Combination of UAV-borne LiDAR and UAV-borne photogrammetry to assess slope stability

- Monitoring and assessing slope stability quickly and accurately over large areas is a technical challenge. In this study, we investigated the combination of two UAV/UAS (Unmanned Aerial Vehicle or System) techniques to compensate for the limitations of each remote sensing technique, in the context of the Belchatow lignite mine (central Poland). The test site is one of the largest open-pit mines in Europe. It is characterized by complex geological and mining conditions (Rybicki, 1996) and has experienced numerous slope failures. Its western slope, located near the Debina salt dome, requires specific mine design to ensure safe and effective lignite exploitation. In this experiment, which is a first on this scale, two UAV-borne LiDAR and UAV-borne photogrammetry surveys were performed, the first in November 2016 and the second in March 2017. The occurrence of a landslide between these two campaigns allowed to precisely identify and study the impacted zone in terms of surface displacements, slip surfaces and fractures changes. It allowed also confirming previous results about the mine stability issues in the covered area, where a geotechnical monitoring was installed just before the first UAV-borne LiDAR and UAV-borne photogrammetry. Conclusions regarding the complementary approaches set-up were also brought, along with practical recommendations for monitoring and rapidly asses slope stability, particularly for inaccessible areas.