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Title: Seismic anisotropy in granite at the Underground Research Laboratory, Manitoba

Abstract

The Shear-Wave Experiment at Atomic Energy of Canada Limited's Underground Research Laboratory was probably the first controlled-source shear-wave survey in a mine environment. Taking place in conjunction with the excavation of the Mine-by test tunnel at 420 m depth, the shear-wave experiment was designed to measure the in situ anisotropy of the rockmass and to use shear waves to observe excavation effects using the greatest variety of raypath directions of any in situ shear-wave survey to date. Inversion of the shear-wave polarizations shows that the anisotropy of the in situ rockmass is consistent with hexagonal symmetry with an approximate fabric orientation of strike 023{degree} and dip 35{degree}. The in situ anisotropy is probably due to microcracks with orientations governed by the in situ stress field and to mineral alignment within the weak gneissic layering. However, there is no unique interpretation as to the cause of the in situ anisotropy as the fabric orientation agrees approximately with both the orientation expected from extensive-dilatancy anisotropy and that of the gneissic layering. Eight raypaths with shear waves propagating wholly or almost wholly through granodiorite, rather than granite, do not show the expected shear-wave splitting and indicate a lower in situ anisotropy, which maymore » be due to the finer grain size and/or the absence of gneissic layering within the granodiorite. These results suggest that shear waves may be used to determine crack and mineral orientations and for remote monitoring of a rockmass. This has potential applications in mining and waste monitoring.« less

Authors:
; ;
Publication Date:
Research Org.:
GeoScope Exploration Technologies, Inc., Calgary, Alberta (CA)
OSTI Identifier:
20076108
Resource Type:
Journal Article
Journal Name:
Geophysical Prospecting
Additional Journal Information:
Journal Volume: 48; Journal Issue: 3; Other Information: PBD: May 2000; Journal ID: ISSN 0016-8025
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 42 ENGINEERING; GRANITES; MANITOBA; SEISMIC S WAVES; ANISOTROPY; EXCAVATION; TUNNELS; GEOLOGIC FRACTURES; UNDERGROUND MINING; UNDERGROUND DISPOSAL; ROCK MECHANICS

Citation Formats

Holmes, G.M., Crampin, S., and Young, R.P. Seismic anisotropy in granite at the Underground Research Laboratory, Manitoba. United States: N. p., 2000. Web. doi:10.1046/j.1365-2478.2000.00195.x.
Holmes, G.M., Crampin, S., & Young, R.P. Seismic anisotropy in granite at the Underground Research Laboratory, Manitoba. United States. doi:10.1046/j.1365-2478.2000.00195.x.
Holmes, G.M., Crampin, S., and Young, R.P. Mon . "Seismic anisotropy in granite at the Underground Research Laboratory, Manitoba". United States. doi:10.1046/j.1365-2478.2000.00195.x.
@article{osti_20076108,
title = {Seismic anisotropy in granite at the Underground Research Laboratory, Manitoba},
author = {Holmes, G.M. and Crampin, S. and Young, R.P.},
abstractNote = {The Shear-Wave Experiment at Atomic Energy of Canada Limited's Underground Research Laboratory was probably the first controlled-source shear-wave survey in a mine environment. Taking place in conjunction with the excavation of the Mine-by test tunnel at 420 m depth, the shear-wave experiment was designed to measure the in situ anisotropy of the rockmass and to use shear waves to observe excavation effects using the greatest variety of raypath directions of any in situ shear-wave survey to date. Inversion of the shear-wave polarizations shows that the anisotropy of the in situ rockmass is consistent with hexagonal symmetry with an approximate fabric orientation of strike 023{degree} and dip 35{degree}. The in situ anisotropy is probably due to microcracks with orientations governed by the in situ stress field and to mineral alignment within the weak gneissic layering. However, there is no unique interpretation as to the cause of the in situ anisotropy as the fabric orientation agrees approximately with both the orientation expected from extensive-dilatancy anisotropy and that of the gneissic layering. Eight raypaths with shear waves propagating wholly or almost wholly through granodiorite, rather than granite, do not show the expected shear-wave splitting and indicate a lower in situ anisotropy, which may be due to the finer grain size and/or the absence of gneissic layering within the granodiorite. These results suggest that shear waves may be used to determine crack and mineral orientations and for remote monitoring of a rockmass. This has potential applications in mining and waste monitoring.},
doi = {10.1046/j.1365-2478.2000.00195.x},
journal = {Geophysical Prospecting},
issn = {0016-8025},
number = 3,
volume = 48,
place = {United States},
year = {2000},
month = {5}
}