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.

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.

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.

Upper bound analysis of tunnel face stability in layered soils

2013 ◽  
Vol 9 (4) ◽  
pp. 661-671 ◽  
Author(s):  
Xiao-Wu Tang ◽  
Wei Liu ◽  
Bettina Albers ◽  
Stavros Savidis
Keyword(s):  
Upper Bound ◽  
Layered Soils ◽  
Tunnel Face ◽  
Face Stability ◽  
Upper Bound Analysis ◽  
Tunnel Face Stability ◽  
Bound Analysis

scholarly journals Upper bound of tunnel face stability using asymmetric yielding

2018 ◽  
Vol 3 (4) ◽  
pp. 288-296
Author(s):  
Itai Elkayam ◽  
Assaf Klar
Keyword(s):  
Upper Bound ◽  
Tunnel Face ◽  
Face Stability ◽  
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.

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