The Hoek–Brown failure criterion and GSI – 2018 edition

TLDR

The Hoek–Brown criterion, introduced in 1980, estimates rock mass behaviour by incorporating intact rock and discontinuities such as joints, characterized by the geological strength index (GSI), and is widely used in underground excavation design, though its applicability limits and input data inaccuracies remain debated. The study aims to introduce minor revisions to the Hoek–Brown criterion, address utilization issues, and illustrate its practical application through case histories. The authors analyze the criterion’s limitations and apply it to multiple case studies to showcase its use in real‑world projects. The case studies confirm that the updated criterion effectively predicts rock mass behaviour in diverse tunnel, slope, and foundation projects.

Abstract

The Hoek–Brown criterion was introduced in 1980 to provide input for the design of underground excavations in rock. The criterion now incorporates both intact rock and discontinuities, such as joints, characterized by the geological strength index (GSI), into a system designed to estimate the mechanical behaviour of typical rock masses encountered in tunnels, slopes and foundations. The strength and deformation properties of intact rock, derived from laboratory tests, are reduced based on the properties of discontinuities in the rock mass. The nonlinear Hoek–Brown criterion for rock masses is widely accepted and has been applied in many projects around the world. While, in general, it has been found to provide satisfactory estimates, there are several questions on the limits of its applicability and on the inaccuracies related to the quality of the input data. This paper introduces relatively few fundamental changes, but it does discuss many of the issues of utilization and presents case histories to demonstrate practical applications of the criterion and the GSI system.