Acoustic emisson study of microfracturing during the cyclic loading of Westerly granite

Journal Article · Fri Apr 10 04:00:00 EST 1981 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB086iB04p02915· OSTI ID:6537541

Sondergeld, C H; Estey, L H

A rectangular prism of Westerly granite was deformed in a uniaxial cycling experiment. Acoustic emission (AE) activity was recorded using eight transducers in real time. Hypocenters of 116 events were determined using a standard least squares approach. Event clustering was definitely evident and could easily be assessed using a stereographic projection of hypocenters. This clustering was observed at volumetric strains well below 0.03%. The distribution of hypocenters changed from cycle to cycle, suggestive of a spatial migration. THe cumulative distribution of hypocenters documents the strongly anisotropic developement of dilatancy in Westerly granite. Once the sample underwent the initial deformation and a zone of weakness was established, subsequent events clustered in and about the initial zone. Volumetric strain, differential stress, acoustic emission event rate, and cumulative numbers were continously measured during the experiment. The cumulative number of events per cycle generally decreased with the number of cycles. The majority of events occurred upon loading. Those that occurred during unloading were few in number and not as systematically related to stress as were those for loading. In general, waveform quality deteriorated with increase cycling and in later cycles waveforms typically displayed low-frequency components in initial onsets followed by a more typical higher-frequency arrival.

• Research Organization: Cooperative Institute for Research in Environmental Sciences, University of Colorado/NOAA, Boulder, Colorado 80309
• OSTI ID: 6537541
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 86:B4; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ACOUSTIC EMISSION TESTING
ACOUSTIC TESTING
COMMINUTION
DEFORMATION
FAILURES
FRACTURES
FRACTURING
GRANITES
HYPOCENTERS
IGNEOUS ROCKS
MATERIALS TESTING
NONDESTRUCTIVE TESTING
PLUTONIC ROCKS
ROCKS
SHRINKAGE
STRAIN RATE
TESTING
WAVE FORMS