Robbins is to supply a 4.3m diameter TBM on site in Siberia by September for excavation of a service and drainage tunnel on the Mansky project to start by year end. The firm is also supplying cutters for a 9.5m diameter Lovat TBM that will bore a parallel, 2.5km long rail tube on the scheme.

The Robbins double shield TBM is being built at its plant in Shanghai. The drive is scheduled to complete in mid-2008. The TBM will be used to access additional open faces, if necessary, Robbins added.

Robbins has also been contracted by Bamtonnelstroy – which is the client for the turnkey project – to supply the back-up for its TBM plus cutters, spares plus a set of rolling stock, including three, 15 tonne locos, 8m3 wagons and segments cars.

Geology along the tunnel alignments, in the Kraznoyyark territory of eastern Siberia, offers a wide range of rock strengths, from 20MPa up to almost 400MPa, and there is a seismic zone. The strata include hornfels, breccia, pegmatite, sandstone, mudstone, gneiss and granite, and there a 655m long section of unstable ground, Robbins said. In that section, inflows of up to 25m3/hr are anticipated in a mix of clay, sandstone, breccia and detritus loam.

For the service and drainage tunnel, the lining will be precast segmental (5+1) for the most part, with pea gravel and grout backfill of the annulus. Provision has also been made for shotcrete in some sections of the drive.

The Mansky project will add capacity to the Krasnoyarskaya railway. Lovat’s single shield hard rock TBM will drive a new tube parallel to a single tunnel, built in 1965. It is currently on the Krolsky rail project in east Siberia.