Hydraulic Impact of Porosity Distribution and Hydrologic Characterization of Porous Pavements

This research focused on the hydrologic characterization of porous pavement and pavement properties that can affect its hydraulic behavior. The first of these properties investigated was the presence of a vertical porosity distribution which can significantly impact the infiltration rate. A method utilizing image analysis was tested and experimentally verified. The representative elemental area (REA) was needed for this imaging method and was found to be 83.9 cm2 (13 in2). To convert the porosity distribution into a permeability distribution the relationship between porosity and permeability was found using homogenous samples. From the resulting permeability distribution an effective permeability was found which was better correlated to the actual permeability than other predictions, especially the one using the average porosity value. The effective curve number (ECN) model was initially used to hydrologically characterize the porous pavements which was a good fit for the drained porous pavements. However, as it does not match the fill and spill behavior of the undrained pavements, the ECN model produces much larger error when applied to them and actually becomes a function of rainfall distribution. For a more accurate approximation of the undrained pavement's behavior, the broken-line model was developed. It is able to approximate the fill and spill behavior using the initial abstraction, the volume that is required before runoff occurs, and the slope, which is a function of the rainfall to infiltration ratio. Both of these models summarize the pavement variables in terms of two parameters, the storage depth and the 24-hour infiltration rate. Because of a question as to the appropriateness of one of the modeling assumptions, experimental verification was conducted to determine the actual magnitude of masking and embedding effects of subbase aggregate on the infiltration rate of the underlying soil. The results showed that aggregate masking and embedding does have an impact on the soil infiltration rate, but the magnitude was less than that predicted by earlier work.