Each GeoStudio product (except for VADOSE/W) runs with a limited set of features when using a GeoStudio Basic license.

SLOPE/W Basic

The slope stability analysis features and capabilities in GeoStudio Basic are more than adequate for conventional analysis of most natural slopes and man-made cut slopes that may be encountered in routine engineering practice. The 10-region and 10-material limit in GeoStudio Basic is more than sufficient to describe the geometry and stratigraphy of common slope stability problems.

Methods that can be used to compute safety factors include the Ordinary, the Bishop Simplified, the Janbu Simplified, the Spencer and the Morgenstern-Price method. As well, the advanced General Limit Equilibrium (GLE) method is available, which is sometimes useful for helping with interpreting the results of the various methods.

Key features available in SLOPE/W Basic include:

- Trial slip surface shapes can be circular or non-circular. Non-circular shapes can be formed from arcs of a circle together with linear segments or just with straight line segments.
- Trial slip surface positions are controlled by specifying a traditional grid of rotation centers together with a range of radii or by specifying a range of entrance points along the crest and a range of exit points in the slope toe area. Block shapes are formed by specifying two grids of points at the break locations along the three-piece linear slip surface.
- The shape of the critical slip surface can be refined and the factor of safety optimized with a special statistical random walk technique based on a Monte Carlo method.
- Mohr-Coulomb strength parameters C (cohesion) and Ø (phi) are available to describe the soil strength. The parameters may be total or effective depending on the pore-water pressure conditions specified. Undrained strengths are specified by making Ø zero.
- Pore-water pressures can be described with a piezometric line with an optional phreatic correction when there are sharp downward curves in the piezometric line.
- Surcharge loads as can be included as concentrated line loads or as surface pressures.
- Water impounded up against a slope (partial submergence) can be considered in an analysis by including the water as a no strength material.
- Tension cracks can be considered by specifying a constant tension crack depth or by specifying a slip surface inclination angle. When a slice base inclination near the crest exceeds the specified angle, a tension crack is formed as part of the slip surface shape.
- Earthquake and seismic effects can be considered as pseudostatic forces by specifying horizontal and vertical seismic coefficients.

Reinforcement can be simulated in a simplistic way with the use of concentrated line loads. This is an adequate and acceptable approach for determining the forces the reinforcement needs to provide to achieve a design factor of safety against the possible slip of the retained soil wedge. Once the required force is known, the details of the reinforcement can be selected and designed independent of the stability analysis.

The full-featured SLOPE/W edition is required for:

- Highly complex geometric and stratigraphic conditions
- Irregular and non-hydrostatic pore-pressure conditions
- Pore-pressures that are a function of overburden or surcharge loads
- Non-linear and anisotropic soil strengths
- Soil strength variations with depth in a stratum
- Soil strength variations related to soil suction and air pressure
- Rigorous and more direct consideration of specific reinforcements such as anchors, nails, geo-fabric, dowels and piles.
- Probabilistic and sensitivity analyses
- Auto locating the position of the critical slips surface and auto locating possible tension cracks.

SEEP/W Basic

The SEEP/W Basic Edition can be used for the analysis of confined and unconfined steady-state seepage problems. The features available are more than adequate for the analysis of classical problems such as confined seepage flow below a structure with a cutoff and unconfined flow through an earth embankment.

An important component of flow in unconfined problems is the unsaturated flow above the water table. Unlike many other software products, SEEP/W correctly considers the unsaturated flow as well as the saturated flow.

For fully saturated flow conditions, the hydraulic conductivity can be specified as a constant. For unconfined flow problems, it is necessary to define a hydraulic conductivity function that describes the reduction in the conductivity or permeability as the soil de-saturates. This can be done easily by simply specifying two data points, as illustrated on the left, which produces the nicely curved function on the right.

More data points can be used to describe the conductivity function, but a two-point approximation is adequate for most practical steady-state seepage problems where there is a significant component of lateral flow as through an embankment, for example.

The SEEP/W Basic computed seepage results can be used directly in a SLOPE/W Basic slope stability analysis, if a piezometric line is not adequate to describe the pore-pressure conditions of a particular problem.

The full-featured edition of SEEP/W is required for transient analyses and for problems with time-dependent boundary conditions.

SIGMA/W Basic

SIGMA/W Basic is particularly useful for estimating the immediate or elastic settlement of multilayered systems. A typical case is the immediate settlement of a round fluid storage tank as illustrated here.

Loads can be applied incrementally to simulate the placement of fill during the construction of an embankment, for example. Similarly, the elastic heave associated with the construction of an excavation can be computed by simulating the removal of the soil.

SIGMA/W Basic can also be used to perform saturated consolidation analyses. Consolidation analyses of a multilayered system are nearly impossible to do with hand-calculations even if it is a one-dimensional analysis. Such 1-D analyses can be done with relative ease with SIGMA/W Basic.

Pore-pressure conditions computed with SIGMA/W Basic can be used in a SLOPE/W Basic stability analyses. Initial plus excess pore-pressures arising in the foundation from the construction of an embankment, for example, can be used in SLOPE/W Basic to check the stability of the embankment after the construction.

The full-featured edition of SIGMA/W is required for non-linear deformation analyses and stage (time) dependent boundary conditions.

QUAKE/W Basic

QUAKE/W Basic is included in the GeoStudio Basic package primarily for illustrative purposes. QUAKE/W Basic is restricted to linear-elastic material properties which limits its use in actual field problems. Using only linear-elastic material properties tends to over estimate the dynamic response of earth structures to earthquake shaking. This can lead to unrealistic motions and excessive dynamic stresses.

Dynamic linear-elastic analyses however are useful for investigating and demonstrating how QUAKE/W analyses are performed, what material properties are required and how the results can be visualized. In addition, QUAKE/W Basic is useful for demonstrating how the QUAKE/W results can be used in SLOPE/W to do a Newmark-type permanent deformation analysis and for determining how the factor of safety varies during an earthquake.

TEMP/W Basic

TEMP/W Basic is intended primarily for the analysis of ground freezing and thawing problems with limited geometric complexity and with constant thermal boundary conditions.

CTRAN/W Basic

CTRAN/W uses the flow velocities from a steady state SEEP/W analysis to model the migration of contaminants. So, the CTRAN/W Basic limitations are primarily the limitations inherent in SEEP/W Basic.

CTRAN/W Basic is particularity useful for tracking the paths of imaginary contaminant particles in time and space. The particles can be tracked forward from a source to a discharge point or backward from a discharge point to the source. Travel times and distances are computed for each particle.

In addition, CTRAN/W Basic is a useful tool for investigating pure dispersion and advection-dispersion problems, particularly one-dimensional problems.

AIR/W Basic

AIR/W is for analyzing air flow through soil. AIR/W is actually an option in SEEP/W. The primary intent is to examine how air flow and air pressure affect water flow and pressure. This makes it possible to look at the true matric suction term (ua–uw).

AIR/W Basic is limited to steady-state conditions, but is powerful enough to include modeling a vapor extraction well under long term pumping conditions, for example. You could specify atmospheric pressure along the ground surface and a vacuum air pressure at the screen of a well. The results would show a drawdown cone of water in the soil, as well as a steady state mass flow rate for the air leaving the well.

The GeoStudio Basic Edition is a feature-limited version of seven products: SLOPE/W for slope stability analysis, SEEP/W for groundwater seepage analysis, SIGMA/W for stress & deformation analysis, QUAKE/W for dynamic earthquake analysis, TEMP/W for geothermal analysis, CTRAN/W for contaminant transport analysis and AIR/W for air flow analysis.

The Basic Edition is ideal for use in routine engineering practice for the analysis of problems with limited geometric complexity. It is licensed for engineering consulting use and is available as a Perpetual Standalone License only.

While primarily intended for analyzing the stability of natural and man-made earth slopes, you can also use GeoStudio Basic for the analysis of confined and unconfined steady-state seepage problems, for the analysis of linear-elastic settlement and stress distribution problems, for the tracking of contaminants within ground water flow and for the analysis of freeze-thaw problems.

The Basic Edition does not contain all of the features found in the full product editions. For example, each product in GeoStudio Basic is limited to 2 multiple/staged analyses within one file, 10 material types, 10 geometric regions, and 500 finite elements. **Modeling Practice**

A common tendency when using powerful modeling software is to build numerical models that are geometrically too complex. The geometric complexity is usually not required to obtain meaningful results. In fact, we at GEO-SLOPE strongly advocate that a numerical model should be a simplified abstraction of the actual field conditions. Adopting this modeling principle makes GeoStudio Basic a very powerful analytical tool for use in practice in spite of its geometric limitations. **Evaluation and Upgrading**

GeoStudio Basic allows you to evaluate a very high-end geotechnical software package with a minimal investment. Starting with GeoStudio Basic is an excellent strategy. Once you are comfortable with using the software and you find that your projects dictate analyzing more complexity, you can upgrade to the full-featured version. Everything that you have learned and done with the Basic Edition will be directly usable in the full-featured edition. Nothing will be lost by first acquiring the Basic Edition and subsequently acquiring the full-featured edition.

National Cheng Kung University Department of Civil Engineering

National Cheng Kung University Department of Resources Engineering

National United University Department of Civil and Disaster Prevention Engineering

National Taiwan University Department of Civil Engineering

Water Resources Planning Institute,Water Resources Agency,Ministry of Economic Affairs Geo-lechnical Engineering Division

CTCI Resources Engineering Services, Inc. Geotechnical Department

National Center for Research on Earthquake Engineering Slopeland Disaster Reduction Division