The anisotropy of ultrasonic waves velocity and attenuation of migmatite samples under uniaxial loading

0426118 - GLÚ 2014 RIV US eng C - Conference Paper (international conference)
Petružálek, Matěj - Lokajíček, Tomáš - Svitek, Tomáš
The anisotropy of ultrasonic waves velocity and attenuation of migmatite samples under uniaxial loading.
47th US Rock Mechanics/Geomechanics Symposium 2013. New York: Red Hook, 2013 - (Pyrak-Nolte, L.), s. 1281-1290. ISBN 978-1-62993-118-0.
[US Rock Mechanics/Geomechanics Symposium /47./. San Francisco (US), 23.06.2013-26.06.2013]
Institutional support: RVO:67985831
Keywords : brittle failures * velocity anisotropy * minimum velocities * rock structures * stress strain state * ultrasonic sounding * uni-axial loading * Velocity changes
Subject RIV: DC - Siesmology, Volcanology, Earth Structure

A method of velocity anisotropy analysis based on conventional ultrasonic transmission technique is presented. Multiple transducers were used to ultrasonic sounding and monitoring of acoustic emission. A sparse network of transducers located on the rock core surface allows approximation of elastic waves velocity distribution as an ellipsoidal surface. The shape and orientation of velocity ellipsoid is a measure of velocity anisotropy. A study of changes in velocity anisotropy and attenuation was performed on uniaxially loaded migmatite samples with distinct foliation. The cylindrical migmatite samples had a horizontal foliation and one of them had a pre-existed crack. The ultrasonic measurement was carried out during applying a uniaxial constant strain-rate loading. Orientation of the velocity ellipsoid corresponded to the anisotropy of rock structure up to activation of a failure plane. Prior to brittle failure, the axis of minimum velocity rotated from its initial direction normal to the foliation to a direction normal to the failure plane, which was determined from location of AE events . The changes in attenuation, induced by uniaxial loading, corresponded to the velocity changes and shown higher sensitivity to the actual stress-strain state of rock samples.
Permanent Link: http://hdl.handle.net/11104/0231884