USING UNMANNED AERIAL SYSTEMS (UAS) TO PRODUCE POINT CLOUDS OF QUARRY WALLS FOR TESTING CHANGE DETECTION SOFTWARE AND THEIR APPLICATION TO STUDYING HIGHWAY ROCKFALL RATES

Active quarries can be used as natural outdoor laboratories for studying rockfalls and rockslides in a controlled setting, away from highways where falling rocks pose a risk to motorists. Regular production blasting changes the contours of quarry walls, exposes new geologic features, and provides opportunities to examine the effects of rock mass weaknesses (discontinuities) on the overall stability and behavior of rock slopes. Therefore, quarries are good places to test change detection software and to evaluate their use for identifying locations along highways where rockfalls might occur regularly.

In this study for the Virginia Department of Transportation (VDOT), UAS missions were flown on three different occasions along active quarry faces at the Acco Quarry, owned by Salem Stone Corporation, near the VDOT Smart Road in Blacksburg, Virginia. During the time between flights, slopes were altered by normal quarry operations. Dense point clouds were generated using structure from motion (SfM) software and compared to each other using the CloudCompare program for change detection.

The smartphone application Pix4D Capture was used to create, plan, and execute flight missions for a DJI Mavic Pro. The resulting images were processed using the programs Pix4D and Agisoft PhotoScan to create the dense point clouds. This undergraduate research project focuses on the use of UAS in a quarry to test methods that might be transferrable to highway studies for monitoring rates of rockfall activity. A separate complementary research project is evaluating the use of UAS for extracting geologic structure data for detailed stability analyses.