Quantifying and mapping the heterogeneity of rock joint roughness and shear strength for rapid field assessment

Rock mass stability is significantly influenced by the heterogeneity of rock joint roughness and shear strength. While modern technology facilitates assessing roughness heterogeneity, evaluating shear strength heterogeneity remains challenging. To address this, this study first captures the morphology of large-scale (1000 mm × 1000 mm) slate and granite joints via 3D laser scanning. Analysis of these surfaces and corresponding push/pull tests on carved specimens revealed a potential correlation between the heterogeneity of roughness and shear strength. A comparative evaluation of five statistical metrics identified information entropy ( H s ) as the most robust indicator for quantifying rock joint heterogeneity. Further analysis using H s reveals that the heterogeneity is anisotropic and, critically, that shear strength heterogeneity is governed not only by roughness heterogeneity but is also significantly influenced by the mean roughness value, normal stress, and intact rock tensile strength. Consequently, a simple comparison of roughness H s values is insufficient for reliably comparing shear strength heterogeneity. To overcome this limitation, a theoretical framework is developed to explicitly map fundamental roughness statistics (mean and heterogeneity) to shear strength heterogeneity. This framework culminates in a practical workflow that allows for the rapid, field-based assessment of shear strength heterogeneity using readily obtainable rock joint roughness data.