Behaviour of cast-iron tunnel segmental joint from the 3D FE analyses and development of a new bolt-spring model

• The numerical model matched well to the experimental performance.
• The influence of structural features such as bolt pretension was examined.
• A series of bolt-spring model were proposed for the rotational bolt behaviour.
• For bolt shear behaviour, a new one spring model was developed.
• The proposed approach was evaluated against previous conventional models.

The behaviour of cast-iron tunnel segments used in London Underground tunnels was investigated using the 3-D finite element (FE) method. A numerical model of the structural details of cast-iron segmental joints such as bolts, panel and flanges was developed and its performance was validated against a set of full-scale tests. Using the verified model, the influence of structural features such as caulking groove and bolt pretension was examined for both rotational and shear loading conditions. Since such detailed modelling of bolts increases the computational time when a full scale segmental tunnel is analysed, it is proposed to replace the bolt model to a set of spring models. The parameters for the bolt-spring models, which consider the geometry and material properties of the bolt, are proposed. The performance of the combined bolt-spring and solid segmental models are evaluated against a more conventional shell-spring model.