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