Research On Three-Dimensional Void Morphology And Clogging Mechanism Of Permeable Asphalt Mixture

Permeable asphalt pavement can quickly eliminate the water accumulation on the pavement surface,but its permeability is greatly affected by clogging effect in the service process.Therefore,it is necessary to clarify the clogging mechanism of permeable asphalt mixture to clarify the evolution law of permeability of permeable asphalt pavement during operation.As the carrier of fluid carrying clogging material,the complex shape of void structure inevitably leads to the complexity of clogging behavior.However,due to the limitation of test methods and image processing technology,the existing studies have not yet clarified the clogging mechanism of deposited particles and the structural characteristics of clogged voids,and failed to clarify the influence mechanism of clogging effect on the permeability of permeable asphalt mixture,resulting in the lack of guidance for the material composition design of permeable asphalt mixture.In view of the above problems,the three-dimensional void morphology of permeable asphalt mixture was constructed based on the computer tomography,and the research on the three-dimensional void morphology was carried out.The clogging mechanism of deposition particles was studied,and the shape characteristics and spatial distribution of outflow and deposition particles were clarified.The structural characteristics of clogged voids were explored,and the shape and distribution of clogged voids were clarified.The influence of deposition particles distribution and structural characteristics of clogged voids on the anti-clogging ability was analyzed,and the optimization research of design method of permeable asphalt mixture was carried out.The main research contents and achievements are as follows:Based on the technology of computed tomography,two-dimensional image was obtained.Wavelet transform denoising,morphological processing and maximum inter class variance method were used to realize image denoising,restoration and void extraction.Based on projection reconstruction theory and fluid flow boundary conditions,a connective void recognition algorithm was developed.The topological refinement method was used to extract the skeleton structure of 3D voids.The calculation method of three-dimensional void morphology parameters was developed.Based on the particle accumulation theory,the filling factor was used to characterize the gradation characteristics of permeable asphalt mixture,and the relationship between three-dimensional void morphology and gradation characteristics was established.Using digital microscope and image processing technology,the shape characteristics of outflow and deposition particles were studied.Based on image registration technology and digital image processing technology,the deposition particle recognition algorithm was developed.The distribution of deposition particles was studied based on the multifractal theory.The influence of gradation type on particle distribution was analyzed.The results show that the smaller the filling factor of permeable asphalt mixture is,the wider the distribution range of deposited particles is.The influence of void morphology of permeable asphalt mixture on the distribution of deposited particles and the shape characteristics of outflow particles was investigated.The results show that the void diameter has the greatest influence on the distribution of deposition particles and the morphology of outflow particles.The algorithm for identifying the clogged voids was developed,which realized the identification of clogged voids.Image processing technology was used to analyze the size distribution and shape characteristics of clogged voids.Based on multifractal theory,the spatial distribution characteristics of clogged voids were analyzed.On this basis,the influence of the morphology of clogged particles,gradation types and void structure on the morphology and distribution characteristics of clogged voids was explored.The results show that the filling effect of fine aggregate affects the morphology and distribution of void structure.The tortuosity of voids has the greatest influence on the morphology and distribution characteristics of clogged voids.Considering the permeability anisotropy of permeable asphalt mixture,the influence of clogging behavior on the permeability of permeable asphalt mixture was explored.Considering the overall and local distribution of the particle,the influence of particle distribution on the permeability of the structure was analyzed.The influence of void morphology on residual permeability was explored,and the relationship between void morphology and anti-clogging ability of permeable asphalt mixture was clarified.The best filling coefficient of permeable asphalt mixture was determined by considering the permeability and anti-clogging ability.Based on the maximum density theory,the optimal gradation range of permeable asphalt mixture was determined,and the road performance,three-dimensional void morphology,permeability and anti-clogging ability of the optimal gradation permeable asphalt mixture were verified.