## 1 Introduction
Currently, scholars have produced many innovations for the estimation of rock joint shear strength parameters, but the essence of these estimations is the optimization of data processing, which always does not consider the influence of the rough surface morphology on shear strength parameters and ignores the influence of that in different locations. However, for the problem of the estimation of shear strength, rock joint roughness is an important parameter. Methods for analyzing the data and carrying out quantitative evaluations for rock joints have been a focus of research in the field of rock mechanics. [PERSON] [24] established the classical JRC-JCS model by conducting a study of 300 natural rock joints, which established the basic paradigm of strength theory. As for the strength theory research path with respect to characterizing the roughness of rock joints to establish the friction angle, some scholars have carried out long-term research on this topic. In this case, they have achieved substantial progress and defined a range of roughness coefficients, among which are the most commonly used, such as the root mean square of slope \(Z_{2}\)[25], structural function SF [26], and profile line roughness coefficient \(R_{\rm p}\)[27]. In addition, from two-dimensional to three-dimensional, some scholars have defined three-dimensional roughness [28; 29; 30], which further promoted the development of strength theory. In contrast, the existing theories could not be unified. On the other hand, along with the accurate strength theory, the inapplicability of engineering and balancing accuracy is still an important issue. Considering the science and engineering applicability, the parameter estimation method is further refined and modified in this study. The generalized shear strength parameter is proposed, and the modified formula with full consideration of roughness is fitted. Shear strength can be accurately obtained by shear tests, and the International Society of Rock Mechanics has established the relevant standards for static and dynamic shear tests. Some scholars have further enriched the standards' applicability by improving testing machines and introducing different influencing factors into the shear test. However, for actual engineering needs, there are many limitations to obtaining the shear strength, especially for a rock joint, because its complex and variable surface morphology makes obtaining a global shear strength impossible using simple sampling tests. Therefore, the shear test is only used as a standard value to verify the correctness of other theories. To overcome the limitations of the shear test, simulation methods based on numerical computation have become a focus of research. Scholars have used different methods to simulate the shear test process so that the shear strength can be obtained with a large number of repetitions, and the particle flow method represented by PFC has achieved substantial progress in simulations [31; 32; 33; 34]. In this study, physical and numerical test on the direct shear is conducted. Relying on the bedding slope of an open-pit mine, the study of rock joint shear strength parameters is carried out, and the generalized shear strength parameter, internal friction angle, and cohesion are determined with different roughness. The influence of the roughness on the shear strength parameters is also summarized. The research results are applied to the slope stability analysis using GeoSMA-3D. As a result, it is meaningful to analyze the stability and optimize the slope again for the bedding slope using the generalized shear strength parameter.