Tests On The Unsaturated Seepage Of Asphalt Pavement And The Study Of The Related Numerical Simulations

According to a lot of investigations on pavement service condition,flood damage has been identified as the primary reason for the decrease in highway performance and its service life and the effective way to prevent flood damage is to install a subsurface drainage system,and thus it’s essential to study further the unsaturated characteristics of highway pavement.On the basis of studying the unsaturated theory and reading a lot of relevant literature,it is to try to get the water seepage rule curve of asphalt-concrete pavement through experiments and then,combining the finite elements simulations,study the unsaturated seepage problem of pavement.Primary works done as follows:(1)The basic unsaturated flow theory is introduced and compared with saturate flow theory.The current types of pavement subsurface drainage system,facilities,and road drainage performance evaluation criteria are introduced as well.(2)Study tests for the law of the asphalt pavement seepage were carried out outdoors by inserting soil moisture sensors in the asphalt surface,applying water with a certain degree of pressure on the surface.Based on the data from the sensors,a water infiltration rule curve of pitch surface reflecting the changes of water content of pitch surface per volumetric under the water with pressure over time.The test curve was checked against the real moisture of asphalt surface obtained through laboratory tests.(3)With the curve from the tests as a standard,by simulating the tests before with seep/w finite element analysis software,analyzing the internal road seepage field and by adjusting the parameters of the relevant material to make simulation curve more consistent with the experimental curves,the method of setting the parameters of the numerical simulations was got.(4)On the basis of the existing research of domestic scholars,with the changing of the unsaturated parameters of the surface,the unsaturated seepage numerical simulations were carried out and the results were compared and contrasted,showing that such changes has almost negligible impact on the medium-sized partical asphalt pavement but has larger impact on the coarse graded bituminous concrete pavement.(5)The boundary conditions during the numerical simulations and the effect of the groundwater level on the results of the calculation were discussed and analyzed,founding that the pooled water conditions can be simulated with the boundary conditions of the pressured-water tap and the source water pipe,and that,the position of the groundwater level has little effect on the simulations,but the maximum value of matric suction head has larger impact on the result of the calculation,thus it should be measured.