Page 427 - Mechanics of Asphalt Microstructure and Micromechanics

Characterization and Modeling Anisotropic Proper ties of Asphalt Concrete 419

Horizontal/Vertical Permeability

6.00
Anisotropic Permeability Ratio (kh/kv) 4.00
5.00

3.00
2.00

1.00
0.00
3.00 4.00 5.00 6.00 7.00 8.00 9.00
Percent Air Voids
FIGURE 12.19 Vertical/horizontal permeability.

area, and the horizontal permeability is generally larger than vertical permeability, this
would yield the largest permeability values. As the contact area increased, the influence
of horizontal permeability decreased. Since the vertical permeability is lower than the
horizontal permeability, the permeability values that were calculated based on larger
contact areas were lower.
Kutay et al. (2006) presented a comprehensive study on the general anisotropy per-
meability behavior of AC. The generalized Darcy’s Law (Equation 12-27) is utilized for
his simulation using the Lattice Boltzman method. In his study, XCT was used to obtain
the void structure, including the connectivity of the voids, and simulation results were

–3
FIGURE 12.20 Flow lines/pressure head (permeable) for k h /k v = 5, k = 5 10 cm/s.