Y. Gunzburger (associate professor, GeoRessources lab, Université de Lorraine), PhD director
J. Kinscher (PhD, research engineer, Ineris, the French national institute for industrial environment and risks), PhD co-director
F. de Santis (Ineris), M. Conin (GeoRessources lab), V. Renaud (Ineris), P. Bernard (IPG Paris), S. Dineva (Lulea University, Sweden)
Laboratory: GeoRessources - Ineris joint lab, Campus Artem, 92 rue Sergent Blandan, BP 14234, F-54042 Nancy cedex, France
Test-site: Garpenberg mine, Sweden (New Boliden company)
Keywords: deep mining, rockburst hazard, induced seismicity, aseismic creep, in-situ monitoring, numerical modelling
Mining induced seismicity generally appears in form of spatio-temporal clusters in the vicinity of the newly excavated volumes. It results from fracturing of the rock-mass and/or shearing on pre-existing fractures. These processes are widely related to the frictional behavior of the rock-mass. When the amount of released elastic energy is sufficient, it can lead to larger events, called rockbursts, which represent one of the major cause of injuries and fatalities in deep mines. These disastrous events are still not well understood; thus their prevention is challenging. Recent investigations on repeating seismic events have shown that short and long-term post-blast aseismic rock behaviors can trigger seismicity on locked asperities. Those asperities appear to be repetitively loaded by the surrounding creeping rock mass. Further investigations and quantification of the coupled seismic and aseismic slip phenomena may provide new perspectives for rethinking and improving standard procedures in seismic-rock burst hazard assessment, geomechanical modelling and seismic monitoring in deep hard-rock mines. Concretely, future quantitative monitoring and modelling of both seismic and aseismic rock mass responses to mining have the potential to predict nucleation processes of larger dynamic ruptures associated with rock burst occurrence.
Objective of the PhD
The scientific objective of the PhD thesis is to quantify aseismic and seismic rock mass response to stope excavation in the Garpenberg mine in Sweden, currently exploited by the New Boliden company, with the sublevel stoping method. At a first, it is aimed at understanding and determining the nature of seismic asperities related to the occurrences of seismic repeaters, considering local geological observations (structural geology) and detailed seismic and geotechnical monitoring. Secondly, this thesis aims at investigating in detail the mechanical coupling between creep and seismic ruptures by combining observations from in-situ monitoring and geomechanical numerical modelling. Results from this analysis will be discussed at the scale of the whole mine and other mines to seek for future innovative monitoring and rock burst hazard assessment.
Profile of the PhD candidate
Master in Applied geosciences/Geophysics/Physics/Rock mechanics/Mining engineering.
The candidate should have good knowledge of both seismology and geomechanics, good programming and signal processing skills, as well as a good level of English.
He/she will work in Nancy, France, at the Georessources - Ineris joint lab. Field investigations at the Garpenberg mine will also be planned.
How to apply
- De Santis, F. (2019). Rock-mass mechanical behavior in deep mines: in situ monitoring and numerical modelling for improving seismic hazard assessment. PhD thesis, Lorraine University.
- De Santis, F., Contrucci, I., Kinscher, J., Bernard, P., Renaud, V., & Gunzburger, Y. (2019). Impact of Geological Heterogeneities on Induced-Seismicity in a Deep Sublevel Stoping Mine. Pure and Applied Geophysics, 176(2), 697-717.
- Hauquin T., Gunzburger Y., Deck O. (2018) Predicting pillar burst by an explicit modelling of kinetic energy. Int. J. of Rock Mechanics and Mining Sciences, 107, 159-171 (doi: 10.1016/j.ijrmms.2018.05.004).
- Naoi, M., Nakatani, M., Otsuki, K., Yabe, Y., Kgarume, T., Murakami, O., ... & Kawakata, H. (2015). Steady activity of microfractures on geological faults loaded by mining stress. Tectonophysics, 649, 100-114.
- Naoi, M., Nakatani, M., Igarashi, T., Otsuki, K., Yabe, Y., Kgarume, T., et al. (2015). Unexpectedly frequent occurrence of very small repeating earthquakes (- 5.1 B Mw B - 3.6) in a South African gold mine: Implications for monitoring intraplate faults. Journal of Geophysical Research: Solid Earth, 120, 8478-8493.