Investigation of roughness algorithms applied to JRC profiles for assessment of weathering

Although JRC profiles are commonly used for shear strength assessment of rock joints, they can also serve as a base model for weathering assessment. In this study, JRC profiles were characterized using eight promising roughness algorithms from diverse fields such as geomorphology, rock mechanics and signal processing. Roughness indices of digitized JRC profiles were assessed at three different sampling intervals to observe how scale impacts their correlation with JRC. Plots of JRC versus roughness indices exhibit one of two general shapes: either a generally (but sometimes monotonically increasing) curve with occasional small peaks at JRC 6-8 and JRC 12-14 or a bimodal shape that peaks consistently at JRC 10-12 and JRC 14-16 followed by a sudden drop in roughness. Z₂ and Mean Absolute Angle show the highest linearity of the eight algorithms. Z₂ has been used numerous times to assess JRC profiles but Mean Absolute Angle is a new and promising roughness algorithm. Standard Deviation (σ) and Signal Energy (E_s) demonstrate remarkable consistency between sampling intervals but their relative non-linearity with JRC suggests they are insufficient in quantifying roughness. A new JRC relationship, based on Z₂ and intercept of the log-log plot of Z₂ versus sampling interval, is presented.