Three-dimensional undrained tunnel face stability in clay with a linearly increasing shear strength with depth

2017 ◽  
Vol 88 ◽  
pp. 146-151 ◽  
Author(s):  
Boonchai Ukritchon ◽  
Kongkit Yingchaloenkitkhajorn ◽  
Suraparb Keawsawasvong
Keyword(s):  
Shear Strength ◽  
Three Dimensional ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability

Three-Dimensional Analysis of Excavating Face Stability Supported by Pipe Roof

2013 ◽  
Vol 275-277 ◽  
pp. 1257-1263 ◽  
Author(s):  
Xiang Yuan ◽  
Shun Hua Zhou ◽  
Quan Mei Gong
Keyword(s):  
Analytical Solution ◽  
Dimensional Analysis ◽  
Load Transfer ◽  
Three Dimensional ◽  
Subgrade Reaction ◽  
Large Section ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
The Stability

This paper analyzes the load transfer characteristics of pipe roof over the excavating face, and the analytical solution of tunnel face stability is established by the method of three-dimensional analysis. Through the calculation of the load transfer of the pipe roof, it indicates that the released load of excavation is passed to the supporting structure and soil which is not excavated by the effect of the pipe roof, and the magnitude of load and coverage of impact are in connection with excavating footage as well as subgrade reaction. The three-dimensional analytical solution of tunnel face stability is used to analyze a project case of Airport Road underpass in Hangzhou. The results show that the tunnel face stability is not guaranteed when excavated on a large section while the stability is enhanced when excavated on separated pilot headings.

Three-dimensional analysis of tunnel face stability in spatially variable soils

2019 ◽  
Vol 111 ◽  
pp. 76-88 ◽  
Author(s):  
Hongzhan Cheng ◽  
Jian Chen ◽  
Renpeng Chen ◽  
Juehao Huang ◽  
Jianhe Li
Keyword(s):  
Dimensional Analysis ◽  
Three Dimensional ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability

scholarly journals Shallow tunnel face stability analysis using finite elements

2021 ◽  
pp. 91-97
Author(s):  
I. Kahoul ◽  
S. Yahyaoui ◽  
Y. Mehidi ◽  
Y. Khadri
Keyword(s):  
Shear Strength ◽  
Safety Factor ◽  
Reduction Method ◽  
Plastic State ◽  
Subway Tunnel ◽  
Fe Modelling ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
2D And 3D

Purpose. This work aims to study the tunnel face stability (Algiers subway Tunnel) and evaluate common numerical procedures that are used for analyzing the tunnel face stability. Two-dimensional (2D) and three-dimensional (3D) Finite Element (FE) modeling using PLAXIS programs. Methodology. Tunneling is executed by the NATM method; two types of calculations are used. The first one is done by reducing the applied face pressure until the face is collapsed. The second calculation method involves the Phi-c (the angle of internal friction and bonding) reduction method, which is based on calculating the safety factor of the shear strength of the soil. Both methods are applied for 2D and 3D FE-modelling. Findings. It is found that determining the applied face pressure is an important consideration to avoid face failure or excessive deformations with numerical methods resulting in more precise findings than analytical methods. Originality. The originality of this work is the use of both 2D and 3D modelling, combined with two approaches: structural analysis of plastic state and Phi-c reduction method based on calculating the safety factor of the shear strength of the soil. Practical value. This study illustrates that the reducing shear strength method is much better than the reducing applied face pressure method. Moreover, the result of 3D FE-modelling gives a better prediction comparing with the 2D FE-modelling results.

Probabilistic analysis of tunnel face stability considering spatially variable undrained shear strength with linearly increasing mean trend

2020 ◽  
pp. 1748006X2092715
Author(s):  
Hongzhan Cheng
Keyword(s):  
Shear Strength ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Undrained Shear Strength ◽  
Tunnel Face ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
The Stability ◽  
Undrained Shear

The inherent spatial variability of soil properties has been considered as one of the main sources of uncertainties in geotechnical problems. The need for probabilistic analysis of the tunnel face stability that takes into account the variability of soil properties has been acknowledged. This article employed a probabilistic-based method, called random finite difference method, for evaluating the stability of tunnel face under the influence of the variability of undrained shear strength in clays. The two-dimensional spatial variation in soil undrained shear strength is modeled by random fields, which are discretized by the Covariance Matrix Decomposition method. The procedure for random finite difference method is presented. An illustrative example is employed to investigate the effect of soil variability. Particular attention has been paid to the situation that undrained shear strength increases with depth. The results demonstrate that ignoring the variability of undrained shear strength will result in overestimates of the tunnel face stability if the support pressure of the tunnel face exceeds the deterministic value, especially for higher coefficient of variation of soil undrained shear strength. Minor differences in the failure mechanism are observed in comparison to the deterministic case, considering only the global failure of the tunnel face is observed. In addition, ignoring the increase of undrained shear strength with depth will lead to conservative designs. The random finite difference method can provide a practical tool for evaluating the stability of a tunnel face in variable soils.

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.

Analytical Approach for Face Stability Estimate of Tunnel with Pipe Roof Reinforcement

2011 ◽  
Vol 243-249 ◽  
pp. 347-350 ◽  
Author(s):  
Hong Wei Song ◽  
Hai Tao Wang
Keyword(s):  
Three Dimensional ◽  
Stability Estimate ◽  
Test Results ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Tunnel Face ◽  
Face Stability ◽  
Calculation Results ◽  
Tunnel Face Stability ◽  
Centrifugal Model

One of the most popular pre-reinforcement structures in the construction of tunnels through weak grounds would be the pipe roof reinforcement. This composite structure consists on installing, prior to the excavation of a length of tunnel, a series of pipes, either parallel to the tunnel axis or at a certain angle with it. By injecting grout through the pipes, the ground in between the pipes is stiffened and the pipes are connected, creating a kind of ‘umbrella’ above the area to be excavated. In this paper, by modifying the upper bound solution for tunnel face stability, the three-dimensional model for expressing the tunnel face stability with pipe roof reinforcement was established. For a typical example, the solutions computed by the proposed approach were compared with the results given by wedge model, trapezoid wedge model and centrifugal-model test to verify the reasonability of the method. It is shown that the calculation results of limit analysis are in close agreement with test results.

Tunnel Face Stability Study in Soft Shallow Tunnel

2014 ◽  
Vol 1079-1080 ◽  
pp. 170-176
Author(s):  
Jun Du ◽  
Zhi Rong Mei ◽  
Yong Zhao Chen
Keyword(s):  
Three Dimensional ◽  
Horizontal Displacement ◽  
Stability Study ◽  
Plastic State ◽  
Shallow Tunnel ◽  
Tunnel Face ◽  
Maximum Displacement ◽  
Face Stability ◽  
Tunnel Face Stability ◽  
The Impact

With Xiamen Jiaheyuan underground access as the project background, tunnel face stability of soft shallow tunnel was analyzed under the condition of no pre-reinforcement by means of three-dimensional finite element method. The results indicated that the ground was relaxed because the tensile stress appeared in front and top of tunnel face after excavation, at the same time, the ground into the plastic state around the tunnel face. From the point of view of deformation, the displacement of tunnel face were such as the longitudinal horizontal displacement reached the maximum, the vertical deposition following by, and the lateral horizontal displacement being the least. Further analysis showed that the longitudinal horizontal displacement in front of tunnel face mostly produced at 1.0D (one excavation width) distance before tunnel face, the maximum displacement was located at the center of tunnel face. The conclusions remind that engineers also pay attention to the tunnel face reinforcement in front and top of tunnel face to minimize the impact of surface environment during tunnel construction in soft shallow tunnels.

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