A second update of the Q system for rock mass classification is underway following the first, 10 years ago in 1993 by Grimstad and Barton. The changes are laid out by Grimstad, Bhasin, Wold Hagen, Kaynia, and Kankes. Emphasis is placed on the wide application of fibre reinforced sprayed concrete, even in the lowest rock mass qualities, and the recent changes in rock support practice and material properties. In extremely poor rock, where some deformation may be expected, the toughness and energy absorption of the sprayed concrete has been taken into consideration in the improved Q-support chart.
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