Dissertation
Simulation of the permanent deformation of asphalt concrete mixtures using discrete element method (DEM)
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2008
DOI:
https://doi.org/10.7273/000005808
Abstract
This study describes a methodology for simulating the permanent deformation resistance behavior of asphalt concrete mixtures using the discrete element method (DEM). The microstructure of asphalt concrete cores was obtained through X-Ray CT imaging techniques. Rheological tests on asphalt binders and mastics were performed to characterize their viscoelastic properties and establish their strength. An Automated Digital Image Processing (DIP) algorithm, called Volumetric-based Global Minima (VGM) thresholding algorithm was developed in the MATLAB environment to process the AC X-ray CT images for DEM simulation. VGM identifies the gray scale intensity boundary thresholds between air, mastic and aggregate phases with reference to volumetric information. It involves three interdependent stages, namely image preprocessing, gray scale thresholding, and post-processing. The first stage involves image pre-processing for contrast enhancement and noise removal. The second stage is the main thresholding routine accepting as input the enhanced images of the first stage and volumetric information for the AC. It consists of two components, namely volumetrics-driven thresholding and three-dimensional representation and sectioning. The third stage further enhances particle separation through edge detection and image segmentation techniques. It was demonstrated that the VGM processed images are suitable for inputting to a numerical simulation technique such as FEM and DEM. This algorithm was shown to be a major improvement over the largely manual techniques used in the past. DEM simulations of unconfined uniaxial static creep tests in compression were performed to predict deformation behavior of the AC models. Moreover, the effect of contact stiffness ratio (Kn/Ks) and aggregate-to-aggregate contact friction ([mu]) on the deformation behavior of the AC model were investigated. Laboratory uniaxial compression static creep tests were performed on the same nine AC mixtures imaged by the VGM technique. The total axial strains and the creep compliance DEM predictions were compared with the experimental results. Overall, the slope of the secondary compression part of the creep compliance curves was satisfactorily predicted.
Metrics
5 File views/ downloads
21 Record Views
Details
- Title
- Simulation of the permanent deformation of asphalt concrete mixtures using discrete element method (DEM)
- Creators
- Habtamu Melese Zelelew
- Contributors
- A. T. Papagiannakis (Chair)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Civil and Environmental Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 289
- Identifiers
- 99901055035201842
- Language
- English
- Resource Type
- Dissertation