Sustainability and Functionality of Railway Network and its Connecting Facilities in Kosovo

The railway network presents a special communication function, which keeps humanity closer. The first developments of the railway network in Kosovo date back to 1874 when the first train entered this area from Thessaloniki through Skopje. This paper aims to provide some data generated during the year 2020 regarding the railway network in Kosovo and its connecting facilities. Construction of railway lines, stations, tunnels, bridges, watersheds, protective walls, canals for surface water drainage has an average lifespan of 92 years. The total length of the railway network is 336.68 km, in which are built 23 tunnels with a total length of 9789.5 m. 26.1% of them are of medium depth, while 73.9% are of shallow depth from the ground surface. 66.07% of the railway lines are active, while 33.42% are non-functional.


Introduction
To recognize and understand the development and importance of the railway network in Kosovo, it is necessary to consider its historical circumstances. It has over 147 years since the first construction of the railway, which connected the southern part with the northern part of Kosovo, and those creating connections with two important capitals, Skopje (North Macedonia) and Thessaloniki (Greece). The greatest development of the railway network and the associated facilities in Kosovo occurred from 1926 to 1960/1963. In this railway network, there are several facilities like stations, bridges, tunnels, canals, protective walls, watersheds, etc. Stations are places where the vehicles stop and depart, making a round trip to transport passengers and goods. There are main and secondary stations in the railway network. Figure 1 shows the types of stations according to the architecture of their construction. They represent a very characteristic feature in the country's architectural and cultural identity [1,2]. Although most of them severely damaged, the historical value of the station buildings cannot be ignored. They imprint the historical and cultural memory of a place, and people repay that prosperous era with new vitality [3,4]. Bridges are engineering facilities for crossing roads into rivers, valleys, or large slippery areas. Each bridge consists of supports and the aerial part, which is placed between the supports where is transmitted the load of the bridge itself and the moving vehicles [5,6]. Its purpose is to connect two points at the shortest possible distance. Four types of bridges are identified on the railway lines ( Figure 2). There are a total of 115 bridges with a length of 2.988m [7].

Figure 2. Types of bridges
Tunnels are underground engineering facilities that are located inside a rock massif [5]. The tunnel is a road that opens underground by piercing a mountain, a hill, to pass by train or vehicle. Tunnels belong to the group of underground engineering facilities with a length much greater than their height and width. Tunnels depending on the geological conditions of the region may have different positions towards the geological structure. The tunnels in the railway tracks are built at an altitude of 331 m to 654 m with an average height of 501 m. The shape of tunnels that is identified in Kosovo is a horseshoe shape (Figure 3), with a height of 6 m and a width of 2.60 m.

Figure 3. Tunnels shape
Watersheds are the places where water passes under the railway. The shape, dimensions, and building materials depend on the size of the catchment that carries water to the railway. During the research are identified different types of watersheds in the railway network of Kosovo ( Figure 4).
Protective walls are construction engineering works that are built to prevent landslides. There are several of those engineering works on Kosovo railways, which are built of rock material, but there are also concrete protective walls ( Figure 5). Canals are engineering facilities that aim to remove surface water that comes in the direction of the railway. They are made of concrete, with different shapes and dimensions (e.g. L1 = 50 cm x L2 = 40 cm, h = 30 cm; L1=50 cm x L2 = 30 cm, h = 30 cm) depending on the amount of water, respectively of the hydrological parameters of the area through, which pass the railway trail. This research identified only one form of canals, with different dimensions ( Figure 6).

Research Methodology
The research methodology is based on two phases: the first phase of field research work and the second phase of office work (in figure 8 is shown in more extended form). Field research was carried out in different monthly stages during the year 2020. The following tools were used for field research: meter tape, GPS-Garmin, camera, notes from the field. The following working materials were used to achieve the goals of this paper: topographic maps of the territory of the Republic of Kosovo at a scale of 1:25000 [12], geological maps (1:100000 and 1:200000), satellite images from Google Earth, Arc Map v.10.1, Excel and field research visits. Topographic maps are georeferenced, and then the digitization of the railway network presented with line geometry is performed. Point and line geometry is used for the digitization of tunnels; polygon geometry is used for cities, while point and polygon geometry is used for stations, all in vector format.

Results and Discussions
The greatest development of the railway network and the associated engineering facilities in this area occurred from 1926 to 1960/1963. The data highlighted in this study ( Based on the categories, lifespan, and construction engineering facility (Table 2), it results that the railway network and its accompanying facilities enter into the first category. Referring to this categorization, it is noticed that all railway segments have survived the time in terms of their sustainability and functionality. Assessed from their lifespan, respectively years of construction, it results that the railway line Hani i Elezit-Fushë Kosovë-Mitrovicë has 147 years (Table 1) since the time it was built and is still functional, although, in recent years several projects have been developed for its repair (reconstruction) (funding from European Union).
Railway lines for industrial transport -the research showed that 49.56 km of railway networks are built for industrial transport purposes in Kosovo ( Table 3). The longest line (13.89 km) of the industrial railway is the one that connects the Mining and Magnesite Industry "Golesh" with the railway station Bardh i Madh. This railway line is used today by the NewCo Enterprise "Ferronikeli" for the transport of nickel-iron from the mine "Gllavica" in Medveca-Lipjan, while the line from the mine "Gllavica" to the mine "Golesh" is not functional.

Collection of archival data and information
Field data collection Data processing, systematization Georeferencing and digitalization Analysis and interpretation of results The research reveals that in the entire railway network of Kosovo, there are 23 tunnels with a total length of 9789.5 m (Table 4). The largest number of tunnels is in the railway line Fushë Kosovë-Hani i Elezit, a total of 7 tunnels with a length of 1216.5 m, and Mitrovicë-Jarinje, a total of 7 tunnels with a length of 2046 m. The third line in a row is Fushë Kosovë-Klina in which are 6 tunnels with a total length of 2529 m (Table 5). From table 5 it can be seen that although in the line Prishtina-Podujeva there are only 2 tunnels, this line dominates in terms of the length, with a total length of 3283 m or with 33.53% of the length of all tunnels in the railway network of Kosovo. The highest percentage in terms of the number of tunnels is the lines Fushë Kosovë-Hani i Elezit and Mitrovicë-Jarinje (Plavkovë) with 20.90% ( Table 5). The tunnels on the railway track are built at an altitude of 331 m (exit of the Gexhë tunnel) to 654 m (entrance to the Baica-Terdevc tunnel) with an average height of 501 m. The shortest tunnel 76m is in the locality Pridvorce, while the longest 1,690 m is in the locality Merdar, while the average length of the tunnels is 426 m ( Table 1). The shape of the portals is mainly in the shape of a horseshoe, with a height of 6m and a width of 260 m at the end, 290 m in the middle. The material, which is used for the tunnel portal cladding (entrance and exit) is rock. The dimensions of the rock blocks which are used for masonry range from 35, 40 to 85 cm. They were carved in certain parts before being placed. According to the standard GN206 [13] (Table 6), it results that the tunnels in the railway network of Kosovo are divided into two groups. In the first group belongs the tunnels with short length and in the second one those with medium length. 90.5% of tunnels in the railway network of Kosovo are of medium length. Referring to the division of tunnels according to depth from the ground surface [5], the research shows that 6 tunneles ose 26.1% of them have average depth and 17 tunnels or 73.9% of them have shallow below (Table 7). Other engineering facilities like bridges, watersheds, protective walls, water drainage canals are also constructed of environmental material combined with sand and river gravel for the preparation of mortar as the connecting elements of masonry. Seven shapes of tunnel opening are known (Table 8) [14,15]. The selection of the shape of the tunnel, its position, lifespan, etc., depend on the geological conditions of the region, the position of the geological structure, the purpose of its use (transport, hydrotechnical, municipal, mining). This research shows that the shape of the tunnel in Kosovo railways is Horseshoe shape and partly segmental. For pedestrian traffic, rectangular shapes of tunnels are appropriate. These types of tunnels are not suitable to resist external pressure due to their rectangular shape and these are not in use these days.

Conclusion
There is no 4 Egg-shaped This tunnel shape has a number of centers and radius length. These are suitable as sewer tunnels to carry sewage water.
There is no

Horseshoe
Horseshoe tunnel shape is a combined shape of arches and circular tunnel. These types of tunnels shape are quite popular.

Form of the tunnel in Kosovo 6 Elliptical
For carrying water, elliptical-shaped tunnels are appropriate. These are suitable in softer material. For better resistance to external pressure, the major axis of this tunnel is maintained vertically.
There is no 7 Segmental Segmental tunnels are suitable for traffic tunnels. It is a section with an arched roof and straight sides. These are generally used for subways or navigation tunnels.
Form of the tunnel in Kosovo

Conclusion
The railway network presents a special communication function. In Kosovo, it has a history of over 147 years. In this railway network, there are several engineering facilities like stations, bridges, tunnels, watersheds, canals, etc. Their size and construction depend on the circumstances of the time of their construction, as well as the material used for their construction. The geological construction through which the tunnels are built is diverse and includes geological formations of different ages and floors. The total length of the railway network for general transport is 336.68 km, of which, functional lengths are 237.34 km, while 99.34 km are not functional. The railway network for industrial transport has a length of 49.56 km. The lifespan of the railway network and the engineering facilities in it are over 90 years. The research revealed that in the entire railway network of Kosovo there are 23 tunnels with a total length of 9789.5 m. 90.5% of the tunnels are tunnels of medium length. According to the depth from the surface of the ground, it results that 73.9% of them have average depth. The tunnels in the railways of Kosovo have a horseshoe shape. Ancillary facilities like stations, bridges, canals, protective walls, watersheds, etc., are of different shapes and dimensions. From 1963 until nowadays no new constructions have been made in this network, except some projects for the repair (funding of the European Union) of a segment in the railway line Hani i Elezit-Fushë Kosovë-Mitrovica. Based on the research, it results that in this railway network, intervention is required through a deeper analysis supported by technical analyzes, laboratory, etc., to bring to the standard state of operation the entire network and the engineering facilities attached to it.

Author Contributions
Conceptualization, H.Ç. and B.J.; writing-original draft preparation, H.Ç. and B.J.; writing-review and editing, H.Ç. and B.J. All authors have read and agreed to the published version of the manuscript.

Data Availability Statement
The data presented in this study are available in article.