Rock Mass Classification and Support Design using the Q-System

Abstract

The Q-system was developed at NGI between 1971 and 1974 (Barton et al. 1974). Since the introduction of the Q-system in 1974 there has been a considerable development within support philosophy and technology in underground excavations. Several new types of rock bolts have been introduced, and the continuous development of fi bre reinforced technology has in many ways changed the support procedure. Application of sprayed concrete has gained acceptance even for good quality rock masses due to demands for a higher level of safety during the recent years. Reinforced ribs of sprayed concrete have replaced cast concrete structures to a large extent. Since the introduction of the system in 1974, two revisions of the support chart have been carried out and published in conference proceedings. An extensive updating in 1993 was based on 1050 examples mainly from Norwegian underground excavations (Grimstad and Barton, 1993). In 2002, an updating was made based on more than 900 new examples from underground excavations in Norway, Switzerland and India. This update also included analytical research with respect to the thickness, spacing and reinforcement of reinforced ribs of sprayed concrete (RRS) as a function of the load and the rock mass quality (Grimstad et al. 2002). In this handbook, the guidelines for RRS in the support chart have been updated. The RRS- guidelines are simpli fi ed with regards to recent case histories in Norway