Research On Key Technology Of Two-layer Porous And Low-noise Asphalt Pavement

Two-layer porous asphalt pavement is composed of two layers of single porous asphalt mixture.In comparison with single layer porous asphalt,its function in reducing pavement noise,improving the effect of drainage and preventing blocking is more prominent.It is studied and applied more and more in Europe,Japan and other countries.As a new type of functional pavement structure,there is still lack of technical reserves in China.In the thesis,a thorough and systematic research on two-layer porous asphalt is carried out,including studies on the pavement structure,material design,construction technology and application.First of all,according to the pavement design method of China,structures of two-layer porous asphalt pavement on semi-rigid base and flexible base were calculated and analyzed respectively.The results show that the two-layer porous asphalt pavement has little impact on deflection and bending tensile stress of the whole pavements system.Then the material design of two-layer porous asphalt pavement was studied.The recommended combination of gradation and structure of PAC-10 and PAC-5 was proposed through the regression analysis.The design method of two-layer porous asphalt mixture and single porous asphalt pavement are basically same.By comparing the test results of vernier caliper and vacuum encapsulation method,the necessity of detecting the density of porous asphalt mixture with vacuum encapsulation method was proposed.In order to solve the core problem of the durability of porous asphalt pavement,the design method of porous asphalt mixture with high anti-raveling characteristic was studied and proposed.High viscosity additive(HVA),which is suitable for using porous asphalt in the high temperature and overloading condition in China,was developed.And test methods and technical standards of this type of material were proposed.The effect of anti-raveling property was analyzed by comparing the quality of asphalt,asphalt content,air voids characteristics,hydrated lime antistripping agent,different types of fiber and so on.The stone loss rate from raveling was reduced from 15%to 10%by optimizing the variables combination based on their influences.In terms of performance evaluation of two-layer porous asphalt pavement,a plane type grain abrasion mechanism based test method was studied to compare the anti-raveling performance of single and two-layer porous asphalt pavement.Furthermore,the drainage ability of two-layer porous asphalt pavement was studied systematically.By testing the horizontal and vertical permeability coefficient,the finite element software was employed to simulate and analyze its drainage characteristics.For problems of poor test reproducibility and poor accuracy of water penetration,automatic electronic water seepage instrument based on automatic weighing and precise timing was developed and applied successfully.To verify the long-term water-draining function,the repeated blocking and scouring simulation experiments were conducted by utilizing soils with different plasticity index.The blocking period cycle and blocking rate of porous asphalt pavement was studied by above mentioned experiment.Test results show that the water-draining function of single layer and two-layer porous asphalt pavement could restore to 80%and 90%of the original permeability respectively after being scoured repeatedly by rain water,and the effect permeability could maintain for 6 to 8 years.To solve the infiltration and blocking problems of ordinary marking paint,the flocculent and dotted permeable marking was developed on the basis of a two-component material.The permeable marking itself has the drainage ability,while it meets the requirements of normal traffic marks.It can effectively eliminate the water accumulated on the side of the mark.By theoretical analysis of noise absorption coefficient of different porous asphalt pavement combination scheme,combined with indoor and field noise test,a superior noise reduction performance was verified for two-layer porous asphalt pavement.The effect is more significant with high driving speed or testing in rainy day.The anti-sliding performance of porous asphalt pavement was studied by laboratory test.More prominent anti-sliding performance was found by using the brake test on site.Surveys showed that the average traffic accident rate on porous asphalt pavement was reduced by 46.7%in comparison with the adjacent sections with dense surface in rainy days(76.2%down on four lanes).Double layered paving(warm in warm)technology was investigated and surveyed for construction of two-layer porous asphalt.Technical parameters of the paver were studied and compared with the conventional layered paving,follow-up paving technology.As there is lack of special double layered paver in China,the feasibility of "cold + hot" paving technology was analyzed by setting bonding layer between the two porous layers.1 km test section of two-layer porous asphalt pavement trial section was successfully built in expressway from Suining to Ziyang.The two-layer porous asphalt pavement construction and quality control technology were founded through the research on the trial section.The above research covers the main technology of two-layer porous asphalt pavement system.The research findings can be used as guidance on structure and material design,mixture production,road construction of two-layer porous asphalt pavement.The achievements including high anti-raveling porous asphalt mixture design,automatic water seepage instrument,plane type abrasion test method,anti-clogging performance study,permeable marking,also have high application value for both single layer and two-layer porous asphalt pavement in China.