Thunderstorm of quicksand

The Tsar Shield leads a tunnel along the bed of the underground river Sinichka

On October 12, the site manager of Tunnel-2001 LLC, Evgeniy Bibikov, spoke at Metrofest. In his lecture, he spoke about the only shield in Russia with a hydraulic weight, “Elena,” whose diameter is six meters. The complex is currently excavating the north-eastern section of the Third Interchange Circuit (TPC) of the metro.

The first patents for hydraulic shields for excavation in unstable soil appeared at the end of the 19th century.

“Many of these ideas seem ridiculous now,” says Evgeniy Bibikov. – A modern mechanized shield is complicated, but this complex can dig a tunnel without subsidence, even in aquiferous soil. Its main feature is the material that is located in the bottomhole chamber.

This is bentonite, clay powder, it is diluted with water and turns into jelly. The solution easily collects stones and sand, which the shield “absorbs”. The suspension itself is pumped into the hydraulic loading chamber. Then it enters the bottomhole space, where it holds the soil mass. The mixture of bentonite and stones is then sent through pipes to a separation unit, which is located on the surface. There the rock is separated and the bentonite solution is reclaimed. The squeezed soil is removed by dump trucks, and the clay suspension is returned to the hydraulic loading chamber.

“We encountered difficult geological conditions at our site,” recalls Bibikov. – For example, in Lefortovo, a layer of quicksand was discovered at a depth of 3 to 15 meters. Out of curiosity, I found a map of Moscow from the 17th century, according to it there was a pond in this place, and we are walking right along the bed of the Sinichka River.

This time Metrofest took place on the territory of Zaryadye Park.

“I regularly participate in this event,” says blogger Alexander Popov. – Specialists from companies that build and design the metro give lectures here.

Vadim Lomov, Head of the Technology and Expertise Department of Mosinzhproekt JSC: 

- The third interchange circuit is a unique project. Mostly shallow stations are built here. Boarding and disembarking will take 5 percent less time. The work is being carried out in dense urban areas.

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The Lefortovo and Aviamotornaya stations are shallow. They are constructed in an open way in pits 20–27 meters deep, structurally designed as a three-span column type with underground vestibules, while Aviamotornaya forms an interchange hub with the Kalininskaya line station of the same name. Lefortovo is being built on the territory of a park near the Sputnik cinema near Soldatskaya and Nalichnaya streets. By the way, this small park will be improved after construction is completed. And next to the station there will be a transport hub of regional importance.