This lecture was compiled from an audio tape of Professor Evert Hoek’s lecture on weak rock masses in 1990 at the University of Leeds, combined with his slides. The lecture was not prepared in paper form in the original proceedings although the discussion which can be heard, was (pp 223-225; Cripps et al., 1993). It is considered important as it sets out Professor Hoek’s philosophy about what makes a rock mass weak, and, in answer to a question from Dr John Sharp he presented an early version of the Hoek-Brown strength criterion which over time has morphed into the Geological Strength Index (GSI). As he stated, there wasn’t then (and still isn’t) any other tool which allows the strength of fractured, isotropic rock masses to be estimated.
Steve Hencher
Emeritus Professor
University of Leeds, UK.