Innovative Use of Drone Technology & 3D Numerical Modelling for Cliff Stability Evaluation

Evaluating the stability of undercut cliff profiles and assessing longevity of significant overhangs within precipitous coastal cliffs in an active marine environment is a challenge. This was accomplished through innovative use of high resolution digital imagery captured by low level high precision drone flights with photogrammetric processing of the imagery. With detailed GIS software manipulation of the generated point cloud data, complete three-dimensional (3D) wireframe DTM and DEM models were developed of key cliff conditions, allowing thorough stability assessment. The availability of full 3D geometries of entire, often inaccessible, cliff areas allowed detailed analysis of stress states existing around major overhangs and sea caves to be accomplished using FLAC3D. The 3D DTM and DEM models also allowed detailed review of the cliff geometries and profiles could be cut in any direction so that undercut and notched cliffs could also be analyzed in greater detail in two-dimensions (2D). The 2D analysis was carried out using discrete element modelling with application of Voronoi Tessellation approaches in UDEC in order to replicate the complex tensional cracking, overturning and block toppling mechanisms observed on many of the cliffs.