Exploring the progressive failure characteristics of a large special-shaped shield tunnel lining based on 'standing' prototype loading tests

摘要

A series of prototype structural loading tests were performed in this paper to explore the mechanical behavior of a large special-shaped shield tunnel lining towards failure. To replicate the real working conditions, the testing specimen was fabricated and tested in a 'standing' state. It was shown that, similar to circular tunnels, the internal forces and overall deformation of the special-shaped lining structure increased with increasing burial depth. However, the maximum negative bending moments of the special-shaped lining structure were present at the shoulder areas rather than at the waist areas. The two key design parameters, effective transverse rigidity ratio and rotational stiffness, were shown to evolve during loading. A unique relationship between the joint rotational stiffness and eccentricity was obtained, which could be divided into an axial force-dominating phase and a bending moment-dominating phase. Different cracks appeared at different loading stages and the crack width also evolved as loading proceeded. Empirical correlations between various structural properties and cracking characteristics were established, based on which the progressive failure process was elucidated. It was found that due to the transferring of bending moment, cracks were mostly concentrated on segmental bodies in the ring(s) adjacent to the longitudinal joints.