Estimating the joint roughness coefficient of discontinuities found in metamorphic rocks

The paper presents the results of different methods of determining the roughness of joints in quartzites, metagreywackes and phyllites obtained from road cuts in central Portugal. The evaluation of the joint roughness coefficient (JRC) was carried out using graphical and analytical procedures. Differences were found between the JRC graphic and the JRC calculated, depending on the method used. The JRC calculated values obtained by the tilt tests and the Schmidt rebound hammer tests were compared to the JRC calculated values established from the rock joint shear tests. It is concluded that if JRC is to be used, it is essential to specify how it was established.