Seismic studies of rock fracture at the Underground Research Laboratory, Canada

The tunnel sealing experiment at the Underground Research Laboratory in Canada is testing engineered barriers (concrete and clay bulkheads) that will restrict fluid flow passing through the excavation damage zone (EDZ) in the host granitic rockmass. 3D elastic stress modeling has shown that keyed bulkheads significantly disrupt and reduce the high differential stresses around the excavation perimeter. The use of microseismic (MS) and acoustic emission (AE) methods are shown to be a valuable tool for delineating the extent of the EDZ, substantiating the stress modeling, and also for identifying how much tunnel perimeter confinement is needed to stop the occurrence of micro-cracking. In addition, active ultrasonic surveys using AE sensors are shown to be able to quantify the change in material properties Such as crack density that have occurred during the development of the EDZ. (C) 2001 Elsevier Science Ltd. All rights reserved.