VIDEO EXCLUSIV | Trace solutions and strategies for large, complex and difficult infrastructure works in Serbia and Bulgaria

One of the leading infrastructure companies in Bulgaria, Trace, which is building Lot 2 of the Ploiești – Buzău Motorway, part of the Moldova Motorway (A7), has several major, complex projects underway, of strategic importance for the transport infrastructure of Serbia and Bulgaria. Today we will present three of these projects and the strategies adopted, while the explanations are given by those who coordinate these works. The three projects are the reconstruction, rehabilitation, and modernization of the Niš-Dimitrovgrad railway on the border with Bulgaria, the extension of metro line 3 in Sofia and the modernization of Plovdiv railway station.

The Nis-Dimitrovgrad railway, the border with Bulgaria, is of continental importance, as it is part of the Pan-European Corridor X.  The president of the European Commission, Ursula von der Leyen, and the president of the Republic of Serbia, Alexandar Vucic, participated in the inauguration of the works.

„We are committed as contractors to design and build, rebuild, modernize this railway. The aim of this project is to speed up the trains on this section, to increase the capacity on the railway and to bring the stations and everything important for passengers to a degree of satisfaction and to the European standards set for such works”, explained, exclusively for Gândul, Eng. Miroslava Milojevic, contract manager.

Currently, trains run at a speed of 15-30 km/h on this stretch of about 90 km, so it is covered in 5-6 hours.

„After the railway will be rebuilt, when it reaches the designed shape, trains will reach 80 kilometers per hour on the Sicevo – Gornji section, and on the remaining section, between Stanicenje and Dimitrovgrad, the speed will be between 100 and 120 km/h „, explained engineer Vasil Shilov, project manager.

According to him, if tourists are delighted with the scenery on the Sicevo – Gornji section (20 km), it is a nightmare for the builder.

„This is a pan-European corridor, so it can’t be closed permanently, and the working conditions are 36 hours of no train movement, followed by 36 hours of trains running and then another 36 hours of interrupted movement. We must be very precise, both in organizing the machinery, the people to achieve the final goal of the project. The main challenge is the Sicevo – Gornji section. It is 20 kilometers long, maybe the most beautiful place of the project if you are a tourist and a nightmare if you are a civil engineer. On one side the road is very close, and on the other side the river Nișava. A place without an entrance, except for the two ends of the section, and all the equipment, all the machinery, all the materials have to be brought to the construction site by wagons,” explained Shilov.

The two engineers also explained what the strategy was in order to comply with the contractual terms imposed by the Serbian Railways company, the administrator of a network of approximately 4,000 km.

„The main strategy was to prepare the project in accordance with the working conditions. It means as much as possible that the elements of the work are prefabricated, because this way we can save time, especially during the 36 hours when train movements are interrupted. The other challenge was to have all the materials installed on site before the work started. You can’t stop the delivery of the materials because it would cause delays,” explained Shilov.

In addition, Miroslava Milojevic also explained what the essential condition is: „Very good communication between people”.  „Let’s have everything organized in such a way that we finish in this short time, in 36 hours, as much as we are allowed to work on the construction site,” explained Milojevic.

# ”NATM” – an innovative solution for the extension of the metro in Sofia

Another project carried out by Trace, and which has a high degree of difficulty is the extension of metro line 3 in Sofia. This is the 12th Metro Station which Trace is constructing for the Sofia Municipal Metropolitan company.

„The costs of the project are 33 million euros, and it involves the construction of a metro station, a tunnel with a length of one kilometer and all the necessary installations to make this section fully operational”, explained Dimitar Mitev, project manager, for Gândul.

„Our main goal is to build an efficient and modern metro line, which will reduce the circulation of personal cars, improve traffic safety in the city. So, our project is very complex because it involves multiple parts of the design and coordination with many subcontractors and a lot of different work that needs to be done simultaneously. It is complex and very difficult”, said Marina Berova, Chief Quantity Surveyor.

Here, the geological and hydrogeological conditions represent the greatest challenge for the engineers at Trace. That’s why a new working model – „New Austrian Tunneling Method” was chosen. This work starts with the portal construction, then cement is injected to stabilize the upper part and then excavation by blasting. Next, the reinforcement is installed, and the tunnel is padded.

„The geological and hydrogeological conditions are among the worst that we could find in the entire territory of Sofia. These conditions require constant monitoring to ensure the security of the construction process and the long-term stability of the tunnel,” Mitev said.

„Overcoming these challenges that my colleague mentioned and maintaining the execution schedule and the budget requires a perfect organization and modern technologies so our strategy had three ingredients I could say… we have a detailed planning and a highly qualified team, experienced and dedicated to hard work”, concluded Marina Berova.

# Modernization of Plovdiv Railway Station, the „3 in 1” challenge

In Plovdiv, Trace is carrying out another important and complex railway infrastructure work, namely the modernization of the city’s railway station, which also involves a tunnel under the tracks as well as a bridge.

„We work very hard here in Plovdiv. Our project has two main objectives. One of them is the renovation of the Plovdiv railway station, and the other is the construction of a tunnel under the railway lines in the station with a width of almost 100 meters. The tunnel provides transport to Plovdiv from the southern to the northern side,” explained the project manager, engineer Nikolai Ivanov.

According to him, the difficulty of the work lies in the fact that Plovdiv is an important railway junction, and 160 trains pass through here every day. „One of the main challenges of the project is that we have to work in traffic. This is why the project is divided into stages. Another challenge for us is the construction of the tunnel. It is located in the center of the city and is an urban, highly developed area. The tunnel passes under the railway station. The organization is very difficult indeed”, added engineer Ivanov.

In addition, all rails must be replaced, and a bridge near the station – rebuilt. „This bridge, at this moment, reduces the capacity of trains. Our project involves a new bridge with approximately identical dimensions”, continued the project manager from Plovdiv.

As all the works are extensive, it is difficult for Nikolai Ivanov to consider one of the works to be the biggest challenge. With great difficulty, however, he chose two of the three – the railway station and the tunnel under the station.

„We designed the best technology and selected it for execution. We found the necessary machinery and the labor force we had to approve. For each stage of the project we relied on the communication between the contractor and the consultant”, concluded Nikolai Ivanov, the project manager of Trace from Plovdiv.

Trace is building Lot 2 of the Ploiesti-Buzău motorway in Romania, from Mizil to near Buzău (Pietroasele). According to the Minister of Transport, Sorin Grindeanu, this section of the Moldova Highway (A7) should be ready next year. In fact, in 2024 „transport” has set itself an ambitious target – to open up some 200 km of high-speed road (motorway and expressway).