scholarly journals A Comparative Study of Protective Schemes for Shield Tunneling Adjacent to Pile Groups

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Penglin Li ◽  
Yuquan Lu ◽  
Jinxing Lai ◽  
Houquan Liu ◽  
Ke Wang
Keyword(s):  
Ground Deformation ◽  
Three Dimensional ◽  
Bending Moment ◽  
Shield Tunnel ◽  
Physical Parameters ◽  
Deep Hole ◽  
Pile Groups ◽  
Control Effect ◽  
Shield Tunneling ◽  
Reinforcement Scheme

Shield tunneling adjacent to pile groups is always an unavoidable problem in urban metro construction. A case was found in the project of Tianjin Metro Line 7, where a shield tunnel would be constructed near the existing pile groups of Shiyou Bridge. The whole shield tunnel is close to pile groups, and the minimum distance is only 0.8 m. Therefore, four kinds of protective schemes are proposed in this paper. It is vital to select an appropriate protective scheme to guarantee the safety during the tunnel construction. In this study, the main mechanical characteristic and physical parameters of site soil were obtained through laboratory tests. Besides, the three-dimensional finite element method was carried out to compare and analyze the effectiveness of the protective schemes in mitigating the effects of tunneling on adjacent pile groups. The results show that the deep-hole grouting scheme has better control effect on the lateral deformation and bending moment of piles, while the pile foundation underpinning scheme has better effectiveness on reducing the settlement of bridge structure and ground deformation. Finally, the deep-hole grouting reinforcement scheme will be adopted to ensure the shield passing through the pile groups smoothly.

Numerical Analysis of Metro Station Construction by Large-Diameter Shield and Pile-Beam-Arch Method

2011 ◽  
Vol 368-373 ◽  
pp. 2711-2715 ◽  
Author(s):  
De Yun Ding ◽  
Xiu Ren Yang ◽  
Wei Dong Lu ◽  
Wei Ning Liu ◽  
Mei Yan ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Large Diameter ◽  
Element Model ◽  
Construction Method ◽  
Shield Tunnel ◽  
Outer Diameter ◽  
Shield Tunneling ◽  
Metro Station ◽  
Dimensional Finite Element ◽  
New Construction

In more and more complicated urban building environment, a new construction method that metro engineering is constructed by large-diameter shield and shallow mining method can be regarded as a great attempt in China. By taking the Gaojiayuan station of Beijing metro line 14 as an engineering background, the main construction steps for the platform of the metro station built by a large-size shield with an outer diameter of 10 m and the Pile-Beam-Arch (PBA) method are introduced. Based on the soil-structure interaction theory, a two-dimensional finite element model is used to simulate the shield tunneling and the platform construction by the PBA method to enlarge the shield tunnel. The ground deformation and structural stress of the platform are predicted. The numerical results can be regarded as a valuable reference for the application of the new construction method in Beijing metro line 14.

Crown reconfiguration and trunk stress in deciduous trees

2008 ◽  
Vol 38 (6) ◽  
pp. 1275-1289 ◽  
Author(s):  
Brian Kane ◽  
Michael Pavlis ◽  
J. Roger Harris ◽  
John R. Seiler
Keyword(s):  
Factor Of Safety ◽  
Three Dimensional ◽  
Bending Moment ◽  
Modulus Of Rupture ◽  
Physical Parameters ◽  
Deciduous Trees ◽  
Cross Sectional ◽  
Tree Crowns ◽  
Wind Speeds ◽  
Crown Dimensions

In light of the risk of litigation following damage related to tree failure in urban and suburban settings, more empirical data related to tree risk assessment are needed. We measured drag and drag-induced bending moment (M) and calculated drag coefficient (CD) and trunk stress (σ) for three deciduous trees at wind speeds up to 22.4 m/s. We measured the modulus of rupture (MOR) of wood samples from trunks and calculated the factor of safety (SF = MOR / σ) for each tree. We also investigated which tree morphometric variables best predicted drag and M and whether simple two- and three-dimensional shapes accurately represented actual tree crowns. Drag, CD, M, σ, and SF differed among species in accordance with physical parameters. More massive trees experienced greater drag and M, but σ was greater for trees with smaller trunk diameters. Tree mass reliably predicted drag and M; crown dimensions, including crown area, were less reliable predictors. Crown reconfiguration varied only slightly among species, and CD values were similar to previously reported values for trees of similar size. Our study has important applications for practitioners who manage tree risk, particularly the critical wind speeds and percentage of trunk cross-sectional area that could be decayed before trunk failure.

scholarly journals Numerical analysis of reducing tunneling effect on viaduct piles foundation by jet grouted wall

2021 ◽  
Vol 15 (1) ◽  
pp. 75-86
Author(s):  
Kamel Asker ◽  
Mohmed Tarek Fouad ◽  
Mohamed Bahr ◽  
Ahmed El-Attar
Keyword(s):  
Numerical Model ◽  
Interaction Mechanism ◽  
Back Analysis ◽  
Bending Moment ◽  
Pile Group ◽  
Tunneling Effect ◽  
Shield Tunnel ◽  
Pile Groups ◽  
Perfectly Plastic ◽  
Jet Grouting

Purpose. The target of this study is divided into two parts. The first part is concerned with capability of numerical model to simulate the tunneling process. The second part is related to studying the interaction mechanism between the tunnel, protection technique, and soil. This study themes are investigated by analyzing different protection technique configuration, considering different stiffness of the grouted wall, and applying different interface coefficient between the wall and the soil. Methods. The method used in this study to check the accuracy of the proposed numerical model is 4-D ABAQUS program. The typical excavation of a tunnel is simulated step by step with an assumed rate of tunnel advancement (0.5 to 1.5 m/hr). The soil material utilized in this model is elastic perfectly plastic (the Mohr-Сoulomb criterion), while elastic material is modeled as solid element (S4R) adopted for lining, grouting, filling gaps, shielding, constructing piles, and jet grouted wall. Findings. Results showed that the closer jet grouting to the tunnel with embedded length of 1.5 times tunnel diameter, the better effect on reducing the lateral deformation and bending moment generated on piles. Otherwise, increasing wall thickness more than double grouted column diameter would not affect its shielding efficiency. Furthermore, either increasing or decreasing friction coefficient even if rough between the grouted wall and soil had no effect on the pile behavior. Additionally, applying Mohr-Coulomb criteria for grouted wall with high stiffness allowed realistic response of the pile group. Originality.Capability of the proposed model is verified by back analysis of Changsha Subway Line 1 project, where the shield tunnel would be constructed near existing pile groups of L off-ramp of the Xinzhong Road viaduct. Practical implications. Increasing grouted wall configuration is more effective than mechanical properties or its interface coefficient with surrounded soil in mitigating tunneling effect on nearby piles. Keywords: tunneling, jet grouting, gield measurements, ABAQUS, Changsha Subway Line 1

scholarly journals An Improved Method for Predicting the Greenfield Stratum Movements Caused by Shield Tunnel Construction

2019 ◽  
Vol 9 (21) ◽  
pp. 4522 ◽  
Author(s):  
Tan ◽  
Zhang ◽  
Zhang ◽  
Zhu ◽  
Tu
Keyword(s):  
Three Dimensional ◽  
Elastic Half Space ◽  
Shield Tunnel ◽  
Theoretical Formula ◽  
Tunnel Construction ◽  
Underground Structures ◽  
Underground Engineering ◽  
Shield Tunneling ◽  
Deep Soil ◽  
Contour Maps

Shield tunneling is becoming the preferred construction scheme for metro construction because of its advantages of fast construction speed and small disturbance. However, limited by process defects, the stratum movements induced by the construction of shield tunnels still affects the safety of nearby underground structures and aboveground buildings. Therefore, the reliable prediction of stratum movements is important. Described in this paper is an analysis method of the Greenfield stratum movements (Greenfield is an area of land that has not yet had buildings on it, stratum movements means the movement of various soil layers) caused by shield tunnel construction combining an elastic half-space model of mirror source–sink method with the use of modified analytical method. Based on the theoretical formula in this paper, not only can the curve of surface settlement trough be calculated, but also the three-dimensional displacement field of deep soil can be obtained. By comparing vertical and horizontal contour maps of Greenfield stratum movements, good consistency between theoretical formula results and centrifugal test results are shown. This solves the defects and limitations of existing two-dimensional formulas; furthermore, based on this, it is convenient to evaluate the effect on the other skewed underground structures through the elastic foundation beam and other similar methods; therefore, this paper can provide a wide guidance and service for the design and construction of underground engineering in the future.

Three Dimensional Numerical Analysis of Ground Settlement Induced by Shield Tunneling

2012 ◽  
Vol 182-183 ◽  
pp. 937-940
Author(s):  
Zhong Chang Wang
Keyword(s):  
Soil Layer ◽  
Three Dimensional ◽  
Ground Surface ◽  
Vertical Displacement ◽  
Ground Subsidence ◽  
Shield Tunnel ◽  
Ground Settlement ◽  
Shield Tunneling ◽  
Tunnel Face ◽  
Maximum Settlement

The fine numerical simulation is used to study the ground settlement of complex stratum owing to shield construction by ANSYS program. It is shown that the closer the distance between soil layer and the axis of tunnel is, the smaller the disturbance of construction is, the obvious the ground surface settlement is. The value of the maximum settlement at the center of the surface is 7.4mm. The maximum settlement of vault is 14mm. The ground subsidence in cross section distribution is shaped of normal distribution. The closer the distance between soil layer and ground surface is, the smaller the vertical displacement is, the bigger the width of settlement trough of soil layers is. The width of settlement trough is 25m. The volume loss rate of shield tunnel is about 0.32%. The width coefficient of ground settlement trough is 0.56. The tendency of ground settlement decrease to become gentle with the advance of shield construction. The ground settlement keeps constant after tunnel face advancing to 30m.

Coupled Numerical Analysis of Tunnel Excavation in Saturated Soft Clay under High Groundwater

2011 ◽  
Vol 368-373 ◽  
pp. 2533-2536
Author(s):  
Hua Yuan ◽  
Hai Tao Wan ◽  
Zhi Liang Zhao
Keyword(s):  
Soft Clay ◽  
Three Dimensional ◽  
Bending Moment ◽  
High Water ◽  
Shield Tunnel ◽  
Deep Soil ◽  
Tunnel Excavation ◽  
Axial Forces ◽  
Reduction Effect ◽  
Saturated Soft Clay

A coupled numerical simulation of a river-crossing shield tunnel excavation in saturated soft clay with high groundwater has been performed using a three-dimensional finite difference model, which takes into account variation of soil permeability with stress, anisotropy of permeability, reduction effect of joints on segment bending stiffness and the hardening process of synchronized grouting material. Groundwater seepage conditions around the tunnel, bending moment, axial forces and strength safety factor of tunnel segment as well as deep soil displacement during tunnel diving are investigated numerically. The analyses provide valuable information concerning the mechanical behavior of tunnel segment and hydrological field in soil around tunnel during advancing. The result also is benefited to control groundwater for river-crossing tunnel in soft clay under high water table.

Study on Influencing Factor of Ground Deformation Induced by Shield Tunneling

2013 ◽  
Vol 734-737 ◽  
pp. 690-693
Author(s):  
Meng Lin Xu ◽  
De Shen Zhao
Keyword(s):  
Ground Deformation ◽  
Influencing Factor ◽  
Ground Movement ◽  
Shield Tunnel ◽  
Shield Tunneling ◽  
Tunnel Excavation ◽  
Security Issues ◽  
Surrounding Environment ◽  
Strata Deformation ◽  
Complex Construction

The complex construction behavior inevitably disturb surrounding environment, even when the tunneling goes through building, which may be wrecked. The security issues of the subway project stems from ground movement and structure dynamic interaction. So it is academic and application good value for study on construction influences of shield tunnel excavation to the neighboring buildings. This paper focuses on the shield tunnel construction strata deformation factors. The results provided the theory basis for safety construction.

Research on Shield Tunnel Three-Dimensional Modeling Method

2013 ◽  
Vol 651 ◽  
pp. 765-769
Author(s):  
Mu Huang ◽  
Xiao Li Rong
Keyword(s):  
Three Dimensional ◽  
Modeling Method ◽  
Shield Tunnel ◽  
Construction Technology ◽  
Shield Tunneling ◽  
Tunneling Model ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Triangular Network ◽  
Line Design

With the development of informational construction technology, the shield tunnel three-dimensional visualization has been more and more used. This paper proposes a modeling method of discrete space curve based on coordinates of shield line design, then calculate and generate shield tunneling model. The model data is stored in the form of triangular network. This method has fast modeling speed and low request of storage space, and is relatively easy to imply. It can be combined with GIS in fast simulation to improve work efficiency.

scholarly journals A Displacement-Based Theory for Predicting the Support Force on the Shield Tunneling Surface in Sandy Soil Layers

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Guang Sun ◽  
Han Liu ◽  
Zhiyuan Guo ◽  
Ranjie Li ◽  
Tao Li
Keyword(s):  
Numerical Simulation ◽  
Sandy Soil ◽  
Soil Layer ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Shield Tunnel ◽  
Soil Pressure ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Support Force

Due to the poor stability of the loose sandy soil layer, if the support force is not properly controlled during the construction process of the shield tunnel using the earth pressure balance method, it is easy to cause the ground to collapse or uplift. Therefore, understanding the support force of the excavation surface of shield tunneling in sandy soil layer is very vital to ensure the stability of the excavation surface. Firstly, it is assumed that the damaged soil is a three-dimensional wedge and a modified three-dimensional wedge in the active and passive failure modes, respectively. The shallow soil pressure theory and the soil plastic limit equilibrium theory are derived by analyzing the stress distribution on the damaged soil. The equation for revealing the inner essence between the support force of the shield excavation surface and excavation surface displacement under the condition of sand-covered soil is used. Secondly, the numerical simulation method analyzes the displacement of the excavation surface when the support force changes under different working conditions, and the relationship curve between the excavation surface support force and the shield tunneling displacement is obtained. The comparison and analysis between the numerical simulation calculation and the theoretical analysis indicate that the deduced calculation equation for the excavation surface support force based on the displacement earth pressure is reasonable.

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