Paper contribution

Reliability Limits of Rock Mass Classifications and a Zonal Approach for Reducing Design Risk

Milan Tumara; Milutin Petrović

Proceedings
EUROCK 2026
Pages
163-168
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

Rock mass classification systems such as RMR, Q, and GSI have become indispensable tools in rock mechanics yet their empirical correlations are often applied with more confidence than warranted. These systems were developed for different purposes and rely on distinct input parameters, making value conversions between them frequently inadequate, as they fail to fully capture the complexity of actual geological conditions—especially in heterogeneous or tectonized rock masses. This paper addresses the reliability limits of such approaches and introduces a practical method for reducing interpretative uncertainty through zoning of the rock mass based on the comparative application of multiple classification systems. The method compares classification results across intervals, identifies zones of agreement and divergence, and defines geotechnical domains through rule-based zoning. This approach enables the identification and delineation of quasi-homogeneous geotechnical domains with similar engineering-geological and geotechnical characteristics, providing a more reliable basis for the assessment of deformability across different parts of a structure. The method supports subsequent zoning tailored to excavation and support design and contributes to improved decision-making in complex geological environments such as deep mine shafts and dams.

Contributors

Authors

  1. Milan Tumara ENERGOPROJEKT-HIDROINŽENJERING, Serbia ORCID 0009-0003-9488-1952
  2. Milutin Petrović HIDROENERGO MVB, Serbia

Index terms

Keywords

Full text

Attachments

Works cited

References

  1. Baecher GB, Christian JT (2003) Reliability and statistics in geotechnical engineering. Wiley
  2. Bieniawski ZT (1989) Engineering rock mass classifications. Wiley, New York
  3. Bieniawski ZT (1992) Design methodology in rock engineering. Balkema, Rotterdam
  4. Barton N, Lien R, Lunde J (1974) Engineering classification of rock masses for the design of tunnel support. Rock Mechanics 6(4): 189–236
  5. Hoek E, Diederichs MS (2006) Empirical estimation of rock mass modulus. International Journal of Rock Mechanics and Mining Sciences 43(2): 203–215
  6. Jovanovski M (2005) Some data about rock mass rating for the rock masses from the Republic of Macedonia
  7. Laubscher DH (1990) A geomechanics classification system for the rating of rock mass in mine design. Journal of the South African Institute of Mining and Metallurgy 90(10): 257–273
  8. Marinos P, Hoek E (2000) GSI – a geologically friendly tool for rock mass strength. Proceedings of GeoEng 2000 International Conference on Geotechnical and Geological Engineering, Melbourne, pp. 1422–1440
  9. Savić D, Tumara M, Petrović M (2021) Importance of geotechnical investigation for design and construction of shafts over 1000 m deep. World Journal of Engineering and Technology 9: 250–267. https://doi.org/10.4236/wjet.2021.92018
  10. Serafim JL, Pereira JP (1983) Considerations on the geomechanical classification of Bieniawski. Proceedings of the International Symposium on Engineering Geology and Underground Construction, Lisbon
  11. Špago A et al. (2015) Correlation dependency between rock mass quality and mechanical properties in carbonate rock masses