A 3D point cloud model of Santa Luzia dam and its contribution for improving the finite element mesh

Abstract

The analysis and interpretation of the structural behavior of concrete dams is usually performed by using finite element models of the dam and its rock mass foundation. The finite element mesh of the dam must accurately represent the real geometry of the structure being traditionally created from the design drawings. Currently, techniques from geospatial sciences (laser scanning and photogrammetry) allow the creation of very rigorous 3D models of objects, based on point clouds of surfaces. The improved knowledge of dam geometry can be useful for creating more realistic meshes of the structure, thus increasing the accuracy of the numerical modeling. The paper presents a use case of data generated from a drone photogrammetric survey of a concrete arch dam. The Santa Luzia dam is the first arch dam built in Portugal (it was completed in 1943). The concrete of this dam is subject to a deterioration process due to expansive reactions of internal origin. A very comprehensive study of the structure was recently carried out, which included the mapping of pathologies in the faces and crest of the dam and the analysis and interpretation of the dam behavior. The mapping of pathologies was carried out using digital image processing techniques, based on orthomosaics generated from photographs obtained from ground and aerial surveys, using photogrammetric software. When generating orthomosaics, point clouds were created which were used to obtain data on the dam's geometry and to improve the finite element mesh created many years ago, based on the dam design drawings. The paper includes a description of the aerial survey and the presentation of the most important phases for obtaining the dam geometry and for preparing the finite element mesh.