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Pressure Tunnel Ralco

NATM design and application support
Estimated cost: Commencement:
June 29, 2001
Completion date:
December 30, 2004
Alto Bio-Bio
Technical data:

Pressure tunnel with a lenght of 7 km (4.3 mi) and a diameter of 10 m (32.8 ft). Excavation in full face, top heading and invert according to encountered rock conditions. Initial support with lattice girders, steel fiber reinforced shotcrete and rock bolts. Grouting pipe spiling as pre-support for areas with deteriorated rock.

Geology description:

Volcanic rock and tertiary sediments; lavas and lavas brechosas andesitas, lavas con niveles de conglomerados finos y arenisacas. Rock intrusions in the form of diorite and diabase.

Geology types:
Bid cost: Final cost:
Service areas:
Cross Section with Excavation Steps
Construction Site - Dam in Background
Power Tunnel Outlet
Excavation of Invert
Installation of Shotcrete Lining at Tunnel Invert