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Rock Mass Rating System

The evaluation of rock mass in terms of engineering is a challenging task as it involves various parameters. In such cases, quantitative values from rock tests, and index tests are used for evaluation of the necessary parameters. Three classification systems proposed by researchers were well-received namely: Barton, Lien, and Lunde (1974), Bieniawski (1974, 1984), and Wickham, Tiedemann, and Skinner (1974). 

Out of these Bieniawski Geomechanics Classification System provides a general rock mass rating (RMR) system increasing with rock quality from 0 to 100. It is based upon five universal parameters namely: strength of the rock, drill core quality, groundwater conditions, joints and fracture spacing, and joint characteristics. Along with these, joint orientation is also considered for tunnelling, mining and foundation activities. The ratings for each of these parameters are presented in Tables below.

The increments were made accordingly for the respective rock mass for the evaluation of RMR. The RMR value thus obtained can be correlated with the table below to classify the quality of rock mass varying from very good rock to very poor rock.