A Theoretical Calculation Method of the Unsupported Span for the Shallow Tunnel in the Soft Stratum

Tian, Xiaoxu; Song, Zhanping; Zhou, Guannan; Zhang, Xiaowei

doi:10.1155/2020/7989036

Cited by 4 publications

(3 citation statements)

References 25 publications

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“…e initial stress field is calculated according to the self-weight stress field. e construction interval is basically within the envelope structure, and the driving load on the ground is not considered; that is, the effect of variable load is not considered [8,24]. In order to ensure the calculation accuracy, fine elements are used around the tunnel.…”

Section: Establishment Of Calculation Model Using Midas Gts/mentioning

confidence: 99%

Risk Analysis of Tunnel Construction Scheme Change based on Field Monitoring and Numerical Analysis

Song

Tian

et al. 2021

Advances in Civil Engineering

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Because of the surrounding environment restriction, some sections of the Lanzhou Metro Line 2 were forced to change the original open excavation method to the concealed excavation method. Among them, the ingate is the transitional section connecting the shaft and the cross passage, which is accompanied by the force conversion of the structure during the plan change process, and accidents are prone to occur. Combining this project situation, a construction scheme for turning the shaft from the cross passage into the ingate of mine line was proposed, and the finite element software is used to simulate the scheme. Numerical analysis shows that the stability of the tunnel supporting structure, shaft, and cross passage all meet the design requirements. The final ground settlement caused by the proposed construction method is 7.1 mm, and the settlement of the vault is 11.97 mm. It also turns out that the proposed construction method causes less deformation, and the method can be applied to the construction of the ingate conversion. The rationality of the method and numerical model was further verified by the comparison between the monitored data of surface settlement and vault sinking and numerical simulation results. Finally, the modified concealed excavation method and the original open excavation construction method is compared. It is concluded that the concealed excavation method is superior to the original open excavation method in terms of construction schedule, construction safety, economic benefits, and impact of construction on the surrounding environment. It indicates that it is a good choice to replace the construction method early if necessary. The successful implementation of this project can provide a reference for the design and implementation of similar urban subway projects.

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Section: Establishment Of Calculation Model Using Midas Gts/mentioning

confidence: 99%

Risk Analysis of Tunnel Construction Scheme Change based on Field Monitoring and Numerical Analysis

Song

Tian

et al. 2021

Advances in Civil Engineering

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“…Initial Support Structure. In the environment sensitive area, the settlement and deformation of the ground surface are important indexes of safety control in the subway engineering [25,26]. e monitoring standard sections are arranged along the tunnel centerline at an interval of 10 m. e layout of the numerical simulation settlement monitoring points and the tunnel convergence measurement points is shown in Figure 10.…”

Section: Comparative Analysis Of Deformation Of Surface Andmentioning

confidence: 99%

Analysis on the Influence of Shaft and Cross Passage Turn to the Main Line of Ingate under Different Construction Schemes

Song

Liu

Zhang

et al. 2021

Advances in Civil Engineering

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In the weak stratum, the construction of ingate is a key technical problem at the place where the shaft and cross passage turn to the tunnel. Based on Lanzhou Metro, the corresponding changes to the construction plan of the ingate of the section tunnel were made. Finite element software is used to carry out three-dimensional modeling and design of subway shaft, cross passage, and tunnel structures in connected sections. The influence of the two construction schemes on surface settlement, deformation, and stress of tunnel support structure and stress conversion of ingate are compared, as well as the fitting degree between numerical simulation results and field monitoring data. Finally, the optimal scheme and key points of construction control are determined. The results show that the optimization scheme has obvious advantages in the control of surface settlement and the deformation of shaft and cross passage support. However, the difference between the stress and deformation of the tunnel supporting structure and the original plan is not obvious. Since the project focuses on shaft, cross passage, and tunnel connection section, the changed construction scheme is better.

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“…Yu et al [21] proposed a composite support system to improve the stability and safety of soft-rock tunnels by using orthogonal experiments, numerical simulation, and field observation. Tian et al [22] obtained a calculation formula for an unsupported span of a shallowly buried tunnel in the soft-rock layer. The research results are of great significance for optimizing the design of tunnel support structures and saving the amount of support materials required [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Using Energy-Absorbing Dampers to Solve the Problem of Large Deformation in Soft-Rock Tunnels: A Case Study

2022

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The commonly used strength design concept of tunnel support structures is inadequate to address the large deformation of soft rock. This study designed a series of energy-absorbing dampers (EDs) with low stiffness and high deformation capacity based on the energy principle. The ED was directly installed on the steel arch, which used its compression deformation to release the surrounding rock pressure and absorb the surrounding rock deformation to ensure the stability of the initial support structure. A compression test analyzed the ED’s mechanical properties, optimizing the structural parameters. The preliminary test results showed that the arc energy-absorbing damper’s (AED-I) peak strength (15.33 Mpa) was lower than the standard compressive strength of C25 shotcrete, with a safety factor of 1.63. The AED-I’s maximum compression ratio was 73.20%. To further improve the AED-I’s reliability and ability to absorb the deformation of surrounding rock, the bending radius of the AED-I’s energy-absorbing steel plate was reduced from 1800 mm to 1300 mm. After optimization, the AED-IO’s peak strength was reduced to 10.5 Mpa, and the safety factor increased to 2.38. The maximum compression ratio of the AED-IO also increased to 75.79%. The AED-IO has been applied to treat the large deformation of soft rock in the Zhongshao Tunnel on the Yuchu Expressway. Compared with a traditional support method, the maximum surrounding rock pressure was only 0.13 Mpa in the section where the AED-IO was applied. The maximum steel arch stress was 122.26 Mpa, far less than its uniaxial compressive strength. The application of the AED-IO ensures the stability of the initial support structure. Meanwhile, using an AED-IO saves CNY 24,323.85 per meter and reduces waste emissions by 20 tons.

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A Theoretical Calculation Method of the Unsupported Span for the Shallow Tunnel in the Soft Stratum

Cited by 4 publications

References 25 publications

Risk Analysis of Tunnel Construction Scheme Change based on Field Monitoring and Numerical Analysis

Risk Analysis of Tunnel Construction Scheme Change based on Field Monitoring and Numerical Analysis

Analysis on the Influence of Shaft and Cross Passage Turn to the Main Line of Ingate under Different Construction Schemes

Using Energy-Absorbing Dampers to Solve the Problem of Large Deformation in Soft-Rock Tunnels: A Case Study

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