RELIABILITY OF DISCONTINUITY DATA COLLECTION BY AN UNMANNED AERIAL VEHICLE (UAV

Current methods of discontinuity data collection for slope stability analysis include Brunton compass and ground-based LiDAR. This study compares discontinuity data acquisition via an unmanned aerial vehicle (UAV) to these established methods in order to determine if UAV technology can be used reliably to collect structural data. Ground-based LiDAR is limited by “shadow zones” where gaps in data are produced by a small scan angle, slope features blocking the outcrop, and position of the surveying equipment relative to the slope face. Unmanned aerial vehicles have the benefit of easily accessing portions of an outcrop that may be otherwise physically impossible to access. Two field sites in Virginia were scanned for this study, a shale pit and a cut slope in Deerfield along highway 629. The Deerfield slope consists of shale, fine-grained metasediments, and minor sandstone of the Brallier Formation (Devonian) folded around the axes of paired anticline-syncline. Roughly 300 Brunton measurements of discontinuities were taken at each site. In addition, ground-based LiDAR scans and UAV photogrammetric data were collected at each location. Once data collection was completed, scans from the LiDAR unit and the UAV were converted into point clouds for use in stability analysis. Cyclone was used for LiDAR data and VisualSFM/Pix4DMapper Pro was used for UAV data. These point clouds were then imported into Split FX for analysis of discontinuity patches and to export data to DIPS for determining principal joint sets and kinematic analysis. Results indicate that UAV is a reliable means of collecting discontinuity data.