 stops. Regarding railway infrastructure, the complete renewal (including embankment reconstruction, ballast track bed reconstruction, and track laying) covers the entire 66.83 km of the main track, plus 12.76 km of secondary tracks, totaling 79.58 km of railway.

Works on Lot 2 Fushë Kosovë - Mitrovicë

Meanwhile, rehabilitation works on Lot 2, also entrusted to GCF, continue. As emphasized by Raffaele Forcella, these works also "involve diversified interventions beyond railway reconstruction, including station buildings, passenger platforms, bridges, underground channels, hydraulic works, roadways, and parking areas".

In addition to the complete reconstruction of the section between Fushë Kosovë and Mitrovicë (34.4 km of main railway line and 9.1 km of station tracks and switches), GCF's sites are also working on rebuilding 18 km of road network parallel and transversal to the railway line (service roads or those affected by the 32 existing level crossings), adapting 16 bridges (steel or masonry) to interoperability standards and Eurocode and TSI requirements, and restructuring 5 stations, 5 stops, and 16 passenger platforms.

The Rail Route 10 Corridor

The Rail Route 10 Corridor spans a total of 252 km, 148 of which traverse Kosovo along the North-South axis from Leshak to Hani i Elezit. It extends from Kraljevo (Serbia) to Belgrade via Lapovo and, to the south, from Gjiorche Petrov (Macedonia) to Skopje. Its integration into the Eastern European/East Mediterranean Corridor (TEN-T, axis 4) will connect the Balkans with Austria, Greece, and Bulgaria.

The modernization of the railway infrastructure is considered by the Kosovo government and the European Union as a prerequisite for the region's economic development and holds strategic importance for the country.

For further information:

With GCF, Kosovo starts rail network modernisation

Kosovo: GCF also hosts the second batch of Rail Route 10

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