Abstract: Differential settlement can easily cause the failure of the circumferential joint of a shield tunnel. Herein, a case study is conducted on the circumferential joint of a shield tunnel connected using diagonal bolts. The failure mechanism of the circumferential joint is revealed using a fullscale test. Thereafter, the results of the fullscale test are introduced to the circumferential joint of a largediameter shield tunnel connected through bolts using a computational mechanics method. The results show the failure process of the circumferential joint of the largediameter shield tunnel connected using diagonal bolts. Field data demonstrate that the circumferential joint is the weakness of the shield tunnel. The differential settlement arises along the longitudinal direction because of the dislocation on the circumferential joint. Thus, identifying the failure process of the circumferential joint in the following three stages is essential. (1) Stage 1, the circumferential shear stress is balanced through friction force, and the shear stiffness of the circumferential joint is large. (2) Stage 2, the dislocation phenomenon develops even when the shear stress of the circumferential joint does not increase, and the shear stiffness reaches zero due to the gaps between a diagonal bolt and the bolt hole. (3) Stage 3, the shear stress increment of the circumferential joint is borne by the diagonal bolt, and the shear stiffness of the circumferential joint varies with the support conditions of the diagonal bolt and plastic hinge. The analytical solution agrees with the test results.

Key words: shield tunnel, circumferential joint, diagonal bolt; analytical solution, fullscale test