Fracturing of migmatite monitored by acoustic emission and ultrasonic sounding

0473251 - GLÚ 2017 RIV US eng C - Conference Paper (international conference)
Petružálek, Matěj - Lokajíček, Tomáš - Svitek, Tomáš
Fracturing of migmatite monitored by acoustic emission and ultrasonic sounding.
50th US Rock Mechanics / Geomechanics Symposium 2016. Vol. 3. Houston: American Rock Mechanics Association (ARMA), 2016, s. 803-810. ISBN 978-151082802-5.
[US Rock Mechanics / Geomechanics Symposium /50./. Houston (US), 26.06.2016-29.06.2016]
Institutional support: RVO:67985831
Keywords : anisotropy * elastic moduli * rock mechanics * rocks * shearing
OECD category: Environmental and geological engineering, geotechnics

Migmatite from the Skalka region (Czech Republic) was chosen as an experimental rock material. It has a macroscopically visible plane-parallel structure (foliation). The foliation was caused mainly by biotite grain arrangement. Four cylindrical specimens of migmatite with sub-horizontal, sub-vertical and oblique foliation were uniaxially loaded up to failure. A network of 8 broadband sensors was employed for acoustic emission monitoring and ultrasonic sounding. A grid search method with an anisotropic velocity model was used for AE hypocenter localization. The source types of successfully localized events were determined from the average first arrival amplitude. Structural anisotropy of the tested rock material caused the anisotropy of its mechanical properties (peak strength, Young's modulus) as well as a different fracturing in dependence on the angle between the axial stress and the foliation plane. The combination of tension and shear microcracking together with sliding in biotite basal planes was found to control the failure of specimens with sub-horizontal foliation. Shearing and sliding were dominant in the failure of specimens with oblique foliation. With greater dip of foliation, the role of sliding increased at the expense of shearing. Due to the favorably oriented system of microcracks already present, the shearing and splitting was at the same level during fracturing of specimens with sub-vertical foliation before nucleation began.
Permanent Link: http://hdl.handle.net/11104/0270417