ABSTRACT
A 18 m deep excavation was recently constructed in very soft Gothenburg clay. The excavation has served as a dry dock for constructing submerged tunnel elements for a new tunnel across the river Göta Älv. The supporting structure consisted of interlocking steel pipe pile wall supported by one level of internal struts. Excavation was undertaken underwater. To support the excavation a 1 m thick underwater concrete slab was cast, followed by placing 1-2 m of temporary gravel ballast on top. Then, the excavation was dewatered, the ballast removed in sections, as a permanent reinforced concrete slab was cast on top of the underwater slab.As part of a third-party design review the performance of the excavation was analyzed using the FEM program PLAXIS using non-linear and anisotropic soil model (the NGI-ADP-model). The analyses were undertaken before excavation started. The paper compares and discusses predicted and measured performance.
