Application of the Kozeny-Kovàcs Model to Predict the Hydraulic Conductivity of Permeable Pavements

Permeable pavements provide a frictional surface for vehicles during rainfall runoff and function as a porous infrastructure interface, allowing the infiltration and evaporation of rainfall runoff, as well as treatment of pollutants when designed for solute and particulate separation. The hydraulic conductivity (ksat) of permeable pavement is an important hydraulic property. A series of empirical and pore structure models using constant head and pore-based measurements, including total porosity (Ft), effective porosity (Fe), and pore size distribution indices generated through X-ray tomography (XRT) were used to study permeable pavement. XRT results indicate that the pore matrix is heterodisperse, with Ft ≠ Fe. Results indicate that the traditional models based on a simple pore structure do not reproduce measured ksat values. More complex pore structure models, even with modification from the original form, gave better results. A modified Kozeny–Kovàcs model was used to reproduce the measured ksat values. The modified model introduces (Fe) and the characteristic pore diameter (De) instead of (Ft) and specific surface area, respectively. Such permeable pavement pore structure parameters with the modified Kozeny–Kovàcs model can be predicted. These results can be useful in the design stage of permeable pavement when a target value of ksat is desired to obtain both friction benefits to improve vehicle safety in wet conditions and to control the infiltration–evaporation of rainfall. The ksat results are combined with continuous simulation modeling using historical rainfall for a Cincinnati, Ohio, highway site on I-75 to provide results illustrating permeable pavement as a low impact development infrastructure component in the highway environment