Surface roughness characterization of rock masses using the fractal dimension and variogram

There has been considerable research dealing with the influence of surface roughness along rock joint surfaces in relation to the peak shear strength of rock masses. Concepts accepted recently for measuring such strength included estimation of a roughness coefficient (JRC) such as developed by Barton's studies. The method for estimating the Joint Roughness Coefficient (JRC) value of a measured roughness profile is subjective. The aim of this research is to estimate the JRC value of the roughness of a surface profile in a rock mass system using an objective method. This study of roughness of surfaces has included measurement of fractal geometric characteristics. Once the irregularity of the surface has been described by the fractal dimension, the spatial variation of the surface irregularities can be described using variogram and drift analysis. An empirical relationship between the roughness profiles of selected JRC range and their fractal dimension with variogram and drift was derived. The new criterion for analyzing the JRC value was checked using an independent set of data. The application of analyses of fractal dimension and variogram and drift were novel for the analysis of roughness profiles. Also, an empirical equation was applied to experimental data and field data.