scholarly journals 3D FEM Model on the Parameters’ Influence of EPB-TBM on Settlements of Single and Twin Metro Tunnels During Construction

2021 ◽  
Author(s):  
Masoud Forsat ◽  
Mohammad Taghipoor ◽  
Masoud Palassi
Keyword(s):  
Three Dimensional ◽  
Injection Pressure ◽  
Effective Parameters ◽  
Grout Injection ◽  
3D Fem ◽  
Supporting Pressure ◽  
Epb Tbm ◽  
The Face ◽  
Clear Distance ◽  
Twin Tunnels

AbstractThe present research exposes the investigation on three-dimensional modeling of the single and twin metro tunnels for the case of the Tehran metro line. At first, simulation implemented on the comparison of the ground movements in the single and twin tunnels. Then the simulation has been performed on the influence of effective parameters of EPB-TBM on the surface settlements throughout excavation. The overcutting, shield conicity, grouting, and the final lining system modeled and the influence of face supporting pressure, grout injection pressure, as well as the clear distance of the tunnels, has been analyzed. The initial results showed a valid ground settlement behavior. The maximum settlements occurred at the end of the shield tail and it was higher in the single tunnel. The face supporting pressure had more effect on the surface settlement in comparison to the grout injection pressure. By increasing the face pressure in the single tunnel, the place of maximum settlement moved back while the grout pressure is insignificant for decreasing the settlements. Furthermore, the influence of the clear distance in the twin tunnels led to zero after the length of 30 m. Accordingly, for more distances, the tunnels must be examined independently and as two different single tunnels.

Effect of Gear-Side Case-Hardening on Residual Stresses of Case-Hardened Gears

2000 ◽  
Author(s):  
Kouitsu Miyachika ◽  
Satoshi Oda ◽  
Hiroshige Fujio
Keyword(s):  
Residual Stresses ◽  
Three Dimensional ◽  
Case Depth ◽  
Case Hardening ◽  
3D Fem ◽  
Face Width ◽  
Dimensional Finite Element ◽  
The Face ◽  
Standard Pressure ◽  
Three Dimensional Finite Element

Abstract This paper presents a study on effects of the case depth, the case-hardened part, the face width, the rim thickness and the standard pressure angle on residual stresses of case-hardened gears. A heat conduction analysis and an elastic-plastic stress analysis for the case-hardening process of spur gears were carried out by the three-dimensional finite-element method (3D-FEM), and then residual stresses were obtained. It was found that the compressive residual stress σ*θ = 30° at Hofer’s critical section of the end of the face width is smaller in magnitude than that of the middle of the face width, and that the absolute value of σ*θ = 30° of the middle of the face width decreases owing to case-hardening the gear-side and the decreasing rate increases with an increasing case depth and a decreasing face width.

scholarly journals Displacement and Deformation of the First Tunnel Lining During the Second Tunnel Construction

2019 ◽  
Vol 5 (2) ◽  
pp. 332 ◽  
Author(s):  
Lin Wu ◽  
Xiedong Zhang ◽  
Zhihua Zhang ◽  
Luqing Luo ◽  
Weichen Sun
Keyword(s):  
Water Pressure ◽  
Three Dimensional ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Tunnel Lining ◽  
Scale Model ◽  
Tunnel Construction ◽  
Soil Arching ◽  
Clear Distance ◽  
Twin Tunnels

A three-dimensional twin tunnels scale model was established utilizing the discrete element method (DEM) with PFC3D. This model aims to investigate the displacement (in horizontal and vertical directions) and deformation of the first tunnel lining in four different cases which the clear distance of twin tunnels are 5, 10, 15 and 20 m during the second tunnel construction process. The numerical results indicate that the clear distance between twin tunnels and the distance between the measurement points of the first tunnel and the excavation area of the second tunnel are two most critical factors that influence the displacement and deformation of the first tunnel lining. Meanwhile, the soil arching effect, gravity, water pressure and lateral pressure also have an impact on the behavior of the first tunnel. The maximum disturbance of horizontal and vertical displacements occurred in the time points of finishing of the second tunnel. However, the horizontal displacement of the first tunnel is much more sensitive to the vertical displacement. The first tunnel turns to the right and down in direction while having an anticlockwise rotation (φ) during the process of construction of the second tunnel. In addition, the displacement and deformation of the lining of the first tunnel are critical to monitor, and the necessary precautions should be taken to decrease the risk of craze. In conclusion, the influence of the second tunnel excavation on the first tunnel lining could be neglected when their distance is more than 15 m.

scholarly journals Analysis of Face Stability during Excavation of Double-O-Tube Shield Tunnel

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Yuyou Yang ◽  
Qinghong Zhou ◽  
Hongan Li ◽  
Xuegang Huang ◽  
Xiaoming Tu
Keyword(s):  
Stability Analysis ◽  
Failure Mechanism ◽  
Three Dimensional ◽  
Soil Mass ◽  
Shield Tunnel ◽  
Face Stability ◽  
Supporting Pressure ◽  
The Face ◽  
Collapse Failure ◽  
Kinematic Theorem

This paper focuses on the face stability analysis of Double-O-Tube shield tunnel. This kind of analysis is significant to ensure the safety of workers and reduce the influence on the surrounding environment. The key point of the stability analysis is to determine the supporting pressure applied to the face by the shield. A collapse failure will occur when the supporting pressure is not sufficient to prevent the movement of the soil mass towards the tunnel. A three-dimensional collapse failure mechanism was presented in this paper. Based on the mechanism of a single circular shield tunnel, the mechanism of Double-O-Tube shield tunnel was established by using the fact that both of the mechanisms are symmetrical. Then by means of the kinematic theorem of limit analysis, the numerical results were obtained, and a design chart was provided. The finite difference software FLAC3D was applied to investigate the face failure mechanism of DOT shield tunnel established in this paper; the critical supporting pressures of the collapse failure mechanism in different strata (sand and silt) were calculated. Through comparative analysis, the theoretical values were very close to the numerical values. This shows that the face failure mechanism of DOT shield tunnel is reasonable, and it can be applied to the sand and silt strata.

The effect of water seepage forces on the face stability of an experimental microtunnel

1993 ◽  
Vol 30 (2) ◽  
pp. 363-369 ◽  
Author(s):  
Frédéric Pellet ◽  
François Descoeudres ◽  
Peter Egger
Keyword(s):  
Three Dimensional ◽  
Field Measurements ◽  
Shallow Depth ◽  
Equilibrium Analysis ◽  
Soft Ground ◽  
Tunnel Face ◽  
Element Analysis ◽  
Face Stability ◽  
Supporting Pressure ◽  
The Face

The face heading stability of underground constructions remains quite difficult to assess, especially when groundwater is present. To investigate this, an experimental microtunnel was excavated at shallow depth in soft ground, below the water table. In agreement with field measurements of the piezometric level changes, a three-dimensional finite element analysis of groundwater flow shows that the head losses are concentrated in the close vicinity of the tunnel face. Both numerical equilibrium analysis and field measurements were used to show that the resulting seepage forces substantially increase the supporting pressure required to ensure face stability. Key words : microtunnel, shallow depth, soft ground, seepage forces, face stability, supporting pressure.

Wake Flow of Single and Multiple Yawed Cylinders

2004 ◽  
Vol 126 (5) ◽  
pp. 861-870 ◽  
Author(s):  
A. Thakur ◽  
X. Liu ◽  
J. S. Marshall
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Wake Flow ◽  
Upstream Region ◽  
Two Dimensional ◽  
Cylinder Wake ◽  
Dimensional Approximation ◽  
The Face ◽  
Drag And Lift

An experimental and computational study is performed of the wake flow behind a single yawed cylinder and a pair of parallel yawed cylinders placed in tandem. The experiments are performed for a yawed cylinder and a pair of yawed cylinders towed in a tank. Laser-induced fluorescence is used for flow visualization and particle-image velocimetry is used for quantitative velocity and vorticity measurement. Computations are performed using a second-order accurate block-structured finite-volume method with periodic boundary conditions along the cylinder axis. Results are applied to assess the applicability of a quasi-two-dimensional approximation, which assumes that the flow field is the same for any slice of the flow over the cylinder cross section. For a single cylinder, it is found that the cylinder wake vortices approach a quasi-two-dimensional state away from the cylinder upstream end for all cases examined (in which the cylinder yaw angle covers the range 0⩽ϕ⩽60°). Within the upstream region, the vortex orientation is found to be influenced by the tank side-wall boundary condition relative to the cylinder. For the case of two parallel yawed cylinders, vortices shed from the upstream cylinder are found to remain nearly quasi-two-dimensional as they are advected back and reach within about a cylinder diameter from the face of the downstream cylinder. As the vortices advect closer to the cylinder, the vortex cores become highly deformed and wrap around the downstream cylinder face. Three-dimensional perturbations of the upstream vortices are amplified as the vortices impact upon the downstream cylinder, such that during the final stages of vortex impact the quasi-two-dimensional nature of the flow breaks down and the vorticity field for the impacting vortices acquire significant three-dimensional perturbations. Quasi-two-dimensional and fully three-dimensional computational results are compared to assess the accuracy of the quasi-two-dimensional approximation in prediction of drag and lift coefficients of the cylinders.

scholarly journals Nonlinear effects of locally heterogeneous hydraulic conductivity fields on regional stream–aquifer exchanges

2015 ◽  
Vol 19 (11) ◽  
pp. 4531-4545 ◽  
Author(s):  
J. Zhu ◽  
C. L. Winter ◽  
Z. Wang
Keyword(s):  
Groundwater Flow ◽  
Effective Conductivity ◽  
Model Simulation ◽  
Three Dimensional ◽  
Small Scale ◽  
Heihe River ◽  
Effective Parameters ◽  
Aquifer Systems ◽  
Basin Scale ◽  
Local Grid

Abstract. Computational experiments are performed to evaluate the effects of locally heterogeneous conductivity fields on regional exchanges of water between stream and aquifer systems in the Middle Heihe River basin (MHRB) of northwestern China. The effects are found to be nonlinear in the sense that simulated discharges from aquifers to streams are systematically lower than discharges produced by a base model parameterized with relatively coarse effective conductivity. A similar, but weaker, effect is observed for stream leakage. The study is organized around three hypotheses: (H1) small-scale spatial variations of conductivity significantly affect regional exchanges of water between streams and aquifers in river basins, (H2) aggregating small-scale heterogeneities into regional effective parameters systematically biases estimates of stream–aquifer exchanges, and (H3) the biases result from slow paths in groundwater flow that emerge due to small-scale heterogeneities. The hypotheses are evaluated by comparing stream–aquifer fluxes produced by the base model to fluxes simulated using realizations of the MHRB characterized by local (grid-scale) heterogeneity. Levels of local heterogeneity are manipulated as control variables by adjusting coefficients of variation. All models are implemented using the MODFLOW (Modular Three-dimensional Finite-difference Groundwater Flow Model) simulation environment, and the PEST (parameter estimation) tool is used to calibrate effective conductivities defined over 16 zones within the MHRB. The effective parameters are also used as expected values to develop lognormally distributed conductivity (K) fields on local grid scales. Stream–aquifer exchanges are simulated with K fields at both scales and then compared. Results show that the effects of small-scale heterogeneities significantly influence exchanges with simulations based on local-scale heterogeneities always producing discharges that are less than those produced by the base model. Although aquifer heterogeneities are uncorrelated at local scales, they appear to induce coherent slow paths in groundwater fluxes that in turn reduce aquifer–stream exchanges. Since surface water–groundwater exchanges are critical hydrologic processes in basin-scale water budgets, these results also have implications for water resources management.

Three Dimensional Numerical Analyses of Bridge Piled-Raft Foundation under Riverbed Erosion

2012 ◽  
Vol 178-181 ◽  
pp. 2373-2377 ◽  
Author(s):  
Wen Tsung Liu ◽  
Yi Yi Li
Keyword(s):  
Bearing Capacity ◽  
Three Dimensional ◽  
Fem Analysis ◽  
Bridge Piers ◽  
Piled Raft Foundation ◽  
River Erosion ◽  
Dimensional Finite Element ◽  
The Face ◽  
Three Dimensional Finite Element

From the 921 earthquake to the major typhoons, including the Morakot typhoon, they damaged original landscape of rivers in Taiwan. In recent years, it alleged that abutment bridge exposed to the most serious security problems. Because of bridge piers in addition to the face of long-term river erosion, the flood on the pier will produce localized erosion near the bridge. The pier will be due to inadequate bearing capacity, resulting in subsidence, displacement, bridge version accompanied by tilting and even caving. The river erosion of soil around the piers deposits and production of contraction will often reduce the bearing capacity. Therefore, how to accurately estimate the scour depth, calculate piers to withstand water impact and analyses its stability for preventing injuries in the first place is the current pressing issues. In this study, three-dimensional finite element method (FEM) analysis program Plaxis 3D foundation is used. Polaris second bridge is selected for analysis. Based on local scouring of the model and various numerical variable conditions, the parameter of bridge pier is studied.

Did They Mind the Gap? Voter/Party Ideological Proximity between the BQ, the NDP and Quebec Voters, 2006–2011

2016 ◽  
Vol 49 (2) ◽  
pp. 289-310 ◽  
Author(s):  
Jean-Philippe Gauvin ◽  
Chris Chhim ◽  
Mike Medeiros
Keyword(s):  
Political Party ◽  
Three Dimensional ◽  
Election Study ◽  
Federal Election ◽  
Party Manifestos ◽  
Longitudinal Approach ◽  
The Face ◽  
Election Results ◽  
Using Data ◽  
Over Time

AbstractThe 2011 Canadian federal election results changed the face of federal politics in Quebec. In a sudden and spectacular reversal of electoral fortunes, BQ support crumbled while that of the NDP surged. While most commentators focused exclusively on the 2011 election itself to explain what had happened, we offer an interpretation that takes a longitudinal approach. Using data from the Canadian Election Study and political party manifestos from 2006 to 2011, we propose a three-dimensional proximity model of voter/party congruence to explore the evolution of the ideological stances of Quebec voters and parties. Empirical results suggest these ideological distances between the NDP and Quebec voters decreased over time, whereas the BQ has distanced itself from voters. Furthermore, ideological distances between party and voters are a significant predictor of vote.

Combining Serial Sectioning, EBSD Analysis, and Image-Based Finite Element Modeling

MRS Bulletin ◽  
2008 ◽  
Vol 33 (6) ◽  
pp. 597-602 ◽  
Author(s):  
G. Spanos ◽  
D.J. Rowenhorst ◽  
A.C. Lewis ◽  
A.B. Geltmacher
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Electron Backscatter Diffraction ◽  
Three Dimensional ◽  
Research Area ◽  
Polycrystalline Materials ◽  
Serial Sectioning ◽  
3D Fem ◽  
Element Modeling ◽  
The Status

AbstractThis article first provides a brief review of the status of the subfield of three-dimensional (3D) materials analyses that combine serial sectioning, electron backscatter diffraction (EBSD), and finite element modeling (FEM) of materials microstructures, with emphasis on initial investigations and how they led to the current state of this research area. The discussions focus on studies of the mechanical properties of polycrystalline materials where 3D reconstructions of the microstructure—including crystallographic orientation information—are used as input into image-based 3D FEM simulations. The authors' recent work on a β-stabilized Ti alloy is utilized for specific examples to illustrate the capabilities of these experimental and modeling techniques, the challenges and the solutions associated with these methods, and the types of results and analyses that can be obtained by the close integration of experiments and simulations.

Preliminary Evaluation of an Electromagnetic Three-Dimensional Digitizer in Facial Anthropometry

1998 ◽  
Vol 35 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Virgilio F. Ferrario ◽  
Chiarella Sforza ◽  
Carlo E. Poggio ◽  
Massimiliano Cova ◽  
Gianluca Tartaglia
Keyword(s):  
Three Dimensional ◽  
Preliminary Evaluation ◽  
Men And Women ◽  
Facial Landmarks ◽  
Coefficients Of Variation ◽  
The Face ◽  
Human Adults ◽  
Facial Anthropometry ◽  
Sufficient Precision

Objective In this investigation, the precision of a commercial three-dimensional digitizer in the detection of facial landmarks in human adults was assessed. Methods Fifty landmarks were identified and marked on the faces of five men, on five women, and on a stone cast of the face of one man. For each subject, the three-dimensional coordinates of the landmarks were obtained twice using an electromagnetic three-dimensional digitizer, and the duplicate digitizations were superimposed using common orientations and centers of gravity. Metric differences between homologous landmarks were assessed, and Dahlberg's error was computed. Results For both men and women, the error was 1.05% of the nasion-mid-tragion distance, while for the cast, it was 0.9%. When the duplicate digitizations were used to mathematically reconstruct the faces, and several distances, angles, volumes, and surfaces were computed, more than 80% of the measurements had coefficients of variation lower than 1%. Conclusions The digitizer can assess the coordinates of facial landmarks with sufficient precision, and reliable measurements can be obtained.

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