Acoustic emission investigation of microcrack generation at geological boundaries

Spies, Thomas; Eisenblätter, J.

doi:10.1016/s0013-7952(01)00053-9

Cited by 25 publications

(18 citation statements)

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“…This region is a curved zone of AE activity with a lateral extent of about 11 m and closely resembles similar patterns of AE clusters previously observed in the Morsleben mine. These structures, exhibiting steady microcracking activity at the same location and showing a circular shape (Spies and Eisenblätter, 2001), are suggested to be caused by inner, penny-shaped fractures at a significant distance from the nearest cavity. In one case, a fracture surface was identified at the cluster location by drilling a borehole (Spies and Eisenblätter, 2001).…”

Section: Observed Ae Activitymentioning

confidence: 99%

“…This microcracking either takes place along grain boundaries or breaks through grains in the salt or at the contact between different geologic units, such as rock salt and anhydrite, that serve as localized zones of weakness (e.g., Spies and Eisenblätter, 1999;Spies and Eisenblätter, 2001;Fahland et al, 2005). The dataset used in this study was recorded by a network of 24 AE receivers ( Fig.…”

Section: Study Site and Monitoring Networkmentioning

confidence: 99%

“…AE events in the mine are located automatically with a triggering approach, and only event parameters such as hypocenter, origin time, automatically determined P-and S-wave onsets, and maximum amplitude are saved in a log file. (The waveforms are not routinely retained; see Spies and Eisenblätter, 2001, Köhler et al, 2009, and Becker et al, 2010, for specifics of the recording system and the localization procedure.) Data are sampled with 200 kHz, and the main signal energy is in the 1-20 kHz frequency range.…”

Section: Study Site and Monitoring Networkmentioning

confidence: 99%

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Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring

Cailleau¹,

Kaiser²,

Dahm³

2014

Bulletin of the Seismological Society of America

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Mining activity may cause different types of seismicity and rock failure.Typical events include (1) fully induced microearthquakes in close proximity to galleries and human activity due to high-stress concentrations (border fractures) and (2) triggered earthquakes within the rock mass at larger distance to the source of the stress perturbation (inner fractures). Type 1 is important to understand the development of rock bursts and evaluate the stability of the mine. Type 2 may be associated with larger events releasing pre-existing stress and being triggered by stress changes due to the mining operation. They are important to assess the seismic hazard related to mining activity.To analyze these different failure processes, we use a dataset of high-frequency acoustic emission (AE) events monitored in an abandoned salt mine. The process of fracture formation in the rock mass was enhanced by the backfilling of a cavity. Thermal stresses induced by the backfilling operation are modeled with a finite-element approach, and observed AE activity is used to quantify the mechanism of event triggering in terms of a Coulomb failure model.Two observations are outstanding. First, the instantaneous triggering of enhanced activity and the slow growth of an inner fracture in relatively far distance to the backfilled cavity is detected. The structure already showed AE activity before the refilling started and was triggered by traction-like stress transfer. Its AE activity correlates well with the calculated Coulomb stress changes at the beginning of backfilling. Second, the sudden occurrence of a macroscopic, induced border fracture at the backfilled gallery which is oriented in agreement with the acting stress field is observed. Although AE activity at the inner fracture was triggered by tiny Coulomb stress changes, indicating a structure already in critical state, formation of the border fracture required significantly larger stresses, hinting at a previously intact rock volume.Online Material: Figure depicting the variability of the static Coulomb stress changes on the inner fracture for different rake values.

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Section: Observed Ae Activitymentioning

confidence: 99%

Section: Study Site and Monitoring Networkmentioning

confidence: 99%

Section: Study Site and Monitoring Networkmentioning

confidence: 99%

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Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring

Cailleau¹,

Kaiser²,

Dahm³

2014

Bulletin of the Seismological Society of America

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“…The catalog information was compiled from the data recorded by a microseismic network that was installed to monitor microcrack processes at the Morsleben salt mine, Allertal region, Germany. This site has been extensively monitored for AE studies (e.g., Spies and Eisenblätter, 2001;Becker et al, 2010;Maghsoudi et al, 2013Maghsoudi et al, , 2014.…”

Section: Datamentioning

confidence: 99%

“…Depending on the hypocentral location and magnitude of an event, several sensors can be saturated and are therefore useless for the location and magnitude estimation procedures. The automated AE location at Morsleben requires a minimum number of 10 phase detections (cumulative number of P and/or S picks) for a valid location (Spies and Eisenblätter, 2001;Becker et al, 2010). Events with fewer picks are identified but not located, and they therefore are not included in the resulting catalog.…”

Section: Datamentioning

confidence: 99%

Maximum Magnitude of Completeness in a Salt Mine

Maghsoudi¹,

Cesca²,

Hainzl³

et al. 2015

Bulletin of the Seismological Society of America

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In this study, we analyze acoustic emission (AE) data recorded at the Morsleben salt mine, Germany, to assess the catalog completeness, which plays an important role in any seismicity analysis. We introduce the new concept of a magnitude completeness interval consisting of a maximum magnitude of completeness (M cmax ) in addition to the well-known minimum magnitude of completeness. This is required to describe the completeness of the catalog, both for the smallest events (for which the detection performance may be low) and for the largest ones (which may be missed because of sensors saturation). We suggest a method to compute the maximum magnitude of completeness and calculate it for a spatial grid based on (1) the prior estimation of saturation magnitude at each sensor, (2) the correction of the detection probability function at each sensor, including a drop in the detection performance when it saturates, and (3) the combination of detection probabilities of all sensors to obtain the network detection performance. The method is tested using about 130,000 AE events recorded in a period of five weeks, with sources confined within a small depth interval, and an example of the spatial distribution of M cmax is derived. The comparison between the spatial distribution of M cmax and of the maximum possible magnitude (M max ), which is here derived using a recently introduced Bayesian approach, indicates that M max exceeds M cmax in some parts of the mine. This suggests that some large and important events may be missed in the catalog, which could lead to a bias in the hazard evaluation.

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Underground In-situ Acoustic Emission in Study of Rock Stability and Earthquake Physics

Plenkers

Manthei

Kwiatek

2021

Springer Tracts in Civil Engineering

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Acoustic emission investigation of microcrack generation at geological boundaries

Cited by 25 publications

References 1 publication

Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring

Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring

Maximum Magnitude of Completeness in a Salt Mine

Underground In-situ Acoustic Emission in Study of Rock Stability and Earthquake Physics

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