The influence of spatial variation on the design of foundations of immersed tunnels: Advanced probabilistic analysis

't Hart, C.M.P.; Morales Napoles, O.; Jonkman, Sebastiaan N.

doi:10.1016/j.tust.2024.105624

The influence of spatial variation on the design of foundations of immersed tunnels

Title

The influence of spatial variation on the design of foundations of immersed tunnels: Advanced probabilistic analysis

Author

't Hart, C.M.P. (TU Delft Hydraulic Structures and Flood Risk; Tunnel Engineering Consultants; Royal Haskoning DHV)
Morales Napoles, O. (TU Delft Hydraulic Structures and Flood Risk)
Jonkman, Sebastiaan N. (TU Delft Hydraulic Structures and Flood Risk)

Date

2024

Abstract

Immersed tunnels are positive buoyant structures during installation and negative buoyant after installation. A tunnel is composed of sequential immersed elements that are coupled to each other in joints. Tunnel elements consist of segments which are compressed to each other by longitudinal post-tensioning. After immersion the tunnel is supported by the seabed and the longitudinal post-tension is cut at the joints between segments. Therefore, the structure is a segmented lining which is sensitive for settlements due to non uniform circumstances over the length of the tunnel. An uneven response of the bedding underneath the tunnel introduce shear forces in joints of an immersed tunnel. Because immersed tunnels need to be buoyant during installation, they have limitations on weight and geometry, the size and therefore the capacity of these shear keys is limited because the height of the tunnel, as shear keys are applied in the walls of the tunnel. The foundation response is influenced by many factors related to subsoil but also to construction and dredging tolerances. The shear forces were derived as a function of different covariance lengths for subsoil stiffness and dredging tolerances for different tunnel layouts. In reliability analyses, using two different probabilistic methods, exceedance probabilities of maximum shear forces are derived for one lay out using Non Parametric Bayesian Networks and Vine Copulas. The analyses give more insight in to the magnitude of the shear forces in joints both in conditioned and unconditioned situations and this can be used for the design of immersed tunnels.

Subject

Bedding
Covariance length
Dredging
Gaussian random fields
Immersed tunnels
Non Parametric Bayesian Network
Soft soil tunnels
Vine Copulas

To reference this document use:

http://resolver.tudelft.nl/uuid:ce82c956-9af7-45be-9312-6509922b4f13

DOI

https://doi.org/10.1016/j.tust.2024.105624

ISSN

0886-7798

Source

Tunnelling and Underground Space Technology, 147

Part of collection

Institutional Repository