Mining-induced microseismicity: Monitoring and applications of imaging and source mechanism techniques (original) (raw)
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Geophysical Research Letters, 1993
General stress and faulting trends have been retrieved through the analysis of mining induced microseismic events (M < 0) at two sites, related to an ms 2.6 rockburst, and an excavation at depth. A comparison of results obtained through principal compbnent analysis (PCA) of seismicity, focal mechanism, and stress inversion, with in-situ measurements of stress and structural mapping data, show that: under stable stress conditions, the P, B, T, and stress inversion axes are consistent with in-situ measurements of stresses; stress inversion and PCA fault-planes lie within 10 to 20 ΓΈ of the most significant mapped features at the sites; and the PCA technique provides a robust approach for the determination of fault-planes. sess the extent to which microseismicity can be used to retrieve general fault trends, and evaluate the consis
Dynamic triggering of microseismicity in a mine setting
Geophysical Journal International, 2015
We examine spatio-temporal patterns of microseismicity recorded during one month in an underground mine by addressing three key questions: (1) where does the seismicity occur? (2) Why does it occur in these locations? and (3) what triggers it? To obtain accurate locations, we perform a multiplet analysis and use a modified version of the double-difference (DD) relocation method. This approach leads to highly accurate relative event locations and requires groups of multiplets only. Most of the 281 relocated events are close to the main shaft and tunnels; thus we postulate seismicity is facilitated by stresses associated with the potential for subsidence in addition to the hoop stresses acting on the two vertical shafts. Most events occurred during certain hours of the day and there is a 68 per cent correlation with reported rock removal; therefore, it is likely they were triggered by static and dynamic stress perturbations caused by the transportation of debris along tunnels instead of our initial guess that blasting was the principal causative mechanism. Given that seismicity is present around the main shaft but absent close to the second one, we conclude that for seismicity to occur both a favourable stress state and additional external perturbing forces must exist, thus leading to dynamic event triggering in an initially stable stress situation. This analysis provides more insight into anthropogenic processes that might trigger seismicity, thereby facilitating identification of hazardous and potential damage areas in mine settings.
Analysis of microseismic cluster locations based on the evolution of mining-induced stresses
Numerical modelling is increasingly being used in the mining industry as part of the planning process. Its areas of application range from the estimation of in situ stresses at planned locations of underground facilities, to the effects of stope sequence alternatives on drift instability. In terms of the size of their study area, numerical models can range from a section of a given level to mine-wide dimensions, with an increase in complexity and input information requirements. Microseismic activities induced by mining operations can be studied using mine-wide numerical models that have been properly calibrated. In this paper, mining-induced seismicity at the Vale Garson Mine is examined between 2006 and 2008 with a numerical model constructed in FLAC3D. Two sets of microseismic activities are used as a basis of the study; events from the microseismic database with energy outputs greater than 100 kJ, and events that have resulted in rockbursts within developments, regardless of thei...
2000
Experiments carried out in a working iron mine validated the microseismic monitoring technique as a means of detecting fracture noise emissions regarded as signals indicating an incipient collapse. In the experiment surface recordings were made of the microseismic signals corresponding to fractures and local collapse phenomena generated at the mine bottom by deliberately destroying pillars. The pillar removal operations and the collapse of the roof were systematically correlated with a series of microseismic events. The experiment served to validate the microseismic monitoring technique as a means of detecting surface precursors of a collapse, to demonstrate the effectiveness of the technique, and to calibrate the principal parameters of a microseismic monitoring System adapted to detection and monitoring in areas where there is a risk of collapse.
Routine Micro-Seismic Monitoring in Mines
Routine seismic monitoring in mines enables the quantification of exposure to seismicity and provides a logistical tool to guide the effort into the prevention and control of, and alerts to, potential rock mass instabilities that could result in rock bursts. One can define the fol-lowing five specific objectives of monitoring the seismic response of the rock mass to mining: rescue of personnel, prevention, seismic hazard rating, alerts -including short term response to unexpected strong changes in certain parameters -and back analysis to improve the efficiency of both the mine layout design and the monitoring pro-cess. A quantitative description of seismic events and of seismicity are necessary, but not sufficient, in achieving the above objectives. The paper describes the basis of a modern digital seismic technol-ogy and seismological parameters used to quantify seismic sources and seismicity for seismic hazard assessment and rock mass stability analysis.
Microseismic monitoring of highwall mining stability at Moura Mine, Australia
Exploration Geophysics, 2001
We present results obtained from a microseismic monitoring at Pit 20DU at Moura Mine in central Queensland. The objective of this study was to investigate the feasibility of using the microseismic method to map roof fracturing associated with highwall mining for highwall mining stability assessment. 14 triaxial geophones were installed in 7 boreholes across the highwall bench, covering an area of 300 m by 400 m. The experiment was carried out from Jun 12 to Jul 25, 1999. More than 7,000 events were recorded. Generally, the recorded events were weak in seismic energy. Many of the events only triggered the nearest one or two geophones. The events were classified into three types on the basis of their frequency content and seismic duration. Each type appears to be associated with different fracturing mechanisms. The first type consisted of two groupings of events. One was located in the main sandstone roof and constrained by existing faults. They may be caused by the release of a local...
2016
6 INERIS and BOLIDEN are developing at Garpenberg mine (Sweden) new methodologies to monitor and to 7 assess both quasi-static stress changes and ruptures in a seismic-prone area subject to deep mass-mining 8 production. To achieve monitoring, a local mine seismic network has been deployed in the beginning of 9 2015 in the Lappberget area between 1100 and 1250 meter depth, in addition to 3D stress monitoring cells. 10 Such network has been designed to fit with the sublevel stoping method and with the paste fill 11 production/distribution system used by Boliden. Geophysical and geotechnical data are acquired 12 continuously and near-to real time transferred to INERIS data centre through e.cenaris e.infrastructure for 13 automated data processing and database management, along with mining datasets. In addition to 14 continuous monitoring, a fine-grid 3D numerical model of the mine has been defined, in which the complex 15 3D shapes of the orebody and a major weakness unit are taken in...
Joint processing of surface and underground microseismic monitoring data in hard mineral mining
Journal of Mining Science, 2015
The article discusses optimization of microseismic monitoring in hard mineral mining. A procedure has been developed to estimate accuracy of positioning of seismic event hypocenters. The advantage of combination observation system with distributed underground receiving antennas and additional sensors installed at a distance from a productive seam plane is illustrated. The obtained results are important for optimizing observation systems and improving efficiency of microseismic monitoring in hard mineral mining.