Estimation of the joint roughness coefficient (JRC) of rock joints by vector similarity measures

Accurate determination of joint roughness coefficient (JRC) of rock joints is essential for evaluating the influence of surface roughness on the shear behavior of rock joints. The JRC values of rock joints are typically measured by visual comparison against Barton’s standard JRC profiles. However, its accuracy is strongly affected by personal bias. In the present study, a new comparison method is proposed for JRC evaluation to overcome the drawback of conventional visual comparison methods based on vector similarity measures (VSMs). The feature vectors are obtained by analyzing the angular variation of line segments of both standard JRC profiles and test profiles obtained from three kinds of natural rocks with a sampling interval of 0.5 mm. The roughness similarity degrees between test profiles and standard profiles are evaluated by the Jaccard, Dice, and cosine similarity measures. The JRC values of the test profiles are then determined according to the maximum relation index based on the similarity degrees. In the present study, a comparative analysis between the VSMs method and the JRC evaluation method using different roughness parameters demonstrated that the VSMs method is effective and accurate for JRC measurement.