Drainage Characteristics Of Double-layer Drainage Asphalt Pavement

Double-layer drainage asphalt pavement structure has good performance in drainage,noise reduction and skid resistance.However,drainage behavior of double-layer drainage asphalt pavement is different from that of single-layer drainage asphalt pavement.In addition,clogging phenomenon in drainage asphalt pavement also lead to performance deterioration.Generally,scholars did experiments in laboratory or did research based on engineering applications,so test period is longer and cost is higher.This paper did research on drainage,anti-clogging and self-cleaning performance to make recommends on pavement design.Based on the quartet structure generation method and the idea of BA network,this paper proposes a random growth method of double-layer drainage asphalt pavement considering optimizing of the pixel.Difference between generated gradation curves and generation curves of actual pavement structure was less than 7.4%,and the parameter of fractal dimension also had good reliability and stability.Based on Euler-Lagrange equation method and fluid-solid coupling theory(FSI)in the CFD(computational fluid dynamic)software Flow-3D,this paper did simulation on seepage phenomenon in channels of double-layer drainage asphalt pavements and the seepage coefficient of several drainage asphalt pavements was calculated based on linear Darcy equation.In addition,max rainfall intensity was calculated based on Boussinesq equation in Comsol.This paper studied relationships between void ratio/connected void ratio and drainage performance of drainage asphalt pavements.According to the results,seepage coefficient of double-layer drainage asphalt pavement was 3.6% more than that of single-layer drainage asphalt pavement.When total thickness of two layers were determined,with the increase of the thickness of the upper layer,seepage coefficient reduced about 1.56%.With the increase of void ratio and connected void ratio,seepage coefficient of the drainage asphalt pavement grew as a polynomial function.This paper proceeded clogging performance numerical performance of single/double-layer drainage asphalt pavement based on Sediment Scour module in Flow-3D.Double-layer drainage asphalt pavement remained more sediment than single-layer drainage asphalt pavement did because aggregates of the up layer were fine,but more sediment distributed in the top layer.When radius of sediment decreased,the volume and proportion of sediment in the top/bottom layer increased 30.4%/120.7%.This paper analyzed self-cleaning effect of double-layer drainage asphalt pavement based on Sediment Scour module and Coupled motion module in Flow-3D.Based on the research,hydrodynamic pressure gradually decreased but self-cleaning performance would improve 26.1% when equivalent particle size of the top layer increased.Changing structure combination of double-layer drainage asphalt pavement(total thickness of layers was determined)only improved self-cleaning performance about 5.7%.