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Assessment of induced seismic hazard and excavation damage in deep underground mines
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mining is a continuous process of extracting valuable minerals from the earth. It is an important part of human society and development that we cannot live without.  Although, it requires an extensive amount of resources, underground mining is comparatively faster and more environmental feasible over surface mining.

However, there are some major challenges involved when mining underground. As underground mining advances to greater depths, the stresses in the rock mass increase, and consequently the level of induced seismicity and damage to excavations usually increases as well. This poses a hazard to the mine personnel and infrastructure that in worst-case scenarios could lead to fatality, revocation of mining rights and temporally or permanent closure of the mine. Therefore, mining at greater depths has become a major operational issue and a challenging planning factor for most underground mines worldwide, especially at depths greater than 900–1000 m.

As a result, there is a great need to explore and gain an understanding of excavation damage associated with seismic events phenomenon in deep underground mines. The occurrence, mechanisms and magnitude at a given site could provide great insights of associated influencing factors and design parameters significant for rock mechanics seismic hazard assessment.

The performed study incorporates four components: firstly, seismic hazard tools (evaluation of seismic hazard tools currently used in deep underground mines), secondly, seismic source (which focuses on an evaluation of seismic event sources associated with excavation damage), thirdly, excavation damage resulting from seismic loading (detailed study of the characteristics of the damage, and correlation with the local geological structures, rock mechanical parameters and local stresses) and fourth, correlation between the seismic event source and excavation damage parameters.

Methods of data collection such as forensic investigation of excavation damage associated with seismic events and a study of old mine damage reports were used to gather required detailed information. Qualitatively and quantitatively analysis was done on gathered information to: evaluate the nature and parameters  of seismic event  sources that potentially caused excavation damage, assess the merit and performance rate of short-term seismic hazards in mines, evaluate excavation damage characteristics, mechanisms as well as severity parameters and finally deduce the relationships between sources of seismic event and excavation damage.

A rock mechanic seismic damage hazard methodology was developed to serve as a main guideline for forensic investigation of excavation damage in seismically active mines, ensure a consistent collection of important data/information by different project team members in mines and to provide guidelines of different types analyses that can be applied on data collected. This is important information that can be obtained and serve as initial stage of integrating different areas of expertise to find complex relationships between seismic sources and excavation damage.   Detailed outcome of the study is presented further in the thesis.

Place, publisher, year, edition, pages
Luleå University of Technology, 2020.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-76671ISBN: 978-91-7790-498-4 (print)ISBN: 978-91-7790-499-1 (electronic)OAI: oai:DiVA.org:ltu-76671DiVA, id: diva2:1369057
Public defence
2020-01-24, F1031, Luleå University of Technology, F-Huset, LULEÅ, 10:00 (English)
Opponent
Supervisors
Available from: 2019-11-11 Created: 2019-11-11 Last updated: 2019-11-25Bibliographically approved
List of papers
1. Source parameters of seismic events potentially associated with damage in block 33/34 of the Kiirunavaara mine (Sweden)
Open this publication in new window or tab >>Source parameters of seismic events potentially associated with damage in block 33/34 of the Kiirunavaara mine (Sweden)
2017 (English)In: Acta Geophysica, ISSN 1895-6572, E-ISSN 1895-7455, Vol. 65, no 6, p. 1229-1242Article in journal (Refereed) Published
Abstract [en]

Forty-six mining-induced seismic events with moment magnitude between −1.2 and 2.1 that possibly caused damage were studied. The events occurred between 2008 and 2013 at mining level 850–1350 m in the Kiirunavaara Mine (Sweden). Hypocenter locations were refined using from 6 to 130 sensors at distances of up to 1400 m. The source parameters of the events were re-estimated using spectral analysis with a standard Brune model (slope −2). The radiated energy for the studied events varied from 4.7 × 10−1 to 3.8 × 107 J, the source radii from 4 to 110 m, the apparent stress from 6.2 × 102 to 1.1 × 106 Pa, energy ratio (Es/Ep) from 1.2 to 126, and apparent volume from 1.8 × 103 to 1.1 × 107 m3. 90% of the events were located in the footwall, close to the ore contact. The events were classified as shear/fault slip (FS) or non-shear (NS) based on the Es/Ep ratio (>10 or <10). Out of 46 events 15 events were classified as NS located almost in the whole range between 840 and 1360 m, including many events below the production. The rest 31 FS events were concentrated mostly around the production levels and slightly below them. The relationships between some source parameters and seismic moment/moment magnitude showed dependence on the type of the source mechanism. The energy and the apparent stress were found to be three times larger for FS events than for NS events.

Place, publisher, year, edition, pages
Springer, 2017
Keywords
Mining-induced seismic events, Source parameters, Hypocentre locations, Shear and non-shear mechanisms
National Category
Natural Sciences Engineering and Technology Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-66726 (URN)10.1007/s11600-017-0066-1 (DOI)000418097100012 ()
Funder
VINNOVA
Note

Validerad;2018;Nivå 2;2017-12-21 (andbra)

Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2019-11-11Bibliographically approved
2. Back Analysis of Short-Term Seismic Hazard Indicators of Larger Seismic Events in Deep Underground Mines (LKAB, Kiirunavaara Mine, Sweden)
Open this publication in new window or tab >>Back Analysis of Short-Term Seismic Hazard Indicators of Larger Seismic Events in Deep Underground Mines (LKAB, Kiirunavaara Mine, Sweden)
2019 (English)In: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136Article in journal (Refereed) Epub ahead of print
Abstract [en]

Back analysis for evaluation of the merits of the short-term seismic hazard indicators (precursors) used in the mines and their potential application for early warning was carried out for fourteen seismic events that potentially caused damage in Kiirunavaara Mine, Sweden, selected according to our designed criteria. Five short-term hazard indicators: Seismic Activity Rate (SAR), Cumulative Seismic Moment (CSM), Energy Index (EI), Cumulative Apparent Volume (CAV) and Seismic Apparent Stress Frequency (ASF) were tested. The behaviour of the indicators was studied using the parameters of all seismic events within a sphere around the hypocenter location of the analyzed seismic source within one month before the main (damaging) event. The size of the sphere equals the estimated radius of the analyzed seismic source (area of inelastic deformation). mXrap software (Australian Centre for Geomechanics) was used for data visualization, manipulation, analysis and extraction. The results from the main analysis showed a good agreement between the expected and actual behaviour of the SAR, CSM and CAV indicators. In overall, CSM and CAV ranked the highest positive/expected behaviour followed by SAR (Table 3). The EI and ASF ranked lowest and showed to be sensitive to the number of events within the source sphere. The rate of false warnings and missed warnings was also investigated for the 25 days-long period before the damaging events. A similar trend was observed as for the main analysed event. The results from this study can be used for further improvement of the short-term hazard estimations and early warning system in deep underground mines.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Induced seismicity in mines, seismic hazards, rockbursts, mine seismology
National Category
Other Engineering and Technologies not elsewhere specified Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-76653 (URN)10.1007/s00024-019-02352-8 (DOI)
Available from: 2019-11-10 Created: 2019-11-10 Last updated: 2019-11-11
3. Qualitative and quantitative analysis of damages caused by seismic events in Kiirunavaara mine, Sweden
Open this publication in new window or tab >>Qualitative and quantitative analysis of damages caused by seismic events in Kiirunavaara mine, Sweden
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:ltu:diva-76667 (URN)
Available from: 2019-11-10 Created: 2019-11-10 Last updated: 2019-11-11
4. Analysis of the rock mass support damages for seismic damaging events in Kiirunavaara mine
Open this publication in new window or tab >>Analysis of the rock mass support damages for seismic damaging events in Kiirunavaara mine
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:ltu:diva-76669 (URN)
Available from: 2019-11-10 Created: 2019-11-10 Last updated: 2019-11-11
5. A methodology for a rock mechanic seismic damage hazard analysis in seismically active mines
Open this publication in new window or tab >>A methodology for a rock mechanic seismic damage hazard analysis in seismically active mines
(English)Manuscript (preprint) (Other academic)
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:ltu:diva-76670 (URN)
Available from: 2019-11-10 Created: 2019-11-10 Last updated: 2019-11-11

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