Quantitative characterization of joint roughness based on semivariogram parameters

The joint roughness coefficient (JRC) is an index defined by geometrical characteristics and correlated to mechanical shear strength. It is empirical and subjective to evaluate JRC by visual comparison. The existing quantitative evaluations of joint roughness are based on statistical parameters (i.e., the root mean square Z2, the structure function SF, and the textural parameter RP), which fail to describe the spatial variability of joint profiles. This paper presents a novel roughness descriptor, semivariogram parameter CA, to quantify roughness characteristics. Based on the theory of geostatistics, a semivariogram function is established. Furthermore, a Gaussian fitting model is applied to obtain the semivariogram parameter CA and its empirical equation, which can be used to evaluate the joint roughness coefficient. Finally, to verify the feasibility of this method, a comparison has been conducted between statistical parameters and the semivariogram parameter for the analysis of Barton's ten standard JRC profiles and 102 additional rock joint profiles.