A photogrammetric method for laboratory-scale investigation on 3D landslide dam topography.

Topography is a crucial characteristic reflecting the stability status of a landslide dam. The methods for measuring landslide dam topography in a laboratory-scale test study are currently operator dependent, time-consuming, or only applicable to the measurement of the two-dimensional section. In this paper, a laboratory-scale photogrammetric method based on the structure from motion (SfM) technique was proposed to measure the three-dimensional (3D) topography of a landslide dam. The SfM technique, which is a revolutionary, low-cost, user-friendly computer vision technique, was employed for reconstructing a landslide dam 3D computer model. A scientific method to determine the topography parameters of a landslide dam was put forward. Meanwhile, two materials with different particle sizes were used to simulate the formation process of the landslide dam in the laboratory-scale. Then, the measurement results of the two materials were compared. Five parameters of a landslide dam topography with 100 parallel measurement results for each parameter were obtained. The results show that the SfM technique could build a high-quality 3D point cloud in a laboratory scale. The proposed method of determining the topography parameters of a landslide dam was useful and has low measurement uncertainty. The material type affected the sparse density of the point cloud and then affected the measurement uncertainty of landslide dam topography parameters. The measurement uncertainty of the gravel-type landslide dam was significantly higher than that of the sand-type landslide dam. This research contributes to promoting the application of a photogrammetric method based on the SfM technique in geotechnical engineering laboratory-scale tests. [ABSTRACT FROM AUTHOR]