Flow visualisation in a geotechnical centrifuge under controlled seepage conditions

Image analysis is a powerful tool to obtain high-resolution displacement data from centrifuge models non-destructively. However, ‘invisible’ features, for example the phreatic surface, cannot be captured. Rather, analysis must rely on traditional measurement techniques, e.g. pressure transducers. Depending on the geotechnical complexity of the model, such discrete technologies might be insufficient. In this paper,we describe the processes used to inject a tracking fluid to visually identify flow patterns through a model slope. The merits of three tracing fluids were assessed: acrylic-resin ink (“artist’s ink”); food-grade dye; and a fluorescent, low viscosity dye (sodium fluorescein). Results showed that the developed injection technique was able to deliver the fluid without otherwise affecting seepage conditions. Depending on the fluid selected, the technique was equally able to examine the migration of a dense contaminant, assess model homogeneity or identify hidden flaws.