Artigos de Revista

There is often a risk of pollution entering or moving in the road environment. This may giverise to problems of various severities dependant on the local environment around and under thepavement. Therefore the risks have, first, to be assessed and them appropriate action taken tominimise the movements and/or the impacts. This chapter describes the criteria to be appliedwhen considering pollution mitigation schemes and the constraints that must be taken intoaccount. Both traffic considerations (which often forms the driver for pollution supply) andeconomic considerations are included in the coverage of the chapter together with somecomments on site sensitivity. In particular, the chapter provides a framework for consideringalternative mitigation strategies against a background of the benefits and limitations of each.Pollution mitigation measures are only mentioned where they are identifiably different fromconventional drainage measures which are covered more fully in Chapter 13.

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This paper addresses the relevant aspects of risk analysis of embankment dams, through the qualitative method of Failure Mode and Effects Analysis (FMEA). In particular the concepts, principles, assumptions and fundamental rules of FMEA are introduced. It proceeds to its application to a particular tailings dam (the Cerro do Lobo dam). The dam

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Este artigo apresenta a possibilidade de incorporação de resíduos muito finos (pó) de barro vermelho e simultânea redução do teor de cimento, tentando tirar vantagem das potenciais características pozolânicas do pó cerâmico. Apresenta-se um estudo experimental desta incorporação em argamassas cimentícias, cujos resultados são bastante promissores, sobretudo do ponto de vista da sustentabilidade da construção.

In the present work, four different PVC formulations, designed for outdoor applications, were submitted to artificialaccelerated ageing under xenon light, without and with spray of water, and to natural exposure. The influence of the combined action of water and radiation was evaluated by means of surface analysis using XPS, SEM and colourimetry, permitting comparison of the results obtained under different exposure conditions. Results show that a long preliminary period of irradiation ( 2000 h) before the exposure to water increases the resistance of PVC surfaces to weather conditions. The role of that initial irradiation period is to create an erodable layer made of shrunk ‘‘PVC’’ that had lost most of its chlorine atoms and, thence, creating a network of cracks. That layer loses easily adhesion to deeper layers due to erosive action of water spray. The more perfect uncovered surface is better at resisting the effect of radiation.

Em Portugal serão construídas, nos próximos anos, algumas centenas de quilómetros de vias férreas de alta velocidade.Em diversos países tem-se verificado que a conjugação de velocidades elevadas de circulação com determinadas características dos solos de fundação conduz a fenómenos de amplificação dinâmica das deformações resultantes da circulação dos comboios.As linhas de alta velocidade, em Portugal, terão inevitavelmente de atravessar zonas onde a velocidade de circulação se pode associar com as condições desfavoráveis das fundações criando os fenómenos dinâmicos referidos.O presente artigo apresenta a problemática da geração de vibrações devidas à circulação de comboios, uma revisão sucinta de alguns métodos existentes para a previsão e análise do fenómeno e analisa as medidas de mitigação existentes.

Porosity and water saturation percent, or their product

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A non-destructive test is proposed to control in situ non-flexible geomembrane seams carried out by means of the thermal hot dual wedge method. It consists in pressurising the gap between the two welds by gas injection at a specific pressure and in monitoring the evolution of pressure over time. The migration of gas across the geomembrane is indicated by a decrease in pressure. A permeation parameter (the time constant) can then be estimated under unsteady-state conditions. Experiments were performed outdoors, under variable ambient conditions, to test the feasibility of the method in field conditions as well as in the laboratory, and under controlled ambient conditions to check the validity of the method. The results show that a poor seam from a mechanical point of view is also a poor seam from a permeation point of view. It is also shown that the non-destructive method presented here may be used in situ to test the entire seam. Hence the test is complementary to peel tests, because it reveals poor seams undetectable by the pressurised dual seam method, in pond applications where non-flexible geomembranes are placed.