Paper contribution

GEOTECHNICAL RISK RANKING MATRICES

Justin Dixon; Trevor G. Carter; Phil J.H. deGraaf; Hazim Abu-Taleb

Proceedings
EUROCK 2026
Pages
187-193
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

Risk assessments for examining problematic geotechnical aspects of major projects have become increasingly popular over the last several decades. Trends in international tunnel contracts to require Risk Registers and Geotechnical Baseline Reports has spurred much of this interest. Environmental risks and public perception issues have driven development in the Mining industry, but still there remains a challenge assessing geotechnical risk. While quantitative assessment has become more sophisticated, inevitably synthesis is needed, still demonstrating credibility. Simplification, based on well-reasoned argument, is required for decision making, but still with quantitative back-up. AI has potential to facilitate simplification advances, by handling ever-increasing volumes of data. In the right circumstances AI will help more informed assessment, but can be completely misleading if used incorrectly. Classically, even the most complex QRA’s have needed to be boiled down to plot on a 5x5 “likelihood versus consequence” matrix. Mostly these are formulated with rankings for financial, project, operational or fatality risk. Incorporating geotechnical ground condition risk is often complex. The recently introduced 3D 5x5x5 matrix diagram, initially developed for open pit closure (Hawley et al., 2024, Carter et al., 2022) paves the way for a different approach for ranking geotechnical risk in an equal way as other drivers. In the 3D 5x5 matrix, one axis is ground condition risk, which can be stability PoF/FoS for infrastructure components (foundations, tunnel linings etc.,) or mechanisms (hydrofracture, overstress) or any other aspect of geotechnical significance. This scale partly addresses likelihood, along with the design confidence axis, which addresses design uncertainty, as well as data sparsity/imprecision, so together on one side of the block diagram give insight in a classic 5x5 matrix format. This paper presents the methodology and approaches for utilizing the 3D diagram to improve understanding and allow better decision-making when undertaking risk assessments for any geotechnically impacted project.

Contributors

Authors

  1. Justin Dixon Fortesque Pty, Australia
  2. Trevor G. Carter TGC-Geo-Solutions, Canada ORCID 0000-0001-6746-959X
  3. Phil J.H. deGraaf Giraffe Mining Pty, Australia
  4. Hazim Abu-Taleb Fortesque Pty, Australia

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References

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