Investigation of granular materials deformations under an unconfined compaction with x-ray computed tomography.

Sammanfattning: The behavior of the asphalt mixtures under large deformations, for example an unconfined compaction is of high practical importance. Quantitative measurement of the spatial distribution of internal structure of asphalt mixtures is crucial to study deformation behavior of asphalt mixtures. Deformation of granular material under an unconfined compaction is investigated in this study, as a groundwork for further research on deformation behavior of asphalt mixtures. Two sets of 3D images of specimens are obtained using X-Ray computed tomography (CT) under an unconfined compaction. Digital image analysis procedure is developed to segment different phases for characterizing spatial distribution of internal structure. Comparative volumetric relationship before and after compaction showed that air void distribution is not changed heavily due to absence of interlocking. Initial and final spatial positions of individual granules are investigated to trace their movement under compaction. It is shown that X-Ray CT could be a useful tool to characterize internal structure of asphalt mixtures and its evolution during deformation.