This thesis presents a study on the impact of soil thickness variability on secondary consolidation of overconsolidated glacial soils beneath immersed tunnel elements, specifically focusing on the Fehmarnbelt Tunnel. The research employs a combination of analytical models, including the Timoshenko beam on Kerr foundation model (TBKF model), the Conte and Troncone method and the Feng et al. method, to analyze the initial, primary, and secondary consolidation phases, respectively. It contributes to a better understanding of the behavior of the soil beneath immersed tunnels and informs more accurate predictions and designs in future projects.

Immersed tunnels, located in waterways, could be a limiting factor in the dredging in waterways. This dredging is required since cargo vessels draught increased the past decades. In this thesis a new method is defined for temporarily, effectively, re-floating immersed tunnels. With this method extra risks arise, for these risks’ measures are given. The validity of this method is proven by applying the method a relevant case study. This case tunnel is the Wijkertunnel, consisting of six elements and a total immersed length of 600 meters. It showed that the maximum deepening available is 6.60 meters. It is concluded that the impact of the risk measures is limited. Finally other immersed tunnels are compared to the Wijkertunnel. For these tunnels the different types are described, and the impact of these differences are discussed. It showed that for all the immersed tunnels the method is viable, except for immersed tunnels with a very few elements.