Practical Model Proposed for the Structural Analysis of Segmental Tunnels

Moreno-Martínez, Jatziri Y.; Mendoza-Galván, A.; Peña, Fernando; Carpio, Franco

doi:10.3390/app10238514

Cited by 7 publications

(3 citation statements)

References 20 publications

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“…Moreover, the mechanical behavior of longitudinal joints is highly nonlinear, mainly divided into the following three stages: the elastic stage; in which concrete is partially plastic while steel bolts remain elastic; the plastic stage; and the outer concrete contact stage [1]. In the past few decades, scholars have studied the structural performance of joints through numerical simulations [2][3][4], experimental methods [5][6][7][8], and analytical approaches [9]. Among them, numerical simulation methods are widely used due to their strong applicability and low cost, but determining parameters remains a key and challenging aspect of numerical simulation methods.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation Study Considering Discontinuous Longitudinal Joints in Soft Soil under Symmetric Loading

He,

Xu,

Yang

2024

Symmetry

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In shield tunneling, the joint is one of the most vulnerable parts of the segmental lining. Opening of the joint reduces the overall stiffness of the ring, leading to structural damage and issues such as water leakage. Currently, the Winkler method is commonly used to calculate structural deformation, simplifying the interaction between segments and soil as radial and tangential Winkler springs. However, when introducing connection springs or reduction factors to simulate the joint stiffness of segments, the challenge lies in determining the reduction coefficient and the stiffness of the springs. Currently, the hyperstatic reflection method cannot simulate the discontinuity effect at the connection of the tunnel segments, while the state space method overlooks the nonlinear interaction between the tunnel and the soil. Therefore, this paper proposes a numerical simulation method considering the interaction between the tunnel and the soil, which is subjected to compression rather than tension, and the discontinuity of the joints between the segments. The model structure and external load are symmetrical, resulting in symmetrical calculation results. This method is based on the soft soil layers and shield tunnel structures of the Shanghai Metro, and the applicability of the model is verified through deformation calculations using three-dimensional laser scanning point clouds of sections from the Shanghai Metro Line 5. When the subgrade reaction coefficient is 5000 kN/m3, the model can effectively simulate the deformation of operational tunnels. By adjusting the bending stiffness of individual connection springs, we investigate the influence of bending stiffness reduction on the bending moment, radial displacement, and rotational displacement of the ring. The results indicate that a decrease in joint bending stiffness significantly affects the mechanical response of the ring, and the extent and degree of this influence are correlated with the joint position and the magnitude of joint bending stiffness.

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Section: Introductionmentioning

confidence: 99%

Numerical Simulation Study Considering Discontinuous Longitudinal Joints in Soft Soil under Symmetric Loading

He,

Xu,

Yang

2024

Symmetry

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“…Throughout shield tunnel construction, besides recognizable jack thrust, surrounding rock pressure, and buoyancy, unpredictable challenges such as adverse assembly load, subpar contact force of the shield shell, and various impact loads can arise [13,14]. The jack's reaction force represents the peak external load on the segment's axial direction during construction [15]. Particularly in curved construction sections, factors such as the eccentricity of the jack thrust, overpowering thrust, brace boot eccentricity, and sudden jack failures can subject the segment to intense localized stress concentrations, leading to segment cracking and damage.…”

Section: Introductionmentioning

confidence: 99%

Effects of Jack Thrust on the Damage of Segment Lining Structure during Shield Machine Tunnelling

Xu,

Chen,

Zhong

et al. 2023

Buildings

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Constructing a tunnel with a large longitudinal slope and a small-radius sharp curve is challenging. During the construction process, it necessitates a series of intricate operations, including adjusting the horizontal and vertical posture of the shield machine, controlling the tunnelling thrust, and consistently ensuring the appropriate over-excavation amount inside and outside of the turn. Improper operations can easily induce undue stress on the segments. This study establishes a finite element numerical model of lining segments subjected to jacking force under various construction conditions. The concrete damage plasticity (CDP) constitutive model was used to characterize the mechanical behavior of concrete under load. The mechanical characteristics and damage behavior of segments under construction conditions, such as significant thrust escape, vertical attitude adjustment of the shield machine, excavation in soft and hard interbedded strata, line turning, sudden failure of the propulsion system, and eccentricity of brace boots, were analyzed. The results revealed that, when advancing according to the maximum thrust design value (50 MPa), cracks in the tensile plastic damage zone near the brace boot plate and the edges of the segment can develop. This can lead to localized corner failure of the concrete at the lining’s edge. Therefore, it is recommended that the jack’s thrust value should not surpass 30 MPa. Maintaining the usual uneven jack thrust state of shield tunnelling along the design axis is unlikely to result in segment concrete cracking. Damage to the segment caused by the eccentricity of the brace boot plate is the most severe; hence, avoiding the eccentricity of the brace boot plate during construction is crucial. The findings of this research can guide the control of jack thrust during shield tunnelling construction and offer insights into the design of segment parameters.

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“…Furthermore, stress transfer mechanisms between the longitudinal joints and segmental joints in precast linings are important factors that affect the stability of the overall structural system. The structural behavior of segmental tunnel linings needs to be modeled accurately for considering all the expected loads and surrounding conditions [ 27 ]. It should be noted that spalling of concrete during fire events in tunnels is a major concern, which needs considerable attention.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Behavior of Ultrahigh-Performance Concrete Tunnel Lining Segments

Abbas

Nehdi

2021

Materials

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Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, durability and sustainability performance. However, its implementation in massive structures is hampered by its high initial cost and the lack of stakeholders’ confidence, especially in developing countries. Therefore, the present study explores, for the first time, a novel application of UHPC, incorporating hybrid steel fibers in precast tunnel lining segments. Reduced scale curved tunnel lining segments were cast using UHPC incorporating hybrid 8 mm and 16 mm steel fibers at dosages of 1%, 2% and 3% by mixture volume. Flexural and thrust load tests were conducted to investigate the mechanical behavior of UHPC tunnel lining segments thus produced. It was observed that the flow of UHPC mixtures decreased due to steel fibers addition, yet steel fibers increased the mechanical and durability properties. Flexural tests on lining segments showed that both the strain hardening (multiple cracking) and strain softening (post-peak behavior) phases were enhanced due to hybrid addition of steel fibers in comparison with the control segments without fibers. Specimens incorporating 3% of hybrid steel fibers achieved 57% increase in ultimate load carrying capacity and exhibited multiple cracking patterns compared to that of identical UHPC segments with 1% fibers. Moreover, segments without fibers incurred excessive cracking and spalling of concrete at the base under the thrust load test. However, more stable behavior was observed for segments incorporating steel fibers under the thrust load, indicating its capability to resist typical thrust loads during tunnel lining field installation. This study highlights the potential use of UHPC with hybrid steel fibers for improved structural behavior. Moreover, the use of UHPC allows producing structural members with reduced cross-sectional dimensions, leading to reduced overall structural weight and increased clear space.

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Practical Model Proposed for the Structural Analysis of Segmental Tunnels

Cited by 7 publications

References 20 publications

Numerical Simulation Study Considering Discontinuous Longitudinal Joints in Soft Soil under Symmetric Loading

Numerical Simulation Study Considering Discontinuous Longitudinal Joints in Soft Soil under Symmetric Loading

Effects of Jack Thrust on the Damage of Segment Lining Structure during Shield Machine Tunnelling

Mechanical Behavior of Ultrahigh-Performance Concrete Tunnel Lining Segments

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