Rock Mechanics and Rock Engineering

, Volume 50, Issue 12, pp 3307–3322 | Cite as

The Q-Slope Method for Rock Slope Engineering

  • Neil BarEmail author
  • Nick Barton
Original Paper


Q-slope is an empirical rock slope engineering method for assessing the stability of excavated rock slopes in the field. Intended for use in reinforcement-free road or railway cuttings or in opencast mines, Q-slope allows geotechnical engineers to make potential adjustments to slope angles as rock mass conditions become apparent during construction. Through case studies across Asia, Australia, Central America, and Europe, a simple correlation between Q-slope and long-term stable slopes was established. Q-slope is designed such that it suggests stable, maintenance-free bench-face slope angles of, for instance, 40°–45°, 60°–65°, and 80°–85° with respective Q-slope values of approximately 0.1, 1.0, and 10. Q-slope was developed by supplementing the Q-system which has been extensively used for characterizing rock exposures, drill-core, and tunnels under construction for the last 40 years. The Q′ parameters (RQD, J n, J a, and J r) remain unchanged in Q-slope. However, a new method for applying J r/J a ratios to both sides of potential wedges is used, with relative orientation weightings for each side. The term J w, which is now termed J wice, takes into account long-term exposure to various climatic and environmental conditions such as intense erosive rainfall and ice-wedging effects. Slope-relevant SRF categories for slope surface conditions, stress-strength ratios, and major discontinuities such as faults, weakness zones, or joint swarms have also been incorporated. This paper discusses the applicability of the Q-slope method to slopes ranging from less than 5 m to more than 250 m in height in both civil and mining engineering projects.


Q-slope Rock slope engineering Slope stability Rock mass classification Empirical method 

List of symbols


Rock quality designation


Joint sets number


Joint roughness number


Joint alteration number


Environmental and geological condition number


Three strength reduction factors a, b, and c


Physical condition number


Stress and strength number


Major discontinuity number


Orientation factor for the ratio J r/J a



The authors sincerely thank Cameron Ryan (Australia), Simon Thomas (Papua New Guinea), and Luis Jorda-Bordehore (Spain) for their case study contributions.


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Copyright information

© Springer-Verlag GmbH Austria 2017

Authors and Affiliations

  1. 1.Gecko Geotechnics Pty LtdMt SheridanAustralia
  2. 2.Nick Barton & AssociatesOsloNorway

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