Open-graded friction course (OGFC) is a functional mixture used in high-intensity rainfall areas where there exists a risk of flash flooding. To ensure its functionality, there is a need to specify the minimum volumetric requirements on the OGFC mixture. This study aimed at developing in-situ permeability and interconnected air voids content requirements for an OGFC pavement under various rainfall intensities. Seven air voids contents (16%, 17%, 18%, 19%, 20%, 21%, and 22%) of OGFC slab specimens were prepared in the laboratory, and volumetric properties (interconnected air voids and total air voids content) and hydraulic conductivities (permeability coefficient) were characterized. A rainfall simulator was developed to quantify the ultimate drainage capacities of OGFC mixtures under simulated rainfall events. It was found that the OGFC mixture with a higher designed air voids content exhibited a higher permeability coefficient and ultimate drainage capacity. However, the in-situ drainage capacity of an OGFC pavement was affected by the number and width of lanes. Based on a field project that was two-way eight-lane, 2% cross slope, 20% air voids content, and 5-cm thick OGFC, the minimum in-situ permeability coefficient was determined as 825 mL/15 s. It was recommended to integrate design factors such as number and width lanes, and local rainfall intensity into the OGFC pavement design process to achieve desirable in-situ drainage functionality.

开级摩擦层 (OGFC) 是一种功能性混合物，用于存在山洪暴发风险的高强度降雨地区。为确保其功能，需要指定 OGFC 混合物的最小体积要求。本研究旨在开发各种降雨强度下 OGFC 路面的原位渗透性和互连空气空隙含量要求。实验室制备了七种气孔含量（16%、17%、18%、19%、20%、21%和22%）的OGFC板坯试件，以及体积特性（互连气孔和总气孔含量）和水力传导率（渗透系数）进行了表征。开发了降雨模拟器来量化模拟降雨事件下 OGFC 混合物的最终排水能力。结果表明，具有较高设计气孔含量的 OGFC 混合物表现出较高的渗透系数和最终排水能力。然而，OGFC 路面的原位排水能力受车道数量和宽度的影响。基于双向八车道、2% 横向坡度、20% 空气空隙含量和 5 cm 厚 OGFC 的现场项目，最小原位渗透系数确定为 825 mL/15 s。建议将车道数量和宽度以及当地降雨强度等设计因素整合到 OGFC 路面设计过程中，以实现理想的原位排水功能。OGFC 路面的原位排水能力受车道数量和宽度的影响。基于双向八车道、2% 横向坡度、20% 空气空隙含量和 5 cm 厚 OGFC 的现场项目，最小原位渗透系数确定为 825 mL/15 s。建议将车道数量和宽度以及当地降雨强度等设计因素整合到 OGFC 路面设计过程中，以实现理想的原位排水功能。OGFC 路面的原位排水能力受车道数量和宽度的影响。基于双向八车道、2% 横向坡度、20% 空气空隙含量和 5 cm 厚 OGFC 的现场项目，最小原位渗透系数确定为 825 mL/15 s。建议将车道数量和宽度以及当地降雨强度等设计因素整合到 OGFC 路面设计过程中，以实现理想的原位排水功能。