Abstract
Light detection and ranging (LiDAR) can quickly and accurately obtain 3D point clouds on the surface of rock masses, and on the basis of this, discontinuity information can be extracted automatically. This paper proposes a new method to automatically extract discontinuity information from 3D point clouds on the surface of rock masses. This method first applies the improved K-means algorithm based on the clustering algorithm by fast search and find of density peaks (DPCA) and the silhouette coefficient in the cluster validity index to identify the discontinuity sets of rock masses, and then uses the hierarchical density-based spatial clustering of applications with noise (HDBSCAN) algorithm to segment the discontinuity sets and to extract each discontinuity from a discontinuity set. Finally, the random sampling consistency (RANSAC) method is used to fit the discontinuities and to calculate their parameters. The 3D point clouds of the typical rock slope in the Rockbench repository is used to extract the discontinuity orientations using the new method, and these are compared with the results obtained from the classical approach and the previous automatic methods. The results show that, compared to the results obtained by Riquelme et al. in 2014, the average deviation of the dip direction and dip angle is reduced by 26% and 8%, respectively; compared to the results obtained by Chen et al. in 2016, the average deviation of the dip direction and dip angle is reduced by 39% and 40%, respectively. The method is also applied to an artificial quarry slope, and the average deviation of the dip direction and dip angle is 5.3° and 4.8°, respectively, as compared to the manual method. Furthermore, the related parameters are analyzed. The study shows that the new method is reliable, has a higher precision when identifying rock mass discontinuities, and can be applied to practical engineering.
Highlights
Rock mass discontinuities refer to planar geological interfaces with a certain direction, large extension, and small thickness, and are mainly generated in rock mass under the action of tectonic stress
3, the average silhouette coefficient was the largest, so the artithat, average silhouette silhouettecoefficient coefficientwas wasthe the largest, artithat,when whenk kwas wasequal equalto to 3, 3, the the average largest, soso thethe artificial ficial quarry slope could be divided into three discontinuity sets
Illustrated by the case of the typical rock slope, we clarified in detail how to identify the main potential directions of DPCA, determine the number of discontinuity sets by the silhouette coefficient (Section 2.3), segment the discontinuity sets by HDBSCAN (Section 2.4), fit the discontinuities by the random sampling consistency (RANSAC) method (Section 2.5), and compare the extracted results with those obtained by Riquelme et al [40] and Chen et al [37] (Section 2.6)
Summary
Rock mass discontinuities refer to planar geological interfaces with a certain direction, large extension, and small thickness, and are mainly generated in rock mass under the action of tectonic stress. Artificial contact measurement methods for the orientations of rock mass discontinuities include compass measurements and the scanning line method [4]. Compass measurements are labor-intensive and have low efficiency They are affected by weather and terrain characteristics (accessibility, instability, etc.). They are of limited utility for obtaining discontinuity orientations of metal mine slopes due to the incorrect work of the compass. The scanning line method needs to enter the exploration site to measure the parameters of the discontinuities, which is very difficult and dangerous to work. This kind of manual contact measurement is Remote Sens.
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