Experimental investigation of the new JRC2D values for the ten typical roughness joint profiles in two directions and their potential applications

The ten typical roughness joint profiles are widely used for quantitatively evaluating rock joint roughness. However, the joint roughness coeffi-cient (JRC) for these two-dimensional (2D) profiles (abbreviated as JRC2D) is represented as a range rather than a fixed value, complicating the es-tablishment of fitting relationships with roughness indicators considering the shear direction. This paper presents a method for determining the JRC2D values of joint profiles in two shear directions. First, the joint profiles were accurately digitized, and joint specimens were made by mortar using templates produced through three-dimensional (3D) printing. Direct shear tests were then conducted on the joint specimens under two shear directions and four normal stresses. Using the JRC-JCS model, the JRC2D values of the ten typical roughness joint profiles in both directions were back-calculated from experimental data. The differences and rankings of the new and traditional JRC2D values were evaluated. Next, the fitting relationships between six roughness indicators and the new JRC2D values were explored for six sampling intervals. Finally, these roughness indi-cators and their functional relationships with the new JRC2D values were used to quantitatively assess the roughness distribution characteristics of four natural rock joint surfaces based on 3D scanning. The results suggest that the use of JRC2D values to evaluate the roughness distribution of 3D joint surfaces is promising and warrants further attention.