Mechanical behaviour of splicing joints in shield tunnel lining subjected to fire

Shield tunnel segment joints are weak links in tunnel structures; however, studies on their fire-resisting performance are limited. In this study, scaled tests were performed on lining joints to investigate their fire-resisting behaviour in relation to installation errors. The results indicated that the lining segment with initial defects exhibited a large peeling depth, whereas those without initial defects exhibited a large spalling area and shallow depth. Moreover, the damage rate of the lining joints with initial defects was 10.52%, and the lining segment with initial defects exhibited a larger residual deformation after cooling. Furthermore, the bending and shear resistance of the lining joints decreased sharply, which was manifested by an increase in the joint opening angles. The stiffness of the lining joints with initial defects decayed faster, and the stiffness loss was greater than in those without initial defects. After the test, the remaining stiffness was reduced by 69.7% compared to that of the lining joint with no defects. The results obtained can be used to further develop the thermal-mechanical coupling of splicing joint structures in shield tunnel linings.