Finite-Element Seepage Analysis
The following are an integrated suite of five geotechnical software packages being used extensively throughout the world on six continents and in more than 70 countries. They are used by practicing engineers for the analysis and design of a wide variety of structures and by universities for teaching and research. The five state-of-the-art software packages for geotechnical modeling in the Microsoft Windows environment are:
- SLOPE/W for slope stability
- CTRAN/W for contaminant transport
- SIGMA/W for stress and deformation
- TEMP/W for geothermal analysis
Features of the Finite-Element Software
SEEP/W, CTRAN/W, SIGMA/W, and TEMP/W are all based on the finite-element method. The CAD-like interface of these products helps to simplify one of the most difficult aspects of using finite-element software: creating the finite-element mesh. You can draw elements individually on the screen or generate elements over a specified region. And you never have to worry about the node and element numbering; as elements are generated, the mesh numbering scheme is sorted for the analysis.
Other features of the finite-element software include:
- Four- to eight-noded quadrilateral elements
- Three- to six-noded triangular elements
- Infinite elements for far-field boundary conditions
- Selectable Gaussian integration order
- Color shading of elements according to material type
- Display of boundary conditions as graphic symbols
- Boundary conditions specified as functions for transient analyses
- No inherent restrictions on the number of nodes and elements
- No restriction on the nodal number difference (bandwidth) in an element
SEEP/W analyzes ground-water seepage and excess pore-water pressure dissipation problems. The comprehensive formulation of SEEP/W makes it possible to consider analyses ranging from simple saturated steady-state problems to sophisticated saturated/unsaturated time-dependent problems.
Many computed parameters such as head can be contoured, and the relative rate of flow can be displayed as velocity vectors.
FEATURES AND CAPABILITIES
SEEP/W can model both saturated and unsaturated flow, a feature that greatly broadens the range of problems that can be analyzed. In addition to traditional steady-state saturated flow analysis, the saturated/unsaturated formulation of SEEP/W makes it possible to analyze seepage as a function of time and to consider such processes as the infiltration of precipitation. The transient feature allows you to analyze such problems as the migration of a wetting front and the dissipation of excess pore-water pressure.
- Steady-state and transient flow conditions
- Confined and unconfined flow
- Two-dimensional flow in a vertical plane
- Three-dimensional axisymmetric flow
- Two-dimensional flow in plan view
- Constant hydraulic head and/or flux conditions
- Transient head and/or flux as a function of time
- Flux as a function of computed head
- Review and automatic modification of seepage face conditions
Boundary conditions can be specified as a function of time. Convergence can be viewed graphically while a problem is being analyzed.
The hydraulic conductivity of the soil is a function of the negative pore-water pressure in unsaturated regions. Also, the rate of change in water content is dependent on the pore-water pressure during transient processes. This data is defined at discrete points that SEEP/W uses to create spline-interpolated smooth functions. These functions can be graphically displayed and modified. Data points can be moved or added interactively by clicking on the function plot, allowing you to visually modify the function until it is acceptable. The function plots can be printed or copied to the clipboard for importing into other Windows applications. The hydraulic conductivity can also be defined as anisotropic in two orthogonal directions.
SEEP/W computes the total flux across user-defined lines drawn through all or part of the mesh. Single or multiple flux sections can be defined for the same problem.
Hydraulic conductivity is dependent on the negative pore-water pressure in the unsaturated zone.
The main processing function can be halted at any time and then later restarted. This allows flexibility in modifying boundary conditions and soil properties at intermediate stages during transient analyses.
VIEWING AND PLOTTING RESULTS
The computed results can be displayed graphically as contours and velocity vectors. Contour values can be displayed by simply clicking on the contour. The variation in the contoured parameter can be gradationally shaded from a high to a low color intensity. The velocity vectors provide a graphical representation of the flow direction; the size of each vector indicates the relative rate of flow. Transient conditions can be displayed by plotting the changing position of the water table as a function of time. Flux quantities can be displayed by clicking on the flux section. Parameters such as head, pressure, gradient, velocity, and conductivity can be contoured.
SEEP/W has a powerful graphing feature that plots a variety of parameters as a function of time or space, i.e., you can plot pore-water pressure distribution along a vertical section through the mesh or plot pore-water pressure changes with time at a given node. The graph data can be imported into another application such as a spreadsheet for further analysis or for preparing presentations.
The migration of a wetting front can be displayed as a transient water table plot.
- Dissipation of excess pore pressure after reservoir drawdown
- Changes in pore-water pressure conditions within earth slopes due to precipitation infiltration
- Mounding of the ground-water table beneath water retention structures such as lagoons and tailings ponds
- Effect of subsurface drains and injection wells
- Drawdown of a water table due to pumping from an aquifer
- Seepage flow quantities into excavations
Computed values such as head, pressure, velocity, gradient, and conductivity can be plotted as a function of time or space.
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Τελευταία Ενημέρωση 27 Ιουλίου 2004 - Last Revised on July 27, 2004
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