The first shield of smu-12 was launched to "Savelovskaya"

The Herrenknecht S-771 mechanized tunnel-boring complex, named "Elena", launched on December 12 from a unique round chamber. A long route awaits the car: during the journey, the shield will pass through the Rzhevskaya and Sheremetyevskaya stations of the Big Circle Line that are under construction. Our correspondent watched the launch of the TBM from an unusually shaped pit.

Construction site No. 17 froze in solemn anticipation. Here everything is prepared for the start of the long journey of the TBM. The territory is orderly and clean, the equipment and pit are fenced for safety reasons, at the very bottom of the round chamber “Elena” is waiting for the start. From an almost 46-meter height, the head of the shield, weighing 320 tons, seems quite miniature.

Sinking will be carried out for the first time by SMU-12. “Elena” will build the right running tunnel towards “Savelovskaya” under the control of the head of section No. 4, Anatoly Kalyadov. The management of Mosmetrostroy JSC, headed by General Director Sergei Zhukov, representatives of UMM and Mosinzhproekt JSC gathered to watch the historic start.

A loud sound signal is heard three times on the site, and the shield begins its 3.5 km long journey. He will have to go through medium and hard limestones, hard clay, marl and loam. The depth of the planned excavation will be from 40 to 70 meters.

“ELENA” WILL PASS IN ANY GROUND

– No rocks on the way are scary for “Elena”. This machine is universal, with a soil load, and can go in any soil,” assures SMU-12 deputy chief engineer Viktor Panov. – When working in hard rocks, you will simply have to change cutting tools more often.

At the same time, as the specialist explains, in winter everything requires special heat and moisture conditions - hydraulics, water, consumable lubricants:

– The main task is not to freeze the car. The complex is insulated, the carts are insulated, and there are heat generators everywhere.

The route near the shield will not be easy. Ahead are about 500 meters of the Oktyabrskaya (OZhD) and Moscow Railway (MZD) railway tracks. The TPMK will pass both under the existing metro and through the Rzhevskaya and Sheremetyevskaya stations under construction. “Elena” finishes in the dismantling chamber at the end of the reversible dead-ends of the “Savelovskaya” BCL in April 2020.

WHY DO YOU NEED A ROUND PIT

An atypical shape for the installation chamber was chosen because there was no space for placing a standard rectangular pit. There are dense buildings and a network of ground traffic flows around.

– According to the designers’ calculations, if a rectangular shape was chosen for this construction site, the spacer system of the pit would have too small distances between the shoots. This would make it impossible to install the panel complex,” explained the chief engineer of SMU-12, Alexander Ivanov.

The technology of constructing a round pit without internal struts was used in the construction of the metro in Moscow for the first time. Fastening here is carried out using reinforced concrete circular belts located on seven tiers with a fence made of secant piles.

SHIELD STARTED IN A SPECIAL WAY

A special feature of this penetration can also be called a separate start of the shield. Due to the small diameter of the pit - 31.5 meters - the complex was not completely assembled. After 100 meters it is planned to stop, install the parts of the TBM located on the surface, and start again. The length of "Elena" when fully assembled will be 80 meters, weight - 490 tons. Then the shield will go without stopping.

Immediately after launch, “Elena” mounted four negative rings and drove the rotor into the ground. As of December 25, 28 linear meters had been completed, 20 rings had been installed.

In addition, as expected, in 2020 the panels coming from the Stromynka side will go into the installation pit.