Last Updated October 17, 2019

SIGMA/W is a finite element CAD 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. SIGMA/W can perform a simple linear elastic deformation analysis or a highly sophisticated, nonlinear elastic-plastic effective stress analysis.

GeoStudio’s Analysis Tree models even the most complex construction sequences. Analyses are added to the Tree, forming a Parent-Child relationship in which each new analysis represents a part of the construction sequence.

The coupled stress and pore-water pressure formulation can be used to model construction sequencing involving fill placement, excavation, and soil-structure interaction.

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 is 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.

The rigorous stress-strain formulation of SIGMA/W, and the seamless workflow of GeoStudio, simplifies the analysis of complex staged construction problems involving cut slopes and fill placement. Simulations of this nature are required to simulate the construction of earth and rock fill embankments, tailings dams, railway and roadway cuts, and more. SIGMA/W’s coupled stress-strain and water transfer formulation makes it possible to also analyze the simultaneous generation and dissipation of excess pore-water pressures, allowing for the design of sub-surface drainage systems with the software.

SIGMA/W can be used to model the deformation of natural and cut slopes under a variety of loading conditions resulting from changes to the groundwater flow system, strength loss due to liquefaction during earthquake shaking or strain-softening, and construction activities. SIGMA/W’s phi-c reduction technique, referred to as a Stress Redistribution analysis, can be used to simulate deformations resulting from strength loss while also providing information about stability. A stress-based SLOPE/W stability analysis can also be completed to calculate a safety factor from the stress-field simulated by SIGMA/W.

Deep excavations for civil, geotechnical, and mining applications often involve complex soil-structure interaction. The rigorous structural element formulations, combined with a comprehensive material model library, make SIGMA/W the ideal tool for modeling struts, pile and sheet walls, anchorage, tunnel lining, and more. SIGMA/W’s Stress Redistribution analysis also makes it possible to simulate load transfers and structural responses for projects involving slope stabilization by means of engineered structures (e.g. soldier pile wall). In all cases, SIGMA/W can be used to ensure that the structures are designed to safely carry the loads and to ensure that overall stability is established with an acceptable margin of safety.

Once you have solved your analysis, 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 prepare the results for your report by adding labels, axes, and pictures, or export the results into other applications such as Microsoft® Excel® for further analysis.

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

- 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
- Strength reduction stability
- plus many more!

SIGMA/W offers simple but powerful analytical capabilities when used in combination with other GeoStudio products.

There are many geotechnical cases where it is desirable to not only perform a deformation analysis, but also to look at stability. In other instances, a SLOPE/W limit equilibrium stability analysis alone is inadequate. For cases like this, the SIGMA/W computed stresses can be used in SLOPE/W to compute the safety factors.

Excess pore-water pressures generated in SIGMA/W by external loads (e.g., fill placement) can be used as initial conditions in a transient SEEP/W analysis. The simulated dissipation rates can be used to develop construction-staging schedules. SEEP/W pore-water pressures can be used by SIGMA/W to simulate in situ effective stresses.

Establishing insitu static stresses can be done simplistically in QUAKE/W. Alternatively, you can use the load sequencing and non-linear constitutive soil models in SIGMA/W to improve the estimation of the static stress conditions, and then use them as the initial static stresses in a QUAKE/W dynamic analysis.