A modified model for estimating peak shear displacement of artificial joints

The peak shear displacement (PSD) of artificial joints was studied by the shear test of cement mortar duplicate joints under constant normal load. First, the splitting rock joints were produced by the Brazilian splitting method, and the high-precision point cloud of joint surface morphology was acquired by three-dimensional (3D) scanning method. The polylactic acid (PLA) base mold was produced by 3D printing technology. The duplicate joints with the same joint surface as the splitting rock joints were obtained by pouring cement mortar on the PLA base mold. Then, shear tests of 20 cement mortar specimens with 5 groups of joint surface morphologies under 4 different normal loads were carried out, and the joint shear stress-displacement curves were obtained. The influencing factors of the PSD were studied. The results indicate that the PSD is inversely related to the joint roughness and positively related to the normal stress (NS). The limitation of Barton’s empirical formula is that it cannot predict (fit) the PSD of the joints with JRC = 0 and reflect the effect of NS on the PSD. To quantitatively study the PSD of joints, an empirical formula that can comprehensively consider the influence of surface roughness and NS is introduced based on the test results. The modified model overcomes the limitation of Barton’s empirical formula which ignored the NS and can well reflect the sensitivity of joint roughness coefficient (JRC) to PSD. The acquisition of PSD can provide a basis for the numerical simulation of rock engineering and provide quantitative research methods for the analysis of stick-slip events.