Rock Mass Quality Rating (RMQR) System: Its Application to Estimation of Geomechanical Characteristics of Rock Masses and to Rock Support Selection for Underground Caverns and Tunnels

The authors proposed a new rock mass classification named as Rock Mass Quality Rating (RMQR), which consists of six main input parameters, quantifies the state of rock mass and helps to estimate geomechanical properties (UCS, cohesion, friction angle, deformation modulus, Poisson's ratio, tensile strength) of rock masses using a unified formula considering RMQR together with intrinsic geomechanical properties of intact rock. The comparisons of the empirical formula together with the values of constants were found to be quite consistent with the experimental results for data compiled from various rock engineering projects in Japan. Based on the databases of the authors, the application of the system was also extended to rock support selection for underground caverns and tunnels by considering the type of instability mode in relation to RMQR value. Some empirical relations, established between RMQR and dimensions of the elements of support systems, seem sufficient for many engineering applications and act as guidelines.