Upper Bound Solution of the Safety Factor for a Shield Tunnel Face Subjected to the Hoek–Brown Failure Criterion

2019 ◽  
Vol 17 (12) ◽  
pp. 1941-1950 ◽  
Author(s):  
Fu Huang ◽  
Yuan Feng ◽  
Zhiqi Zhang ◽  
Xiaoli Yang ◽  
Tonghua Ling
Keyword(s):  
Safety Factor ◽  
Upper Bound ◽  
Failure Criterion ◽  
Shield Tunnel ◽  
Tunnel Face ◽  
Bound Solution ◽  
Upper Bound Solution ◽  
Shield Tunnel Face

scholarly journals Upper Bound Solution of Safety Factor for Shallow Tunnels Face Using a Nonlinear Failure Criterion and Shear Strength Reduction Technique

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Fu Huang ◽  
Zai-lan Li ◽  
Tong-hua Ling
Keyword(s):  
Safety Factor ◽  
Upper Bound ◽  
Reduction Technique ◽  
Nonlinear Failure Criterion ◽  
Upper Bound Theorem ◽  
Tunnel Face ◽  
Bound Solution ◽  
Strength Reduction Technique ◽  
Bound Theorem ◽  
The Stability

A method to evaluate the stability of tunnel face is proposed in the framework of upper bound theorem. The safety factor which is widely applied in slope stability analysis is introduced to estimate the stability of tunnel face using the upper bound theorem of limit analysis in conjunction with a strength reduction technique. Considering almost all geomaterials following a nonlinear failure criterion, a generalized tangential technique is used to calculate the external work and internal energy dissipation in the kinematically admissible velocity field. The upper bound solution of safety factor is obtained by optimization calculation. To evaluate the validity of the method proposed in this paper, the safety factor is compared with those calculated by limit equilibrium method. The comparison shows the solutions derived from these two methods match each other well, which shows the method proposed in this paper can be considered as effective.

scholarly journals Upper Bound Analysis for Collapse Failure of Shield Tunnel Face Excavated in Unsaturated Soils Considering Steady Vertical Flow

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Jia-hua Zhang ◽  
Wei-jun Wang ◽  
Biao Zhang ◽  
Dao-bing Zhang
Keyword(s):  
Steady Flow ◽  
Upper Bound ◽  
Unsaturated Soils ◽  
Soil Mass ◽  
Shield Tunnel ◽  
Upper Bound Theorem ◽  
Tunnel Face ◽  
Supporting Pressure ◽  
Collapse Failure ◽  
Shield Tunnel Face

Natural soils are mostly in an unsaturated state and the corresponding mechanical properties differ significantly from a saturated one. In traditional stability analysis for a shield tunnel face, the soil mass is typically assumed to be dry or saturated for convenience of analysis. In this work, based on the upper bound theorem of classical plasticity theory and the log-spiral failure mechanism, face stability of the shield tunnel excavated in unsaturated soils under vertical steady flow is studied. The profile of shear strength is determined by virtues of the unified effective stress approach and the analytical solution of matric suction under unsaturated steady flow. On this basis, the analytical expression for the supporting pressure is deduced and the sequential quadratic programming is employed to search for the optimal upper bound solution. Through parametric analysis it is found the fitting parameters of SWCC and the groundwater level affect the supporting pressure notably. Besides, the relevant influence of vertical discharge is also significant when clayey soils are concerned.

Upper Bound Solution of Rationalized Janbu Method

2011 ◽  
Vol 90-93 ◽  
pp. 2393-2400
Author(s):  
Jin Hai Wang ◽  
Yong Wang ◽  
Hong Wang
Keyword(s):  
Safety Factor ◽  
Upper Bound ◽  
Slip Line ◽  
Shear Force ◽  
Normal Force ◽  
Reliability Design ◽  
Bound Solution ◽  
Upper Bound Solution ◽  
Theoretical Analyses

The theoretical defects of conventional Janbu method are systematically analyzed in this study. On the basis of these theoretical analyses, three inequalities are brought up to rationalize the results of inter-slice shear force, the point of inter-slice normal force and the point of normal force on slip line. The new iteration formulas of rationalized Janbu method are deduced and the process of rationalized upper bound solution is given out. The results of the example given in the end show that the rationalized Janbu method can distinctly improve the results’ reasonableness, and can work out the corresponding reasonable thrust line. And the results of rationalized Janbu method under given safety factor can provide relatively reasonable slipping force and slipping moment for reliability design of reinforcing slope.

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