超、卸载作用下考虑接头影响的盾构管片承载性能研究OA北大核心CSTPCD

Surface loading or lateral excavation unloading can easily induce diseases in shield tunnels, posing risks to construction and operational safety. Existing research struggles to comprehensively and quantitatively evaluate the load-bearing capacity of shield tunnels under overload and unloading condi-tions. Most numerical models are limited, considering only the singular influence of circumferential or longitudinal joints. These models often simplify joints as tangential and normal springs, inadequately addressing joint nonlinearity, or embed bolts directly into concrete, overlooking the load-bearing con-tribution of bolt preload, thus lacking in joint detail. This study develops a refined numerical model of shield tunnel segments, incorporating both circumferential and longitudinal joints, to analyze the stress characteristics and load-bearing performance under conditions of top overload and lateral unloading. It determines the load-bearing limits and corresponding deformation thresholds under various conditions, validated by full-scale testing. The results show that good agreement between numerical calculations and full-scale tests, with ellipticity deformation discrepancies under 10％. The model's calculation ac-curacy improves by approximately 6％ over models considering only circumferential joint effects, and by about 30％ over homogeneous ring models that neglect joint effects, enabling dynamic simulation of structural deformation and damage evolution in shield tunnel segments. The study reveals the shield tunnel's surplus load-bearing capacity. With tunnel overloads reaching 138 kPa or lateral pressure un-loading at 26.3％, the structure's ellipticities are 27.4‰ and 22.1‰, respectively, marking the limit state of normal service. Exceeding this limit, the joint's plastic hinge formation leads to structural soft-ening and eventual failure, with a significant increase in joint opening and segment misalignment. Be-yond 26.3％ lateral unloading, the curve of joint opening and segment dislocation becomes irregular, and fluctuations become markedly pronounced beyond 36.8％ unloading, indicating a more complex and sensitive structural stress response during tunnel lateral unloading.