Abstract: Obtaining the 3D profile of the rock joint in the field is crucial for slope stability evaluation. Constrained by the high usage costs, cumbersome operational procedures, and stringent requirements for measurement subjects, precision equipment such as 3D laser scanners are difficult to widely apply to engineering sites. The paper proposes a method to obtain the 3D roughness of rock joint based on the profile measurement. The shear characteristics of rock joint are assessed using Tatone's peak shear model. The goal is to determine a suitable profile interval for reconstructing the rock joint, ensuring that the relative error of the peak shear strength between the reconstructed and original rock joint is less than 5%. Then, two-dimensional profile measurement of the rock joint is obtained by using a mechanical hand proflograph. The coordinate data for each profile measurement is extracted by considering the relationship between the size of the image digitization matrix and the actual length. The existing data is subjected to spatial interpolation using the Griddata function to generate a reconstructed three-dimensional rock joint, facilitating the study of relevant roughness. According to both the theoretical analysis and the direct shear test, the relative error of the peak shear strength of the two rock joint is less than 5%, which meets the requirements of engineering applications. The study shows that the method can accurately obtain the three-dimensional roughness of the rock joint and has the advantages of simple operation, low cost and low influence by the measurement environment, which provides a reference for related rock joint roughness analysis and shear strength research.

Key words: 3D reconstruction, profile measurement, profile interval, spatial interpolation