Underground secrets: how stations on the Big Circle Line of the metro are built

April 15

The number of operating stations on the Big Circle Line has increased to 12. In early April, the Narodnoye Opolchenie and Mnevniki stations were opened for passengers. What kind the new section has become, everyone can evaluate for themselves — just go down to the metro. We offer you to look further and find out how to lay tunnels for trains on the most difficult section, which of the BCL objects will be included in the Guinness Book of Records, how new platforms will be heated, and what is the difference between the open and closed construction method.

Tunnel networks for the deepest BCL station

The journey from Savelovskaya to Maryina Roscha by the Big Circle Line will take less than five minutes. So far, this is only in the plans, the implementation of which is already in the third year, several hundred builders are engaged. These people can be safely called heroes, because the north-eastern section is the most difficult in the BCL project. The distance between the Maryina Roscha station under construction and the current one is only a few meters, so the builders have to work very carefully, without using large-sized equipment. In order to eliminate the breakage of the structures, it was decided to make first the so-called pilot tunnels with a diameter of six meters, and then expand them to the required 8.5 meters. The work is carried out manually, during the day the builders manage to pass about a meter, while tunnel-boring complexes usually move 10 times faster.

We put on helmets, vests and go down to under the ground to see with our own eyes how the construction of one of the most difficult stations of the Moscow subway is going. About a minute in an open iron elevator, a push — and we're down. Here, the tunnel is noticeably widened to make it easier to load trolleys and store the necessary equipment. After a few steps, it splits into two smaller ones. At first glance, it seems that this is the future railway switch before the new platform, but this impression is erroneous. There are still dozens of meters ahead by the wooden flooring of the service passage to the intersection with the main tunnels of the BCL.

The builders explain that a whole network of underground passages has been built for the station. There are three main tunnels — two side tunnels with railways and a central one, where the passenger platform will be mounted later. The remaining tunnels, laid perpendicular, are needed for the removal of soil and the supply of equipment, and in the future for the utilities.

The expansion of the right station tunnel has been completed, and the power connection will begin here in the summer. In the meantime, the work is concentrated in the left tunnel. To speed up the deadlines, the builders meet each other halfway. The placer removes the temporary reinforced concrete lining, then, using small-scale mechanization tools, workers expand the tunnel and remove excess rock, and then a special placer installs permanent walls made of cast-iron tubing.

"The tube-laying machine is hydraulically operated: it goes down, it is telescopically and with special grip catches the tube, and then lifts it and puts it in the place where it needs to be mounted. Builders manually tighten the bolts," our guide Pavel Klochko, Deputy head of section No. 3 of SMU-8 Metrostroy LLC tells about the process of tunnel bulkhead.

The tubes are laid in rings, fixing them on the mounting bolts. The average speed is a ring per day. The completed work must be examined by inspectors - the underground surveyors to exclude narrowing and distortions. If the geometry of the ring is observed, the bolts are changed to permanent ones with EVA washers.

"After the tunnel completion, it is caulked. The seams between the tubes are caulked, all the dirt is cleaned, the seams are sandblasted, then they are sealed with lead wire and covered with a special quick-shrink mixture that protects this wire. And the water that is behind the tubing, then does not infiltrate into the tunnel," adds Pavel.

The piercing of the central hall is also nearing completion. A little more — and the builders will connect the tunnel with the escalator incline and the entrance lobby. In the meantime, the descent from the entrance lobby ends in a dead end. You can get to the site of the future station through the tunnel for rock removal and an inconspicuous door between the tubes of the neighbouring underground corridor. Inside the same one there is a tunnel, still without a platform, only on the walls there are arched openings lined with shaped tubing. When the platform mounting begins, these arches will be opened forming passages. The remaining columns after lining will remind pot-bellied porcelain teapots.

The work is also complicated by the extreme depth of the tunnels, in some places reaching 75 meters. The new Maryina Roscha station is located more than 70 meters under the ground. Thus, it will be the deepest one on the Big Circle Line and the second in Moscow (only the Park Pobedy station is deeper — 84 meters).

At this depth, the rock is quite hard (limestone and marl), so as agreed by Rostekhnadzor (Federal Environmental, Engineering & Nuclear Supervision Agency), drilling and blasting operations are used during construction. To load the rock into trolleys, conventional shovels and the PPM-1 power shovel are used. "This is the smallest of these machines, called the ‘penny’. It is pneumatic, that allows you to abandon electricity or diesel, protecting the builders during underground work," Pavel Klochko says.

Lowering the equipment to such a depth and removing a large amount of rock quickly is also problematic. To speed up the work, three shafts and several technical tunnels with rails for trolleys were created.

"Throughout the entire length of the construction of the station complex, there are three shafts with a depth of about 87 meters. All the rock that we get during the development is loaded into trolleys, under the ground, a diesel truck takes them to the shafts, and then they go up. This cycle takes a very long time, so the station can not be built faster than we would like, "adds Dmitry Fayzrakhmanov, Deputy Chief Engineer of SMU-8 Metrostroy LLC, already on the surface.

The elevator can take only one trolley, so the work on the soil unloading practically does not stop. At the top, the trolley is emptied and sent down again. When transporting rock, the elevator operator gives two warning signals. If there are four warning signals, the elevator lifts the workers. Each of them is registered in a special log before the descent and at the exit to the surface.

According to Dmitry, the construction continued even during the pandemic, because the timely commissioning of the metro section is important for citizens. The responsible approach of the builders will allow this year to complete all the tunnelling work and start finishing the station.

"At the moment, 350 people are engaged in the construction of the station per day (together with subcontractors). By the end of this year or the beginning of the next year, the number of people is planned to increase to 680. Construction is carried out around the clock, people work in a shift mode, the cycle is completely closed," Dmitry Fayzrakhmanov adds.

It is planned to complete the construction of the Maryina Roscha station in 2022. It will be opened simultaneously with the BCL Rizhskaya and Sokolniki stations. Today, their overall readiness is 65 percent.

The Maryina Roscha station is built by 64 percent. If the changes below are not yet noticeable, then the ground entrance lobby is almost ready. Here, shell and core condition has been completed, installation of equipment and utilities has begun, and an inclined tunnel for the largest escalator has been made. Its appearance is fascinating and frightening at the same time, because even with the working light, the space below is barely distinguishable. It is strictly forbidden to go down the narrow stairs without personal protective equipment.

"The 130-meter inclined tunnel is the longest not only in Russia, but also in the world. It is nominated in the Guinness Book of Records," - emphasizes the Deputy Chief engineer - “Work has already begun on the installation of a decorative umbrella, and in two months specialists will begin to mount the trusses of the future escalator."

According to him, the station entrance lobby will also be technically unique. The transformer substation, ventilation units, and some other equipment that is usually located below were brought to the surface. This made it possible to reduce the number of underground works.

The entrance lobby will be bright and spacious thanks to the panoramic windows. Its highlight will be decorative spheres made of stainless steel with a diameter of 2.5 meters. One part of the ball will be located inside the premises, and the second-outside. The space in the centre of the hall will be visually expanded thanks to the arched ceiling and decorative lighting. And in order for the design to have something in common with the neighbouring Savelovskaya station, on the tunnel walls the tubing finish will be left.

Platform just around the corner: what is hidden in the Vorontsovskaya pit

If you take a quick look at the Vorontsovskaya station on the southern section of the BCL, it may seem that the completion of the work is still far away: cranes stand on the site, wooden small bridges are laid everywhere, there are temporary stairs. But this is only the first impression. Going down the steep stairs to the under the ground, you find yourself in an unexpectedly bright and spacious room — the future ticket hall of the second entrance lobby. Here are laid out slabs, which will soon cover the walls.

"Now the workers are erecting facing marble, as well as suspension systems on which the ceiling will be fixed. In this entrance lobby facing Vlasov Street, the passengers will get through the underground crosswalk," - says Alexander Sitnikov, project manager of the Vorontsovskaya station construction.

Three escalators lead from the second entrance lobby to the platform. Steps and railings have already been mounted, and metal gleams out from under the protective construction film. The electrical wiring is not connected yet — the escalators are not working. Therefore, you have to walk down the service stairs passing the technical rooms.

"It's seven floors down. On each floor there are service and technical rooms: ventilation chambers, switchboard rooms, workshops, staff rooms, bathrooms. There are about 500 technical rooms in total. They are mostly ready. The finishing remains," explains Alexander Sitnikov.

We now, now descend, then pass through secret doors that merge from a distance with temporary walls of wooden slats and matting. You can easily get lost in these underground passages. According to the project manager, the workers are guided by the drawings for the first time. Finally we find ourselves on the platform. Rails have been already laid here to the neighbouring stations. When the pit is filled in in May 2021, the workers will have to align the tracks, it means to level them and to concrete. "After filling in the pit, the structures usually shrink, so you need to level up to a millimetre," says Alexander.

Noncontroversial is an island-type station, the tracks run on both sides of the platform. Now the platform is a series of reinforced concrete walls and columns. The engineer, standing by the rails, directs a red beam from a rectangular box placed on a tripod to the column. This is a laser level, its beam helps to accurately measure the distance for laying facing plates.

"We will cover the columns with fibber-reinforced concrete. This is new material. It is good because it is easy to replace it if necessary, for example, if it is damaged. Each column will have six large plates, any plate can be removed and replaced by another. In addition, the fiber-reinforced concrete is perfectly amenable to processing with anti-vandal impregnation," Alexander Sitnikov comments.

The walls will be covered with marble and glass, the floor - with granite, the ceiling - with metal. The finish will be made in natural colours, reminiscent the colour of stones and earth.

Sergey Sobyanin: Vorontsovskaya BCL station will be completed by the end of the year

The platform of Vorontsovskaya station rests on four escalators that lead to Kaluzhskaya station and to the first entrance lobby. In the near future, these escalators will connect the Kaluzhsko-Rizhskaya line with the BCL. Recently, engineers had to close the Belyaevo — Novyie Cheryomushki section for laying the tunnel and rails but the work has already ended. Ahead — the creation of an opening between the Kaluzhskaya and Vorontsovskaya and the digging of a new pit to connect the monolithic structures (foundations) of the two stations.

"It was necessary to block traffic temporarily between the Belyaevo and Novyie Cheryomushki stations, since Vorontsovskaya is located below these stations and tunnels had to be laid under Kaluzhskaya station. The maximum depth of the Vorontsovskaya station is 32 meters, " says the project manager.

Sizzle, knocking, crashing. We go down to the maximum depth, under the platform. Here, workers lay the cable by unwinding giant coils. They are building a cable and ventilation duct.

"We no longer use electricity for the heating system of the premises and escalator steps, because even strong metal structures wear out from the current. Now we will heat the water in the heaters that we will install in the ventilation ducts, and let this heated water through the pipes throughout the station," Alexander Sitnikov explains.

A cage rises from the floor to the ceiling under the platform. On it, a worker welds metal pipes. Alexander says that there will be jamming tapes here: trains are not silent and, so that passengers do not hear them, all sounds are muffled under the platform.

This is the Alexander Sitnikov’s, seventh metro station. He says that there are no identical stations from the point of view of construction, layout, design. During the construction of the Vorontsovskaya station, for example, it was necessary to counteract the underground river Samorodinka.

"There was a powerful water flow, the cutting tools with which we dug the tunnel were constantly worn out. We kept lowering water level all the time…Bur we did it. It is the overcoming of such difficulties that I like in the construction of the metro," the expert sums up.

Between the completion of construction and the opening of the station, it usually takes several months — this is the stage of commissioning. It is necessary for running in the tracks, checking the equipment and including a new section in the metro system. Before launching passenger trains, the new section is tested by technical trains.

The BСL may become the longest circle line of metro in the world. Its length will be 70 kilometres long and will include 31 stations and three electric depots (including the existing Kakhovskaya - Kashirskaya section). The new underground circle will provide 19 transfers to the radial metro lines, four to the Moscow Central Circle and 11 to the stations of the Moscow Railway and Moscow Central Diameters.

Source: mos.ru

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