A model for estimating the peak shear strength of rock joints based on 3D quantified surface description

In order to further study the relationship between the characteristics of three-dimensional morphology and the peak shear strength of rock joints,the Brazilian splitting test was used to obtain the natural splitting joint surface, and the high-precision point cloud of the joint surface was obtained by 3D scanning technology. The 3D model of the natural joint surface was obtained by reverse modeling. Combining with the 3D printing technology, the PLA base mould,which is consistent with the natural joint surface, was made. The base mould obtained by 3D printing was poured with the natural joint surface through cement mortar. PLA mold and replica material are quite different,the rep- lica material is not easy to bond with PLA mold during solidification process,which makes the demoulding process more convenient and does not destroy the joint surface. The direct shear tests were carried out on 20 groups of cement mortar joints to obtain the peak shear strength. After shearing,the joint surfaces show some different degrees of wear, and the wear distributions are approximately consistent with the equivalent height difference distribution. Moreover,the wear is obvious in the location where the equivalent height difference distribution shows shear failure mode. Then,a new peak shear strength model for rock joints was proposed using the new roughness parameter which can reflect that the different geometric parameters of the asperities have different contributions to the shear strength. It is shown that the predicted peak shear strength is well consistent with the experimental data. A simplified model was proposed based on the new model. The calculation precision of the simplified model is lower than that of the new model,but the calcu- lation process is more convenient.