Study On Noise Reduction Mechanism And Mix Proportion Design Method Of Polyurethane Porous Elastic Road Surface Mixture

With the development of China’s social economy,the number of motor vehicles has continuously created a historical high,the urban road network has gradually improved,the tire/road noise problem has gradually emerged,and road traffic noise has gradually become one of the main problems of government management.Paving low noise pavement is an effective way to solve road traffic noise.Domestic and foreign studies have found that polyurethane elastic road surface(PERS)is one of the most effective low noise pavement types to reduce tire/road noise.In this paper,through a series of experiments,the sound absorption performance,vibration reduction performance and comprehensive noise reduction ability of PERS mixture are analyzed and studied,and the design method of PERS mixture based on noise reduction function-road performance is further proposed,which provides theoretical basis and technical support for the research,design,popularization and application of PERS.Firstly,the mechanism of tire/road noise generation is analyzed by acoustic principle,and the composition of traffic noise is explained from the two factors of tire/road noise generation and enhancement.Among them,the pump gas effect and tire vibration are the sources of tire/road noise,and the cylinder effect and resonance effect further form the enhanced noise.The PERS mixture has a large porosity and a large proportion of rubber particles.With the coupling effect of porous sound absorption and elastic vibration reduction,the noise reduction effect of the mixture is further improved.Secondly,considering different void ratio and rubber particle content,11 kinds of PERS mixture specimens were prepared.The influence of different factors on PERS noise reduction effect was studied by impedance tube test,uniaxial compression dynamic modulus test and tire vertical falling noise test,and the noise reduction mechanism of polyurethane elastic porous mixture was analyzed.The test results show that the PERS porosity is positively correlated with the sound absorption coefficient of the mixture,and the rubber particle content is negatively correlated with the dynamic modulus of the mixture.The dynamic modulus of the mixture decreases with the increase of temperature.Under the conditions of 20°C and 10 Hz loading frequency,the dynamic modulus of PERS-VIII specimen is 1/48 of that of AC mixture and 1/27 of that of PAC mixture.The larger the void ratio and the larger the rubber particle content in the PERS mixture,the lower the sound pressure level of the tire vertical drop test and the better the noise reduction effect.Under the same conditions,the noise reduction ability of the PERS-VIII mixture was 9.7 dB compared with that of the ordinary AC mixture and 4.8dB compared with that of the porous PAC mixture.Through the theoretical analysis of grey correlation degree,the correlation degree between porosity and the noise reduction ability of PERS mixture is 0.658,which is slightly greater than that of the rubber particle content of 0.641,indicating that porosity has greater influence on the noise reduction ability of mixture than the rubber particle content.Finally,considering the contradiction and balance between the noise reduction function and road performance of PERS mixture,a design method of PERS mixture based on reduction function-road performance is proposed.The optimal gradation,rubber particle content and optimal polyurethane content of PERS mixture were studied.The experimental results show that the PERS mixture with 25 % target porosity,20 % rubber particle content and 4.5% polyurethane content is the optimal solution in terms of noise reduction ability and mechanical properties.The road performance of PERS mixture,such as high and low temperature stability and water stability,was verified.The test showed that the PERS mixture had low temperature sensitivity,good high and low temperature stability,but the water stability was general.It was suggested that the water stability should be taken as an important design index in the design of PERS mixture in the future.