Large-scale testing of the mortise and tenon joint performance of the tunnel lining of prefabricated frame tunnelse

Although prefabricated frame tunnels are widely used, research on their structural performance is limited, especially research on the weakest joints in prefabricated tunnels. In this study, a large-scale physical model test is used to study the mechanical properties of joints with bolts and without bolts under static loading, mainly considering the joint concrete and steel strain, opening amount, deflection, rotation angle, toughness, and ductility. The failure of the two joint types is quantitatively analysed using the virtual hinge angle and plasticity index. In addition, a finite element model is established, the model test results are compared, and the effects of the axial force and bolt preload on the joint performance are evaluated. The results show that the concrete strain and steel strain of the two joint types do not exceed the limit values under the ultimate load, providing sufficient ductility. The mechanical properties of the bolted joint are improved by the anchoring and crack arrest mechanism of the bolt. The deflection produced in each stage is lower and the deformation resistance is stronger for the bolted joint than for the boltless joint. Due to its larger damage area and greater number of cracks, the bolted joint exhibits a smaller rotation angle and stronger load-bearing capacity, and the material performance of the joint concrete is fully utilized. Increasing the axial force of a joint can significantly improve its bearing performance, but increasing the bolt preload has no significant effect. In the design of prefabricated frame tunnel joints, bolts can be added to improve the bearing capacity and deformation resistance.