Particle shape determination by two-dimensional image analysis in geotechnical engineering

Particle shape of soil aggregates is known to influence several engineering properties; such as the internal friction angle, the permeability etc. Previously shape classification of aggregates has mainly been performed by ocular inspection and e.g. by sequential sieving. In geotechnical analysis has been a lack of an objective and rational methodology to classify shape properties by quantitative measures.Recent development in image analysis processing has opened up for classification of particles by shape. In this study 2D-image analysis has been adapted to classify particle shape for coarse grained materials. This study covers a review of soil classification methods for particle shape and geometrical shape descriptors. The image analysis methodology is tested and it is investigated how the results are affected by resolution, magnification level and type of shape describing quantity. Evaluation is carried out on as well idealized geometries as on soil samples. The interpreted results show that image analysis is a promising methodology for particle shape classification. But since the results are affected by the image acquisition procedure, the image processing, and the choice of quantity, there is a need to establish a methodology to ensure the objectivity in the particle shape classification.Validerad; 2012; 20120516 (juarod