| The Discrete Element Method (DEM) is a numerical technique which has been used to model discontinuous granular systems such as powders, soil and fractured rock. This thesis seeks to advance the state-of-the-art in the micro-mechanical as well as the large-scale levels of investigation using an ellipse-based DEM code.; A previous numerical study of the strength of two dimensional bedded systems demonstrated behavior very similar to "real" soil systems, including the presence of shear banding. However, the study was based on a limited number of particles with rigid, stress-controlled boundaries, the presence of which may have influenced the quantitative results as well as the location and behavior of shear bands. In this thesis, a "periodic" boundary was developed, implemented and tested, then applied to the same conditions as the previous rigid-boundary study. These results are then compared to the previous rigid boundary data.; Although the results are qualitatively similar, the use of periodic boundaries generates a measurable reduction in the strengths of the samples and accents a different mode failure than that experienced by rigid boundary samples.; In addition, the ellipse-based DEM is used to simulate a large-scale model of a shallow plate loaded vertically to failure. In order to perform this test, a new corner element was first developed and implemented in the DEM code. The results obtained from the numerical model indicate excellent agreement to the classical ultimate bearing capacity equation. These results suggest that the ellipse-based DEM code can be used to model other large-scale geotechnical engineering problems involving complex loading up to and including the onset of failure. (Abstract shortened by UMI.)... |
