| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| João dos Santos Romano Pires | 6.11 MB | Adobe PDF |
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Advisor(s)
Abstract(s)
À realização de escavações em meio urbano está associada a indução de movimentos - assentamentos e deslocamentos horizontais nos terrenos adjacentes. Esses movimentos de subsidência afetam as estruturas na vizinhança das escavações, nelas induzindo danos. A tipologia e grandeza dos movimentos induzidos dependem das características do terreno e da estrutura de contenção periférica, bem como do respetivo método construtivo e da rigidez das estruturas adjacentes. Pretende-se avaliar o efeito da consideração da rigidez das estruturas adjacentes na superfície de subsidência associada à realização de uma escavação, comparando-a com a situação de campo livre. Para tanto propõem-se o recurso a modelação numérica (com o programa Plaxis) e o desenvolvimento de modelos de contenção periférica tipo. Foram desenvolvidos três modelos numéricos de escavações entre paredes, a saber: i) escavação em campo livre; ii) escavação com edifício na vizinhança fundado a 3 m de profundidade e, iii) escavação com edifício na vizinhança fundado a 5,6 m de profundidade. Na modelação, para cada uma das profundidades citadas, o edifício foi considerado às distâncias 0 m, 3 m e 6 m da parede de contenção. Por fim foram estabelecidas comparações entre os resultados obtidos e os que se obteriam da utilização de métodos empíricos. Os estudos empíricos escolhidos foram os métodos de Hsieh & Ou (1998) e o de Ou & Hsieh (2011). Os resultados obtidos para os modelos numéricos que experimentam uma curva de subsidência do tipo côncava confirmaram o esperado inicialmente, isto é, a consideração do edifício na imediação da escavação fez com que os assentamentos do terreno envolvente diminuíssem. Os resultados obtidos para os modelos em que a curva de subsidência é do tipo tímpano apresentaram um comportamento ligeiramente diferente. De facto, quando o edifício está perto da parede resultou o efeito esperado (redução dos assentamentos), mas quando o edifício foi afastado da parede, na zona mais perto da parede, esse efeito não se registou. Os métodos empíricos, sendo válidos apenas para o caso de campo livre, não permitem modelar estes efeitos de construções na vizinhança da escavação.
Carrying out excavations in urban areas is associated with the induction of movements - settlements and horizontal displacements in adjacent ground. These subsidence movements affect structures in the vicinity of the excavations, inducing damage to them. The typology and magnitude of the induced movements depend on the characteristics of the terrain and the peripheral retaining structure, as well as the respective construction method and the stiffness of adjacent structures. It is intended to evaluate the effect of considering the stiffness of adjacent structures on the subsidence surface associated with the execution of an excavation, comparing it with the free field situation. To this end, it is proposed to use numerical modeling (with the Plaxis software) and develop models of standard retaining structures. Three numerical models of excavation between walls were developed, namely: i) excavation in free field; ii) excavation with a building in the vicinity founded at a depth of 3 m and, iii) excavation with a building in the vicinity founded at a depth of 5.6 m. In the modeling, for each of the mentioned depths, the building was considered at distances of 0 m, 3 m and 6 m from the retaining wall. Finally, comparisons were made between the results obtained and those that would be obtained from the use of empirical methods. The empirical studies chosen were the methods of Hsieh & Ou (1998) and that of Ou & Hsieh (2011). The results obtained for the numerical models that experience a concave-type subsidence curve confirmed what was initially expected, that is, the consideration of the building in the vicinity of the excavation caused the ground settlements to decrease. The results obtained for the models in which the subsidence curve is of the spandrel-type showed a slightly different behavior. In fact, when the building is close to the wall, it resulted in the expected effect (reduction of the ground settlement), but when the building was moved away, in the area closest to the wall this effect was lost. Empirical methods, being only valid for the case of free field, are not able to model these effects of constructions in the vicinity of the excavation.
Carrying out excavations in urban areas is associated with the induction of movements - settlements and horizontal displacements in adjacent ground. These subsidence movements affect structures in the vicinity of the excavations, inducing damage to them. The typology and magnitude of the induced movements depend on the characteristics of the terrain and the peripheral retaining structure, as well as the respective construction method and the stiffness of adjacent structures. It is intended to evaluate the effect of considering the stiffness of adjacent structures on the subsidence surface associated with the execution of an excavation, comparing it with the free field situation. To this end, it is proposed to use numerical modeling (with the Plaxis software) and develop models of standard retaining structures. Three numerical models of excavation between walls were developed, namely: i) excavation in free field; ii) excavation with a building in the vicinity founded at a depth of 3 m and, iii) excavation with a building in the vicinity founded at a depth of 5.6 m. In the modeling, for each of the mentioned depths, the building was considered at distances of 0 m, 3 m and 6 m from the retaining wall. Finally, comparisons were made between the results obtained and those that would be obtained from the use of empirical methods. The empirical studies chosen were the methods of Hsieh & Ou (1998) and that of Ou & Hsieh (2011). The results obtained for the numerical models that experience a concave-type subsidence curve confirmed what was initially expected, that is, the consideration of the building in the vicinity of the excavation caused the ground settlements to decrease. The results obtained for the models in which the subsidence curve is of the spandrel-type showed a slightly different behavior. In fact, when the building is close to the wall, it resulted in the expected effect (reduction of the ground settlement), but when the building was moved away, in the area closest to the wall this effect was lost. Empirical methods, being only valid for the case of free field, are not able to model these effects of constructions in the vicinity of the excavation.
Description
Dissertação elaborada para a obtenção do grau de Mestre em Engenharia Civil na área de especialização de Estruturas.
Keywords
Escavações profundas Meio urbano Paredes de contenção Curvas de subsidência Assentamentos do terreno Método dos elementos finitos Deep excavations Urban environment Retaining walls Subsidence curves Ground settlements Finite element method
Citation
PIRES, João dos Santos Romano - Modelação numérica de escavações. Lisboa: Instituto superior de Engenharia de Lisboa, 2022. Dissertação de Mestrado