Neutrino Detector Site

Andrea T. Hughes - March 2004

At 2070 meters below ground the SNO cavity in INCO's Creighton mine is the largest in the world excavated at this depth. Construction required the latest advances in rock stabilization and ground control techniques. At this depth the rock is under a pressure of about 50 MPa (over 550 atmospheres or 8,000 psi).

The SNO site is located in the "hanging wall" rock 200m from the mining zone to minimize interference from blasting or rock burst activity.

Aerial view of Creighton mine, shaft number nine. Home to SNO..

The cavity design, incorporating large safety factors, was barrel shaped and is stabilized by some 800 "cable bolts", each cemented 30 feet into rock.

The excavation began in March 1990 and was completed in May 1993. The procedure was to blast out 15 foot benches and shovel the rock down a central hole, where it was scooped out via ramp access.

Over 60,000 tonnes of rock was blasted, trammed and hoisted to the surface. Throughout the excavation cable bolts were installed with bolted steel screening and sprayed concrete.