Artigos de Revista

To characterize the gas permeability of seamed or non-seamed geomembranes, laboratory tests were carried out using a new permeability test: the gas permeability pouch test. Circular and rectangular

A primeira centrifugadora geotécnica portuguesa está instalada no Laboratório Nacional deEngenharia Civil. Dada a natureza pioneira à escala nacional da aplicação em causa, fundamenta-se atécnica de modelação física proposta. Introduzem-se os fundamentos da técnica de modelação física comcentrifugadora. Recorrendo à análise dimensional, deduzem-se as condições de semelhança com interesseno âmbito da geotecnia e analisa-se o mérito das abordagens experimentais actualmente disponíveis parao estudo de problemas geotécnicos.

Compara-se o mérito relativo da modelação física convencional e da modelação física comcentrifugadora através de um problema modelo - a determinação experimental da capacidaderesistente de uma sapata fundada sobre areia seca. Apresenta-se o tratamento detalhado dosrequisitos de semelhança a respeitar pelos modelos físicos de sapatas, explicitando a leis demodelação relevantes para o problema em estudo. Analisam-se as consequências da adopção decada uma das técnicas de modelação alternativas, quer em termos de condições de semelhança,quer em termos de resultados experimentais obtidos. Da comparação das duas técnicas resultaum balanço francamente favorável à modelação física com centrifugadora.

N/A

N/A

N/A

N/A

The characterisation of the dynamics of Figueira da Foz beach, in the West coast of Portugal, is presented based on the analysis of previous studies and results obtained from the application of a numerical model. Advances on the understanding of the beach dynamics have been achieved by the quantification of the annual and seasonal longshore transport and several beach profile parameters. An evaluation of the contribution of the wave climate components on the longshore transport was also obtained. The results allow sustaining a prediction of the effect of a future change of the wave climate on the longshore transport. Figueira da Foz shoreline change was simulated based on different conceptual scenarios and the results, although not quantitatively conclusive, allow the understanding of the influence of the neighbouring beach hard rock outcrops on the recent evolution.

Barotropic tidal propagation, circulation and salinity intrusion in the Guadiana estuary are described, based on two-dimensional numerical simulations supported by field data. Results are integrated through selected indicators, which provide detailed insight into the variability of the estuarine dynamics with the tides, the river flow and the spatial location. The estuarine dynamics is strongly affected by the generation of non-linear tidal constituents. Quarter-diurnal constituents distort the tide along the estuary, resulting in strong flood dominance. As a consequence, the estuary experiences accretion for low river flows. Residual velocities are directed upstream in shallow areas and downstream in the main channel. This pattern is responsible for higher salinities near the eastern margin, explaining the observed cross-sectional distribution of benthic organisms. The Coriolis effect and the residual currents patterns contribute to the efficient mixing of the river plume, promoting the renewal of the estuarine water. Residence times, computed with a new method based on particle tracking simulations, vary between four months and one week, for river flows between 8 and 300 m3/s. Maximum salinity intrusion depends on the tidal amplitude, which accounts for 8 km of its variability, and on the river flow. For very low river flows, the 0.5 isohaline penetrates up to 40 km into the estuary. The oligohaline, mesohaline and polyhaline regions extend for about 5 km each, and their locations shift by about 20 km with the tide. The estuary is stratified for river flows above 100 m3/s, and well mixed for river flows below 10 m3/s.

N/A