Research On Anti-scouring Ability Of Asphalt Pavement Surface-base Course Under Saturation

In response to the national call of "strong foundation and thin surface",the semi-rigid base asphalt pavement structure is generally adopted in the initial stage of expressway development in China.Whether it is flexible base,rigid base or semi-rigid base,it is inevitable to produce all kinds of cracks such as cracking,block crack,top-down crack and so on after the highway is built and put into operation.Coinciding with the season of rain and snow and ice melting,the pavement water will penetrate into the pavement structure along the cracks,and the dynamic water pressure generated under the driving load will wash out the pavement structure.Due to the great differences in material properties between semi-rigid base layer and asphalt surface layer and the influences of interlayer treatment on their bonding ability,the interlayers become so weak and waterish in pavement structure.Once the water damage occurs between the foundation and the surface layer,it will threaten the service life and driving safety of the road,and cause immeasurable economic losses.Therefore,there is a lot of great significance to study the anti-erosion performance between the foundation and the surface layer.Through experimental analysis and finite element simulation calculation,this paper analyzes the influence of different factors on the anti-scouring performance between layers.The main research contents are as follows:(1)Based on the bonding mechanism between asphalt pavement foundation and surface layers,the effects of different treatment materials,temperature and dynamic water scouring time on the interlayer bonding performance are studied through the dynamic water scouring test.Then combined with the improvement mechanism of interlayer contact state,the influence of various factors on the anti-scouring performance of interlayer is analyzed.(2)Based on CEL fluid-structure coupling analysis technology,the fluid-structure coupling finite element model between the base-surface layers is established,and the friction test results are taken as the contact states between layers under different treatments.Then the influence of interlayer action,temperature,driving speed and axle load on the anti-scouring performance of the interlayer is analyzed by calculating the variation law of vertical stress and vertical displacement of points.The results show that :(1)In the laboratory short-term test,it is not reliable to evaluate the anti-scouring performance of interlayer of base surface only by the apparent morphology or mass loss.(2)In this paper,the interlayer anti-scouring performance of different interlayer binders is evaluated by the shear strength and the percentage of strength decline during scouring time,and the overall ranking of strength is as follows: the emulsified asphalt PC-2< modified emulsified asphalt PSP < high penetration emulsified asphalt PCR < glass fiber lower sealing layer X < crushed stone lower sealing layer S < fiber reinforced broken stone lower sealing layer XS.When the interlayer binder is used,the contact state between the substrate and the surface will change accordingly.The difference of the contact state between the layers directly affects the anti-scouring performance of the interlayer.According to the test results,the anti-scouring performance between the base and the surface layer is improved obviously when the XS underlayer is sealed with fiber reinforced gravel,which can be used as a reference in engineering practice.(3)In the state of saturated water,the internal structure of asphalt pavement will be subjected to the scouring effect of dynamic water and the "pumping effect" caused by driving load.When the driving load ends,the interlayer water will continue to produce scouring effect on the base-surface interlayer due to the inertia effect.And the base layer is often more vulnerable to the damage of dynamic water scour than the surface layer.(4)The larger the axle load is,the faster the driving speed is and the higher the temperature is,the dynamic water scouring effect between the base-surface layer is more obvious,and the anti-scouring performance between the layers will correspondingly decrease.And the temperature and axle load have the greatest influence on the anti-scouring performance.