scholarly journals Numerical study on transverse deformation characteristics of shield tunnel subject to local soil loosening

2021 ◽  
Author(s):  
Dong Su ◽  
Weijie Chen ◽  
Xuetao Wang ◽  
Maolong Huang ◽  
Xiaochao Pang ◽  
...  
Keyword(s):  
Numerical Study ◽  
Shield Tunnel ◽  
Deformation Characteristics ◽  
Transverse Deformation ◽  
Local Soil

scholarly journals Failure Characteristics of Joint Bolts in Shield Tunnels Subjected to Impact Loads from a Derailed Train

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Qixiang Yan ◽  
Zhixin Deng ◽  
Yanyang Zhang ◽  
Wenbo Yang
Keyword(s):  
Impact Load ◽  
Numerical Study ◽  
Design Method ◽  
Shield Tunnel ◽  
Failure Behavior ◽  
Impact Loads ◽  
Fe Model ◽  
Fe Modelling ◽  
Bolt Failure ◽  
The Impact

Impact loads generated by derailed trains can be extremely high, especially in the case of heavy trains running at high speeds, which usually cause significant safety issues to the rail infrastructures. In shield tunnels, such impact loads may not only cause the damage and deformation of concrete segments, but also lead to the failure of segmental joint bolts. This paper presents a numerical study on the failure behavior of segmental joint bolts in the shield tunnel under impact loading resulting from train derailments. A three-dimensional (3D) numerical model of a shield tunnel based on the finite element (FE) modelling strategy was established, in which the structural behavior of the segmental joint surfaces and the mechanical behavior of the segmental joint bolts were determined. The numerical results show that the occurrence of bolt failure starts at the joints near the impacted segment and develops along the travel direction of train. An extensive parametric study was subsequently performed and the influences of the bolt failure on the dynamic response of the segment were investigated. In particular, the proposed FE model and the analytical results will be used for optimizing the design method of the shield tunnel in preventing the failure of the joint bolts due to the impact load from a derailed HST.

scholarly journals Deformation Characteristics of Existing Twin Tunnels Induced by Double Shield Undercrossing with Prereinforcement: A Case Study in Hangzhou

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xinjiang Wei ◽  
Mobao Zhang ◽  
Shaojun Ma ◽  
Chang Xia ◽  
Xingwang Liu ◽  
...  
Keyword(s):  
Soft Soil ◽  
Earth Pressure ◽  
Plain Concrete ◽  
Horizontal Displacement ◽  
Shield Tunnel ◽  
Deformation Characteristics ◽  
Pressure Balance ◽  
Concrete Wall ◽  
Shield Tunnelling ◽  
Epb Shield

This paper is based on the case of the earth pressure balance (EPB) shield tunnelling project of the new Metro Line 2 undercrossing the existing Metro Line 1 in the soft soil urban area of Hangzhou. Because the EPB shield must break through a plain concrete wall before undercrossing the existing tunnels, the pipe roof prereinforcement was adopted to stabilize the soil between the existing tunnels and the new shield tunnel. The deformation characteristics of the existing tunnels in the process of double shield undercrossing were discussed. According to the variation of shield position, the settlement development could be divided into three stages: shield approaching subsidence, shield crossing heave, and shield leaving subsidence. The horizontal displacement shows a back and forth variation characteristic consistent with the direction of shield tunnelling. At the junction of tunnel and station, the shield undercrossing caused considerable differential settlement between the existing tunnel and the station. The construction of pipe roof prereinforcement will lead to the presettlement of the existing tunnels. The settlement of the existing tunnels caused by the attitude deviation of pipe roof and grouting disturbance should be reduced in reasonable ranges. In addition, the maximum longitudinal settlement of the existing tunnel during the shield second undercrossing was also discussed. It was considered that the influence of wall breaking is greater than the sequence of shield undercrossing. The driving parameters of shield tunnelling should be optimized before the second crossing.

A Numerical Study of the Impact of Tunnel Depth on Surface Displacement in Shield Tunnel Construction

2013 ◽  
Vol 423-426 ◽  
pp. 1248-1252
Author(s):  
Hui Ting Zhan ◽  
Hong Yuan ◽  
Jia Yu Wu ◽  
Yu Sen Yuan
Keyword(s):  
Numerical Study ◽  
Surface Displacement ◽  
Soil Surface ◽  
Rate Of Change ◽  
Shield Tunnel ◽  
Tunnel Construction ◽  
Displacement Curve ◽  
3D Finite Element Method ◽  
Tunnel Depth ◽  
The Impact

Using 3d finite element method can simulate the process of shield tunnel construction. The paper studies the impact of different tunnel depth on the deformation of soil, when considering different excavation steps in the process of tunnel construction. The results show that the shallower the tunnel depth, and the greater the amount of the surface displacement during the tunnel construction. In the process of the tunnel excavation, the soil surface displacement in front of the shield machine is the result of superposition of the uplift and subsidence. When the tunnel depth increases, the surface displacement curve becomes smoother, and the rate of change becomes slower.

scholarly journals Numerical Study on the Disturbance Effect of Short-Distance Parallel Shield Tunnelling Undercrossing Existing Tunnels

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Zhen Huang ◽  
Chenlong Zhang ◽  
Helin Fu ◽  
Huangshi Deng ◽  
Shaokun Ma ◽  
...  
Keyword(s):  
Numerical Model ◽  
Short Distance ◽  
Maximum Stress ◽  
Numerical Study ◽  
Soil Layer ◽  
Field Monitoring ◽  
Surface Settlement ◽  
Shield Tunnel ◽  
Double Line ◽  
Shield Tunnelling

The construction of new tunnels poses a threat to the operational safety of closely existing tunnels, and the construction mode of parallel undercrossing over short distances has the most significant impact. In this study, a new double-line shield tunnel parallel undercrossing of existing tunnels in Hefei, China, is taken as an example. A three-dimensional (3D) numerical model using FLAC3D finite difference software was established. The dynamic construction of the new double-line shield tunnel undercrossing the existing subway tunnel over a short distance and in parallel was simulated. The pattern of existing tunnel settlement and change in lining stress caused by the shield tunnelling process were analyzed. The reliability of simulation was verified through field-monitoring data. Finally, based on the numerical model, the effects of change in stratum sensitivity on the settlement of existing tunnel, lining internal force, and surface settlement are discussed. The results show that during shield tunnelling, the maximum ground settlement is 3.9 mm, the maximum settlement at the arch waist of existing tunnel near the new tunnel is 7.75 mm, and the maximum vault settlement is 5.38 mm. The maximum stress of lining of existing tunnel before the excavation is 7.798 × 105 Pa. After the construction of double-line shield tunnel, the maximum stress of lining is 1.124 × 106 Pa, an increase of 44% than that before the construction. The surface settlement and tunnel settlement are sensitive to the weakening of soil layer strength, and lining stress is not affected by the weakening of soil layer strength. The field-monitoring results are consistent with the numerical simulation results, and the model calculation is reliable. This study plays an important role in ensuring construction safety and optimizing the construction risk control of a tunnel.

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