Research On Noise Reduction Method Of Expressway Under Extension Conditions

With the increasing number of automobiles,the original expressway can not meet the traffic demand.The expansion of expressway can alleviate the tense demand of regional traffic corridors in China.Among them,widening on one or both sides of the old road will have greater noise impact on the original residents around the original road.The purpose of this paper is to provide a feasible solution to reduce the impact of road noise on the residents around expressway through the design of the height,form and material of noise barrier,combined with the design of porous noise-reducing pavement and forest belts,starting with the change law of Expressway noise before and after expansion.First of all,the noise variation law of Expressway before and after expansion is simulated.Sound PLAN software is used to establish road models before and after the widening of highway joints,and the sound points in horizontal and vertical directions around the highway.The attenuation propagation of traffic noise in horizontal space,the attenuation variation of noise barrier effect before and after the expansion,and the noise propagation law of different low noise pavement before and after the expansion are analyzed.The results show that in horizontal direction,traffic noise decreases with the increase of the distance between the sound receiving point and the middle line of the road,especially within 30 meters from the center line of the road,and the noise increases obviously after expansion.The greater the speed of the vehicle,the greater the noise,the greater the noise value will increase by 1 dB(A) for every 10km/h increase of the speed of the vehicle,and the effect of the truck on the noise will be greater than that of the car;the low-noise road surface is only the source of noise from the type of the road surface.The size is corrected.Secondly,the structure and material characteristics of the sound barrier are studied.Based on Sound PLAN software,a road model with different noise barriers is constructed.The effects of height,structure and material type of noise barriers on reducing traffic noise are analyzed respectively.The reliability of noise prediction results is verified by field measurement.The results show that the height of the barrier can effectively affect the barrier effect,and the insertion loss can increase by 3～4dB(A) for every one meter increase in the height of the barrier.When the effective height is equal,the noise reduction effect of vertical noise barrier is the best,which can reach 5～13dB(A).The barrier effect of cylindrical noise barrier at the top is better than that of bending noise barrier.The use of sound-absorbing materials has a certain effect on the attenuation of the sound pressure level inside the road,only about 2dB(A).The measured data can well verify the reliability of the calculation results of "RLS-90" road noise prediction model.Then,the noise reduction performance of double-layer porous asphalt pavement is studied.Based on CT scanning technology and three-dimensional reconstruction method,the model of drainage pavement structure was established.The model of pump air noise and the model of vehicle tire rolling vibration and noise were established by using Abaqus finite element software.The noise reduction effects of thin and thick double-layer porous asphalt pavement,single-layer porous asphalt pavement and common asphalt pavement are compared and analyzed,and the distribution of noise and sound energy in different frequency range is analyzed.The results show that the noise reduction effect of porous asphalt pavement is better than that of ordinary asphalt concrete pavement.The noise reduction effect of double-layer porous asphalt pavement is better than that of single-layer porous asphalt pavement.The noise reduction range can reach 2～4dB(A).Compared with ordinary asphalt pavement,double-layer porous asphalt pavement can reduce noise by about 6 dB(A).Finally,different combination noise reduction schemes are studied.Based on Sound PLAN software,the noise reduction effects of different sound barriers,double-layer porous asphalt pavement and forest belt greening combination were analyzed.The results show that the noise reduction effect of the combination of sound barrier and double-layer porous asphalt pavement is better than that of single form,and the noise reduction is about 10 dB(A).The combination of sound barrier,forest belt and double-layer porous asphalt pavement has more significant effect on noise reduction.