ABSTRACT
This paper presents a new approach for quantitatively incorporating variability of rock mass conditions in assessments of Geological Strength Index (GSI) within the generalised Hoek-Brown strength criterion (Hoek et al., 2002). This paper presents a fully quantitative relationship to calculate GSI using the Rock Quality Designation (RQD) rating to characterise block volume and the Barton-Bandis joint shear strength parameters to define discontinuity surface condition. All of the parameters proposed in the new relation may be objectively measured using simple index tests, and so uncertainty in their characterisation defined probabilistically.
