Dynamic response characteristics of permeable asphalt pavement based on unsaturated seepage

During rainfall, asphalt pavement structure layers are often not saturated. To study the dynamic response of unsaturated permeable asphalt pavement under moving load, 3-D finite element models for asphalt pavements with coupling of water–air–force were built based on unsaturated seepage theory. The vertical stress, the transverse stress, and the pore-water pressure, the vertical displacement responses of the asphalt pavement under moving loads were investigated. In addition, the results were compared and analyzed with that of the saturated permeable asphalt pavement. The results showed that the maximum transverse stress of the unsaturated asphalt pavement was about 200 kPa, while the saturated asphalt pavement was about 300 kPa. It is showed that the discharge of water has a great effect on avoiding cracks in the pavement. The maximum pore-water pressure of the unsaturated asphalt pavement is 56.67 kPa, and that of the saturated asphalt pavement decreases by 40.70 % in the same condition. The change of displacement in the area near the upper layer is more remarkable, and the maximum displacement of the saturated asphalt pavement is less than that of the unsaturated asphalt pavement. The vertical stress, transverse stress and pore-water pressure of the unsaturated asphalt pavement are smaller than saturated asphalt pavement. The asphalt pavement is prone to structural damage such as fatigue cracking and pit slot by dynamic water scouring when it is saturated condition. Therefore, the drainage inside the pavement is very important for the service life of the asphalt pavement. It ensures the asphalt pavement is unsaturated during rainfall. In future road construction, more permeable pavements should be considered.