Evaluation of surface infiltration performance of permeable pavements.

Many different test methods are used in practice to evaluate the surface infiltration performance of permeable pavements. This has led to inconsistency in reporting of test results. This study recognizes the differences in nature between a soil infiltration study and the surface infiltration evaluation of permeable pavements, and identifies the main issues associated with the current practice of surface infiltration testing. It proposes that hydraulic conductivity be adopted as the flow property for measurement and reporting instead of the commonly used infiltration rate. The advantages of measuring hydraulic conductivity are elaborated from both theoretical and practical implementation points of view. The theoretical merits of providing a consistent and integrated treatment of surface infiltration performance of a permeable pavement during the design, construction and maintenance phases are presented. The practical benefits are addressed from the following aspects: consistency between laboratory and field testing, uniformity in reporting of test measurements, rationality in construction quality control and acceptance checking, effectiveness in surface infiltration performance monitoring, and enhanced ability in implementing effective maintenance management. It is emphasized that the techniques and methods needed for measuring hydraulic conductivity of permeable pavement materials, for laboratory testing as well as on-site field testing, are already readily available and have been used by researchers and some practitioners for surface infiltration testing. Two falling-head test methods are recommended: one applies Darcy's law and determines hydraulic conductivity in the conventional way; another measures the time history of falling head and calculates hydraulic conductivity using a modified Darcy equation. It is also highlighted that the measurement of hydraulic conductivity offers a convenient platform for assessing the durability of a permeable pavement against clogging.