Improved watershed analysis for segmenting contacting particles of coarse granular soils in volumetric images

摘要

The watershed analysis has been widely used to segment contacting particles in volumetric images obtained from X-ray Computed Tomography (X-ray CT). However, the watershed analysis cannot discriminate between contacts of two particles and "necks" of peanut-shaped particles. Then, peanut-shaped particles are mistakenly oversegmented as two particles. To addresses this issue, this study developed an improved watershed analysis, which defines a dimensionless parameter alpha to discriminate contacts and necks. An image morphological reconstruction technique was developed to modify the distance map based on the parameter alpha. The watershed transform was performed on a modified distance map to overcome oversegmentation. The accuracy and effectiveness of the proposed technique were validated by six sand specimens. The influence of oversegmentation on particle size and shape characterizations were also demonstrated. The results showed that the improved 3D watershed analysis can effectively segment 3D particle contacts while preserving the continuity of necks for different granular soils. (C) 2019 Elsevier B.V. All rights reserved.