Novel approaches for the evaluation of the roughness of discontinuities and failure surfaces in landslides and rock slopes

The evaluation of surface roughness has several important applications in the field of engineering geology. Discontinuities, such as joints and faults, control the stability of potentially unstable rock mass volumes at various scales. At the outcrop- and bench-scale, surface asperities contribute to the shear strength of discontinuities, angle of friction and apparent cohesion defining the stability of discontinuity-bounded blocks. At the slope scale, the roughness waviness of basal and lateral release surfaces has a significant impact on both the overall stability and the kinematics of rockslides. On the surface of large landslides, spatial variations in morphological roughness represent subsurface changes in orientation of the basal surface. The importance of geological surface roughness has long been recognized; however, the methods routinely used for its evaluation still employ fixed orientation, and two-dimensional approaches. Field-based assessments are not fully exploiting high-resolution three-dimensional datasets collected through remote sensing methods. In this work, we demonstrate the application of a suite of innovative digital tools developed to allow the characterization of surface roughness across different spatial scales, using datasets from both internationally renowned landslides and typical rock slopes. The proposed algorithms provide a detailed roughness analysis of discontinuity and topographic surfaces that can be applied both at the outcrop scale and the landslide scale. As numerical modelling and 3D remote sensing become standard in engineering geology, high-resolution characterization of surface roughness at multiple spatial scales will become increasingly important. This work lays the foundation for the enhanced fidelity of complex numerical modelling and improved methodologies for risk assessment and slope stability analysis.