Determining the stress reduction factor in highly stressed jointed rock / Определение коэффициента снижения напряжений в высоконапряженных трещиноватых породах

A number of Australian underground mines are using empirical rating systems to characterize the ground conditions in developmental headings for geotechnical design. The two best-known rating systems are Barton’s Rock Tunnelling Quality Index (Q-System, also known as the NGI System) and Bieniawski’s Rock Mass Rating (RMR, also known as the Geomechanics Classification). As the RMR makes no allowance for high ground stresses at depth, Barton’s Q-System is more likely to be used in deep Australian underground mines. The Q-value is determined from equation 1 using the six parameters listed in table 1. The numerical value of Q ranges from 0.001 (exceptionally poor) to 1000 (exceptionally good) quality rock. <...>