Acoustic Emission Measurements
Report of the project:
Acoustic emission (AE) measurements are carried out in mines as part of geo-mechanical investigations regarding the stability of underground cavities and the integrity of the rock mass. Micro cracks are detected and located by analyzing high-frequency seismic energy in the frequency range between 1 and 100 kHz.
Monitoring with acoustic emission networks: Locations of sensors (red) and acoustic emissions (blue)
Source: BGR
Long term acoustic emission measurements are performed since 1994 in the repository for radioactive waste disposal Morsleben in the salt mine Bartensleben in three selected sections with dimensions of approximately 100 to 200 m. Three networks of up to 32 piezoelectric sensors were installed in boreholes in the mine. The results of the acoustic emission measurements are interpreted in conjunction with results of other geo-mechanical investigation methods such model calculations, laboratory tests and in situ measurements of deformations and stresses.
The event rates and the slopes of the magnitude-frequency distributions (b-values) show distinct spatial and temporal variations. Deviations of the observed event rates from the theoretical event rates expected from numerical stress modeling, the decrease of b-values and the occurrence of micro-crack clusters indicate changes in the rock system up to macroscopic cracking. The measurements show the loosening up of rock salt in in the vicinity of the backfilled chambers and concentrations of micro cracks at the border between rock salt and anhydrite.
The long-term acoustic emission measurements in the repository for radioactive waste disposal Morsleben provide a dataset of currently approximately 15 million located events per year.
Literature:
Becker, D., Cailleau, B., Dahm, T., Shapiro, S., Kaiser, D. (2010): Stress triggering and stress memory observed from acoustic emission records in a salt mine. Geophysical Journal International, 182, 933-948. doi:10.1111/j.1365-246X.2010.04642.x
Becker, D., Cailleau, B., Kaiser, D. & Dahm, T. (2014): Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring. Bulletin of the Seismological Society of America, 104, 1785-1801. doi:10.1785/0120130286
Fahland, S., Eickemeier, R. & Spies, T. (2005): Bewertung von Gebirgsbeanspruchungen bei Verfüllmaßnahmen im ERAM. 5. Altbergbaukolloquium vom 3. bis 5. November 2005.- Verlag Glückauf GmbH; TU Clausthal.
Hesser, J., Kaiser, D., Schmitz, H. & Spies, T. (2015): Measurements of Acoustic Emission and Deformation in a Repository of Nuclear Waste in Salt Rock. In: Engineering Geology for Society and Territory - Volume 6. Springer International Publishing, 551-554. doi:10.1007/978-3-319-09060-3_99
Kaiser, D., Spies, T. & Schmitz, H. (2013): Mikroakustisches Monitoring in Bergwerken zur Bewertung aktueller Rissprozesse. In: Tagungsband GeoMonitoring 2013.- Leibniz Universität, 39-55; Hannover.
Kaiser, D. (2011): Mikroakustische Messungen in einem Salzbergwerk zur Bewertung von Rissprozessen. – DGG-Kolloquium Induzierte Seismizität : 71. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, Köln, 23. Februar 2011. Mitteilungen / Deutsche Geophysikalische Gesellschaft. Sonderband 1/2011, 39-52.
Köhler, N., Spies, T. & Dahm, T. (2009): Seismicity patterns and variation of the frequency-magnitude distribution of microcracks in salt. Geophysical Journal International, 179, 489-499. doi:10.1111/j.1365-246X.2009.04303.x
Maghsoudi, S., Cesca, S., Hainzl, S., Dahm T., Zöllner, G. & Kaiser, D. (2015): Maximum Magnitude of Completeness in a Salt Mine. Bulletin of the Seismological Society of America, 105, 1491-1501. doi:10.1785/0120140039
Maghsoudi, S., Cesca, S., Hainzl, S., Kaiser, D., Becker, D. & Dahm (2013): Improving the estimation of detection probability and magnitude of completeness in strongly heterogeneous media, an application to acoustic emission (AE). Geophysical Journal International, 193, 1556-1569. doi:10.1093/gji/ggt049
Maghsoudi, S., Hainzl, S.,Cesca, S., Dahm, T. & Kaiser, D. (2014): Identification and characterization of growing large-scale en-echelon fractures in a salt mine. Geophysical Journal International, 196, 1092-1105. doi:10.1093/gji/ggt443
Manthei, G. & Eisenblätter, J. (2008): Acoustic Emission in Study of Rock Stability. Acoustic Emission Testing.- Springer Verlag, 239-310; Berlin Heidelberg.
Manthei, G., Eisenblätter, J. & Spies, T. (2007): Source mechanisms of acoustic emission events between large underground cavities in a salt mine. Advances in acoustic emission: Proceedings of the Sixth International Conference on Acoustic Emission. - Acoustic Emission Group, Lake Tahoe, Nevada, 288-293.
Spies, T. & Eisenblätter, J. (2001): Acoustic emission investigation of microcrack generation at geological boundaries. Engineering Geology, 61, 181. doi:10.1016/s0013-7952(01)00053-9
Spies, T., Eisenblätter, J. & Manthei, G. (2002): Neue Entwicklungen in der Mikroakustik am Beispiel von Messungen im Endlager Morsleben. Zeitschrift für Angewandte Geologie, 2/2002, 30-37; Hannover.
Spies, T., Hesser, J., Eisenblätter, J. & Eilers, G. (2004): Monitoring of the rock mass in the final repository Morsleben: experiences with acoustic emission measurements and conclusions. Proceedings of DisTec 2004, 301-311; Berlin.
Partner:
Gesellschaft für Materialprüfung und Geophysik GMuG mbH, Bad Nauheim