Statistical study of acoustic emissions generated during the controlled deformation of migmatite specimens

0480961 - GLÚ 2018 RIV GB eng J - Journal Article
Vilhelm, J. - Rudajev, V. - Ponomarev, A. V. - Smirnov, V. B. - Lokajíček, Tomáš
Statistical study of acoustic emissions generated during the controlled deformation of migmatite specimens.
International Journal of Rock Mechanics and Mining Sciences. Roč. 100, December 2017 (2017), s. 83-89. ISSN 1365-1609. E-ISSN 1873-4545
R&D Projects: GA ČR GA13-13967S; GA ČR(CZ) GA16-03950S
Institutional support: RVO:67985831
Keywords : laboratory measurements * steplike loading * cyclic loading * migmatite sample * aftershock series * autocorrelation analysis
OECD category: Geology
Impact factor: 2.836, year: 2017

Acoustic emissions generated during the mechanical loading of rocks provide information about the process of their fracturing and therefore have been used in the research of rock fracturing for many years. Laboratory
loading experiments are used as a model of seismic processes in the field. Continuous loading is typically used to
model natural tectonic processes, whereas stepwise loading can represent local stress field changes and evolution, similar to some features of rock fracturing due to water injection in the borehole with step-like injection history. During continuously increasing loading, acoustic impulses of a swarm character are generated. During stepped stress, however, the emission of acoustic signals generated has the character of an aftershock series and can be described by Omori's law for aftershock decay. The present work focuses on a detailed analysis of the seismoacoustic emissions generated in rock specimen during the stepwise increasing deformation during laboratory loading tests. A cylindrical specimen of migmatite was subjected to cyclical and stepwise loading with controlled deformation. The stepwise deformation increase was approximately 0.8 mStrain per one step and deformation rate was cca 8 mStrain/s. This sudden increase of deformation was accompanied by peak stress increase with duration of approximately 2 s. During load testing, seismoacoustic emissions were monitored and time series of acoustic impulses were recorded. It was found that the higher the level of stress, the longer the duration of aftershock sequence. Analysis of the autocorrelation functions of individual sequences showed significant changes in parameters at maximum specimen stress. An increase was found in the values of first autocorrelation coefficients, which can be used to assess the stability of the rock specimen.
Permanent Link: http://hdl.handle.net/11104/0276602