Deep excavations in urban areas - finite element modelling for three geotechnical scenarios

Abstract

In the last decades large and deep cut-and-cover excavations for basements and for transport infrastructures became very common in urban areas. The solutions that have been constructed comprehend a large number of structural systems and soil-structure interaction problems. Among the distinct geotechnical works, deep excavations and their retaining structures were probably the ones whose analysis and design experienced more progress by the use of finite element models since the seventies. The chapter presents three topics which are not much widely treated in the specialized bibliography and that have been of major concern of FEUPs geotechnical group and co-workers: deep excavations in thick deposits of soft clay and rules for a reliable control of the excavation induced movements, with emphasis on the influence of settlements during the consolidation period; vertical stability of permanent Berlintype walls in stiff cohesive soils, combining distinct types of numerical modelling, including finite element limit analyses, since the purpose was to characterize a retaining structure under marginal stability conditions; elliptical shafts constructed by the sequential excavation method, a novel type of structure particularly convenient in granite residual soils. Finally, some ideas are presented on possible future developments in the field.