附录 外文资料原文及翻译
Porous Elastic Road Surface as An Ultimate Highway Noise
Measure
S. MEIARASHI
Advanced Material Team, Material & Geotechnical Research Group, Public Works
Research Institute, Japan
mei@pwri.go.jp Abstract:Highway traffic noise in urban areas of Japan is a serious problem, not only for residents along highways, but also for highway administrators. Only 13 percent of urban highways have met the environment standard for noise. Noise barriers cannot be used as a noise countermeasure on the majority of highways on which access is not controlled. Noise levels of areas along some urban highways exceed the standard by 15 dB(A) or more. This problem is impeding new highway construction in urban areas. Porous asphalt pavement has recently been introduced on urban highways in Japan. Its noise reduction effect of 3 dB(A) is insufficient, because it only improves the noise environment satisfaction rate by a few percent. Furthermore, the durability of its noise reduction effect usually seems to be only three years, which is shorter than its life-cycle as pavement.
The Public Works Research Institute (PWRI) has, since 1993, been developing a new low-noise pavement named “Porous Elastic Road Surface” (PERS). This new pavement has a porous structure composed of granulate rubber made from old used tires as its aggregate and urethane resin as its binder. Its porosity is approximately 40 percent. The pavement was first proposed in Sweden in the 1970s, however, Swedish researchers have failed to improve it as a practical pavement. Noise reduction levels are 15 dB(A) for cars and 8 dB(A) for trucks. The author estimates that the potential noise reduction levels in Leq exceed 10 dB(A). More than 90 percent of highways in urban areas would meet the standard if this noise reduction level were achieved. The PWRI has already solved several of the problems with PERS, for example,
insufficient adhesion between the pavement and the base course, low skid resistance, and its poor fireproof performance. Its technical level has already reached the stage of test construction on urban highways.
This paper examines the general performance of PERS obtained through past development at the PWRI. It also summarizes the results of recent research done to further improve the noise reduction levels of PERS and the first test construction using PERS in Japan. The final noise reduction target for any type of vehicle is between 15-20 dB(A). The author expects that PERS will reduce highway traffic noise problems in urban areas of Japan to a minor, negligible level in the near future.
Key words:
pavement, noise reduction, highway traffic noise, skid resistance, durability, adhesion 1．Introdution
The Public Works Research Institute (PWRI) has, since 1993, been developing a new low-noise pavement named “Porous Elastic Road Surface” (PERS). This new pavement has a porous structure composed of granulate rubber made from old used tires as its aggregate and urethane resin as its binder. Its porosity is approximately 40 percent. The pavement was first proposed in Sweden in the 1970s, however, Swedish researchers have failed to improve it as a practical pavement. Noise reduction levels are 15 dB(A) for cars and 8 dB(A) for trucks. The author estimates that the potential noise reduction levels in Leq exceed 10 dB(A). More than 90 percent of highways in urban areas would meet the standard if this noise reduction level were achieved. The PWRI has already solved several of the problems with PERS, for example, insufficient adhesion between the pavement and the base course, low skid resistance, and its poor fireproof performance. Its technical level has already reached the stage of test construction on urban highways
This paper examines the general performance of PERS obtained through past development at the PWRI. It also summarizes the results of noise reduction levels of PERS at the first test construction site in Japan. The first part deals mainly with improvement of noise reduction effect with changing its porosity and thickness,
adhesion to the base course, durability, wear resistance, wet friction, and fire resistance, whereas the second part focuses on the laboratory performance testing in advance to identify a new construction method of PERS before trial construction on highways and the noise reduction effect observed at the construction site
2.Latest technology
2.1 Noise reduction
The author has conducted four noise measurements in total at the PWRI testing course to improve the noise reduction effect of PERS, including the first one described above. The second noise measurement in 1995 was focused on the influence of porosity on noise reduction. Figure 2 shows that noise reduction of PERS is almost saturated at the porosity of 35% and over. In the third noise measurement of 1996, a major issue was the effect of PERS thickness on noise reduction. The optimal PERS noise reduction levels for passenger cars, light trucks, and heavy trucks are 14-16 dB(A), 4-5 dB(A), and 3-5 dB(A), respectively. Figure 3 reveals that the noise reduction of PERS becomes a maximum at the thickness of 3 cm. Considering the relatively small difference of noise reduction between 3 cm thickness of PERS and 2 cm thickness of PERS, and material cost reduction, the optimal thickness of PERS seems to exist between 2 cm and 3 cm. The optimal PERS noise reduction levels for passenger cars, light trucks, and heavy trucks are 13-19 dB(A), 8-9 dB(A), and 6-10 dB(A),
respectively.
trucks are 8-10 dB (A). As a result, the author had to improve wet friction while sacrificing noise reduction for passenger cars
performance than DAP, with far better deformation performance than conventional pavement such as DENAP
Figure 4 - Accelerated pavement test
2.5 Fire resistance
Fire resistance was thought to be a potential problem, since rubber may burn fiercely. The fire hazard problem has been studied by PWRI. Squares of PERS 5×5 m were placed outside a laboratory, 36 liters of diesel oil or gasoline were sprinkled on the surface as well as on an adjacent (conventional) asphalt pavement. The fluid was then ignited with a torch, and factors such as pavement materials, height of flames and generation of smoke were observed and the tests were also filmed.
In the experiments, three surfaces were compared: dense asphalt concrete, porous asphalt concrete and the 5×5 m panels of PERS. The results, as given in Table 1, show that regarding spreading speed and flame height, the PERS was safer than the dense asphalt concrete. Figure 8 illustrates these tests.
Table 1 - Fire resistance test condition
Surface type
Burning of fuel and pavement materials
Denap
Fuel oil spreading over the pavement surface strongly burned with reddish flames but the pavement did not
2.5-3.0 m
Fuel oil burned incompletely, producing a column of black smoke.
Flame height
Smoke generation