Q-slope

Q-slope is an empirical method for assessing the stability of rock slopes (slope stability).

The Q-slope method provides a simple yet effective empirical means of assessing the stability of excavated rock slopes in the field. Intended for use in reinforcement-free road or rail cuttings or individual benches in open cast mines, Q-slope allows geotechnical engineers to make potential adjustments to slope angles as rock mass conditions become apparent during construction. Through case studies in South-East 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 40-45º, 60-65º and 80-85º 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, Jn, Ja & Jr) remain unchanged in Q-slope. A new method of Jr/Ja ratios for both sides of potential wedges, using relative orientation weightings is presented. The term Jw, which is now termed Jwice, takes into account long-term exposure to various climatic and environmental conditions (e.g. intense erosive rainfall, 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.

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