Measurement of pore water pressure in asphalt pavement and its effects on permeability

• We propose a fiber optic hydraulic pressure sensor composed of FBG and other parts.
• The pore water pressure in asphalt pavement was measured by using this sensor in situ.
• The pore water pressure in asphalt pavement would increase with the increasing vehicle speed.
• The pore water pressure in pavement at depth of 4 cm is higher than it at depth of 10 cm.
• The permeability of asphalt mixture at different hydraulic pressures was obtained.

On the effect of pore water pressure in a saturated asphalt pavement, fluid velocity and water infiltration rate will increase, which have a disadvantage influence on asphalt mixture strength. In order to measure the pore water pressure in pavement, a fiber optic hydraulic pressure sensor (FOHPS) is designed. The theoretical correlation between the applied pressure and the center wavelength shift of the FOHPS is derived by laboratory experiment. The pore water pressures in asphalt pavement at some running speeds were measured in situ. Furthermore, a falling head permeameter method was used to measure the permeability coefficients of asphalt mixture exposed to hydraulic pressures which were from 40 kPa to 350 kPa, and the correlation between permeability and hydraulic pressure was obtained. The experimental results showed that the pore water pressure would increase with the increasing car’s speed, but the lifetime of pore water pressure decreases with the increasing speed. The permeability coefficients of SMA-13 and AC-20 mixtures decrease with the increasing hydraulic pressure, but the water infiltration rate increases on an approximate linear curve as the hydraulic pressure increased from 40 kPa to 350 kPa.