Alternative Method for Assessing the Roughness Coefficients of Rock Joints

Abstract

The roughness of rock joints is a relevant factor considerably influencing the shear strength of rock masses, which is critical for the mechanical stability of large civil engineering structures. One of the geotechnical methods for determining the roughness coefficients of rock joints is on the basis of the visual comparison of the joint surfaces with the standard two-dimensional profiles whose roughness coefficients are known. Visual comparison is rather a subjective method, but it may be improved by a fully computerized image recognition procedure, and the two-dimensional standard profiles may be replaced by three-dimensional database profiles. To attain a higher stage of objectivity, a new alternative method was proposed on the basis of the application of Fourier’s formalism to three-dimensional surface profiles. The image database recognition was facilitated by introducing two parameters that were defined as height and shape indicators of surface reliefs.