Pore Pressure and Viscous Shear Stress Distribution Due to Water Flow within Asphalt Pore Structure

There has been a concentrated effort in modeling fluid flow in asphalt pavements, and most of the existing work has been limited to evaluation of directional permeabilities. The effects of other phenomena, such as development of flow-induced pore pressure and viscous shear stress distributions at the pore–solid interfaces, on moisture damage in an asphalt pore structure have not been fully understood. A three-dimensional (3D) numerical fluid flow model was developed using the lattice Boltzmann (LB) method to simulate water flow within the pore structures of various hot mix asphalt (HMA) pavements. In this article, an in-depth analysis of variations of pore pressures and viscous shear stresses caused by water flow within the 3D pore structure of different HMA specimens is provided. The relationship between the pore geometry and the pore water pressure and viscous shear stresses were studied. Pore pressures and viscous shear stresses were computed after 3D fluid flow simulations conducted within the real pore structures of numerous HMA specimens. X-ray computed tomography (CT) was used to acquire 3D pore structures of HMA specimens, and the obtained images were input into the LB model. The results indicated that the pore water pressure gradient is highly nonlinear within the ∗ To whom correspondence should be addressed. E-mail: kutay@ msu.edu. pore structure of HMA pavements, as opposed to a linear gradient commonly observed in homogeneous pore structures (e.g., granular soils). The viscous shear stresses were observed to be the largest at the constrictions located at the mid-depth of the specimens. Furthermore, a one-toone relationship was observed between the reduction in the pore area and viscous shear stresses developed during the water flow.