Simplified Calculation and Validation of Water Infiltration Rate of Asphalt Pavement on Filled Subgrade

In order to determine the water infiltration rate (WIR) of asphalt pavement on a filled subgrade, a three-layer structure consisting of an asphalt surface layer, base course, and subgrade was examined. Based on a two-dimensional saturated seepage theory, a simplified calculation model for pavement WIR was established. The effects of the vertical permeability coefficient of the asphalt surface layer, distributional density and width of cracks, and thickness and permeability coefficients of the base course and subgrade on the pavement WIR are discussed. Results indicate that pavement WIR exhibits a power function relationship with the crack density when other influencing factors are constant. As the number of cracks increases, pavement WIR increases. WIR has an approximately linear relationship with crack width; the wider the crack, the greater the pavement WIR. For asphalt surface layer, 0.1 mm/s (0.01 cm/s) is the permeability coefficient threshold. Above 0.1 mm/s (0.01 cm/s), the surface layer permeability coefficient accelerates infiltration. When the coefficient is less than this value, it has little effect on WIR. For the base course horizontal permeability coefficient, 0.1 mm/s (0.01 cm/s) is the threshold. When the value is less than 0.1 mm/s (0.01 cm/s), the base course thickness and the permeability coefficient have little effect on pavement WIR. For the subgrade permeability coefficient, 0.1 mm/s (0.01 cm/s) is taken as the threshold. When the coefficient is less than 0.1 mm/s (0.01 cm/s), the effects of subgrade thickness and permeability coefficient on pavement WIR are slight. Finally, field test data were used to discuss the current recommended values. For pavement without alligator cracking, the calculated average WIR is 0.46 x 10(-3) mm(3)/(s.mm(2)) [0.04 m(3)/(d.m(2))]. The calculated average pavement WIR with alligator cracking is 0.43 x 10(-2) mm(3)/(s.mm(2)) [0.37 m(3)/(d.m(2))], which is 2.5 times larger than the value recommended by current drainage specifications 0.17 x 10(-2) mm(3)/(s.mm(2)) [0.15 m(3)/(d.m(2))]. The results can provide valuable reference for the drainage design of subgrade and pavement. (c) 2021 American Society of Civil Engineers.