受荷状态下盾构隧道管片锈蚀劣化破坏过程研究

Research on corrosion deterioration and failure process of shield tunnel segments under loads

为研究服役期盾构隧道衬砌结构性能衰退演变规律,从隧道结构长期处于水土荷载和周围离子侵蚀环境耦合作用下的特点出发,根据服役盾构管片压弯荷载受荷特征,采用弯矩、轴力导入的方式,等效地模拟盾构隧道管片的实际受力状态,结合围堰式的电化学加速锈蚀方式,研发了可实现压弯受荷状态下进行盾构管片加速锈蚀劣化的试验系统,重点分析不同工况下盾构隧道管片锈蚀劣化发生发展规律。主要结论有:未锈蚀管片裂缝形态主要以受拉横向裂纹为主;未加载锈蚀管片在锈蚀阶段仅产生顺筋锈胀裂纹,裂纹宽度体现出先增大后趋于稳定的特点,加载破坏阶段锈蚀区混凝土在锈胀裂纹和受拉裂纹共同作用下将出现混凝土局部剥离与错动现象;压弯受荷状态下,管片裂缝的扩展是钢筋锈蚀与外加荷载共同作用的效果,管片受拉裂纹与锈蚀裂纹体现出相伴发生发展的规律,管片承载能力存在较大降低。研究成果可为设计基准期内盾构隧道管片衬砌结构长期安全性能评价提供重要参考。

In order to study the performance degradation of shield tunnel lining structure during the service period, based on the characteristics of shield tunnel lining under the long-term coupling effect of the water-soil load and the surrounding erosion environment, the stress states of shield tunnel segment were realistically simulated by the importing method of bending moment and axial force. Combined with the cofferdam-type electrochemical accelerated corrosion method, the test system which can achieve segment corrosion deterioration under loading conditions has been developed, and then the regularity of occurrence and development of corrosion deterioration of shield tunnel segments was analyzed under different conditions. The results show that： the fracture pattern of non-corroded segments reflects the main characteristics of transverse tensile cracks. In the accelerated corrosion stage, the corroded segments which are not loaded only produce corrosion crack along the reinforcement, and the crack width reflects the characteristics of the first increase and then tending to be stable; in addition, the concrete in corroded area tends to partially strip and dislocate under the combined effects of corrosion-induced expansion crack and tensile crack in the loading destruction stage. Crack propagation in segment under loading conditions is the result of the combined effects of corrosion of reinforcements and imposed loads, the collaborative occurrence and development of tensile cracks and corrosion cracks can be observed, leading to an obvious decrease in the bearing capacity of segments. The results can provide important reference and experimental data support for accurate evaluation on the long-term safety of shield tunnel in design reference period.