Study On The Characteristics And Mechanism Of Permeability Performance Decay Of Porous Asphalt Pavement Under The Condition Of Void Clogging

Porous asphalt pavement is an important development way for the pavement to achieve a high-quality because of its safety,comfort and low noise.However,due to mud,sand,and tire debris carried by vehicle pedestrians,the road surface is easy to be clogged,causing the water seepage performance to decline or even be lost.In order to ensure the durability of the seepage function of the porous asphalt pavement,it is necessary to deeply investigate its seepage and clogging laws.At present,the seepage and clogging laws of porous asphalt course?PAC?are mostly focused on the macroscopic aspect,and the description of the clogging process is empirical.Moreover,it is difficult to determine the evolution law of the meso-void characteristics in the PAC clogging process using traditional research methods,thus cannot reveal the decay mechanism of water seepage function in the process of porous asphalt pavement clogging.Therefore,the key factors affecting PAC seepage and clogging characteristics were analyzed from macroscopic and microscopic aspects in this paper,the pore characteristics and the migration law of clogging particles in PAC were quantified,and the evolution law of pore characteristics in PAC was clarified.Firstly,six kinds of PACs with different gradation were designed and their pavement performance was verified.Secondly,using aeolian sand,silty soil and sandy soil mixture as clogging materials,the decay laws of water seepage coefficient of PAC were studied under repeated clogging conditions and cyclic clogging-cleaning conditions,respectively.And the recovery effect of PAC water permeability coefficient under three cleaning methods was studied,the influence of different factors on water permeability coefficient under different clogging conditions is analyzed,and the clogging prediction model under different clogging conditions is established.Finally,X-ray CT and image processing techniques were used to analyze the microscopic voids of PAC-13 before and after clogging?cleaning?when the aeolian sand was used as plugging material,and the prediction model of PAC water seepage and clogging based on mesoscopic void parameters was established.The main conclusions are:?1?The initial water permeability coefficient of PAC increases with the increase of the porosity and the nominal maximum aggregate size.There is a significant linear correlation between the initial water permeability coefficient and the porosity and effective porosity.The anti-clogging performance of the PAC-13 is better than the PAC-10.PAC with larger voids have more loading times.The attenuation rate of the permeability coefficient of PAC specimens caused by different clogging materials is different,among which aeolian sand is the largest,sand-soil mixture is the second,and silty soil is the smallest.?2?With the loading of the clogging material,the water permeability coefficient of PAC specimen changed exponentially in the form ofK_N?28?k ₀e^-?N.Under the condition of repeated clogging,the clogging factor?and the number of clogging loading N are affected by factors such as porosity V,effective porosity V',initial water permeability coefficient k₀,non-uniformity coefficient C_u,curvature coefficient C_c and particle size ratio R₁₅ and R_S.The results show that the particle size of PAC-13 is mainly in the range of 0.15?2.36mm,and that of PAC-10 is mainly in the range of 0.075?2.36mm.?3?The spatial distribution of porosity is irregular in PAC.The porosity are inversely proportional to the number of voids,and directly proportional to the equivalent diameter and fractal dimension.After cleaning,the number of voids and equivalent diameter of PAC were between un-clogged and clogged,and the fractal dimension did not change significantly.The migration depth of clogging material increases with the increase of porosity,and the most serious position of clogging is about 10 mm from the top to the bottom of the mixture.There is a good linear relationship between the measured porosity by volume method and the calculated porosity,void number,equivalent diameter and fractal dimension of PAC samples before and after clogging and cleaning.