On the evaluation of JRC effect on the shear strength of rock joints: reverse modelling of rock joints using a geostatistical semivariogram model and 3D printing

ABSTRACT: Barton’s criterion assumes that the rock joints with the same JRCs tested under the same conditions (same normal loading, same shear loading rate, etc.) have to result in the same shear strength. This paper aims at challenging this assumption. Reverse modeling of natural rock joints was applied to randomly generate the joint profiles with given JRCs (JRC 5 and 19) based on a previously developed statistical model. Then, a 3D printer was used to manufacture physical molds based on the morphology of generated joint profiles for casting mortar. Finally, direct shear tests were conducted in the lab on the cast mortar joint specimens with various surface morphologies. The experimental results indicated that the joint profiles with almost the same JRC values, but with different surface morphologies, lead to different shear strengths. It is concluded that the JRC might not appropriately represent the shear strength of rock joints, even for joints with the same properties.