Longitudinal Deformation of Deep Shield Tunnels Caused by Upper Load Reduction

Zheng, Jinlei; He, Shiquan; Li, Yiming; He, Jiaxin; He, Jianping

doi:10.3390/ma14133629

Cited by 10 publications

(3 citation statements)

References 23 publications

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“…Consequently, the austenite stability of IAT‐1 might be higher due to higher carbon enrichment which leads to a lower martensite start temperature (

M_{normals}

) by enlarging the difference of chemical free energy (

Δ G

) between the parent austenite ( γ ) and product martensite (

α'

), which can be estimated by Equation (), which is known as the Andrew equation. [ 34 ]

M_{normals} false(° normalC false) = 539 - 423 false(wt % C false) - 30.4 false(wt % Mn false) - 17.7 false(wt % Ni false) - 12.1 false(wt % Cr false) - 7.5 false(wt % Mo false)

…”

Section: Resultsmentioning

confidence: 99%

Yield Strength Enhancement Without Ductility Loss Through Controlling the Intercritical Annealing Time in Medium‐Mn Steels

Elbeltagy

Shen

et al. 2023

Adv Eng Mater

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Herein, the effect of shortening the intercritical annealing (IA) time in a two‐step process “intercritical annealing and tempering (IAT)” on the microstructure and the mechanical properties of medium‐manganese steel (MMnS) made of Fe–0.05C–7Mn–1.5Cu–1.5Ni–1.5Al–1.5Si–0.5Mo (wt%) and containing copper‐rich (CRP) and Ni(Al/Mn) precipitates is investigated. The atom probe tomography (APT), electron backscattering diffraction (EBSD), and the synchrotron X‐ray diffraction (SYXRD) are used to study precipitation, phase microstructure evolution, the austenite stability, and deformation mechanisms. Shortening the IA step, which is carried out at 700 °C, from 2 min (IAT‐2) to 1 min (IAT‐1), results in a yield strength (YS) increment of around 218 MPa with less than 1% loss of ductility. While the enhanced yield strength in IAT‐1 is attributed to the four times higher precipitates’ number density (n), the insignificant loss of ductility is attributed to the enhanced austenite stability factor from 4.5 to 9.2 in IAT‐2 and IAT‐1, respectively. The simultaneous increase in YS without ductility loss reflects that controlling the IA time is a promising strategy to overcome the yield strength and ductility trade‐off without the need for higher additions of costly alloying elements such as Ni, Al, Mn, and Cu.

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“…Consequently, the austenite stability of IAT‐1 might be higher due to higher carbon enrichment which leads to a lower martensite start temperature (

M_{normals}

) by enlarging the difference of chemical free energy (

Δ G

) between the parent austenite ( γ ) and product martensite (

α'

), which can be estimated by Equation (), which is known as the Andrew equation. [ 34 ]

M_{normals} false(° normalC false) = 539 - 423 false(wt % C false) - 30.4 false(wt % Mn false) - 17.7 false(wt % Ni false) - 12.1 false(wt % Cr false) - 7.5 false(wt % Mo false)

…”

Section: Resultsmentioning

confidence: 99%

Yield Strength Enhancement Without Ductility Loss Through Controlling the Intercritical Annealing Time in Medium‐Mn Steels

Elbeltagy

Shen

et al. 2023

Adv Eng Mater

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“…Commonly used elastic foundation beam models include Winkler's foundation model, Pasternak's foundation model and Vlasov's foundation model (Zheng et al, 2021). The twoparameter Pasternak's foundation model considers the shearing effect of soil based on Winkler's foundation model foundation beam and contains only two parameters.…”

Section: Calculation Of Pile Foundation Deformationmentioning

confidence: 99%

Calculation of surface settlement and pile foundation deformation caused by shield machine tunnelling along curve section

et al. 2022

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The shield machine tunnelling along the curve section causes more disturbance to the surrounding environment than the straight section. Pile foundation is the most commonly used foundation form in high-rise buildings, and high-rise buildings have extremely high requirements for controlling non-uniform deformation. Therefore, it is necessary to study the surface settlement and the deformation law of pile foundations caused by shield machine tunnelling along the curve section. Considering the shield machine tunnelling factors along the curve section and the coupling effect of piles and soil, the analytical calculation formula of the ground settlement and the pile foundation deformation caused by the shield machine tunnelling along the curve section is deduced. According to the actual project situation, a finite difference model (FDM) is constructed, and the correctness of the FDM and analytical prediction formula is verified by comparing the on-site monitoring data. The research shows that the error among the FDM results, the analytical prediction results, and the on-site monitoring data are small, and the surface settlement and pile foundation deformation meet the construction control standards. The friction resistance of the shield shell, the integrative gap at the shield tail (IGST), and the over-cutting gap (OG) are the main factors leading to the surface settlement. However, the shield shell friction and OG are the main reasons leading to the inner settlement of the curve section being more prominent than the outer side. The difference in the pile foundation settlement on both sides of the curve section is slight, the maximum settlement difference rate is 1.8%, and the maximum horizontal deformation rate of the pile foundation on the inner and outer sides is 9.2%, which shows that the horizontal deformation of the pile foundation is more sensitive to the asymmetrically distributed construction factors.

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“…The difference in the internal force calculation results of the segment under the two models is compared and analyzed. By comparing and analyzing the difference between the deformation calculation results of the two models and the field-measured values, the reliability of the model is verified [39][40][41]. Finally, the model that is closer to the measured data is selected to calculate the ultimate bearing capacity of the shield segment and evaluate its safety.…”

Section: Introductionmentioning

confidence: 98%

Comparative Analysis and Safety Evaluation of Shield Segment Structure Model under Surcharge Loading

Liu,

Jiang,

et al. 2023

Materials

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In shield tunneling projects, the selection of an accurate model to calculate the mechanical response of segment structure plays a crucial role in the design and cost of the project. The shell–spring and beam–spring models are two widely used methods for this purpose. However, it is still not clear how accurate and different these models are in calculation results under surcharge load. Therefore, to accurately calculate the internal forces and deformation of the segment structure and clarify the difference between the two models’ results, the shell–spring and beam–spring models were established based on a subway shield tunnel project in Zhengzhou city. The reliability of the models was verified by comparing and analyzing the differences in deformation results between the models and field measurements. Furthermore, the safety of the segment structure was evaluated according to the ultimate bearing capacity of the normal section. The results declare that: (1) In the shell–spring model, the internal force gradually reduces from the edges towards the center of the segment width, and the shield segment exhibits a prominent non-plane strain state. (2) The internal force of the beam–spring model is larger than that of the shell–spring model. The axial force difference between the two models is relatively small; meanwhile, there is a larger disparity in the bending moment. However, with an increase in surcharge loading, the discrepancy in internal forces between the two models gradually decreases. (3) The calculation results of the shell–spring model are close to the field-measured values and the shield tunnel model test values, which verifies the accuracy and reliability of the shell–spring model. Therefore, it is more reasonable to use the shell–spring model to calculate the mechanical response of the segment structure. (4) With an increase in surcharge loading, the safety of the shield tunnel decreases gradually. Therefore, surcharge loading above the shield tunnel should be reasonably controlled to meet the requirements of the normal use of the shield segment. This manuscript aims to provide a reference for the future design and optimization of the shield tunnels’ lining structure.

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Longitudinal Deformation of Deep Shield Tunnels Caused by Upper Load Reduction

Cited by 10 publications

References 23 publications

Yield Strength Enhancement Without Ductility Loss Through Controlling the Intercritical Annealing Time in Medium‐Mn Steels

Yield Strength Enhancement Without Ductility Loss Through Controlling the Intercritical Annealing Time in Medium‐Mn Steels

Calculation of surface settlement and pile foundation deformation caused by shield machine tunnelling along curve section

Comparative Analysis and Safety Evaluation of Shield Segment Structure Model under Surcharge Loading

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