Abstract: In this paper,the influences of connecting air voids on the seepage characteristics of the porous asphalt mixture were investigated; the micro-distribution characteristics of the porous asphalt mixture is discussed based on industrial CT; a seepage-flow numerical model of the mixture is established; the internal flow characteristics of wa- ter within the porous asphalt mixture is analyzed by using the finite volume method; and the water flow characteris- tics affected by the diameter,the tortuosity and the minimum sectional size of the connecting air voids are dis- cussed.The results indicate that (1) the air void diameter greatly influences the flow velocity and the velocity is approximately proportional to the square of the void diameter; (2) the larger the tortuosity is,the smaller the ve- locity and the flow are; (3) as the bending structure has little influence on the velocity and the flow,it can be neglected and the tortuosity is solely taken into consideration; (4) if the minimum sectional diameter of the con- necting air voids is taken as the equivalent diameter of the whole water path for analyzing the seepage characteri- stics,the calculated permeability coefficient may be smaller than the actual value,so that a revision is necessary.

Key words: porous asphalt mixture, drainage characteristic, connecting air void, seepage, tortuosity, minimum sectional diameter