The Seoul Metropolitan Government is managing and expanding the use of permeable block pavement on roads by revising relevant ordinances and standards. As a result, the installation rate (area ratio) of permeable blocks in Seoul increased approximately five times from 2.2% in 2014 to 11.0% in 2021. At the same time, awareness of related issues has been rising, with reports of low-quality permeable blocks being supplied that differ from their test certificates, as well as concerns over the reliability of the test certificates themselves.
Despite ongoing concerns, the current methods for assessing the permeability performance of permeable blocks installed on-site face practical limitations in terms of time, space, and cost. Additionally, these methods often lack accuracy, leading road management departments to avoid their use. Therefore, there is an urgent need to develop a method that allows for quick and easy evaluation of the permeability performance of permeable blocks directly in the field.
This study developed the K-SWIFT method, a simplified on-site permeability testing method, as an alternative to the existing ASTM C 1701 standard. Field evaluations of permeability performance were conducted at 36 locations. To validate the field applicability of the K-SWIFT method, the field test results of the permeable blocks were compared and analyzed against the actual values obtained from laboratory tests.
The K-SWIFT method involves releasing 3 liters of water from a height of 60mm through a 20mm diameter outlet, allowing the water to flow freely onto the surface of the permeable block pavement. The permeability coefficient is then evaluated on-site based on the wetted area of the pavement. To assess the permeability coefficient using the wetted area, it is essential to establish a correlation with the actual permeability coefficient values. In this study, the blocks used in the field tests were extracted, and the actual permeability coefficient values were determined through constant head permeability tests following the KS F 4419 standard. Furthermore, a correlation analysis was conducted by comparing the wetted area measured using the K-SWIFT method, yielding a high correlation coefficient(R² = 0.87). Therefore, it was concluded that the K-SWIFT method can reliably estimate the actual permeability performance on-site.
Meanwhile, when intuitive evaluation of permeability performance is needed due to time and space constraints on-site, the K-SWIFT method has been found capable of estimating the permeability coefficient using only the length of the wetted major axis, rather than the entire wetted area. A comparison of the correlation between the wetted major axis length and the constant head permeability coefficient (KS F 4419) yielded a high R² value of 0.87. For slopes within the typical range of pedestrian pavements (approximately 3% or less), a wetted major axis length of less than 1.5m indicates good permeability performance. Conversely, if the length exceeds 2.0m, the permeability performance can be considered poor. For lengths between 1.5m and 2.0m, it was determined that the blocks should be extracted and evaluated through laboratory constant head permeability tests in accordance with KS F 4419.
Based on the findings of this study, a field permeability performance evaluation method using the K-SWIFT approach is proposed. Additionally, revisions to the Seoul Metropolitan Government’s “Design, Construction, and Maintenance Standards for Permeable Block Pavements (ver. 2.0)” were derived.