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| SIGMA/W - Stress-deformation analysis. |
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SIGMA/W is a finite element software product that can be used to perform stress and deformation analyses of earth structures. Its comprehensive formulation makes it possible to analyze both simple and highly complex problems. For example, you can perform a simple linear elastic deformation analysis or a highly sophisticated, nonlinear elastic-plastic effective stress analysis.
The many constitutive soil models allow you to represent a wide range of soils or structural materials. In addition, when coupled with SEEP/W, SIGMA/W can model the pore-water pressure generation and dissipation in a soil structure in response to external loads.
These features enable SIGMA/W to analyze almost any stress or deformation problem you will encounter in geotechnical, civil, and mining engineering projects.
Easy to Use
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Defining a Stress-Deformation Model
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The unique CAD-like technology in SIGMA/W allows you to generate your finite element mesh by drawing regions on the screen. You can then specify material properties and interactively apply boundary conditions, structural elements, trusses, and fill or excavation layers. If you make a mistake, you can correct it using the Undo command.
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| Viewing the Analysis Results |
Once you have solved your problem, SIGMA/W offers many tools for viewing results. View a deformed mesh or displacement vectors at any magnification. Generate contours or x-y plots of more than 30 computed parameters, including deformation, total and effective stress, strain and pore-water pressure. Display shaded yield zones. View the stress state at any node or element Gauss point as a Mohr Circle with the associated space-force diagrams. Plot shear or moment distribution along structural elements. Then export the results into other applications, such as Microsoft Excel or Word, for further analysis or to prepare presentations.
Typical Applications
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SIGMA/W can model almost any stress or deformation problem, including:
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Settlement of footings, fluid-filled tanks, or earth structures
Deformation within or underneath an embankment or earth dam
Closure around a tunnel
Lateral movement of braced or anchored excavations and surface settlement around the excavation
Floor rebound of open-pit, sloping excavations
Volume changes (uncoupled consolidation or heave) resulting from pore-water pressure changes
Staged fill placement, earth removal
Soil-structure interaction, including free un-bonded anchors, cross excavation struts, and trusses
Fully-coupled consolidation analysis
Simulation of tailings deposition
Permanent deformations resulting from strength loss
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| Formulation |
SIGMA/W is formulated for 2-dimensional plane strain or axisymmetric problems using a small displacement, small strain, incremental load formulation. For each load step, incremental displacement at each node resulting from the incremental load is computed and added to the displacement at the beginning of the load step to give the total displacement. For soil models with nonlinear material properties, SIGMA/W solves the equations iteratively using the Newton-Raphson technique; soil properties are updated every iteration until a converged solution is achieved.
You can simulate the filling and excavation of materials by activating or deactivating finite elements at various stages of the construction process. SIGMA/W can be used with SEEP/W for un-coupled consolidation analyses. SEEP/W calculates transient pore-water pressure changes due to the applied load, while SIGMA/W calculates deformations resulting from the pore-water pressure changes.
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| Features: |
- Analysis types include drained total and effective stress, undrained total and effective stress, 2D plane strain, 3D axisymmetric, consolidation and swelling, and insitu stress.
- Constitutive soil models include linear-elastic, anisotropic linear-elastic, nonlinear-elastic, elastic-plastic, and Modified Cam-clay.
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- Boundary condition types include X and Y displacements, forces, pressures, and spring constants, as well as self-weight gravity loading.
- Structural beam and bar elements for soil-structure interaction.
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- Staged loading for fill placement or earth removal.
- Un-coupled volume change due to pore-pressure changes
- Fully-coupled stress-pore pressure analyses
- User Add-In constitutive models
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Use SIGMA/W stresses in SLOPE/W or QUAKE/W
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Using finite element computed stresses in SLOPE/W makes it possible to conduct a rigorous stability analysis using the same stress values resulting from the deformation analysis. In addition, you can use SIGMA/W stresses as the initial stress state for a dynamic earthquake analysis in QUAKE/W.
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| Use SIGMA/W pore-water pressures in SLOPE/W or SEEP/W |
Excess pore-water pressures generated by static loading, such as fill placement, can be brought into SEEP/W to study how long it takes to dissipate the excess pressures in the foundation. You can use SLOPE/W to analyze the effect of these excess pressures on stability during construction, allowing you to determine the need for staged loading.
Engineering Methodology Book
When you purchase a SIGMA/W 2007 license you also receive a copy of the SIGMA/W Engineering Methodology book, Stress-Deformation Modeling with SIGMA/W 2007. This book is not a software manual but a full-length book that discusses why and how to model. It does not describe how to use the commands in the software or which buttons to click - that is provided in detail in the Online Help. Instead it is about thinking: how to think before, during and after setting up and solving a model. The Engineering Methodology book has chapters devoted to: |
| Numerical Modeling: What, Why and How
Fundamentals and Practical Modeling Considerations
Geometry and Meshing
Material Properties
Bounday Conditions
Analysis Types
Coupled Stress-Pore Pressure Analysis
Functions in GeoStudio
Structural Elements
Staged Construction Sequencing
Numerical Issues
Visualization of Results
IllustrationExamples
Theory |
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