Several vertical shafts with extension diameters of up to 7.7 meters were needed for the modernization and enlargement of the sewage system in the 4.6-million-strong metropolis St. Petersburg. The four shafts at depths of 65 to 83 meters serve as connecting constructions, collecting basins or access shafts to the existing duct system. In the year 2006, VSM technology from Herrenknecht proved its efficiency in a construction project in Russia for the first time. At that time, a VSM7700 successfully sunk four shafts under extreme conditions at temperatures of down to minus 25 degrees Celsius. Mechanized VSM technology has the advantage of being able to work under water almost completely without subsidence, thus allowing the sinking of shafts even in St. Petersburg’s unstable geology.
As a result, the four new shafts were constructed with a vertical shaft boring machine from Schwanau again. When building the new VSM10000, Herrenknecht engineers were able to draw on the experience gained from operating the first machine. As an example, the cutting drum was optimized to guarantee continuous tunnelling. In addition, the concrete segments (lining segments) to be used were newly designed in order to optimize assembly and handling.
The improved machine started tunnelling for the first 69-meter deep shaft in August 2010. After only 41 days and average tunnelling performances of 1.7 meters a shift, the machine reached its target. Until mid-2012, the Herrenknecht VSM10000 successfully sunk the three further shafts with depths of up to 83 meters.