## 1 Introduction  
The joints in engineering rock mass may undergo reciprocating shear dislocation under seismic or blasting loads, resulting in their wear and degradation and in the weakening of their mechanical properties. Therefore, the study of the damage accumulation and degradation mechanism of rock joints under reciprocating loads is significant. Over the past few decades, the cyclic loading protocol has been considered an effective method for studying the mechanical behavior of rock joints under dynamic loading. In terms of the research on the mechanical properties of joints under cyclic loading, the representative studies are those conducted by [PERSON] [1], [PERSON] [2], [PERSON] [3, 4], [PERSON] [5], [PERSON] [6], and [PERSON] [7]. Other similar studies [8, 9, 10, 11, 12, 13] have shown that the mechanical behavior of joints is related to the number of load cycles, joint asperity, and loading boundary conditions. The roughness and the shear strength of the joint plane have a stable relationship, so a quantitative relationship can be established between them. At present, the two-dimensional profile line methods used to describe rock surface morphology can be divided into the description of the morphology line height difference parameter, the description of the morphology line texture parameter, the description of the fractal effects, and the description of the JRC curve. The height difference parameter description of the morphology line is a parameter used to describe the variation in the morphology height distribution [14], including the average height of the center line \(Z_{0}\), the height root mean square \(Z_{1}\), and other indexes. The texture parameter description of the morphology lines is used to study the convex shape and other information about the surface [15], including the root mean square \(Z_{2}\) of the first derivative of the surface morphology and the root mean square \(Z_{3}\) of the second derivative of the surface morphology. [PERSON] [16] conducted direct shear tests on 136 joint plane samples and grouped them to obtain 10 standard JRC curves. The three-dimensionalroughness parameter can describe the surface morphologies of joints more accurately and reasonably. [PERSON] et al. (2017); [PERSON] et al. (2017) proposed five morphological parameters to describe the three-dimensional joint surface roughness, including the mean shear inclination angle of the joint surface \(\theta_{s}\), surface roughness coefficient R\({}_{s}\), anisotropy coefficient K\({}_{a}\), joint surface bending degree T\({}_{s}\), and morphology roughness degree \(\theta_{p+}\), \(\theta_{p-}\). [PERSON] (2018); [PERSON] (2018) found that only the joint elements with positive slope angles in the shear direction contributed to the shear strength. [PERSON] (2018); [PERSON] (2018) also found, for the first time, that the rock joints' three-dimensional morphologic parameters were related to the shear strength, and the parameters \(A_{0}\) (the maximum possible contact area) and \(\theta_{max}^{*}\) (the maximum apparent dip angle in the shear direction) were proposed. [PERSON] (2018) introduced the average roughness degree \(\theta_{s}\) calculated based on triangular networks to characterize three-dimensional joint surfaces. This parameter can reflect the spatial and anisotropic characteristics of joint surfaces. Based on [PERSON]'s three-dimensional morphology parameter theory, [PERSON] (2018) proposed a three-dimensional roughness parameter, \(A_{0}\theta_{max}^{*}/(C+1)\), in order to reasonably relate joint surface roughness to shear strength. Based on the development of 3D morphology measurement technology, a series of 3D roughness indices (Sen _et al._, 2018; Sen _et al._, 2018) have been developed based on 3D morphology data. The main purpose of this study was to quantitatively investigate the damage evolution and roughness degradation of joint surfaces under constant, normal load conditions. Cyclic shear tests were performed on specimens with artificial joints under different normal stress levels.