(updated 4/4/2001)

UTEXASED4 is a computer software application for computing the stability of earth and earth-rock slopes and embankments. It is a Windows-based program that uses limit equilibrium procedures to calculate a factor of safety against failure. The factor of safety is defined with respect to shear strength, i. e. the factor of safety is the ratio of the soil shear strength to the equilibrium shear stress. Values of the factor of safety at or less than unity are considered to represent instability and failure of the slope.

UTEXASED4 is intended for use in graduate and advanced undergraduate civil engineering courses specializing in geotechnical engineering. The software has been specifically developed for educational purposes and its use is restricted to educational applications. Use for any commercial purposes is explicitly not allowed.

UTEXASED4 is a slope stability computer program with a Windows-based graphical user interface for both entering and displaying the input data as well as displaying the results of computations. The program can be used to the stability (factor of safety) for inhomogeneous slopes and embankments using both circular and noncircular slip surfaces. Spencer's procedure of slices is used to compute the factor of safety. Automatic searches can be performed to locate the critical circular or noncircular slip surface with the lowest factor of safety. Searches with both circular and noncircular slip surfaces are fully animated to show each trial slip surface as they are tried along with the location of the slip surface which currently yields the lowest factor of safety. Also, a special, separate "interactive" search scheme allows the user to select trial slip surfaces, one by one, and compute the factor of safety for each surface. As the factor of safety is computed for each slip surface, contours of factor of safety are drawn and updated to guide locating the most critical slip surface with the lowest factor of safety. In this way students can see how the factor of safety changes with the location of the critical circle and eventually locate the most critical circle on their own and using their own judgement.

UTEXASED4 allows several representations for the soil shear strength, including:

- Conventional linear Mohr-Coulomb envelopes described by a cohesion intercept (c or c') and friction angle (f or f').
- Linear increase in undrained shear strength (S
_{u}= c) below a horizontal reference datum. - Curved Mohr-Coulomb envelopes.

Shear strengths may be expressed in terms of either total stresses or effective stresses.

For effective stress analyses pore water pressures may be specified in two ways as described below:

- A constant value of Bishop's pore water pressure coefficient, r
_{u}, may be specified. Pore water pressures are then calculated by multiplying the total vertical stress (gz) by the pore water pressure coefficient. - A piezometric line may be specified where the pore water pressures are computed as the vertical distance between the piezometric line and point of interest times the unit weight of water. Pore water pressures are assumed to be zero above the piezometric line.

Distributed surface loads can be used to model external water loads as well as loads imposed by footings, material stockpiles, etc. Distributed loads are specified in the input data by specifying the coordinates of points on the surface of the slope and the corresponding value of stress (pressure). The distributed loads are assumed to act normal (perpendicular) to the surface of the slope and to vary linearly between points where the loads are specified.

Internal soil reinforcement representing geosynthetic geogrids and geotextiles, piles, soil nails, tie-back anchors and other forms of slope strengthening can be included in an analysis. Each reinforcing element is specified as input data by a series of points along the reinforcing element and the value of the longitudinal (axial) and transverse (shear) force at each point. The forces in the reinforcement are assumed to vary linearly between the points where the forces are specified. In the slope stability computations forces are assigned to individual slices at the points where the reinforcement intersects the slice. The force applied to each slice is equal to the specified force in the reinforcement at the point of intersection. Reinforcement elements may be horizontal, vertical or inclined. Also, as noted above both longitudinal (axial) and transverse (shear) forces can be entered.

The complete User's manual and description of the example problems are available in Adobe PDF file format by clicking on the following links:

UTEXASED4 is distributed to educational institutions for a nominal fee to support the distribution and maintenance of the software. Pricing is based on the number of faculty teaching in the geotechnical engineering program, as follows:

- $200 per faculty member in the geotechnical engineering program.
- $600 minimum.
- One-half price if orders are prepaid (payment is sent with your order), i. e. $100 per faculty, $300 minimum.
- All orders outside the United States must be prepaid.

If you are interested in obtaining a copy of the UTEXASED4 software please contact Dr. Stephen G. Wright at swright@mail.utexas.edu

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