Study on reasonable sampling interval and range of compressional-torsional structural plane based on undulation angle characteristic parameters

Structural planes within rock masses often control their stability. Characterizing the morphology of structural planes with characteristic parameters and developing shear-strength models for those planes are widely used approaches that play a critical role in stability assessment and reinforcement design. The characterization effect of characteristic parameters is controlled by the sampling interval and range. This study focuses on the compressional-torsional structural planes controlling the stability of high rock slopes in the Zhongyuntai mountain cutting high rock slope in Lianyungang City, Jiangsu Province, China. Surface morphology data of the discontinuities were collected using 3D laser scanning technology to determining the optimal minimum sampling interval and range for 2D and 3D undulation angle feature parameters to enhance the accuracy of roughness characterization. The findings indicate: (1) A sampling interval of less than 1.0 mm is recommended for assessing the roughness of compressional-torsional structure surfaces using undulation angle parameters. (2) The stability of a single sampling line in characterizing the roughness of the entire structure surface using 2D undulation angle parameters is difficult to be stable with the change of sampling range. Using the mean value for characterization exhibit higher stability, and the sampling range should be no less than 500 mm. (3) The 3D undulation angle feature parameters exhibit higher stability across different sampling ranges, suggesting a sampling range exceeding 500 mm, with an optimal range surpassing 700 mm.