OREANDA-NEWS. The builders of Tonnelny Otryad-18 LLC have driven 1,900 meters underground by the beginning of April on the New Mana Tunnel Project. They are going to complete the tunneling in summer this year.

The tunneling is conducted using the Lovat-RME375SE Tunnel Boring Machine from the eastern tunnel entry to the western tunnel entry simultaneously with installation of prefabricated tunnel lining. They have driven 1,924 meters of the tunnel shaft by the 6th of April.

The New Mana Tunnel is built under challenging geological conditions. The tunnel has been driven within the initial 120-meter-long tunneling section mainly through the rock disintegrated to detritus. The rest of the tunnel is driven in hard rocks with a hardness ranging from f=16 to f=20 (maximum on the Protodiakonov hardness scale).

After driving the cap part of the tunnel through the 120-meter-long section in June 2012 and after the preparatory operations and the tunnel-boring machine assembly had been completed, the builders started the tunneling using the Lovat-RME375SE Tunnel Boring Machine with a cutting diameter of 9.54 m. The 120-meter-long bottom part of the tunnel was first driven by the tunnel-boring machine and the tunneling was then conducted over the whole cross-section.

A service/drainage gallery has been built from September 2007 to April 2010 using the tunneling and drilling/blasting driving techniques. The Lovat RME-139SE Tunnel Boring Machine with a cutting diameter of 3.56 meters has driven 2,166.2 meters of the gallery, and prefabricated reinforced concrete lining was installed simultaneously with the tunneling. A tunnel section of 300.74 meters was driven using the drilling and blasting technique, with the permanent lining provided by concrete spraying. The total length of the gallery will be 2,470.93 meters. The gallery has the flat bottom for vehicle traffic used for servicing the main tunnel.

Railway tracks that are 5.8 kilometers long have been built for access to the new tunnel on the eastern tunnel entry side.

The New Mana Tunnel of a total design length of 2,464.868 meters is scheduled for opening for permanent service in the First Quarter of 2014.