Investigation of Tunnel Stress Path During Face Advancement

2007 ◽  
Vol 23 (4) ◽  
pp. 451-458 ◽  
Author(s):  
C.-N. Chen ◽  
W.-Y. Huang
Keyword(s):  
Three Dimensional ◽  
Stress Path ◽  
Circular Tunnel ◽  
Tunnel Face ◽  
Stress Evaluation ◽  
State Of Stress ◽  
Tunnel Section ◽  
Principal Stress Space ◽  
Center Section ◽  
Algorithmic Procedure

AbstractTunnel stress path during excavation was investigated in the study scope. The triple-center section is commonly designated for highway tunnels, but the analytical solution of the stress state for a non-circular tunnel section with multiple bench excavations is difficult to obtain. Our investigation provides an algorithmic procedure which reliably evaluates stress adjustment of a bench excavation with respect to the three-dimensional state of stress. Evaluation of a safety factor at the tunnel face during advancement is performed following the stress path and principal stress space.

scholarly journals Effect of Longitudinal Gradient on 3D Face Stability of Circular Tunnel in Undrained Clay

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhengxing Wang ◽  
Yuke Wang ◽  
Shumao Wang ◽  
Bin Li ◽  
Hu Wang
Keyword(s):  
Upper Bound ◽  
Three Dimensional ◽  
Optimization Procedure ◽  
Upward Movement ◽  
Circular Tunnel ◽  
Longitudinal Gradient ◽  
Tunnel Face ◽  
Face Stability ◽  
Collapse Pressure ◽  
Limit Pressure

The longitudinal gradient existed in shield-driven tunnel crossing river or channel has a longitudinal gradient, which is often ignored in most stability analyses of the tunnel face. Considering the influence of the longitudinal gradient into A(a) continuous velocity field, the present paper, conducting a limit analysis of the tunnel face in undrained clay, adopted to yield the upper-bound solutions of the limit pressure supporting on a three-dimensional tunnel face. The least upper bounds of the collapse and blow-out pressures can be obtained by conducting an optimization procedure. These upper-bound solutions are given in the design charts, which provide a simple way to assess the range of the limit pressure in practice. The influence of the longitudinal gradient becomes more significant with the increase of γD/su and C/D. The blow-out pressure for tunneling in a downward movement could be overestimated and the collapse pressure for tunneling in an upward movement could be conversely underestimated, with ignoring the influence of the longitudinal gradient.

scholarly journals Measurement and Simulation Analysis of Vertical Cross Longitudinal Settlement between Turning Shield and Foundation Pit

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hua Yin ◽  
Hong Zhang ◽  
Rui Zhang
Keyword(s):  
Loss Rate ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
Stress Path ◽  
Additional Stress ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Foundation Pit ◽  
Tunnel Face ◽  
Unloading Deformation

Using numerical simulation technology, the dynamic three-dimensional model of the turning shield and the foundation pit under the condition of vertical intersection is established. The disturbance law of the longitudinal settlement of the foundation pit under the condition of shield construction is studied, and the stress path in the soil is analyzed. The results show that with the gradual advance of the turning shield construction, the settlement mode of the foundation pit changes with the shield construction. During the construction of the turning shield, when the tunnel face is located in front of the foundation pit and under the foundation pit, the ground loss rate is inconsistent, which leads to the change of settlement mode. Under the influence of turning shield construction disturbance, the soil undergoes compression deformation caused by larger additional stress increase; after shield crossing, the soil undergoes unloading deformation caused by more obvious stress relaxation.

scholarly journals Face Stability Analysis of Shield Tunnels in Homogeneous Soil Overlaid by Multilayered Cohesive-Frictional Soils

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Kaihang Han ◽  
Chengping Zhang ◽  
Wei Li ◽  
Caixia Guo
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Support Pressure ◽  
Tunnel Face ◽  
Arch Effect ◽  
Theory Approximation ◽  
Homogeneous Soil ◽  
Frictional Soils

In order to better interpret failure features of the failure of soil in front of tunnel face, a new three-dimensional failure mechanism is proposed to analyze the limit support pressure of the tunnel face in multilayered cohesive-frictional soils. The new failure mechanism is composed of two truncated cones that represent the shear failure band and a distributed force acting on the truncated cones that represents the pressure arch effect. By introducing the concept of Terzaghi earth pressure theory, approximation of limit support pressures is calculated using the limit analysis methods. Then the limit support pressures obtained from the new failure mechanism and the existing approaches are compared, which show that the results obtained from the new mechanism in this paper provide relatively satisfactory results.

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

scholarly journals Photoelastic Analysis of Three-Dimensional Stress Systems using Scattered Light

1940 ◽  
Vol 44 (349) ◽  
pp. 74-88 ◽  
Author(s):  
R. Weller ◽  
J. K. Bussey
Keyword(s):  
Elementary Theory ◽  
Scattered Light ◽  
Three Dimensional ◽  
Plane Section ◽  
Stress System ◽  
Principal Stresses ◽  
State Of Stress ◽  
Polarised Light ◽  
Photoelastic Analysis ◽  
Good Agreement

SummaryA method has been developed for making photoelastic analyses of threedimensional stress systems by utilising the polarisation phenomena associated with the scattering of light. By this method, the maximum shear and the directions of the three principal stresses at any point within a model can be determined, and the two principal stresses at a free-bounding surface can be separately evaluated. Polarised light is projected into the model through a slit so that it illuminates a plane section. The light is continuously analysed along its path by scattering and the state of stress in the illuminated section is obtained. By means of a series of such sections, the entire stress field may be explored. The method was used to analyse the stress system of a simple beam in bending. The results were found to be in good agreement with those expected from elementary theory.

The influence of near face behaviour on monitoring of deep tunnels

1991 ◽  
Vol 28 (2) ◽  
pp. 226-238 ◽  
Author(s):  
F. Pelli ◽  
P. K. Kaiser ◽  
N. R. Morgenstern
Keyword(s):  
Numerical Modelling ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Back Analysis ◽  
Total Change ◽  
State Of Stress ◽  
Stress Changes ◽  
The Face ◽  
Tunnel Design

Convergence, radial displacements, and stress changes are often recorded during the advance of a tunnel for the observational tunnel design approach. In deep tunnels, instruments must be installed from underground and can seldom be placed in undisturbed ground. Consequently, observations are only partial records of the total change induced by an excavation and the influence of the three-dimensional state near the face must be considered. This paper presents results from numerical simulations to assess face effects on monitoring data. The influence of such aspects as in situ state of stress, anisotropy, nonlinearity, and plasticity (yielding ground) are evaluated. Guidelines for underground monitoring of deformations are given. Key words: tunnelling, monitoring, back-analysis, convergence, extensometers, numerical modelling.

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