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Introduction
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GeoFEAS 2D is `2D Geotechnical Finite element Elastoplastic Analysis Software´. It is the software product for stress-deformation analysis of soil under static conditions. This software conducts the powerful elasto-plastic finite element analysis in many engineering fields such as slope stability analysis, earth retaining works excavation analysis, tunnel design, etc. This product consists of three programs, (1) preprocessor, (2) processor, and (3) postprocessor. Finite element analysis conditions are created in preprocessor as CAD software. Elasto-plastic problems are analyzed in processor. Also analysis results are processed for visualization in postprocessor. FEM model can easily be created with the CAD-like input method. It also supports import from SXF file.

FORUM8 and Ukai laboratory have been engaged in joint development. The solver of this product utilizes the ground analysis program developed by Ukai laboratory, Department of Civil and Environmental Engineering of Gunma University and the Pre-Post processor is developed in-house and then coupled together as a total solution.


Information

New product introduction

Paper / Presentation


Functions and features
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Analysis method

Analysis category
 # Static total-stress analysis

Analysis models
 # Plane strain analysis
 # Axisymmetric analysis

Earthquake resistant river structure standard

Main features

# Stage analysis
The stage analysis, or the phased construction analysis can be performed. It is possible to change material parameters, boundary conditions, and stress release factors at each stage.

# Shear strength reduction (SSR) analysis
The shear strength reduction (SSR) analysis can be performed using three kinds of elastic-perfectly plastic constitutive laws. It is possible to evaluate global safety factor and slip surface by SSR analysis at each stage.

# Local factor of safety
It is possible to calculate the local safety factors at each Gaussian point.

# Coordination with seepage analysis
It is possible to use nodal water pressure loads from seepage analysis (Note: This is for the analysis using load module).

# Combination of stage and SSR analyses
It is possible to perform both deformation and stability analyses at the same time by combining stage and SSR analyses, and to deal with a wide range of soil related problems such as filled/excavated area, slope stability, bearing capacity, etc.

# Mixed assignment of constitutive laws
It is possible to assign different constitutive laws for each material.
   
2007 Guidelines for Quake-Resistance Testing of River Structures
    Deformation analysis: Before liquefaction, Under liquefaction, Volume compression after liquefaction
   
2016 Guidelines for Quake-Resistance Testing of River Structures
    Soil liquefaction analysis based on the March 2016 Edition of " Guidelines for Quake-Resistance Testing of River" established by River Improvement and Management Division, Water and Disaster Management Bureau, Japan Ministry of Land, Infrastructure, Transport and Tourism is feasible. "Deformation analysis prior to an earthquake (before liquefaction)", "Deformation analysis after an earthquake (after liquefaction)", and "Amount of land subsidence (deformation analysis) caused by bulk compression of liquefaction layer" can all be assigned to each stage of the analysis for a very thorough analysis. 

Self-weight induced deformation analysis involves deformation analysis before an earthquake (before liquefaction)" and deformation analysis after an earthquake (after liquefaction), and then taking the difference of the results from each analysis to compute the amount of land subsidence caused by liquefaction. The amount of land subsidence (deformation analysis) caused by the bulk compression of the liquefaction layer is calculated separately to the deforamtion analysis before and after an earthquake. By adding the value for the amount of land subsidence caused by the bulk compression of the liquefaction layer to the value for the amount of land subsidence caused by liquefaction, the overall displacement of the model of interest can be determined. 
Work flow of deformation analysis


Boundary conditions
It is possible to define the following four boundary conditions.
 # Supporting point (horizontal and vertical rollers, fixed, pin, enforced displacement)
 # Multi point constraint (MPC)
 # Spring supporting point
 # Pin connection


Element libraries
It is possible to define the following finite elements.

Category Element 2D Axisym-metric Note
Line Beam o - First order element
Bar o - First order element
Axial spring o - Including spring supporting point
Shear spring o - Including spring supporting point
Torsion spring x -  
Distributed axial spring x -  
Distributed shear spring x -  
Surface Three-node triangle o o First order element for 2D & axisymmetric analyses
Four-node quadrilateral o o First order element for 2D & axisymmetric analyses
Six-node triangle o o Second order element for 2D & axisymmetric analyses
Eight-node quadrilateral o o Second order element for 2D & axisymmetric analyses
Joint Four-node line joint o o Apply between 2D first order elements
Six-node line joint o o Apply between 2D second order elements
o: supported, x: unsupported.


Constitutive law models
# Constitutive law models for elements in plane strain and axisymmetric analyses
It is possible to use the following constitutive law models for elements in plane strain and axisymmetric analyses. Linear and laminated elasticity models can be used as no-tension materials.

Category Constitutive law Note
Elastic Linear elasticity Isotropic
Laminated elasticity Anisotropic
Shear stiffness reduction material 1 2007 Guidelines for Quake-Resistance
Testing of River Structures /
2016 Guidelines for Quake-Resistance
Testing of River Structures
Shear stiffness reduction material 2 2007 Guidelines for Quake-Resistance
Testing of River Structures
2016 Guidelines for Quake-Resistance
Testing of River Structures
nonlinear elastic D-min Technique by CRIEPI
Nonlinear HD (Hardin-Drnevich)
RO (Ramberg-Osgood)  
UW-Clay (Ugai-Wakai)  
Elastic-perfectly plastic MC (Mohr-Coulomb) Associative/nonassociative flow rule
DP (Drucker-Prager) Associative/nonassociative flow rule
MC-DP (Mohr-Coulomb / Drucker-Prager) Nonassociative flow rule
Elasto-plastic PZ-Sand (Pastor-Zienkiewicz)  
PZ-Clay (Pastor-Zienkiewicz)  
No-tension Linear elasticity  
Laminated elasticity  
Bi linear Liquefied material 1 2007 Guidelines for Quake-Resistance
Testing of River Structures
Liquefied material 2 2016 Guidelines for Quake-Resistance
Testing of River Structures


# Constitutive law models for beam, bar, spring, and joint elements
It is possible to use the following constitutive law models for beam, bar, spring, and joint elements.

Element Constitutive law Support Note
Beam(M-φ) (1) Linear elasticity o  
(2) Bi-linear x x  
(3) Tri-linear x x  
Bar (1) Linear elasticity o  
(2) Bi-linear o  
(3) Tri-linear x  
Spring (1) Linear elasticity o Including spring supporting point
(2) Bi-linear o Including spring supporting point
(3) Tri-linear x  
Joint (1) Linear elasticity o  
(2) MC (Mohr-Coulomb elastic-perfectly plasticity) o  
o: supported, x: unsupported.


Loads
It is possible to use the following loads.
 # Nodal force load (2D, axisymmetric)
 # Uniform pressure load (2D, axisymmetric)
 # Self weight load (2D, axisymmetric)
 # Seismic inertia load (2D)
 # Nodal water pressure load (2D, axisymmetric)

Note
GeoFEAS2D can consider effects of water pressure change on soil by taking into account water pressure as nodal load.


Postprocessor (After-treatment)
Output analysis of processor (Analysis section) is processed.Output / confirmation of result figures and numerical values are carried out.
In this program, the following can be output mainly.

 # Model figure
 # Deformation figure
 # Vector diagram
 # Contour figure
 # Distribution map
 # Numeric output


Combination with the UC-1 Earth retaining work design (Option)
In Temporary sheathing work design, it allows examining the effect to surrounding ground by "enforcement displacement method" which works vertical overburden pressure on the bottom of excavation if needed, giving the FEM analysis model that modeled only ground to the displacement of earth retaining wall from elastoplastic analysis as enforced displacement.
Elastoplastic result of
Temporary sheathing work
Earth retaining work FEM
(Input screen of the forced displacement method)
Earth retaining work FEM
(Contour figure of the forced displacement method)


Cooperation with UC-1 Consolidation settlement calculation

The new and improved version of GeoFEAS2D can be linked with "Consolidation Settlement Calculation", another popular UC-1 Series product, to take into account consolidation due to compression (consolidation settlement and immediate settlement) when performing liquefaction analysis. Consolidation Settlement Calculation program allows users to set up a complete scenario of consolidation settlement from the creation of soil geometry and assignment of soil layers and vertical load to the calculation of the settlment due to consolidation. The soil model created with its soil geometry and soil layers defined, and subjected to vertial load for consolidation settlement calculation using Consolidation Settlement Calculation program can be imported to GeoFEAS2D for a seamless soil liquefaction analysis.

Assessment on the influenece of sunshine
obstruction on site soils


Auto mesh function
In case of model creation of like tunnel, mesh division by defining minimum required lines such as stratum boundary reduces the time of model creation.


Applicable scope
This product is mainly applicable to the following problems.
 # Stress-deformation analysis of soil
 # Slope stability analysis
 # Earth retaining works excavation analysis
 # Analysis of surrounding soil effect by shield tunnel construction
 # NATM tunnel construction analysis
 # Study of water pressure variation effect on soil
 # Study of soil-structure interaction
 # Ground response acceleration method


■Enhancement of CIM function on the geotechnical analysis series products
We enhanced the CIM (Construction Information Modeling) function of various products in the geotechnical analysis series. The programs can cooperate terrain data or data created with each geotechnical analysis programs smoothly.  
Data linkage using terrain data file (*.GF1)
Geotechnical Finite element Elastoplastic Analysis Software (GeoFEAS)2D Ver.3

The amount of displacement imported to Flexible structure sluiceway design for further analysis
By importing results of ground deformation analysis (settlement / horizontal displacement distribution) to the "Flexible structure sluiceway design", the level2 seismic test for the longitudinal direction can be performed.
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GeoFEAS2D Flexible structure sluiceway design

It can modelize only ground that a surrounding ground effect analysis is conducted in the Temporary sheathing work design. The ground deformation can be calculated by giving the wall displacement as the forced displacement. 
Dynamic effective stress analysis for ground (UWLC)

Acceleration rate imported to Slope stability analysis for further analysis
When applying the Newmark method to high embankments with a height of about 30 m or more, it is necessary to input the response acceleration waveform of the slip soil mass as the ground motion.
Data linkage between "Dynamic effective stress analysis for ground (UWLC)" and "Slope stability analysis" corresponds to the Newmark method analysis calculated by using the response acceleration waveform.
The level2 seismic stability calculation for high embankment and large embankment.
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UWLC Slope stability analysis
2-D seepage analysis(VGFlow2D)

Water line data imported to GeoFEAS2D
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VGFlow2D GeoFEAS2D

Water level data imported to UWLC
Water line and potential line imported to Slope stability analysis
Saturated / unsaturated seepage FEM analysis results can be reflected by file linkage (*.PRS [water line], *.PTN [isopotential line]).
GeoFEAS Flow3D (limited to the seepage analysis)

Water level data imported to LEM3D
Analysis results computed with GeoFEAS Flow3D (limited to the seepage analysis) or third party's product can be imported to 3-D slope stability analysis(LEM). It creates underground water level required for landslide analysis and enables the 3D slope stability analysis.
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VGFlow3D LEM3D

Applied Standard and References
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Applied Standard
  • 2007 Guidelines for Quake-Resistance Testing of River Structures
  • 2016 Guidelines for Quake-Resistance Testing of River Structures ll. Levee ed

References
  • Potts, D., Axelsson, K., Grande, L., Schweiger, H. and Long M.: Guidelines for the use of advanced numerical analysis, Thomas Telford, 2002.
  • 鹿島建設土木設計本部編:新・土木設計の要点(5),トンネル,鹿島出版会,2003
  • 田中忠治,鵜飼恵三,河邑眞,阪上最一,大津宏康:地盤の三次元弾塑性有限要素法,丸善,1996.
  • Zienkiewicz, O.C., Chan, A.H.C., Pastor, M., Schrefler, B.A. and Shiomi, S.: Computational Geomechanics with Special Reference to Earthquake Engineering, JOHN WILEY & SONS, 1999
  • 後藤學:実践有限要素法,大変形弾塑性解析,コロナ社,1995
  • O.C.ツェンキーヴィッツ,ロバート・L.テイラー,矢川元基訳:マトリックスと有限要素法[改訂新版], 科学技術出版, 1996
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