3D response analysis of a shield tunnel segmental lining during construction and a parametric study using the ground-spring model

Geomech. Geophys. Geo-energ. Geo-resour.

Oreste

2023

Under the application of the fluctuating Tunnel Boring Machine (TBM) jack thrust and the non-uniformly distributed total pressure of the slurry around the lining, the bending and the shear deformation occur on the segmental lining along the longitudinal direction, which cause a stress concentration and increase the damage risk of the segmental tunnel lining. The analysis of the circular joint stiffness is a critical step during the evaluation of the stress state of the segmental lining so as to decrease the associated risk of damage. In order to investigate the lining rings and the circular joint separately, an integrated numerical model which is composed of segment elements and joint elements was developed. Furthermore, stiffness equations for describing in the detail the circular joint behaviour of the tunnel segmental lining are derived. The new stiffness equation of the circular joint is also used to analyse the segment lining behaviour based on a well-known indoor test result by the scientific literature, and satisfactory results were obtained. A simplified estimation of the bending stiffness of the circular joint based on the Boltzmann equation is then suggested in order to obtain quickly its calculation. Finally, based on a specific numerical model, the calculated joint stiffnesses are adopted to analyse the vertical displacement of a real case (The Ningbo metro tunnel in China). Through a developed sensitivity analysis, some useful suggestions are proposed to reduce the damage risk of the segmental lining.

Section: The Circular Joint Behaviour Of a Segmental Liningmentioning

confidence: 99%

The important role of stiffnesses values of circular joints on the stress state developed in the tunnel segmental lining

Geomech. Geophys. Geo-energ. Geo-resour.

Oreste

2023

“…With the vigorous development of infrastructure in China, the application of tunnels is becoming more and more popular. Many tunnels lined with segmental linings were constructed with the shield tunneling method due to its merits of slight environmental disturbance, acceptable applicability, and high efficiency (Chaipanna and Jongpradist, 2019; Chen et al., 2020a, 2020b; Gong et al., 2017; Liu et al., 2020). In shield-driven tunnels, concrete segmental linings with various shapes have been extensively used.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of size effect on the deformation behavior and damage evolution mechanism of segmental tunnel lining rings

Zhao¹,

International Journal of Damage Mechanics

et al. 2023

This article investigates the size effect of segmental tunnel linings on the deformation behavior and the damage evolution mechanism using the Finite Element Method (FEM). A series of models with different diameters are established under the same loading condition to control the variable. The bolts and the rebar apply the elastic-plastic model. The Concrete Damage Plasticity model has been considered for the concrete lining. The vertical convergence deformation, internal force of these models, and damage to the segment body are selected for comparison. The number and location of the yielded bolts are explored for the analysis of the overall structure stiffness and damage evolution mechanism. In terms of plastic hinge theory, an extended discussion is carried out to explain the differences in damage evolution mechanisms in different-sized linings. The results show the large-diameter lining rings have a relatively greater increasing rate of convergence deformation. Furthermore, fewer plastic hinges emerged in large-scale lining rings before the structures reached their ultimate strength. According to the experimental results, we can know that the failure of large-diameter has the characteristic of more brittle damage than that of small-diameter one and these large-size structures are prone to become unstable geometry.

“…However, the computational complexity of the model and the difficulty in determining the spring stiffnesses restricted the application of this model (Wu et al 2015). In order to evaluate longitudinal differential deformations and stress states inside concrete segments, a 3D discontinuous contact model was built considering both the circumferential contact and longitudinal contact (Arnau and Molins 2012;Chaipanna and Jongpradist 2019;Liu et al 2021b, c). However, the 3D model has a very complex initial configuration and also is time-consuming during the calculation and for these reasons is not friendly for a quick evaluation in the engineering design stage.…”

Section: Introductionmentioning

confidence: 99%

The Buoyancy of the Tunnel Segmental Lining in the Surrounding Filling Material and its Effects on the Concrete Stress State

Oreste

2022

Geotech Geol Eng

Segmental lining is subject to significant upward buoyancy forces when a grouting material (slurry), initially fluid, is adopted to fill the gap between its external profile and the wall of a tunnel excavated with a TBM machine. The analysis of the effects of these forces is important in order to correctly dimension the segmental lining and avoid damage to the lining and subsequent costly maintenance and restoration actions. Given the complexity of the behavior of a segmental lining consisting of segmental rings and circular joints that alternate in the longitudinal direction of the tunnel, a specific numerical model has been implemented, adopting the Finite Element Method (FEM). This model is able to obtain the development of the vertical displacements of the segmental lining starting from the TBM tail, together with the bending moments and the shear forces induced inside it. The developed model is able to assess the risks of breaking and damaging the concrete and steel bolts that are used to connect the segmental rings at the circular joints; therefore, it represents a useful design tool for being able to correctly dimension the segmental lining also in relation to the risks produced by the appearance of considerable buoyancy forces around it, due to the presence of the initially fluid filling material. The proposed numerical model was applied to a real case (Ningbo metro tunnel) and allowed to obtain satisfactory results from the comparison of the calculated displacements with in situ measurements. Some sensitivity analyzes developed on the studied case have made it possible to detect which are the influencing parameters that have the greatest impact on the behavior of segmental lining in the presence of the studied buoyancy forces.