Dynamic Response of Fully Permeable Pavements: Development of Pore Pressures under Different Modes of Loading

Permeable pavements are widely recognized as an effective way to improve the environmental and ecological aspects of conventional dense pavements. Based on traditional pavement materials, permeable pavements are often designed to be partially permeable or to consist of merely permeable surfaces. Recently, the development of novel polyurethane-bound pervious mixtures (PUPM) has made the widespread application of fully permeable pavement (FPP) structures possible, which will increase the environmental benefits of permeable pavements. In this case, the saturation of a pavement has a major influence on the performance of FPP. The generation and dissipation of pore pressure is recognized as a critical factor, influencing the bearing capacity of permeable pavement structures. In literature, only few studies focus on the pore pressure in permeable pavements under traffic loading. This study aims to measure and characterize the changes in pore pressure in a full-scale permeable pavement under various saturation conditions under traffic loading. To achieve this objective, pore pressure data was collected from laboratory testing as well as from a full-scale test track constructed with a polyurethane-bounded pervious mixture (PUPM) wearing course. Based on this study, it is found that when permeable pavement material is subjected to cyclic loading, the pore water pressure is much larger than the pore air pressure; in fact, the latter is found to be negligible. During the irrigation process and dynamic vehicle loading, the pore water pressure increases as the saturation increases. The changes of pore water pressure are not obvious in the PUPM surface layer when comparing the results to the pervious layers below the wearing course. Under cyclic vehicle loading, the accumulated pore water pressure of each layer increases with the number of loading cycles and also increases as the saturation increases. These findings support the quest for an in-depth understanding of the stress state and the degradation mechanisms in FPP. The results provide practical conclusions and recommend optimized design properties for a wide application of FPP.