A laboratory acoustic emission experiment under in situ conditions

In this paper, we revisit acoustic emission (AE) data from an in situ rock fracture experiment conducted at the Underground Research Laboratory (URL) in Manitoba, Canada. The Mine-By experiment, a large-scale excavation response test, was undertaken at a depth of 420 m and involved the mechanical excavation of a cylindrical tunnel. During the experiment a small array of 16 Panametrics V103 AE sensors enclosed a 0.7 m x 0.7 m x 1.1 m rectangular prism of Lac du Bonnet granite located in the tunnel wall. The V103 sensors were later calibrated in the laboratory, and a source parameter analysis was undertaken using a spectral fitting method. Corner frequency and moment magnitude were found to be inside the ranges 250 kHz < f(c) < 490 kHz and -7.5 < M-w < -6.8, respectively. Static stress drops ranged from 0.3 to 4 MPa, which is consistent with large seismicity recorded at the URL.