In late September, TBM manufacturer Robbins reported that assembly of a 5m diameter main beam TBM was completed for the Olmos Transandino Project in Peru where it will drive over half of a tunnel across the Andes.
The TBM is scheduled to begin boring in the first quarter of 2007 when it will be used to excavate a 13.8km long section of the 20km trans-Andean tunnel at altitudes of more than 1,000m above sea level. Rock burden above the tunnel will equate to more than 1,800m.
Robbins said that the high cover creates several challenges, including very high ambient air temperatures of up to 52ºC in the tunnel. To help combat this, two interacting air-cooling systems will be used. The set-up involves air chillers mounted on the TBM backup and also free standing air chillers to cool the tunnel air to 32ºC or below.
Contractors Odebrecht Peru Ingeneria y Construccion SAC (OPIC) awarded Robbins the contract for supply of the TBM, backup, spares, cutters and operational personnel earlier in the spring this year. The TBM will have to drive through quartz porphyry and andesite geology with an UCS of up to 225Mpa.
The TBM has the capacity to install rockbolts, wire mesh, ring beams and shotcrete for ground support. It is also equipped with a probe drill to help determine conditions in advance of the face. Final tunnel lining will be a cast in-situ concrete lining installed after the TBM has been removed from the tunnel.
The Olmos project will transfer water from the Andes to a reservoir for hydroelectricity generation and irrigation. With a planned transfer capacity in excess of 2bn m3 of water annually, the tunnel will facilitate generation of 600MW of electricity and irrigation of over 150,000ha of farmland. Concesionaria Trasvace Olmos SA, a subsidiary of Norberto Odebrecht of Brazil was granted a 20 year concession to build and operate the project in July 2004 from the Peruvian state and the regional government.
