A 6.2 m diameter Robbins Double Shield TBM has crossed the finish line in Sochi, Russia, completing a 4.5 km long section of tunnel that will ultimately become part of the transportation infrastructure for the 2014 Winter Olympic Games.
The TBM advanced through difficult ground at average rates of 100m to 120m per week for contractor OJSC Bamtonnelstroy, a division of the SK Most Company.
The section of tunnel will ultimately become a service tunnel for Complex #3 — a section of Sochi’s transportation infrastructure under construction, which includes road and rail tunnels.
A second 10.0m diameter Robbins Double Shield TBM is currently excavating the parallel 4.6km long main railway tunnel using a continuous conveyor system for efficient muck removal.
A 13.2m diameter highway tunnel is also under construction.
While the service tunnel is now complete and lined, work still remains on the main rail tunnel. The 10.0m diameter Double Shield was modified and repaired by Robbins site personnel prior to the start of excavation. The TBM is currently 726m into its portion of tunnel, with an expected completion date of March 2012.
All together, over 20 road and rail tunnels totaling 40km are under construction from Adler to Alpika areas, in anticipation of the 2014 Winter Olympic Games in Sochi. Project owner DCRC-Sochi, a subsidiary of Russian Railways, hopes to complete all rail and road infrastructure by June 2013.
The 6.2m Robbins TBM achieved high rates despite difficult conditions. The tunnels run through mixed ground including massive to completely fractured limestone with clay seams.
Some sedimentary rock including sandstone and siltstone is present, along with fault zones consisting of breccias and conglomerates.
In May 2010, the machine was stopped after encountering a significant fault zone consisting of broken rock and running soft ground. Field service personnel and crew successfully freed the machine by excavating a bypass tunnel around the TBM, freeing the cutterhead.
Following the restart, a combination of continuous probe drilling and ground treatment with cement silicate and foam kept the machine moving forward.