Research On Preparation And Properties Of The Tunnel Noise Reduce Materials

With the rapid development of the transportation of China, the noise pollution generated by tunnel as an important part of highway grapped more and more attention. Tunnel is a semi-enclosed space, and in this space,the direct sound and reverbration sound mixed together and last up to 30 seconds. So,we can see the tunnel as a high noise environment.However,in our country, because of the need of fireproof, most of the tunnel does not been taken any noise reduction measure but adopted cement and concrete material which has a very low sound absorption coefficient just for fire. Information shows that the noise value of our tunnels were 90dB around that will cause great harm for the drivers, passengers and staffs who have been long engaged in the tunnel maintenance. Therefore, study on noise reduction material of the tunnel, put forward relevant measures and predict the noise of the tunnel is of great significance.Room acoustics theory and some research correlated shows that reduce the room constant by paving a kind of low noise road surface,or lying sound-absorbing material on the tunnel wall is an effective and feasible way to cut down the tunnel's noise.The paper is based on this.In this paper, acoustic characteristics of low noise asphalt pavement is studied,and a kind of sound absorbing materials made of expanded perlite which used for tunnel's wall is prepared.Then,we taked Wuhan Yangtze River Tunnel for example to predict the noise level in it,found that an obvious noise reduction effect of 13.58dB shoud be achieved once the pavement and material is employed.In this paper, by exploring the acoustic properties of open-graded friction course asphalt mixture (OGFC),we regard it as a porous sound-absorbing material, can be used as the tunnel low-noise asphalt pavement; At the same time,the effect on sound absorption coefficient by porosity, the maximum nominal size, structure thickness were sthdied. Meanwhile, both the standing wave tube and the reverberation room method are to be used to measure the sound absorption coefficient,and noise reduction coefficient (NRC) of 0.42 was found,that means it will reduce road noise 6.79dB compared with ordinary concrete pavement. Besides,in the theoretical models, it is reasonable and feasible to explain the sound absorbing mechanism of this porous material using Professor Ma Taiyou's tube model.In order to proof fire, a low-cost inorganic materials-expanded perlite as the main sound absorption materials, ordinary Portland cement as the cementing material were used to prepare the sound-absorbing material of tunnel wall.Furthermore, air-entraining agent was added to introduction an appropriate amount of pores to increase absorption properties;fiber to improve strength, as well as sound absorption coefficient; hydrophobic agent to cutdown the reduce of the absorption coefficient due to the moisture in the tunnel.At the End a kind of sound-absorbing material which average absorption coefficient of 66.2%, flexural strength and compressive strength higher than 1MPa was got.