The Influence Of Pore Pressure On The Performance Of The Asphalt Pavement And Its Monitoring

The fundamental cause of water damageis that pore water pressure under vehicle load reducesthe cohesive force of asphalt concrete.Permeability of surface layer is the decisive factor for thedistribution of pore water pressure.The paper studies the distribution of pore water pressure and itseffect on the performance of asphalt concrete by the combination of laboratory experiments,numerical simulation and on-site monitoring. The research result laid the foundation for revealing themechanism of water damage and taking effective measures to prevent water damage. The specificcontents of this article are as follows:Firstly, density test ofthe core samples in rut board were carried out,the porositywas calculated.Its internal porosity distribution is obtained by CT scanning technology, and permeability of asphaltmixture is analyzedby measurement of permeability coefficient of asphalt samples under differentwater pressure. The results showed that the distribution of internal porosity in asphalt thicknessdirection was decreasedthen increased,the relation between permeability coefficient and seepagepressure follows a power law function, there is no apparent correlation between porosity andpermeability coefficient.Secondly, hydrodynamic erosion test on the core samples of rut board was conduct to measurethe influence of hydrodynamic pressure on the performance of asphalt mixture. The penetration test isrepeated and the freeze-thaw splitting test is also conducted to evaluate the effect of hydrodynamicpressure and flushing times on permeability and water stability of asphalt mixture.Experimentalresults show that the permeability coefficient variation of asphalt mixture is decreased when porosityincreased andit has no apparent relationshipwith hydrodynamic pressure or erosion times. TSR valuedecreased with the increaseof water erosion times and dynamic pressure.Thirdly, considering the asphalt as porous medium, a three-dimensional pavement model isestablished based on the classic fluid-structure interaction theory of porous medium by using the finiteelement softwareABAQUS,and the relationship function of the permeability with respect to thehydrodynamic pressure is adopted in the numerical simulation.The distribution of stress, displacementand pore water pressure on the saturated asphalt pavement structure was simulated.And effectsofpermeability coefficient, load and surface elastic modulus change on pore water pressuredistributionwas discussed.Finally, the pore water pressure in saturated water rut plate under the rut meter wheel loads were test in laboratory by the fiber Bragg grating pressure sensor, the result shows that pore water pressureis about160kPa.Then,the pore water pressure in saturated asphalt pavement under the vehicle loadsmeasurements is collected from the field test. The results show that the maximum pore water pressurearrived peak value on the bottom of upper layer. Whentruck traveling at a low speed the pore waterpressure in pavement is similar to the laboratory rut broad test. The finite element calculated porewater pressurevalues are compared with the field measurement, then, the causes of the difference isanalyzed.