Under the long-term action of a water-soil load and ion-erosive environment, the mechanical behavior of a shield tunnel structure will be degenerated gradually. Based on the degeneration mechanism, a test regarding the corrosion of segment members under loading was carried out and the evolution law about the mechanical behaviors of segments under the combined action of a high water-soil load and erosive environment was analyzed. A decline model for the bending stiffness of the deteriorated segment was established. The structural mechanical behavior of the deteriorated segments of the Nanjing Weisan Road river-crossing tunnel was analyzed, with the results showing that: 1) a high water-soil load creates favorable conditions for the rapid deterioration of the lining structure under an erosive environment; 2) in the process of deterioration of the segment, the occurrence and development of tensile cracks is accompanied by that of corrosion cracks, which presents the characteristics of non-uniform corrosion along the reinforcement; 3) under a constant water-soil load, segment deformation develops in a non-linear way with an increase of the reinforcement corrosion rate, while the bending stiffness of the segment declines significantly with an increase of the corrosion rate; and 4) the structural mechanical behavior is represented by the evolution law of a structural stiffness decline, a deformation increase, a bending moment decrease and a basically unchanging axial force under the four structural deterioration conditions of 0%, 10%, 20% and 30%, respectively. The study results provide guidance and reference for precisely evaluating the long-term safety of a shield tunnel lining structure under the combined action of a water-soil load and erosive environment during the design reference period.
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