Research On Attenuation Law And Mechanism Of Noise Reduction Function Of Porous Asphalt Pavement Under The Condition Of Void Clogging

The large porous structure is the main reason for the origin noise reduction of the porous asphalt concrete（PAC）.As a new pavement structure,PAC also takes into account the water seepage,anti-skid and anti-glare and other functions,and it has become an important part of the construction of sponge city.However,the void structure of the PAC will be clogged by the road contaminants during the use of the road,causing its noise reduction function to decline or even be lost.In order to explore the way to optimize the PAC noise reduction function,it is necessary to deeply investigate the noise reduction function attenuation law and mechanism because of the void clogging.At present,most of the research on PAC noise reduction function is the empirical summary of actual data and most studies show that the larger the porosity,the stronger the noise reduction ability.However,complex void structures are the key to determining PAC noise reduction performance.Based on the summary and reference of the current research results,this study comprehensively studied the attenuation law and internal mechanism of PAC noise reduction function under the condition of void clogged by combining theoretical analysis,laboratory test and mathematical statistics.In this study,10 groups of PAC specimens with different mixture parameters were designed.Three kinds of clogging materials and three kinds of cleaning methods were used to simulate the void clogging-cleaning phenomenon of PAC.The variation law of acoustic characteristics of PAC under initial conditions and void clogging conditions was studied by using the tire-rolling-down method and standing wave tube method.Based on X-ray CT technology,the influence mechanism of void clogging on the attenuation of PAC noise reduction function is expounded from the perspective of microstructure.Finally,based on the statistics and analysis of experimental data,the PAC noise reduction function attenuation prediction model is constructed.Based on the above work,the research has achieved the following results:（1）PAC has the ability to reduce road traffic noise significantly.PAC reduces noise by 3-8dB on average,and the initial sound absorption coefficient is generally between 0.5 and 0.8.PAC has strong absorption capacity for medium and high frequency noise,which reduces people’s aversion to road traffic noise.The asphalt mixture parameters significantly affect the acoustic characteristics of PAC.Increasing porosity,reducing particle size and increasing thickness are effective ways to enhance the noise reduction ability of PAC.（2）Under the condition of continuous clogging,the porosity affected the attenuation rate of PAC noise reduction function and the sound absorption coefficient of PAC remained between 0.3 and 0.4 after complete clogging.Under the condition of cyclic clogging-cleaning,the noise reduction ability of PAC with large porosity decays slowly,the attenuation of small porosity is faster and the irreversible loss of sound absorption performance is more.The noise reduction durability of PAC can be improved by increasing the design porosity.（3）The phenomenon of void clogging weakens the noise reduction ability of PAC.The drift sand has the greatest negative impact on the noise reduction function,and the silty soil has the smallest impact.The sand-soil mixture has the middle impact.The void cleaning partially or completely restored the noise reduction ability of PAC.The effect of high-pressure water washing was the best,and the effect of manual cleaning was the worst.The vacuum pump suction cleaning was between the two and was close to the effect of high-pressure water washing.（4）The change of void microstructure is the key of the attenuation of noise reduction function.The microscopic size of the void is positively correlated with the noise reduction function of PAC,which can be characterized by the F_min.The angularity of void meso-contour is negatively correlated with the noise reduction function of PAC,which can be characterized by S.The mechanism of the attenuation of the noise reduction function of PAC during clogging can be explained by adhesion,filling and“necking”phenomenon.（5）There are two kinds of attenuation prediction models for PAC noise reduction function,one is the macroscopic prediction model based on asphalt mixture parameters and clogging parameters,the other is the microscopic prediction model based on void microscopic characteristic parameters.The reliability of the two prediction models is good.