6.3
Segmental lining
137
Figure 6-24 Flat ring joint in the Great Belt Tunnel [16]
One method is to construct the ring joint as a tongue and groove system. The tongue typically occupies more than half of the segment thickness and has a height of 10 to 25 mm. In order to enable the deined transfer of the coupling forces, coupling strips of rubber bitumen can be provided in addition to the boards to distribute loading from the thrust cylinders. This is illustrated in Figure 6-25. Reinforcement of the tongued and grooved element to resist the coupling forces is dificult to implement while keeping the required concrete cover. Assembly inaccuracies and the resulting secondary loading can rapidly lead to damage to the ring joint. In order to minimise such damage, the groove is made larger than the tongue. The available play is normally only a few millimetres and is quickly taken up by production and installation tolerances. In addition to the detail with tongue and groove, convex-concave detail of ring joints is also known, as shown in Figure 6-26. In this case also, the edges of the concave surface are at risk of damage during installation.
Figure 6-25 Segment detail with tongue and groove ring joint [52]
Figure 6-26 Convex-concave ring joint detail [263]