Employer: Sofia Municipality, Metropolitan PLC 

Project execution period: 2010 – 

Description of the project:

The successful completion of the construction of Metrostation 9-I "Vassil Levski Stadium", implemented in close cooperation with the Japanese specialists from Taisei Corporation, has raised Geotechmin’s confidence in its ability for independent realization of such underground projects. The company has won the tender for "Design and construction of Metrostation 11-II with adjoining tunnel section and an underground car-park above the two facilities" in a competition among eight Bulgarian and foreign participants. In April 2009 Geotechmin signed a contract with Metropolitan PLC for this part of the second metro diameter of Sofia Metro.

In terms of logistics, the construction process is extremely complicated due to the specific location of the site – under the busy Cherni Vrah Blvd. near Kempinski Hotel Zografski. Technologically, this is one of the most difficult underground sites that have ever been built in the Bulgarian capital. MS 11-II is being constructed at a depth of 25 to 32 m which makes it the deepest metro station in Sofia. Geotechmin’s specialists have chosen such a metro structure that allows traffic to continue flowing along the boulevard throughout the whole construction process.

The project includes design and construction of a station, a metrotunnel and an underground car-park. The metrostation is being built in three, four or five underground levels depending on the particular section. Its multi-level design is determined by the highly inclined terrain. The adjoining metrotunnel running in the direction of Hladilnika District is being built on the third underground level. On the second and first levels above the tunnel a car-park and a shopping area are being constructed. The length of MS 11-II together with the tunnel section is 207 m, and the width is 18 m.

Various technological methods are being used at this site. The excavation works to the level of bottom slab are carried out through the Milan Method. The stability of the diaphragm walls is ensured by anchoring. The construction of the inner structure is carried out using the bottom-to-top method. Prestressed concrete is used for the roof and floor slabs. The site is designed to resist an earthquake measuring 9.0 on the Richter scale.