Broken Ice Photogrammetry in Model-Scale Experiments with Sloped Structure

Abstract

Testing a physical model of an ice-resistant marine structure in an ice tank is one of the methods used for design validation. For a stationary structure design, not only is the possible global ice load of interest but also the processes of creation and evolution of ice rubble in front of the contacting surface. While the load registering technique in model-scale experiments is very well-developed, the photogrammetric analysis of broken ice morphometry and locomotion is not. The photographs taken to illustrate the breaking process do not usually accompany the information necessary for the photogrammetric reconstruction of the scene. This paper outlines a systematic approach to the photogrammetric analysis of the scenes in model-scale conditions. Using this approach, the broken ice dimensions were measured in seven model-scale experiments for which the model of a sloped marine structure was reconstructed. In these experiments, a 700 mm wide slope with an inclination angle of 53° caused an upward flexural failure of the model’s granular ice. Reference global load histories for these experiments are provided. For the first contact episodes, the successful reconstruction of the broken ice mosaic in the polynya showed the insignificant contribution of compressive failure. In continual ice–structure interaction, the morphometry of the ice blocks visible on the slope of the rubble pile and on the surface of the surrounding ice sheet was retrieved from orthorectified video frames. The results were compared with the after-test nadir drone view of the polynya. The error in estimating the top-side area and the maximum linear dimension of the ice block fell into the interval of 0–10%. The morphometric information of the broken ice floes obtained in ice tank experiments with physical models can be used for the improvement of the mechanical models of ice fracture and failure against inclined offshore ice-resistant structures.