Mechanical behavior of novel fast-slide joints in shield tunnels: Insight from an improved analytical method with experimental and numerical validation

The novel fast-slide joint, developed for the emerging synchronous push-and-assembly shield tunneling technology, has been preliminarily implemented. Nevertheless, as this joint represents a structurally vulnerable component relative to the prefabricated concrete segments, it is imperative to evaluate its ultimate bearing capacity under diverse extreme load scenarios. An improved analytical method was developed to facilitate the investigation of the bending behavior of the fast-slide joint. This method discretized the stress and strain distributions on the contact area of concrete segments and presented a simplified constitutive model to describe the tension-deformation relationship of the sliding connector. Through this approach, the method effectively eliminated the need for complex stress integration corresponding to various loading stages, which was required in traditional analytical approaches. An iterative scheme, based on the Newton-Raphson algorithm, was implemented in the proposed method to consider the variations in joint contact states and the nonlinear properties of the joint materials. The proposed method was validated through a combination of full-scale segment joint tests and refined finite element (FE) models, which also elucidated the final failure mode of the fast-slide joint and uncovered the underlying mechanism responsible for the development of penetrating cracks. Parametric analyses were carried out to assess how joint configuration and different loading conditions influence the bearing capacity. Furthermore, the proposed method was shown to offer significant advantages in computational efficiency, with drastically reduced computation times relative to those of the refined FE models.