Paper contribution

Integrated Drone‑Based Stope Geometry Reconciliation and Stability Assessment at the Dannemora Mine

Xander Gwynn; Sophie Wilson; Michael Meyer; Carlos Carranza-Torres

Proceedings
EUROCK 2026
Pages
701-706
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

This paper describes an integrated approach that combines drone-based 3D stope surveys, updated geotechnical data, in‑situ stress measurements and numerical modelling to assess stope geometry, stress concentrations and backfill performance at the Dannemora underground iron ore mine. An initial study established a mine-wide geotechnical model; empirical assessments indicated that many existing and planned stopes plot outside the nominally “stable” zone of published stability charts, despite generally favourable historical stope performance. This discrepancy motivated the development of a mine‑scale FLAC3D model and acquisition of detailed drone-based 3D stope surveys to test the actual stability of the stopes and to verify backfill behaviour. The drone surveys demonstrate discrepancies between planned and achieved stope geometries, particularly in width and backfill surface elevation and confirm that tailings backfill occupies a substantial portion of the existing voids with little evidence of large-scale caving. These geometries were used to refine the numerical model and check consistency between modelled behaviour and observed stope performance. The integrated dataset shows that, although empirical methods place many stope walls outside nominal stability envelopes, numerical modelling and drone-based reconciliation indicate generally stable behaviour when supported by high rock mass quality, systematic backfilling and appropriate sequencing. The paper outlines implications for stope design and sequencing and how drone surveys can be integrated to provide ongoing stability verification and design refinement.

Contributors

Authors

  1. Xander Gwynn SLR Consulting, United Kingdom
  2. Sophie Wilson SLR Consulting, United Kingdom
  3. Michael Meyer Grangex AB, Sweden
  4. Carlos Carranza-Torres SLR Consulting, United Kingdom

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Works cited

References

  1. AMKVO AB (2023) Underground LiDAR and drone inspection services. Uppsala.
  2. Barton, N., Lien, R. and Lunde, J. (1974) ‘Engineering classification of rock masses for the design of tunnel support’, Rock Mechanics, 6, pp. 189–236.
  3. Bieniawski, Z.T. (1973) ‘Engineering classification of jointed rock masses’, Transactions of the South African Institution of Civil Engineers, 15, pp. 335–344.
  4. Capes, G. and Milne, D. (2008) ‘A compilation of dilution graph data for open stope hangingwall design’, in Potvin, Y. et al. (eds) First Southern Hemisphere International Rock Mechanics Symposium. Perth: Australian Centre for Geomechanics.
  5. Clark, L.M. and Pakalnis, R. (1997) ‘An empirical approach for estimating unplanned dilution from open stope hangingwalls and footwalls’, CIM Bulletin, 90, pp. 57–61.
  6. Holmgren, J. (2015) Induced seismicity in the Dannemora Mine, Sweden. MSc thesis. Uppsala: Uppsala University.
  7. Hoek, E., Carranza-Torres, C. and Corkum, B. (2002) ‘Hoek–Brown failure criterion – 2002 edition’, in Proceedings of the 5th North American Rock Mechanics Symposium. Toronto: University of Toronto, pp. 267–273.
  8. Itasca Consulting Group (2019) FLAC3D: Fast Lagrangian Analysis of Continua in 3 Dimensions. Version 7.0. Minneapolis, MN: Itasca Consulting Group Inc.
  9. NGI (Norwegian Geotechnical Institute) (2015) Using the Q-System: Rock Mass Classification and Support Design. Oslo: NGI.
  10. Potvin, Y. (1988) Empirical open stope design in Canada. PhD thesis. Vancouver: University of British Columbia.
  11. Schlofeldt, P. and Carter, T.G. (2018) ‘Improved estimation of GSI and rock mass strength using volumetric fracture intensity’, International Journal of Rock Mechanics and Mining Sciences, 110, pp. 48–67.
  12. SSAB (1982) Mining of Dannemora Mine, Sweden: SSAB.
  13. Stephansson, O., Søråkk, P. and Myrvang, A. (1986) ‘State of stress in Fennoscandia’, in International Symposium on Rock Stress. Stockholm.
  14. Stress Measurement Company Oy (2023) In-situ stress measurements at Dannemora Iron Mine. Report for Grängesberg Exploration Holding AB.
  15. Vattenfall Power Consultant AB (2009) Rock mass characterisation in the Dannemora Iron Ore Mine. Report for Dannemora Mineral AB.