Discrete Element Method for Modeling the Mechanical Behavior of Unsaturated Granular Material
Authors
Abstract
Although a significant portion of conditions encountered in geotechnical engineering, for investigating engineering behavior of soil, involves unsaturated soils; the traditional analysis and design approach has been to assume the limiting conditions of soils being either completely dry or completely saturated. In unsaturated soils the capillary force produce attractive forces between particles. Discrete Element Method (DEM) is an appropriate tool to consider the capillary effects. The calculations performed in DEM is based on iterative application of Newton’s second law to the particles and force-displacement law at the contacts. In the present study, the behavior of unsaturated soils in pendular regime is simulated utilizing DEM. Triaxial compression tests were modeled as two-dimensional, considering capillary force effects. Finally, capillary effects on Macro parameters of a simulated granular soil (stress, axial strain, volumetric strain and void ratio) and Mohr Coulomb failure criteria parameters were studied.
Keywords
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2. Cundall, P. A. and Hart, R. D., “Numerical Modelling of Discontinua”, Engineering Computations, Vol. 9 (2), pp. 101-113, 1992.
3. Mogami, T., “A Statistical Approach to the Mechanics of Granular Materials”, Soils and Foundations, Vol. 5 (2), pp. 26-36, 1965.
4. Bocquet, L., Charlaix, E., and Restagno, F., “Physics of Humid Granular Media”, Comptes rendu physique, Vol. 3 (2), pp. 207-215, 2002.
5. Richefeu, V., El-Youssoufi, M., and Radjai, F., “Shear Strength of Unsaturated Soils: Experiments, DEM Simulations, and Micromechanical Analysis”, 2nd International Conference on Mechanics of Unsaturated Soils, Weimar, Germany, 2007.
6. El Shamy, U., and Groger, T., “Micromechanical Aspects of the Shear Strength of Wet Granular Soils”, International Journal for Numerical and Analytical Methods in Geomechanics, Vol. 32, pp. 1763-1790, 2008.
7. Hotta, K., Takeda, K., and Iinoya, K., “The Capillary Binding Force of a Liquid Bridge”, Powder Technology,Vol. 10, pp. 231-242, 1974.
8. Adams, M. J., and Perchard, V., “The Cohesive Forces between Particles with Interstitial Liquid”, Institute of Chemical Engineering Symposium, Vol. 91, pp. 147-160, 1985.
9. Zhu, H. P., Zhou, Y. Y., Yang, R. Y., and Yu, A. B., “Discrete Particle Simulation of Particulate Systems: Theoretical Developments”, Chemical Engineering Science,Vol. 62, pp. 3378-3396, 2007.
10. Butt, H. J., “Capillary Forces: Influence of Roughness and Heterogeneity”, Langmuir,Vol .24, pp. 4715-4721, 2008.
11. Israelachvili, J. N., “Intermolecular and Surface Forces”, Academic Press, London, 1992.
12. Scholtès, L., Chareyre, B., Nicot, F., and Darve, F.,“Discrete Modeling of Capillary Mechanisms in Multi-Phase Granular Media”, CMES, Vol. 1, No. 1, pp. 1-22, 2009.
13. Pitois, O., “Assemblée de Grains Lubrifiés: Elaboration D'un Système Modèle Expérimental et Etude de la loi de Contact”, Thèse de doctorat, Ecole Nationale des Ponts et Chaussées, Paris, 1999.
14. Mikami, T., Kamiya, H., and Horio, M., “Numerical Simulation of Cohesive Powder Behavior in a Fluidized Bed”, Chemical Engineering Science,Vol. 53(10), pp. 1927-1940, 1998.
15. Muguruma, Y., Tanaka, T., Kawatake, S., and Tsuji, Y., “Numericalsimulation of Particulate Flow with Liquid Bridge between Particles (Simulation of a Centrifugal Tumbling Granulator)”, Powder Technology, Vol. 109, pp.49-57, 2000.
16. Yang, R. Y., Zou, R. P., and Yu, A. B., “Numerical Study of the Packing of Wet Coarse Uniform Spheres”, American Institute of Chemical Engineers , Vol. 49, pp. 1656-1666, 2003.
17. Willett, C. D., Adams, M. J., Johnson, S. A., and Seville, J. P. K., “Capillary Bridges between two Spherical Bodies”, Langmuir, Vol. 16, pp. 9396-9405, 2000.
18. Lian, G., Thorton, C., and Adams, M. J., “A Theoretical Study of the Liquid Bridge Forces between two Rigid Spherical Bodies”, Journal of Colloid an Interface Science, Vol. 161, pp. 138-147, 1993.
19. Chen, Y., Zhao, Y., Gao, H., and Zheng, J. “Liquid Bridge Force between two Unequal-Sized Spheres or a Sphere and a Plane”, Particuology, Vol. 9, pp. 374-380, 2011.
20. Kraan, M., “Techniques for the Measurement of the Flow Properties of Cohesive Powders”, Ph.D Dissertation Delft University, Delf, 1996.
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