Experimental evaluation of 3D imaging technologies for structural assessment of masonry retaining walls

Abstract

This manuscript addresses the problem of identifying and quantifying bulging and leaning deformations in masonry retaining walls that are currently assessed with qualitative visual inspections. The primary aim of this research is to explore Structure from Motion Photogrammetry (SfM) as an accurate, objective, and data-centric alternative to visual inspection for monitoring such deformities. This work conducted controlled laboratory trials that compared SfM inspections of retaining wall like structures with a baseline three-dimensional (3D) imaging method, Structured-light Scanning (SLS), while assessing various wall configurations and camera types. The 3D imaging data collected in these trials were used to create full field point cloud comparisons between baselines and test models using CloudCompare. The findings indicate that both SfM and SLS produce accurate 3D models of retaining wall structures with SfM showing promise as a cost-effective solution for quantitative full field retaining wall inspections. The selection of specific 3D imaging method should be informed by project specific accuracy requirements and site conditions. This study has also highlighted a need for the careful consideration of SfM distortions such as the ‘banana effect’ when employing the technology on uniform planar surfaces, such as some straight retaining walls.

Keywords

• Retaining walls
• Structural inspection
• Structure from motion photogrammetry (SfM)
• Structured-light scanning (SLS)
• Point cloud comparison