Underground turnaround “Agates”

Mosmetrostroy began on September 18 the construction of two ventilation tunnels that will connect the future ventilation shaft with the left branch at the Likhobory electric depot. The excavation is planned to be completed in three months. The right branch to the depot has been operational since its opening in March 2018. There, a ventilation shaft, according to the project, was built next to the tunnel. To commission the left branch, due to difficult hydrogeological conditions, a non-standard approach was required. It was decided to pass through two ventilation tunnels with a shield of small diameter (3.6 meters) in order to provide the necessary total cross-sectional area for full design ventilation of the entire branch. In addition, the tunneling itself will become unique: the TBM will not be lifted to the surface, but deployed directly underground.

The decision to build two ventilation tunnels and deploy the shield underground will reduce the work time, ensure safety throughout the entire tunneling, and also avoid increasing its cost. When using conventional methods in conditions of such complex soil, this would be almost inevitable. Therefore, the option of constructing one ventilation tunnel using a mountain method was excluded.

Tuning works are carried out by SMU-12. For the first time in the history of the Moscow metro, the shield will be deployed in a special underground chamber. By tradition, named after a woman, the TBM of the Japanese corporation IHI “Agatha” will first pass through the first ventilation tunnel and join the tunnel of the left branch leading to the depot. Then it will be turned around and sent to pass the second one. The excavation will be carried out in difficult conditions: there will be quicksand and Jurassic clay in the way of the shield.

– There will be a sharp turn. Everything will have to be done with small-scale mechanization: with the help of traverses, jacks, winches, almost manually,” comments Oleg Melnikov, Deputy General Director of Mosmetrostroy JSC, commenting on the upcoming work.

Also, for the first time in Mosmetrostroy’s practice, the shield was fed into the shaft vertically through a shaft with a diameter of 6 meters. It was lowered to a depth of 38 meters into a specially prepared installation chamber (9.5 meters in diameter), from which it began excavation.

It will take a month to turn the shield around. The total length of the two tunnels will be 168 meters. After excavation, SMU-4 will start working: its employees will install fans and engineering systems.

Currently in Likhobory, all trains run by shuttle on the right branch, which complicates the work of the electric depot. When the ventilation tunnels are ready, full operation of the entire line will become possible.