The seismic behavior of the anchor joint in shield-driven tunnel is very difficult to determine with the conventional methods due to the extensive simplifications. This paper proposed an improved approach to investigate the seismic response of the anchor joint, considering both the soil-structure-interaction effect and the actual geometric features. Two three-dimensional numerical models were established, including the soil-tunnel system and the refined model of the anchor joint. A seismic analysis study was first conducted on the soil-tunnel model under different seismic input waves to obtain the responses of the joint opening and offset. Then, these results were imposed on the refined model of anchor joint to further examine its detailed performance under seismic excitations. The joint opening and offset under earthquake excitations from different directions were discussed. The distribution characteristics of the stress of the anchor joint were interpreted. Finally, safety evaluations on the anchor joint were executed based on the overall seismic responses. The results show that the maximum opening and offset of the anchor joint under the two-directional horizontal earthquake are greater than those under the unidirectional conditions, while different deformation trends are observed for the joints at distinct locations. The maximum opening of the anchor joint can reach 0.73 mm, whereas the peak offset is only 0.35 mm. The local plastic strain of the anchor joint increases under the seismic action, but all of the joints are still kept in the safe state under the most unfavorable conditions. The developed method in this paper can also be accessed by the seismic study on other types of joints with complex structural components in shield tunnels.

Anchor joint is conducive to improving the automation level of the shield tunneling method, whose mechanical behavior is still not fully clear due to the complicated interaction among various structural components. In this paper, a refined FEM model is established and adopted to investigate the anchor joints’ assembly and tensile performance. The operation principles of the anchor joint are first introduced for better understanding. Then, a detailed description is presented for the developed refined FEM, including the material properties, structural features, and verification. After that, 76 working conditions in total are set, and an in-depth study is conducted to examine the influence of surface roughness, gap sizes, and strength grades on the assembly and tensile behavior of anchor joints both quantitatively and qualitatively. The results show that the surface roughness mainly influences the maximum assembly load and tensile capacity of anchor joints. The gap size obviously impacts both quantitative and qualitative assembly characteristics and tensile behavior for anchor joints, whose effect is more significant than the surface roughness. The strength grade has a different influence on the distinct mechanical behavior of anchor joints. There is a positive correlation between anchor joints’ assembly and tensile behavior. To satisfy the requirement of enough tensile capacity and reasonable assembly difficulty, a good solution should be to reach an appropriate balance between the assembly and tensile behavior of anchor joints.