Simulation on Water Flow in Permeable Pavement Influenced by Voids Decrease

Abstract

The permeable pavement has good drainage capabilities, but the voids are easy to be clogged. Describing the internal flow and potential surface flow of permeable pavement is essential for pavement design and driving safe maintenance. In this paper, indexes including connected porosity, equivalent area of the voids channels, and the bending rate were selected to depict the permeable pavement internal flow when the voids decreased due to clogging. A simulation model was proposed based on Darcy’s law by using the images from computer tomography (CT) scanning; then, the seepage flow inside the voids was obtained to evaluate the drainage of porous asphalt mixture. The potential surface flow situation including waterlogging, critical runoff depth and drainage time was calculated. Surface hydrodynamic pressure between the tires and pavement was also compared. Results showed that the connectivity of internal voids was crucial to quantify the voids clogging. The internal flow nearly disappeared when the porosity decreased by less than 15% due to the blockage. The drainage function was influenced by the porosity, thickness, and length of the drainage path. The surface layer’s thickness should be determined according to the indexes such as the maximum runoff depth without water skiing, the drainage time, and the road facilities, among others. Surface hydrodynamic pressure distribution illustrated it might decrease by 33% for every 10 km/h deceleration. A short flow path length and a more considerable cross slope within a reasonable range could decline drainage time. It was suggested that all these factors might be considered when designing and maintaining the permeable pavement.