Revisiting rock classification to estimate rock mass properties

This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation, spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index (GSI) and relationships to estimate the Hoek–Brown failure criterion parameters, mb, s and a, are presented.