Page 459 - Mechanics of Asphalt Microstructure and Micromechanics

Multiscale Modeling and Moisture Damage 451

For the solid in the system:
ρ
g ≈+ 1 ( su + P ) − ε th (13-27)
1
ρ 0 K w 1−− g
nn
g g t
Where K g is the bulk modulus of the solid, s is the saturation in the wetting fluid,
and e g is its volumetric thermal strain.
th
The constitutive behavior of pore fluid flow is governed by Darcy’s Law. Under
saturated conditions, the volumetric flow rate of the wetting liquid through a unit
area of the medium, snv m , is proportional to the negative of the gradient of the piezo-
metric head.
∂φ
ˆ
snv =− ⋅ (13-28)
k
m x ∂
ˆ
Where k is the permeability of the medium and f is the piezometric head, defined
as:
u
ϕ =+ w (13-29)
z
g ρ
w
Where z is the elevation above some datum and g is the magnitude of the gravita-
tional acceleration, which acts in the direction opposite to z.
13.3.3.3 Finite Element Modeling
This section presents results on how the poroelasticity model predicts the excess pore
water pressure accumulation and dissipation. A 2D finite element mesh is shown in
Figure 13.14. A body of pavement 3 m long and 60 cm thick is confined by impermeable,

FIGURE 13.14 2D fi nite element mesh.