Management of Post-mining Large-scale Ground Failures: Blast Swarms Field Experiment for Calibration of Permanent Microseismic Early-warning Systems

Abstract

ACCEPTED May 09, PAGEOPH.Abstract -In France, decades of coal and iron ore mining have left extensive underground cavities beneath or in the vicinity of urban areas. This poses an environmental challenge for society. To ensure post-mining risk management and public safety, wherever remediation is not possible, numerous real-time microseismic monitoring systems are being installed. The objective is to detect remote rock mass fracturing processes, precursory events and acceleration phases for appropriate and timely action. Although no consistent collapse has occurred in any of the monitored areas yet, single 3D probes record many microseismic events of very low amplitude which create difficulties in the quantitative data analysis. The development of specific quantitative processing has therefore become a major issue in our research work. For that purpose, a field experiment was carried out on six of the instrumented sites. It consisted of sequences of small blasts in mine pillars which were accurately controlled in terms of the location, orientation and energy of the explosive source. The data analysis was used to calibrate parameters (velocity model, 3D sensor orientation, etc.) for reliable 3D localization and to develop an empirical law to estimate the source energy from the sensor energy. This work now enables us to analyze real microseismic events with a much better level of accuracy and to obtain enough information and confidence to discuss these data in terms of site stability.

Multi-parameter monitoring of a solution mining cavern collapse: First insight of precursors

“…It was parameterized on a routine basis included P-wave picking using an STA/LTA algorithm (Allen, 1982) and 3-D location of events based on the non-linear inversion method (Contrucci et al 2010;Lomax and Curtis, 2001). In practice it was difficult to achieve reliable automatic on-line S-wave picking and thus improved 3-D location, although polarization analysis frequently demonstrated the presence of S-wave energy in the seismograms.…”

“…Until now, in highrisk areas, the microseismic technique has been the most successful in providing very sensitive volumetric monitoring over extensive urbanized areas (Couffin et al, 2003;Senfaute et al, 2000). However, the lack of any feedback from adequately-instrumented ground collapses has not allowed researchers to answer basic questions concerning early-warning signs and the mechanisms and dynamics of failure (Contrucci et al, 2010 ;Tastet et al, 2007), although numerical modeling approaches have provided some insights into these issues (e. g. Bérest et al, 2008;Dris et al, 2008;Al Heib et al, 2001).…”

Mining Induced Seismicity - Monitoring of a Large Scale Salt Cavern Collapse

“…It was parameterized on a routine basis included P-wave picking using an STA/LTA algorithm and 3D location of events based on a non-linear inversion method (Contrucci et al 2010b). …”

Resolving source mechanisms of microseismic swarms induced by solution mining

“…To prevent these disasters in the Lorraine region and other post-mining districts, current research aims to better understand the governing failure mechanisms and dynamics and to improve the efficiency of local microseismic and geodetic monitoring, which represents a major instrument of the French post-mining risk management (e.g. Couffin et al 2003;Didier 2008;Contrucci et al 2010).…”