Calculation of 3D displacement and time to failure of an earth dam using DIC analysis of hillshade images derived from high temporal resolution point cloud data

Point cloud data capturing land surface elevation at two instants in time are commonly used to detect landslides occurrence. In this paper, it is hypothesised that this same point cloud data has the potential to yield much more valuable quantitative information regarding landslide behaviour, including the direction, magnitude, and rate of surface displacement. Given point cloud data contains roughness information, shaded projections (hillshade images) of the slope at two or more instants in time can be processed using digital image correlation (DIC) to track displacement in the plane of the projection. If multiple view angles are used to generate the hill shade images, 3D surface displacements of the landslide surface should theoretically be resolved. Furthermore, if point clouds are generated with sufficiently high temporal resolution, it should be possible to estimate the time to failure. The objective of this paper is to test this hypothesis using point clouds generated at high temporal resolution using digital images of a 3.5 m high earth dam field experiment brought to failure under high reservoir water conditions and an extreme rainfall event. This experiment indicates that the proposed method was successful in generating 3D displacement estimates within 2 cm of collected total station data and an estimated time to failure was within four minutes of the observed slope failure.