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Conference Papers Year : 2013

Accurate 3D location of mine induced seismicity in complex near-field underground conditions


The monitoring of mine induced seismicity and rockburst hazard can be carried out at different scales of resolution. The strategy usually adopted aims to get a global coverage of the mine layout, based on a large-scale array of low-frequency seismic sensors which may extend up to tens of squared kilometers, in order to monitor the numerous disseminated mining works and enable a periodical rating of seismic hazard. However, some major drawbacks must be dealt with. First, the microseismic detection limits for each mining work considered as a stand-alone rockburst prone area induces the loss of all those small magnitude events occurring in the vicinity of the working faces. Moreover, quality of the seismic source location reveals insufficient to pinpoint unambiguously its very origin in the surrounding geology and mining voids. These two limits affect strongly the capabilities of ground engineers to detect for sure significant change in the seismic regime of any specific seismogenic zone. Refining the monitoring may be reached by the deployment of mobile local-scale arrays made of short period sensors around those mining works rated at higher risk. These permit to record a much more complete microseismic catalogue while enhancing drastically the accuracy and reliability of the expertise. However, the processing of small magnitude events recorded locally calls for some precautions due to some nearfield conditions adverse to accuracy. Besides the increasing complexity of the rock mass when dealing with higher frequency waves, the presence of important ancient backfilled works more or less interlaced with multilevel fast advancing mining works may be a very issue. This is often the case for highly productive methods based on retreat mining, cut-and-fill or sub-level mining. Because installing a socalled high resolution microseismic network rises new expectations in the understanding of the seismic activity versus the local geology and the mining process, the authors have undertaken the development of an evolving 3D velocity model taking into account not only the underground geological aspects encountered, but also and above all the dynamic mining process itself. Besides synthetic numerical tests that have been run to assess the relevance of this issue, we applied this new numerical procedure to a true microseismic dataset recorded during the controlled collapse of a large solution mined cavern lying 220 meters deep. Tens of thousands of microseismic events were recorded with the critical enlargement of the cavern towards the surface. 3D surveys of the cavern itself together with geophysical loggings of its geological overburden have been used to dimension the presence of this volume full brine and calibrate this innovative location procedure applied to selected microseismic swarms. Detailed comparisons with conventional 3D location studies have been established emphasizing the considerable gain brought by a more realistic three dimensional velocity model including the pre-existent and evolving voids before and during seismic crisis. This gain includes a much better separation of the fracturing processes in the cap rock and on the sidewalls of the cavern, discerning unambiguously the impact of the roof falls at the bottom of the cavity, delineating geological rock strata and discontinuities playing clearly a role in the physics of the collapse phenomena. Such a numerical procedure is currently being improved and automated for operational implementation in a deep mine.
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ineris-00973707 , version 1 (04-04-2014)


  • HAL Id : ineris-00973707 , version 1
  • INERIS : EN-2013-281


Stella Coccia, Armand Lizeur, Pascal Bigarre, Isabelle Contrucci, Emmanuelle Klein. Accurate 3D location of mine induced seismicity in complex near-field underground conditions. 8. International Symposium on Rockbursts and Seismicity in Mines (RaSIM 8), Sep 2013, Saint-Petersburg, Russia. pp.NC. ⟨ineris-00973707⟩


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