Robbins TBM overcomes high overburden at Olmos

Sep 09, 2008

A 5.3 m (17.4 ft) Robbins TBM is standing up to the pressure in Peru. The Main Beam machine is boring a 13.9 km (8.6 mi) long tunnel through the Andes Mountains, beneath up to 2,000 m (6,500 ft) of hard, potentially squeezing rock.

The Olmos Trans-Andean tunnel has been more than 100 years in the making, with several attempts made in the 1950’s using drill and blast techniques. The tunnel, more than 20 km (12 mi) long in total, will transfer water from the Huancabamba River on the Eastern side of the Andes to drought-ridden areas on the Pacific Ocean Watershed.

The TBM was launched in March 2007 for sub-contractor Odebrecht Peru Ingenieria y Construccion, S.A.C (OPIC). General contractor Concesionaria Trasvace Olmos, S.A. won a 20-year build-operate concession from the Peruvian National Government and Lambayeque Regional Government in July 2004.

The machine is boring in complex geology consisting of quartz porphyry, andesite, and tuff from 60 to 225 MPa (8,700 to 32,600 psi) UCS. Over 400 fault lines are present along the entire tunnel, including two major fault lines approximately 50 m (160 ft) wide. The overburden has created another problem — high in-tunnel temperature, predicted to exceed 54 degrees Celsius (130 degrees Fahrenheit). To cope with the high temperature Robbins has designed the machine with a unique ventilation and air cooling system. Two interacting systems are being used to cool the tunnel to 32 degrees Celsius (90 degrees Fahrenheit) or below. The high jobsite elevation (1,080 m / 3,500 ft) results in less dense air and less heat transfer capacity per cubic meter of air, so the two systems will make it possible to blow more air into the tunnel for a maximum cooling effect.

The Robbins machine has overcome not only tough geological conditions but also unpredictable weather. A flood in April 2008 covered the jobsite in a thick layer of mud and debris and washed out the only access road leading to the construction area. Despite the three-week delay the machine is still on schedule for a projected finish in March 2009. The machine is now averaging 3.2 m (10.5 ft) per hour, with production rates of up to 38.3 m (126 ft) per day. As of August 2008 the TBM had advanced 6,000 m (20,000 ft).

By March 2010, the first phase of the tunnel project will be operational and will supply more than 2 billion cubic meters (500 billion gallons) of water annually for irrigation of 560 km2 (130,000 acres) of farmland. The second phase will involve construction of at least two more drill and blast tunnels and two stations for hydroelectric power. The facilities will be capable of generating 600 MW each.

The Robbins Company (Headquarters)
29100 Hall Street
Suite 100
Solon, OH 44139
Brianna Home, Marketing Director
Desiree Willis, Technical Writer
Phone: +1 253 872 0500
Fax: +1 440 248 1702


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