The history of the underground in Turkey began with the construction in 1875 of the so-called Tünel in Istanbul, being the second oldest underground railway in the world. In the city of Ankara, the history of the underground is newer and began with the construction of the Ankaray light rail, between 1992 and 1996. The M1 line was subsequently opened (1997) and is to be extended by lines M2, M3 and M4.
The Ministry of Transport of Turkey (currently AYGM), through the Directorate General of Infrastructure Works, entrusted COMSA with building of the Kizilay-Çayyolu (M2) and Batikent-Sinçan (M3) Ankara metro lines, with a total track length of 64 kilometres and 22 stations. The projects have required a total investment of 100 million euros and have been implemented in conjunction with the company Açilim Insaat.
The M2 work has involved 11 stations, a shaft for sidings and ventilation, 33 kilometres of track throughout its length underground, 7 sets of sidings and 11 emergency exits for the TMB section. The new M2 starts in Kizilay station, where it connects to M1 line south terminus, and will run along the south of the city. On the other hand, the M3 line starts at the other end of M1 line, and will connect the north-east of Ankara.. A link has therefore been established between the north and south of the city, with a total distance of 46.4 kilometres between the outlying stations and 34 stations. The project also envisages connecting the M2 to the Ankaray light rail line.
Meanwhile, the M3 line project has involved 11 stations, two of which are completely underground and the rest on the surface. The section has a total length of 31,3 kilometres, having approximately 20,8 kilometres of ballast track and 10,5 kilometres of slab track. Its implementation has involved the civil engineering, architecture, infrastructure and superstructure and electrical and mechanical work required for commissioning of the line in early 2014.
Every underground project is always a challenge because the real properties of the soil remain uncertain until works’ execution and they can vary drastically from section to section. In Ankara Metro, the challenge is even more complex as the project is located in an important urban area.
Several tunnels and connecting galleries were executed during the project using the NATM (New Austrian Tunnelling Method) with a diameter range between 4.0 and 6.6m. One of the key points of the worksite was the execution of the Mesa Station in M3 Line. The station was designed as a box (187m long, 20m wide and with a variable deepness up to 35m to allocate an intermediate level). The original project foresaw the execution of perimetral diaphragm walls, reinforced intermediate slabs and a top-down excavation. In order to cope with clients’ requirements, the solution was changed to perimetral piles (diameter 0.80m) with passive anchorages in different levels.
The connection galleries were designed to be executed using the NATM as well, but they have been changed to the Cut&Cover method in order to increase works’ safety, given that they were located under one of the main city roads and just a few meters from the National Parliament.
Track was designed for a commercial speed of 80km/h in standard gauge (1.435mm). A total length of 14,6km is slab track whilst 31,3km are ballasted track, both of them using UIC54 rail in 18m bars. The bars were welded with Flash Butt Welding (FBW) in plain line and alluminothermic welds were executed in turnouts. Fastenings were DFF 21 in the slab track sections and W14 in the ballasted ones. Some slab track sections were provided with elastomeric mats to improve N&V performance.
The electrification of the line is via third rail using 15m aluminium bars fixed to the sleepers every 6 meters with ceramic insulators and a protective cover to avoid any contact.
The scope of the works were fulfiled with the execution of the mechanical installations that guarantee the required level of operation: 61 elevators, 109 automated stairs, 108 ventilators in tunnel and stations, 160 pumps and 12 F&S units.
About COMSA
COMSA’s 120-year history and its international presence vouch for its capacity to undertake all kind of projects in the infrastructure sector. It began operating in 1891 with track work projects and station renovation. Today it finds itself among the leading construction companies in Spain and it has a strong international presence. The company is specialized in construction and maintenance of railway lines; high speed and conventional lines; metros and trams; railway installations; construction, conservation and maintenance of roads; emblematic buildings; maritime, port, airport, hydraulic and urban projects, tunnels and subterranean works. COMSA is the infrastructure company of COMSA EMTE, one of Spain’s top groups in integrated infrastructures, engineering, environment and technology. COMSA EMTE is present in 25 countries and develops activities in the five continents.
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