Vol. t59. 2002 J damaged zone on the rock mass. Collins el al. examine
the benefits of employing small-scale microseismic and acoustic emission
systems to investigate the temporal fracture mechanics of microcrack
formation associated with a tunnel sealing experiment at the Underground
Research Laboratory nuclear waste test site in Canada. They associate
microseismic events with clusters of acoustic emissions and outline that
both types of sources are generally characterized by deviatoric failure
components. Using the same experimental setup, Hazzard el al. employed a
bonded- particle model to simulate shear microfraclures induced by the
lunnel excavation. Comparing Ihe modeling results with information
provided by the moniloring of microseismicity and acoustic emissions,
the authors identify similarities in both the presence of foreshocks
associated with macro-slip events, and the pallerns of energy release
during loading. Hildyard and Young allempt to model the seismic wave
interaction with fractured rock surrounding underground openings,
through exper- iments such as a rockbursl simulation, in situ events
generating acoustic emissions, and laboratory fractures. Their results
highlight that realistic wave modeling around openings requires the
presence of a stress-dependent fracture stiffness coupling the surfaces
of the fracture. Ultrasonic attenuation tomography and enhanced velocity
tomography were studied by D bski and Young for an earlier laboratory
experiment of thennally induced fractures in granite.
