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 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.

scholarly journals Probabilistic Analysis of Tunnel Face Stability below River Using Bayesian Framework

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Weiping Liu ◽  
Xiaoyan Luo ◽  
Jinsong Huang ◽  
Lina Hu ◽  
Mingfu Fu
Keyword(s):  
Probabilistic Analysis ◽  
Three Dimensional ◽  
Friction Angle ◽  
Bayesian Framework ◽  
Computational Time ◽  
Support Pressure ◽  
Tunnel Face ◽  
Face Stability ◽  
Mcmc Simulation ◽  
Tunnel Face Stability

A key issue in assessment on tunnel face stability is a reliable evaluation of required support pressure on the tunnel face and its variations during tunnel excavation. In this paper, a Bayesian framework involving Markov Chain Monte Carlo (MCMC) simulation is implemented to estimate the uncertainties of limit support pressure. The probabilistic analysis for the three-dimensional face stability of tunnel below river is presented. The friction angle and cohesion are considered as random variables. The uncertainties of friction angle and cohesion and their effects on tunnel face stability prediction are evaluated using the Bayesian method. The three-dimensional model of tunnel face stability below river is based on the limit equilibrium theory and is adopted for the probabilistic analysis. The results show that the posterior uncertainty bounds of friction angle and cohesion are much narrower than the prior ones, implying that the reduction of uncertainty in cohesion and friction significantly reduces the uncertainty of limit support pressure. The uncertainty encompassed in strength parameters are greatly reduced by the MCMC simulation. By conducting uncertainty analysis, MCMC simulation exhibits powerful capability for improving the reliability and accuracy of computational time and calculations.

scholarly journals Analysis of Face Stability of Circular Tunnel in Purely Cohesive Soils Driven by Shield

2018 ◽  
Author(s):  
Jinhui Liu ◽  
Wantao Ding ◽  
Mingbin Wang
Keyword(s):  
Analytical Model ◽  
Yield Criterion ◽  
Failure Process ◽  
Support Pressure ◽  
Cohesive Soils ◽  
Soil Arching ◽  
Circular Tunnel ◽  
Tunnel Face ◽  
Face Stability ◽  
The Face

Based on the kinematic approach of the limit analysis and slip-line theories, this paper proposes a new 2D analytical model to evaluate the collapse support pressure to ensure the face stability of a circular tunnel in purely cohesive soils driven by a shield. The normality conditions, the yield criterion and the vertical soil arching effect are considered in the analytical model. Two upper bound solutions corresponding to the ratio of the cover to the diameter (C/D) are derived from considering the mechanisms based on the motion of rigid multi-blocks. Comparisons are made with existing upper and lower bound solutions published in previous articles. The results are close to the solutions of practical engineering. The failure mechanisms proposed in this study provide a better explanation for the failure process in the heading of the tunnel face.

scholarly journals A soft computing approach to tunnel face stability in a probabilistic framework

2021 ◽  
Author(s):  
Enrico Soranzo ◽  
Carlotta Guardiani ◽  
Wei Wu
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Soft Computing ◽  
Support Pressure ◽  
Tunnel Face ◽  
Soft Computing Techniques ◽  
The Face ◽  
Tunnel Face Stability ◽  
Artificial Neural ◽  
Face Support

AbstractTunnel face is important for shallow tunnels to avoid collapses. In this study, tunnel face stability is studied with soft computing techniques. A database is created based on the literature which is used to train some broadly adopted soft computing techniques, ranging from linear regression to the artificial neural network. The soil dry density, cohesion, friction angle, cover depth and the tunnel diameter are used as the input parameters. The soft computing techniques state whether the face support is stable and predict the face support pressure. It is found that the artificial neural network outperforms the other techniques. The face support pressure is predicted with the artificial neural network for statistically distributed samples, and the failure probability is obtained with Monte Carlo simulations. In this way, the stability of the tunnel face can be reliably assessed and the support pressure can be estimated fairly accurately.

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