Abstract
A beam-spring model with constant rotational stiffness is a practical tool for the prediction of the general deformations and bending moments in circular tunnel linings. However, in reality, the rotational stiffness of a segmental joint is not constant, due to nonlinear deformations and local yielding in the vicinity of the joint. These are a result of the specific geometry at the joint, which is related to water-tightness measures and buildability issues. For quasi-rectangular tunnels this nonlinearity should not be neglected, as the bending component in the lining is significantly larger compared to circular linings. To date, there are only few studies that have investigated a calculation method for consideration of the joint’s nonlinear moment-axial force and shear-axial force interaction behavior and its consequences on the calculated lining behavior. In this paper, an iterative incremental method is proposed to tackle this issue, based on rotational stiffness curves derived from 3D nonlinear finite element modelling of the joints, and substantiated by testing. The significance of the variable rotational stiffness is highlighted through a comparison with results based on a constant stiffness assumption. Further, using the proposed calculation method, the effects of the circumferential joints, the bending moment transmission and several other parameters on the full-ring behavior of quasi-rectangular tunnels are discussed for a wide interval of design parameters. The results provide some new insights into the behavior of this non-traditional tunnel type. Although the presented results are related to specific overall and local geometries, the presented method is considered to be useful for the design of other special tunnel geometries.
Highlights
When a shield tunnel is constructed, the choice of a suitable cross-section for the tunnel is very important, especially when the tunnel is built in a city center
In the full-ring model, rotational stiffness and radial shear stiffness are considered for the longitudinal joints while radial shear stiffness and tangential shear stiffness are considered for the longitudinal joints while radial shear stiffness and tangential shear stiffness are considered for the circumferential joints
The authors are aware that these values are related to the specific geometry of the quasi-rectangular shield tunnel under consideration but are confident that these can be integrated in a lining joint database in the future
Summary
In large special-section shield tunnels with more than 10-m diameter, a configuration with more longitudinal joints is indispensable to make the segment transportation and manipulation in the assembly feasible. Some joints will be at locations where large internal forces exist, such as JF3, JF6, JF8, JF10 (Figure 2). In these joints, the nonlinear behavior will become apparent, affecting the overall lining behavior. Due to the existence of the interior column, the shear forces are much larger than commonly found in circular tunnels, affecting the structural convergence deformation to a great extent. For these reasons, full-scale experiments are necessary to provide straightforward results for the joint’s mechanical properties.
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