Characterizing rock masses by the RMi for use in practical rock engineering .2. Some practical applications of the Rock Mass index (RMi)

The RMi system is based on defined inherent parameters of the rock mass and is obtained by combining the compressive strength of intact rock and a jointing parameter. The jointing parameter represents the main jointing features, namely block volume (or density of joints), joint roughness, joint alteration, and joint size. This paper discusses the following applications of RMi: a) an improved method to determine the constants s and m in the Hoek-Brown failure criterion for rock masses; b) quantification of the descriptive classification in. the new Austrian tunnelling method (NATM), and c) estimation of stability and rock support in underground openings. Rock support charts are presented for the three main groups of rock masses: discontinuous (jointed) rock masses, continuos (massive rock and highly jointed) rock masses, and weakness zones. Mathematical expressions have been developed for all applications, which allow the use of computers in the calculations. The applications of RMi in rock engineering arguably include a wider range of rock masses than arty of the classification systems currently in use.