Paper contribution

What are the representative values for the mechanical properties of a rock joint?

Johan Spross; Fredrik Johansson; Ignacio Pérez-Rey

Proceedings
EUROCK 2026
Pages
769-774
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

The European design standard (code) for geotechnical structures – Eurocode 7 – has been updated in a second generation. The new code has a larger scope than the current code: the new code will also concern the safety of dams and levees, as well as rock engineering structures above ground. For many European countries, this will likely be a considerable change, as neither rock slopes nor dams until now have been designed using a European design code. In this context, there is a need to study how spatial variability in rock mass properties best is managed in the verification of limit states, i.e. determination of their representative values (formerly characteristic values). In this paper, we discuss specifically how representative values can be determined using statistical methods for relevant rock properties, like the friction coefficient of rock joints, for verification of the structural safety regarding sliding stability of dams founded on rock. As a basis for the investigations in the paper, we use data from laboratory direct shear tests on the peak shear strength of rock joints. The result illustrates the importance of having a sufficient number of samples and the need for a thorough understanding of the effect of the sampling location. We hope that this contribution will stimulate a broader discussion in the scientific rock engineering community on limit state verification of rock engineering structures, as there are currently very few studies on this issue.

Contributors

Authors

  1. Johan Spross KTH Royal Institute of Technology, Sweden ORCID 0000-0001-5372-7519
  2. Fredrik Johansson KTH Royal Institute of Technology, Sweden ORCID 0000-0002-8152-6092
  3. Ignacio Pérez-Rey CINTECX, Universidade de Vigo, Spain ORCID 0000-0003-0883-7211

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References

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