Structural characteristics of landslide failure boundaries using three-dimensional point clouds: a case study of the Zhaobiyan landslide, China

Rock landslide failure boundaries contain large amounts of rock mass structure information, providing many details that help researchers understand the causes of landslide failure. Taking the Zhaobiyan (ZBY) landslide triggered by the 2008 M_S 8.0 Wenchuan earthquake as an example, we systematically introduce a workflow for analyzing the structural characteristics of landslide failure boundaries using three-dimensional point clouds. First, multi-source data of the failure boundaries are obtained via terrestrial laser scanning and unmanned aerial vehicle photography. Next, on the basis of the hue, saturation, value color reconstruction technique, and the density-based spatial clustering of applications with noise, more than 3,870,000 orientations and eight groups of joint faces are extracted from these data. Finally, the spacing, persistence, and roughness of the joint faces are calculated. According to the roughness, we determined that the north flank of the ZBY landslide is a smooth friction face resulting from tectonic shear. With increasing movement distance of the landslide on the slip surface, the roughness is increasingly controlled by landslide slickensides instead of the structure. Furthermore, we confirmed that both sides of the ZBY landslide are primarily controlled by planar shearing failure with the linkage of Joints J1 and J2, which are located on the north and south flanks, respectively. The damaged areas on the two flanks caused by shear failure reached 86.53% and 73.02%, respectively, of the flank areas. The main scarp is composed of wedge failures at different scales, and the area damaged by tension reached 89.28% of the main scarp area.