Contribuição da superfície dos pavimentos para a produção de ruído

O ruído rodoviário constitui actualmente um problema grave de qualidade ambiental, que resulta essencialmente dos mecanismos de contacto entre o pneu e a superfície do pavimento. Por conseguinte, a avaliação em termos acústicos das superfícies da rede rodoviária é importante. Assim, neste artigo estuda-se a contribuição de um conjunto de 7 superfícies de pavimentos em serviço para a produção de ruído rodoviário: 1 em betão betuminoso denso; 1 em betão betuminoso rugoso, 2 em microbetão betuminoso rugoso; 1 em betuminoso rugoso com betume modificado com borracha e 2 misturas abertas com betume modificado com borracha. A metodologia de ensaio baseou-se no Método Estatístico de Passagem. Para o estudo foram seleccionados 2 veículos ligeiros e um pesado de 2 eixos, os quais fizeram um total de 188 passagens a 3 níveis de velocidade. A cada passagem registouse o nível de ruído máximo, a velocidade efectiva dos veículos, a velocidade do vento e a temperatura do ar e da superfície do pavimento. Desta avaliação resulta que, relativamente ao betão betuminoso denso, as superfícies mais silenciosas são as de microbetão betuminoso rugoso e de mistura aberta com betume modificado com borracha, apresentando reduções entre os 4 e os 8 dB(A).Auto-estradas do Norte, S.A (AENOR)Estradas de Portugal (E.P.) Direcção de Braga

Contribution of asphalt rubber mixtures to noise abatement – time effect

Wearing course layers with a rubberized asphalt binder have been lately recommended as a measure to mitigate noise. Their acoustical performance in an early age seems to be superior to that shown by conventional layers. Nevertheless, there is no deep knowledge in relation to their behavior throughout their lifetime. The research carried out aims at observing and studying this type of mixes. For this purpose, several road sections with gap-graded mixtures, two of which with rubberized asphalt, were selected. On each road section the tyreroad noise generated by two light vehicles was measured by means of pass-by tests. After three years, those tests were repeated under the same conditions. The results focused on the comparison of the noise level versus speed among layers at the same testing time and on the same layers with different ages. The results obtained three years ago showed that gap-graded asphalt rubber mixtures have a similar performance than that of other type of gap-graded thin mixtures. The same performance was observed in the recent tests. On average, an increase of 4.0 to 4.5 dB(A) was determined for the two surfaces with rubberized asphalt, which had the same increase on noise as the control surface.(undefined

Desempenho de barreiras acústicas : dois métodos de avaliação

Em Portugal tem-se verificado um crescimento exponencial da colocação de barreiras acústicas, como meio de resposta às exigências de qualidade ambiental definidas pela Comunidade Europeia. Este facto tem como consequência a necessidade de verificação do desempenho destes dispositivos, particularmente do isolamento sonoro aéreo. Assim, no presente artigo apresentam-se as orientações da Norma Europeia CEN/TS 1793-5:2003, relativa ao método de ensaio para determinar o isolamento sonoro aéreo dos dispositivos de redução do ruído, e uma metodologia expedita, que poderá ser usada como indicativa do desempenho destes dispositivos. Para as duas metodologias apresenta-se o princípio e procedimento de ensaio, o equipamento e a forma de avaliação do desempenho. Apresenta-se ainda a avaliação do desempenho de 3 barreiras acústicas, constituídas por materiais diferentes, feita através do método expedito. Finalmente, são feitas algumas considerações quanto aos métodos apresentados, prevendo-se que a metodologia preconizada na norma europeia seja de difícil execução in situ, especialmente em zonas de relevo acidentado. A avaliação do desempenho das barreiras acústicas com o recurso a estas metodologias, em diferentes fases do seu ciclo de vida, poderá constituir uma solução vantajosa e fiável

Noise absorption of gap graded mixtures with rubberized asphalt

Sound absorption is a material property which contributes to reduce noise levels when sound propagates from the source to the receiver. Porous materials have particularly good absorption characteristics, not only because of the high percentage of air voids, but also due to their flow resistance and tortuosity. Road surface layers made of gap graded mixtures are among those absorptive materials. Because these mixtures have a void content that may be considered of medium level, this study aims to characterise their absorption capacity, particularly of those with rubberized asphalt binder. For this purpose, absorption measurements in a Kundt’s tube were performed on cores extracted from slabs with different gap graded asphalt. In order to study the effect of the rubberized asphalt, the mixtures were produced in laboratory with two types of rubberized asphalt and with unmodified asphalt. The effect of the binder was pondered with this procedure. Furthermore, the effect of porosity was considered bycomparing the results of mixtures which have considerably high and low void contents.(undefined

Assessment of the traffic noise on thin layers

Traffic noise is an important branch of the environment pollution which deeply affects the population and for that reason it has been included in the set of pavement performance indicators. Nevertheless, the knowledge on the environmental impact of the existing surface pavement layers is very limited, particularly for what respects to tyre/road noise of thin layers. These layers are at the present time widely used in a great extent with rubberized asphalt both in urban and rural roads especially in the north of Portugal due to environmental concerns. In this paper the comparison of the tyre/road noise (Lmax) generated in roads with thin surface layers is made. The noise levels generated by light and heavy vehicles are set according to the Statistical Pass-By Method (SPB) of which test methods is described in the standard ISO 11819-1:1997. At management level the information provided by tyre/road noise tests is essential to support environmentally sustainable construction and maintenance alternatives. Furthermore, at project level, the results give some insight about the relation surface layers/traffic composition

Contribution of alternative road surfaces to noise abatement

The increase of noise due to traffic particularly in urban areas has led road administrations to look for low noise surfaces in order to reduce noise impact and to improve environmental quality. This paper aims at assessing the effect of alternative road surfaces on noise abatement. It presents the main results obtained with two distinct experiments, originally intended for other purposes, which address a significant number of non conventional road surfaces. These experiments included nine road surfaces: three of them were gap graded, three contained rubberized asphalt, one had porous asphalt and two had dense asphalt. On these road sections the tyre-road noise generated by two-axle heavy trucks and three-axle heavy trucks and several light vehicles at three levels of speed were measured by means of pass-by tests. Surface texture tests were also performed. The results focused on: i) noise level variation versus speed; ii) estimated noise level for each speed level versus type of surface; iii) the variation of estimated noise level with regards to a reference surface. The best performances were achieved by gap graded mixtures with and without rubberized binder and small grain sizes. The fair behaviour shown by the porous asphalt indicates that the surface texture determined by the grain size seems to influence the noise level more than porosity. Further research on tyre-surface noise should include wide ranges of testing speeds for heavy vehicles, tests with the surface wet, tests that can provide texture spectrum and sound absorption tests

Análise da qualidade funcional e do impacto ambiental de uma estrada urbana

Este artigo tem por objectivos descrever os principais indicadores da qualidade funcional e da qualidade ambiental utilizados correntemente a nível da rede e apresentar um caso de estudo de uma estrada integrada em meio urbano reabilitada recentemente. Esta estrada contempla três camadas de desgaste diferentes, duas das quais com textura optimizada, com o objectivo de se estudar o seu efeito no ruído de contacto pneu/pavimento. Para a observação dos parâmetros técnicos de qualidade funcional (irregularidade, textura e resistência à derrapagem) foi utilizado um veículo do tipo multifunções e para a medição do ruído foram efectuadas medições junto à berma com a passagem de veículos a diversas velocidades. Com base nesses parâmetros, por um lado, prevê-se que a curto prazo seja necessário desenvolver-se actividades de conservação da qualidade funcional do pavimento. Por outro lado, verificou-se que as camadas de desgaste optimizadas reduzem consideravelmente o impacto do ruído de tráfego no ambiente

Analysis of the functional quality of pavements from texture measurements

The surface texture of a pavement, including uneveness, is largely determinant of drivers’safety and comfort. It is undoubtedly a major cause of road traffic accidents all over the world. Statistics show that one million killed and 50 million injured are reported every year by Competent Authorities. The effect of traffic noise has also become a critical public issue. On the road networking the surface characteristics of pavements also contributed to nearly 80-90% of roadway traffic noise. Not only engines or exhaust systems generate noise. The impact of tire-surface at speeds above 50 km/h also needs to be added to prime offenders. Functional requirements such as roadway safety, environmental quality, driving comfort and operating costs in the road network are assessed by indicators whose limits are continuously adjusted. The roadway texture is again a main intervenient. This paper aims at describing the texture indicators that can be used for the assessment of the texture of a pavement from a network point of view, based on profiles acquired at high speeds, including megatexture. First an overview of the concepts related to texture and the effects of texture, including unevenness, on safety, driving comfort, ride quality and environmental quality is given. Then, a case study related to a highly trafficked road in the north of Portugal is presented. This study is the second phase of a broader study that started with the analysis of the structural capacity of that road. In this second phase, a high speed profilometer was used to measure the pavement profile with a sampling rate which is considered to be adequate for the analysis of longitudinal profile, macrotexture and unevenness. Indicators such as the mean profile depth, the IRI and the rutting depth and the corresponding effects were addressed

Definição e características de superfícies de baixo ruído

As superfícies de pavimentos de baixo ruído são atualmente a medida de redução do ruído preferida pela maioria dos decisores por ser uma medida relativamente barata e por estarem na génese do ruído rodoviário. No entanto, para se averiguar se uma determinada superfície pode ser classificada de “baixo ruído” é fundamental a adoção de um sistema de classificação. Os principais objetivos deste trabalho são apresentar o problema da classificação de pavimentos, discutir a seleção de um limite ou de uma superfície de referência para apoiar a seleção de superfícies com desempenho acústico melhorado e identificar as características que conduzem a níveis de ruído de contato pneu-pavimento mais baixos, abordando-se particularmente a contribuição da macro e da megatextura.FEDE

Contribution of portuguese pavement surfaces to traffic noise

This paper aims at assessing the relative effect of Portuguese pavement surfaces on traffic noise. It presents the main results obtained with two distinct experiments, originally intended for other purposes, which address a significant number of thin layers and porous layers. These experiments included nine road surfaces: three of them were gap graded, three contained rubberized asphalt, one had porous asphalt and two had dense asphalt. On these road sections the tyre-road noise generated by two-axle heavy trucks and three-axle heavy trucks and several light vehicles at three levels of speed were measured by means of pass-by tests. Surface texture tests were also performed. The results focused on noise level variation versus speed and estimated noise level for each speed level versus type of surface. The best performances were achieved by gap graded mixtures with and without rubberized binder and small grain sizes. The fair behaviour shown by the porous asphalt indicates that the surface texture determined by the grain size seems to influence the noise level more than porosity