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A simple, yet physically meaningful, homogenization approach to determine the 'equivalent' elastic properties for a layered medium is proposed. The proposed approach makes use of the Reuss and Voigt approximations without employing auxiliary stresses and strains related to the different elastic properties of the material layers. When assuming that the constituent materials are isotropic, some special features of the equivalent homogeneous medium are discussed for special cases in which all layers have either the same Poisson's ratio, elastic modulus or shear modulus. A methodology to determine the equivalent anisotropic elastic properties of multi-layered soils is proposed, in which all required quantities are physically meaningful and can be determined directly. The applicability of the proposed methodology is demonstrated through tests on two types of soils, one of which has a varved structure while the other is isotropic. [ABSTRACT FROM AUTHOR]

The influence of particle shape and orientation on the thermal conductivity of low volume, particulate composites was examined through two-dimensional numerical simulations using the finite element method, FEM. The simulations demonstrate that the conductivity of such composites is influenced by not only the relative volume and conductivity of the embedded particles, but also their general shape, elongation, and orientation relative to the direction of global heat flow. The functional form of the Halpin-Tsai equation was utilized to characterize the composite thermal conductivity through a derived expression of the geometric distribution factor, ζ. The proposed expression of ζ differs from commonly assumed values and is shown to be highly dependent on the shape of the embedded particles. This approach was further extended to examine and explicitly characterize the anisotropic behavior of composites containing multiple, randomly distributed particles of a uniform size and shape based on their relative orientation. This work demonstrates the viability of using numerical tools to examine composites with complex geometries. [ABSTRACT FROM AUTHOR]

This paper discusses the coupled effects of capillary suction and fabric on the behavior of partially saturated granular materials at pendular state when discrete liquid bridges form around particle contacts. Experimental results show that the soil-water characteristic curves of granular materials are affected by the internal structure formed during reconstitution of the specimen. The effect of capillary suction on the shear strength of moist sand varies with the direction of shearing relative to the bedding plane which is generally perpendicular to the major principal direction of the fabric tensor. When treating capillary attraction as interparticle forces at particle contacts, a micromechanics analysis shows that the coupling between capillary-attracting forces and fabric results in an additional stress tensor, which describes the anisotropic effect of capillary suction on the behavior of moist sand. [ABSTRACT FROM AUTHOR]

This paper investigates the induced anisotropy and multi-scale shear characteristics of granular materials by quantifying force chain distribution in two-dimensional specimens of rigid particles under quasi-static loading. A new criterion is proposed and implemented into the existing algorithm which can effectively solve the identification instability of force chains at branching and merging points. Force chain is then classified into three categories according to the variation of force chain quantity and average stress with segment length: stable segments, meta-stable segments and unstable force chain segments. The stable force chain segments dominate the load-bearing behavior of the granular materials. The directional distribution of force chain segments is more anisotropic and more sensitive to the applied stress than contact normal vectors, which show obvious local peaks in both vertical and horizontal directions at high deviatoric stress. Therefore, the probability density of directional distribution of force chains needs to be described by the first two deviatoric components of Fourier expansion with deviators A1 and A2, which are indicators reflecting the intensity of the induced-anisotropy of the granular materials. As the absolute values of A1 and A2 increase, the induced anisotropy is more significant. The final shear failure types are determined by the quantities of force chains orienting in two potential shear failure directions: if there is an obvious difference between the quantities of the two directions, single shear band occurs within the direction with less force chains; otherwise, conjugated double shear bands occur and lie in the two potential shear failure directions. [ABSTRACT FROM AUTHOR]