TESTING THE USE OF UNMANNED AERIAL SYSTEMS (UAS) TO EXTRACT GEOLOGIC STRUCTURE DATA FROM UNSTABLE ROCK SLOPES IN SOUTHWEST VIRGINIA FOR VDOT STUDIES

Small unmanned aerial systems (sUAS) have revolutionized the collection of geologic structure data for evaluating the safety and stability of rock slopes when stability is controlled by the orientations of discontinuities in a rock mass. Prior to the use of sUAS, engineering geologists collected structure data manually, often by rappelling down cliff faces, taking hundreds of orientation readings for plotting on stereonets.

In this study for the Virginia Department of Transportation (VDOT), sUAS missions were flown along active quarry faces at the Acco Quarry, owned by Salem Stone Corporation, near the VDOT Smart Road in Blacksburg, Virginia. Dense point clouds were generated using structure from motion (SfM) software, and the discontinuity orientations were extracted using CloudCompare and Split-FX software. The data were plotted on stereonets and used to evaluate overall stability of the quarry walls.

The smartphone application Pix4D Capture was used to create, plan, and execute flight missions for a DJI Mavic Pro. Pictures were taken during missions using the aircraft’s stock camera. The images were processed using the programs Pix4D and Agisoft PhotoScan. Orthophotomosaics, 3D digital models, and contour maps were created and imported into ArcMap. Strike, dip, and dip direction measurements were determined as described above.

This undergraduate research project focuses on exploring the use of sUAS to create and plan autonomous flights using mission planning software, and analyzing the results using several different computer applications. A separate complementary research project will evaluate the use of change detection software for identifying areas of rockfall based on sUAS flights and point clouds generated over time.