scholarly journals Upper Bound Solution for the Face Stability of Shield Tunnel below the Water Table

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Xilin Lu ◽  
Haoran Wang ◽  
Maosong Huang
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Fe Simulation ◽  
Shield Tunnel ◽  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Face Stability ◽  
The Face ◽  
Upper Bound Limit Analysis

By FE simulation with Mohr-Coulomb perfect elastoplasticity model, the relationship between the support pressure and displacement of the shield tunnel face was obtained. According to the plastic strain distribution at collapse state, an appropriate failure mechanism was proposed for upper bound limit analysis, and the formula to calculate the limit support pressure was deduced. The limit support pressure was rearranged to be the summation of soil cohesionc, surcharge loadq, and soil gravityγmultiplied by their corresponding coefficientsNc,Nq, andNγ, and parametric studies were carried out on these coefficients. In order to consider the influence of seepage on the face stability, the pore water pressure distribution and the seepage force on the tunnel face were obtained by FE simulation. After adding the power of seepage force into the equation of the upper bound limit analysis, the total limit support pressure for stabilizing the tunnel face under seepage condition was obtained. The total limit support pressure was shown to increase almost linearly with the water table.

Influence of Pipe Roof Reinforcement on Face Stability of Underwater Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1029-1033 ◽  
Author(s):  
Kai Wang ◽  
Hai Gui Kang ◽  
Hai Tao Wang
Keyword(s):  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Face Stability ◽  
Seepage Pressure ◽  
Kinematic Method ◽  
The Face ◽  
Tunnel Face Stability ◽  
Underwater Tunnel ◽  
Groundwater Flow Condition

The effect of seepage force on tunnel face stability with pipe roof reinforcement was studied based on the kinematic method of limit analysis. This method can be employed to define the safety factor and its corresponding critical failure mechanism for a given tunnel. The studies revealed that the existence of groundwater may seriously affect the face stability. Under the steady-state groundwater flow condition, most part of the total support pressure is owing to the seepage pressure acting on the tunnel face. There was a relatively large reduction in the seepage pressure by adopting the pipe roof reinforcement technique.

Effect of seepage forces on tunnel face stability

2003 ◽  
Vol 40 (2) ◽  
pp. 342-350 ◽  
Author(s):  
In-Mo Lee ◽  
Seok-Woo Nam ◽  
Jae-Hun Ahn
Keyword(s):  
Model Test ◽  
Upper Bound ◽  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Face Stability ◽  
Seepage Pressure ◽  
Bound Solution ◽  
Upper Bound Solution ◽  
Tunnel Face Stability

In this study, two factors are simultaneously considered for assessing tunnel face stability. The first is the effective stress acting on the tunnel face calculated by upper bound solution, and the other is the seepage force calculated by numerical analysis under the condition of steady-state groundwater flow. The seepage forces calculated by numerical analysis are compared with the results of a model test. The upper bound solution taking into consideration the seepage force acting on the tunnel face, shows that the minimum support pressure for the face stability is equal to the sum of the effective support pressure that is obtained from the upper bound solution based on effective stress and the seepage pressure acting on the tunnel face. It was found that the average seepage pressure acting on the tunnel face is proportional to the hydrostatic pressure at the same elevation, and the magnitude is about 22% of the hydrostatic pressure for the drainage type tunnel and about 28% for the waterproof type tunnel. The seepage forces obtained from the results of a model test showed similar trends as those calculated by numerical analysis.Key words: face stability, upper bound solution, seepage force, model test.

scholarly journals An Analytical Continuous Upper Bound Limit Analysis of Pore Water Effect on the Tail Stability of Underwater Shield Tunnels during Construction

2020 ◽  
Vol 143 ◽  
pp. 01015
Author(s):  
Wenjie Song ◽  
Yanyong Xiang
Keyword(s):  
Pore Water ◽  
Upper Bound ◽  
Limit Analysis ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Surface ◽  
Support Pressure ◽  
Tunnel Support ◽  
Transverse Stability ◽  
Upper Bound Limit Analysis

An analytical continuous upper bound limit analysis is developed to analyse the effects of seepage on the transverse stability of underwater shield tunnels. The approach is based on an analytical continuous upper bound limit analysis method for cohesive-frictional soils. It employs the complex variables solution of the displacement field due to tunnel deformation and movement, and the analytical solution of the pore water pressure field for steady state seepage due to pore water influx at the tunnel perimeter. The most critical slip line position and the minimum required tunnel support pressure are determined by using a particle swarm optimization scheme for various generic situations. The method is verified via finite element simulation and comparison with the solution from using rigid block upper bound limit analysis. The parametric analysis revealed among other things that both the infimum of the necessary tunnel support pressure and the most critical plastic zone increase when the hydraulic head at the ground surface increases, but decrease when the tunnel influx increases due to the fact that pore water pressure at the tunnel perimeter decreases with the tunnel influx.

scholarly journals Face Stability Analysis of Shield Tunnel Using Slip Line Method

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Weiping Liu ◽  
Shaofeng Wan ◽  
Xinqiang Song ◽  
Mingfu Fu ◽  
Lina Hu
Keyword(s):  
Stability Analysis ◽  
Slip Line ◽  
Yield Criterion ◽  
Limit Equilibrium ◽  
Shield Tunnel ◽  
Support Pressure ◽  
Tunnel Face ◽  
Face Stability ◽  
Line Method ◽  
The Stability

The sufficient support pressure is essential to guarantee the safe construction of shield tunnel. Thus, it is necessary to analyze the stability and assess the limit support pressure of the tunnel face. The main methods for face stability analysis mostly focused on finite element method, limit equilibrium method, and numerical simulation method. In this paper, the slip line method is applied to analyze the stability of the tunnel face. The soil is supposed as ideal isotropic, homogeneous, and incompressible continuous material, which obeys the Mohr–Coulomb yield criterion. A mathematical model of the limit equilibrium boundary value problem is established. The slip line method is used to solve the slip line field and stress field of the soil behind the tunnel face. Limit support pressure and failure mechanism of the tunnel face are then obtained. In addition, comparisons between the results of this study and those of existing approach are performed, and the influence factors are also discussed. The results show that the slip line method is proven to be reliable for the evaluation of limit support pressure of the tunnel face stability.

scholarly journals Rotational Failure Mechanism for Face Stability of Circular Shield Tunnels in Frictional Soils

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Yuan Zhou ◽  
Yuming Zhu ◽  
Shumao Wang ◽  
Hu Wang ◽  
Zhengxing Wang
Keyword(s):  
Failure Mechanism ◽  
Upper Bound ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Circular Cross Section ◽  
Support Pressure ◽  
Tunnel Face ◽  
Face Stability ◽  
Rotational Failure ◽  
Frictional Soils

Face stability analyses of shield-driven tunnels are often carried out to determine the required support pressure on the tunnel face. Although various three-dimensional mechanisms have been proposed for circular faces of tunnels in frictional and/or cohesive soils to obtain the limit support pressure, the most critical one has not yet been found. Based on a rotational failure mechanism for the frictional soils, this paper modifies the circular cross section as an ellipse to make the generating collapse surface inscribe the entire circular tunnel face. Using the kinematical approach of limit analysis yields an upper bound to the limit support pressure. Through comparisons with the existing results in the literature, the improved mechanism can better estimate the upper bound and is very similar to the observed failures in the experimental tests. The influences of the pore water pressure are also included in the stability analysis of tunnel faces. Calculated upper-bound solutions are presented in a condensed form of charts for convenient use in practice.

Study on the Stability of Large Cross-River Shield Tunnel Face with Seepage

2013 ◽  
Vol 405-408 ◽  
pp. 1371-1374 ◽  
Author(s):  
Xi Lin Lu ◽  
Feng Di Li
Keyword(s):  
Numerical Analysis ◽  
Water Level ◽  
Coupling Effect ◽  
Shield Tunnel ◽  
Support Pressure ◽  
Seepage Force ◽  
Tunnel Face ◽  
Increasing Trend ◽  
The Stability ◽  
Shield Tunnel Face

By 3D numerical analysis, the seepage force on the tunnel face was obtained and shows linearly increasing trend with the water level. By considering the average seepage force on the wedge boundary of 3D trapezoidal wedge model, the limit support pressure to keep stability of tunnel face under seepage condition was obtained. The total limit support pressure increases almost linearly with the water level. In order to consider the deformation seepage coupling effect, the 3D coupled deformation and seepage numerical analysis was further used to investigate the influence of the water level on the failure of tunnel face, the results show the failure mode changes with the increase of water level, and the limit support pressure increases nonlinearly with the water level.

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