Poços elípticos pelo método de escavação sequencial na vertical : o caso do Metro do Porto

Documento confidencial. Não pode ser disponibilizado para consultaTese de doutoramento. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 200

Design and Behavior of Salgueiros Station for Porto Metro

The paper presents the design and construction of an elliptical excavation for Porto Light Metro. Due to its original shape the solution took full advantage of the arch effect in the ground, adapting the Sequential Excavation Method to the vertical direction and achieving a novel, light and economic solution. In a first phase, the paper describes the construction method, referring also to economic and planning aspects of the excavation performed. The design is presented and discussed, including the presentation of the geotechnical tests performed and a brief analysis on the parameters assumed. The final part of the paper analyses monitoring results, focusing on the most surprising aspects of the behavior and on the main differences to the numerical calculations

ANÁLISE EXPERIMENTAL DAS CARACTERÍSTICAS MECÂNICAS DOS COMPONENTES E MATERIAIS DE PONTES EM ARCO DE ALVENARIA DE PEDRA

Este artigo descreve os estudos experimentais realizados em pontes em arco de alvenaria de pedra com o objetivo de obter uma caracterização realista dos componentes e materiais das pontes. O trabalho faz parte de um estudo mais abrangente centrado na caracterização numérica e experimental de pontes em arco de alvenaria de pedra sob a ação do tráfego ferroviário. A campanha experimental decorreu em duas pontes ferroviárias inseridas na rede ferroviária Portuguesa, o viaduto de Durrães e a ponte PK124, ambas localizadas na Linha do Minho. Em ambas as pontes foram aplicadas técnicas de ensaio “in-situ”, como a extração de carotes, ensaios com macacos planos e com pressiómetro de Ménard e laboratoriais em amostras representativas dos materiais constituintes das pontes, cujos principais resultados e conclusões são aqui apresentados

Unsaturated response of clayey soils stabilised with alkaline cements

The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils is still mostly unknown and unquantified. This is also motivated by the difficulties associated with the experimental procedure required to fully characterise the unsaturated response of the soil, including its direct influence on traditional strength tests. The present paper presents the soil water retention curves obtained for a Portuguese soil before and after being stabilised with Portland cement (OPC) and an alkali-activated cement (AAC). Saturated undrained triaxial tests were also performed for the same curing conditions (0, 28, and 90 days). Previous attempts to characterise the retention curve of soils stabilised with AAC are unknown, and the results showed that the pore volume structure is already formed after 28 days, prior to the full development of the gel matrix responsible for the strength increase between 28 and 90 days. The curve changed after stabilisation, and with each binder, as the OPC presented a higher air-entry value and a narrower suction range compared to the AAC solution. The significant differences between the curves obtained from each binder suggest the future development of a methodology to assess the quality of the AAC stabilisation.ERDF -European Regional Development Fund(undefined

Influence of discrete fibre reinforcement on the uniaxial compression response and seismic wave velocity of a cement-stabilised sandy-clay

A sandy clay from the northeast region of Portugal has been reinforced with polypropylene fibres and cement, and seismic wave velocity measurements and uniaxial compression strength tests were performed. Results showed that the fibre induce variations on the wave's velocity that cannot be related to real changes in the material stiffness. Therefore, care should be used when using this technique in fibre reinforced soils. The addition of fibres resulted in an increase of compression strength of the mixtures, for every cement content. Regarding the stiffness, the fibres proved to be increasingly effective with na increase in cementation, especially at the early stages of the stressestrain curve, when the secant deformability modulus increases with fibre content. However, no influence of the discrete reinforcement was detected on the peak and post-peak stages of the loading process. Fibre length showed also to be influential on strength and stiffness

Influence of fibre reinforcement on the post-cracking behaviour of a cement-stabilised sandy-clay subjected to indirect tensile stress

An experimental campaign was carried out to determine the influence of polypropylene fibre content and length on the post-cracking response of a sandy-clay stabilised with different cement contents. Three main sets of specimens were prepared: cement-stabilised specimens with two cement contents (5% and 10%); fibre-reinforced specimens with three fibre contents (0.1%, 0.2% and 0.3%) and cement-fibre-reinforced specimens combining the mentioned fibre and cement contents. Tensile tests on the fibres and indirect tensile tests and triaxial compression tests on the prepared specimens were conducted. Results show that the post-cracking behaviour is strongly affected by the combination of fibre and cement content as well as fibre length. Pull-out was the governing failure mode. Post-peak tension loss rate increased with fibre content, as a result of the loss of influence of the fibres on the post-peak behaviour. On the contrary, an increase in fibre content resulted in higher pre-peak strength gain rates and higher peak stresses.info:eu-repo/semantics/publishedVersio

Improvement of a clayey soil with alkali activated low-calcium fly ash for transport infrastructures applications

The improvement of geotechnical properties is often achieved by the addition of traditional binders, such as cement or lime. However, the use of such binders implies a considerable financial and environmental cost that needs to be mitigated. An unconventional solution, similar to cement in terms of performance but more environmentally friendly, consists in the use of binders made from alkaline activated industrial residues. The technique consists on the activation of raw materials (such as fly ash or blast furnace slag) rich in Si, Al, or even Ca, with high pH alkaline solutions. The present work was developed aiming the possible stabilisation, using different fly ash contents, of a clayey soil with sand. The activator solution was composed of sodium hydroxide and sodium silicate. The extended experimental campaign included unconfined compressive strength (UCS), California Bearing Ratio (CBR), pulse velocity tests and triaxial tests to assess the geomechanical improvement induced by the new binder. As a mean of comparison, the experimental campaign included also the stabilisation of the same soil with either cement or lime. The obtained data indicates that the use of alkaline activation as a soil stabilisation technique provides competitive geomechanical results, when compared with those obtained with traditional binders.(undefined

Túneis urbanos sujeitos a solicitações não uniformes : O túnel do Largo do Carregal na cidade do Porto

Dissertação apresentada para obtenção do grau de Mestre em Estruturas de Engenharia Civil, na Faculdade de Engenharia da Universidade do Porto, sob a orientação do Prof. Dr. António Silva Cardos

Portuguese strengths and fragilities on safety and health practices

Despite improvements over the years, accidents continue to be a scourge in the construction sector, leading to an increase in the number of journal articles addressing the issue, in an attempt to help construction industry to increase safety performance [1]. This paper aims to, helping construction industry and particulary tunneling community, describe the Portuguese approach to most typical health and safety problems in underground excavations performed with the Sequential Excavation Method (SEM). The article will address various topics, from safety management and organizational practices, to collective and personal protection equipment, to emergency planning. nt problems in safety and health matters are similar to several other countries, the paper will expose a compilation of Portuguese best practices used to solve that problems. This enunciation of best practices describes experience from most important and recognized Project Owners and Contractors in Portugal. In a second phase it will be analysed Portuguese weaknesses, identifying preventive measures, and their comparative importance, that should be adopted in Portugal in order to reduce accidents and health diseases