### Integrated into the GeoStudio Suite

SIGMA/W is integrated into the GeoStudio suite, and therefore has access to the GeoStudio features for creating your model, analyzing it, and viewing results.

### Comprehensive Stress-Strain Formulation

SIGMA/W uses a finite element-based formulation for performing stress and deformation analyses of earth structures. Its comprehensive stress-strain formulation makes it possible to analyze both simple and highly complex problems. SIGMA/W can perform a simple linear elastic deformation analysis or a highly sophisticated, nonlinear elastic-plastic effective stress analysis, which may involve soil-structure interactions, coupled stress and pore-water pressure response, and stress-based stability considerations. The many constitutive soil models allow you to represent a wide range of soils or structural materials. In addition, 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.

### Incremental Load Formulation

SIGMA/W is formulated for 1 or 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.

### Typical Applications

SIGMA/W can model almost any stress/deformation problem, including:

- Settlement of footings, fluid-filled tanks, or earth structures
- Deformation within or underneath an embankment or earth dam
- Lateral movement of braced or anchored excavations and surface settlement around the excavation
- Floor rebound of open-pit and sloping excavations
- Volume change resulting from pore water pressure change
- Staged fill placement and excavation
- Soil-structure interactions, including anchors, struts, and trusses
- Fully-coupled consolidation analysis
- Tailings deposition
- Permanent deformations resulting from strength loss
- Strength reduction stability
- Subsurface drainage design for soft soils
- Closure around a tunnel and stresses in the tunnel lining

### Obtain Converged Solutions for Challenging Problems

SIGMA/W implements a rigorous stress redistribution algorithm that is capable of handling the most challenging non-linear stress-strain material models.

### Saturated-Unsaturated Formulation

SIGMA/W is formulated to handle both saturated and unsaturated soils, which provides greater flexibility for handling coupled engineering problems.

### Coupled Consolidation Analysis

The coupled stress and pore-water pressure formulation can be used to model construction sequencing involving fill placement, excavation, and soil-structure interaction. The rigorous formulation simulates the instantaneous changes in pore-water pressure associated with a change in stress, followed by the subsequent time-dependent dissipation or recovery of pore-water pressures and the associated deformations.

### Model Construction Sequences with Ease

The Analysis Tree in GeoStudio provides a powerful and simple way to model even the most complex construction sequence. Analyses are added to the Tree, forming a Parent-Child relationship in which each new analysis represents a part of the construction sequence and forms the initial condition for the subsequent construction activities.

### In situ Condition Options

In situ stresses can be established using
either Poisson’s ratio or by specifying an initial K
_{0} value for the
material. This provides the ability to model heavily over-consolidated soils in
which the horizontal stresses exceed the vertical.

### Comprehensive Constitutive Model List

SIGMA/W offers a comprehensive list of constitutive models including Linear-Elastic, Anisotropic Linear-Elastic, Elastic-Plastic Mohr-Coulomb, Hyperbolic, Modified Cam-Clay, and the add-in functionality common to all GeoStudio products. An add-in can be used to incorporate your own types of constitutive behaviour, such as elastic viscoplasticity.

### Total and Effective Stress Material Categories

The ability to use total stress, effective stress, or coupled material models simultaneously in all analysis types, creates significant flexibility for modeling real-world engineering problems.

### Estimate Material Properties for Typical Materials

Material properties, such as the E-Modulus versus Stress function, can be estimated using built-in properties for typical materials. The estimation process requires only fundamental material information such as the soil classification.

### Comprehensive Range of Generalized Boundary Conditions

SIGMA/W supports a comprehensive list of boundary condition options including normal/tangential stress, X-Y stress, hydrostatic pressure, displacement, force, or spring boundaries. In keeping with the entire GeoStudio suite, SIGMA/W makes broad use of generalized functions for boundary condition definition. As such, actual field data over time or user-specified functional relationships can be pasted into SIGMA/W. SIGMA/W also allows zero-rotation boundary conditions to be used on structural components.

### Hydrostatic Stress Boundary for Water Surcharge Loads

The hydrostatic stress boundary provides a convenient approach for modelling the water surcharge load in either an in situ analysis or a transient coupled stress and pore-water pressure analysis. This makes it possible to model problems such as rapid drawdown in a single analysis.

### Soil-Structure Interaction

SIGMA/W’s structural elements can be used to model anchors, nails, tie-backs, wall systems, piles or any other soil-structure interaction problem in geotechnical engineering.

### Integrated with SLOPE/W for Stress-Based Stability Analyses

The stresses and/or pore-water pressures from a SIGMA/W analysis can be used directly in SLOPE/W to do a stress-based stability analysis.

### Stress Redistribution Analysis

The stress redistribution analysis can be used to conduct a strength reduction slope stability analysis, model stress transfer onto structures such as pile walls installed within failed slopes, or calculate permanent deformations resulting from strength loss due to liquefaction or strain softening.

### Model in 1D, 2D or Axisymmetric View

SIGMA/W includes analysis options for modeling pseudo three-dimensional problems.

### Powerful Graphing Options

Graphing is critical for the interpretation of stress-strain problems. The powerful graphing options in GeoStudio make it possible to plot critical information such as lateral displacement, surface settlements, pore-water pressure versus time, bending moments, shear distribution in structures, and more. All of this data can be exported or copy/pasted directly into spreadsheet software.

### View Stresses in a Mohr Circle

A Mohr Circle can be plotted at any gauss point or node to further interrogate the results.

### View Deformed Mesh and Yield Zone

Interpretation of the results is enhanced through the ability to view a deformed mesh, displacement vectors, and the location of the yield zone.

### Sensitivity Analysis with SIGMA/W

A sensitivity analysis can be readily conducted with SIGMA/W by cloning multiple analyses using the Analysis Tree and then making slight changes to each one.