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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 110
Edited by: J. Pombo
Paper 15

A Numerical Study on the Permanent Deformation of Gap-Graded Granular Mixtures

R. de Frias Lopez, J. Ekblad and J. Silfwerbrand

Department of Civil and Architectural Engineering, Royal Institute of Technology, Stockholm, Sweden

Full Bibliographic Reference for this paper
R. de Frias Lopez, J. Ekblad, J. Silfwerbrand, "A Numerical Study on the Permanent Deformation of Gap-Graded Granular Mixtures", in J. Pombo, (Editor), "Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 15, 2016. doi:10.4203/ccp.110.15
Keywords: granular mixtures, permanent deformation, discrete element method, fabric of soils, static strength.

Permanent deformation accumulation of unbound granular layers under traffic plays a critical role in the performance and need for maintenance of pavements and railway structures. In this paper, the discrete element method is used to study the permanent strain behaviour of binary mixtures of elastic spheres, as an idealization of gap-graded mixtures, under triaxial monotonic loading. The effects of stress level and soil fabric structure, based on a recently proposed classification system founded on micromechanical considerations, are assessed by subjecting mixtures with varying fines contents to different stress levels. Additionally, mixtures are loaded to static failure to study the dependency of the permanent strains on the closeness of the applied stress to failure stress, in accordance with existing empirical models. Numerical results are also compared with the experimentally determined behaviour of granular materials. The findings indicate that numerical mixtures are able to reproduce some of the most significant features observed in laboratory tests on granular materials, further encouraging the use of numerical simulations to enhance the understanding of granular media behaviour. Additionally, a good correlation between fabric structure and performance is obtained, giving additional support to the use of the studied fabric classification system for performance characterization.

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