Ultimate limit state analysis of a segmented tunnel lining

Because of low hindrances during construction and lack of space in populated areas, shield driven tunnels are becoming more and more popular. Since 1997 these segmented tunnel linings are also constructed in the Netherlands but are difficult to accomplish in soft soils. Because of unexpected damages in the early constructed tunnels a full scale test set up has been build at the Delft University of Technology to obtain knowledge on the lining behaviour. The conducted tests were performed in the SLS in which it became clear that the joints in between the segments play an important role in the global lining behaviour. In order to asses the safety level of a concrete lining, and the ultimate load capacity, failure tests have been performed in the ULS. Generally a lining might fail due to concrete failure or by an ongoing rotation of the segment joints. With the aid of the collected test data a detailed description of the failure mechanisms is obtained. The influence of the segment joints and ring joints on the global lining behaviour is analysed especially at extreme loading conditions. Based on the measured segment joint rotations and lining deformations, interaction forces between adjoining rings are analysed. With the obtained knowledge on lining behaviour a FE model is developed in Diana for predicting internal forces and external deformations for loadings in the ULS. With the aid of this model different loading combinations can be analysed and eventually the influence of soil can be incorporated. Because the load capacity of the lining and its failure mechanisms is known, a probabilistic safety analysis may be performed for assessing the safety level of tunnel linings.