عنوان مقاله [English]
نویسنده [English]چکیده [English]
Until now, all of the calculations about determining of water content around the particles in unsaturated soil have done with supposing the spherical shape of particles and most of quantities such as matric suction and interparticle stress due to water meniscus were calculated by using that simple assumption.
In this paper, three packing methods of ellipsoidal particles are studied and by considering changes in meniscus geometry, matric suction and water content volume are evaluated as functions of meniscus radii for soil particles under the pore-water regime. This analysis provides a theoretical basis for describing several well-known phenomena in unsaturated soil behavior. A series of rigorous analytical equations was developed for describing the total volume of menisci between contacting ellipsoidal soil grains by treating the zero contact angle. Matric suction characteristic curves modeled using the analytical solutions displayed behavior similar to real unsaturated soils by using the ellipsoidal particles.
The results show that by increasing the filling angle, the volumetric water content of horizontal arrangement is about 2 to 5 times higher than other states, while by changing in the radius ratio of the lens, this amount is more for vertical alignment. So, the matric suction for elliptical particles is quantified with little inclination towards the water content change which achieved four times larger for double diameter ratio.
 H. Fricke, “The electric conductivity and capacity of disperse systems”, Physics, Vol. 1, 1931, pp.106–115.
 M.R.J. Wyllie, and A. R. Gregory, “Formation factors of unconsolidated porous media: Influence of particle shape and effect of cementation”, Journal of Petroleum Technology, Vol. 5, 1953, pp.103–109.
 R.E. Meredith, and C. W. Tobias, “Conduction in heterogeneous systems”, Adv. Electrochem. Electrochem. Eng., Vol. 2, 1962, pp.15–47.
 R.W. Zimmerman, “Effective conductivity of a two-dimensional medium containing elliptical inhomogeneities”, Proc. R. Soc. London, Ser. A, Vol. 47, 1996, pp.1713–1727.
 D. Coelho, J. F. Thovert, and P. M. Adler, “Geometrical and transport properties of random packings of spheres and aspherical particles”, Phys. Rev. E., Vol. 55, 1997, pp.1959–1978.
 K. Shinohara, M. Oida, B. Golman, “Effect of particle shape on angle of internal friction by triaxial compression test”, Powder Technology, Vol. 107, No. 1-2, 2000, pp.131–136.
 J. Dodds, “Particle Shape and Stiffness-Effects on Soil Behavior”, Atlanta, Ga, USA: Institute of Technology, 2003, pp.121–122.
 Q-B.mLiu, W. Xiang, M. Budhu, D-S. Cui, “Study of particle shape quantification and effect on mechanical property of sand”, Rock and Soil Mechanics, Vol. 32, No. 1, 2011, pp.190–197.
 K. Johanson, “Effect of particle shape on unconfined yield strength”, Powder Technology, Vol. 194, No. 3, 2009, pp. 246-251.
 C. Tuitza, U. Exnera, M. Frehnera, B. Grasemanna, “The impact of ellipsoidal particle shape on pebble breakage in gravel”, International Journal of Rock Mechanics and Mining Sciences, Vol. 54, 2012, pp. 70-79.
 R. Barbosa, and J. Ghaboussi, “Discrete finite element method”, Engineering Computations, Vol. 9, 1992, pp. 253-266.
 A.W. Bishop, “The principle of effective stress”, Teknisk Ukeblad I Samarbeide Med Teknikk, Oslo, Norway, Vol. 106, No. 39, 1959, pp. 859-863.
 A.W. Bishop, “The measurement of pore pressure in the triaxial test,” Conf. British Nat. Soc. Of Int. Soil Mech. and Found. Engrg., Butterworth’s, London., 1961, pp. 38-46.
 A.W. Bishop, I. Alpan, G.E. Blight, and I.B. Donald, “Factors controlling the shear strength of partially saturated cohesive soils,” ASCE Conf. Shear Strength of Cohesive Soils, Boulder, CO, 1960, pp. 503-532.
 D.G. Fredlund, and H. Rahardjo, “Soil Mechanics for Unsaturated Soils”, Wiley Inter Science, 1993.
 X. Lin, and T.T. NG, “A three-dimensional discrete element model using arrays of ellipsoids”, Geotechnique, Vol. 47, No. 2, 1997, pp. 319-329.
 N. Lu, and W. J. Likos, “Unsaturated Soil Mechanics”, John Wiley & Sons, 2004.
 H.G. Matuttis, S. Luding, and H.J. Herrmann, “Discrete element simulations of dense packings and heaps made of spherical and non-spherical particles”, Powder Technology, Vol. 109, No. 1, 2000, pp. 278-292.
 M. Sallam, Amr, “Studies on Modeling Angular Soil Particles Using the Discrete Element Method”, Ph.D. Dissertation, University of South Florida, United State of America, 2004, pp. 182-185.
 J. Ting, M. Khawaja, L. Meachum, and J. Rowell, “An ellipse-based discrete element model for granular materials”, International Journal for Numerical and Analytical Methods in Geomechanics, Vol. 17, 1993, pp. 603-623.
 J. Ting, L. Meachum, and J. Rowell, “Effect of particle shape on the strength and deformation mechanisms of ellipse-shaped granular assemblages”, Engineering Computations, Vol. 12, 1995, pp. 99-108.