Reconstruction of Korshunov tunnel in Taishet – Lena section of Eastern Siberia Railway Line started in autumn 2009. New tunneling was required within the installation that is 950-meters long. The tunnel is in a seismically hazardous zone. In addition, hole blasting operations are conducted at the ore mine of a large ore dressing and processing mill, which affect adversely the tunnel condition. The reconstruction includes the removal of the old lining, consolidation of the tunnel walls and vaults, erection of the new lining and reinforcement of the tunnel entries.
The work is carried out from both ends of the tunnel. As of the beginning of this year, 630 meters have been driven on the top heading and 244 meters have been driven on bottom heading. Permanent cast-in-place reinforced lining is being erected in the tunnel. The work is often carried out under very harsh weather conditions. Frost down to 57 degrees centigrade occurred this winter, and heavy snowfalls were a big nuisance for the builders. The reconstruction will be completed in the first half of 2012.