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Análise de risco de arribas costeiras: Proposta e aplicação de metodologia em dois casos de estudo
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Abstract(s)
A presente dissertação teve como foco a análise de risco de instabilidade de arribas costeiras, com o objetivo de adaptar e propor um método de avaliação de risco sob a forma de matriz, aplicado a dois casos de estudo no município de Torres Vedras. A metodologia adotada incluiu o reconhecimento e caracterização visual in situ das arribas, a execução de sondagens geológicogeotécnicas com ensaios SPT, a recolha de amostras para ensaios laboratoriais, bem como o
zonamento e a parametrização geotécnica do maciço. Realizou-se ainda o levantamento geomecânico das arribas, através da técnica de amostragem linear, a elaboração de fichas de campo e à análise cinemática dos planos de rotura. Os dados obtidos permitiram aplicar as tabelas de perigosidade e vulnerabilidade, sendo os resultados posteriormente esquematizados sob a forma de matriz de risco, aplicada aos casos de estudo de Amanhã/Vigia e Formosa. Complementarmente, recorreu-se ao software RS2 da Rocscience para a análise da probabilidade de rotura. Os resultados demonstraram um grau de risco global mais elevado para a arriba da Praia Formosa, associado à sua maior vulnerabilidade e perigosidade, comparativamente com Amanhã/Vigia. Conclui-se que a matriz de risco proposta se revelou eficaz na gestão integrada de risco costeiro, constituindo uma ferramenta de apoio à decisão em áreas com elevada relevância socioeconómica e ambiental.
This dissertation focused on the analysis of coastal cliff instability risk, aiming to develop and propose a risk assessment method in the form of a matrix, and apply it to two case studies in the municipality of Torres Vedras. The adopted methodology included in situ visual recognition and characterization of the cliffs, the execution of geological-geotechnical boreholes with SPT tests, and the collection of samples for laboratory testing, as well as zoning and geotechnical parameterization. A geomechanical survey of the cliffs was also carried out using the scanline sampling technique, together with the preparation of field sheets and kinematic analysis of the potential failure planes. The data obtained enabled the application of hazard and vulnerability tables, with the results subsequently schematized in a risk matrix for the case studies of Amanhã/Vigia and Formosa. Additionally, the RS2 software (Rocscience) was used to perform probability of failure analysis. The results showed a higher overall risk level for the Formosa cliff, associated with its greater vulnerability and hazard, compared to Amanhã/Vigia. It is concluded that the proposed risk matrix proved effective for integrated coastal risk management, serving as a decision-support tool in areas of high socioeconomic and environmental relevance.
This dissertation focused on the analysis of coastal cliff instability risk, aiming to develop and propose a risk assessment method in the form of a matrix, and apply it to two case studies in the municipality of Torres Vedras. The adopted methodology included in situ visual recognition and characterization of the cliffs, the execution of geological-geotechnical boreholes with SPT tests, and the collection of samples for laboratory testing, as well as zoning and geotechnical parameterization. A geomechanical survey of the cliffs was also carried out using the scanline sampling technique, together with the preparation of field sheets and kinematic analysis of the potential failure planes. The data obtained enabled the application of hazard and vulnerability tables, with the results subsequently schematized in a risk matrix for the case studies of Amanhã/Vigia and Formosa. Additionally, the RS2 software (Rocscience) was used to perform probability of failure analysis. The results showed a higher overall risk level for the Formosa cliff, associated with its greater vulnerability and hazard, compared to Amanhã/Vigia. It is concluded that the proposed risk matrix proved effective for integrated coastal risk management, serving as a decision-support tool in areas of high socioeconomic and environmental relevance.
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Keywords
Coastal cliffs Hazard Vulnerability Risk matrix Probability of failure Arribas costeiras Perigosidade Vulnerabilidade Matriz de risco Probabilidade de rotura