Tutorial_07_Finite_Element_Groundwater_Seepage.pdf

Finite Element Groundwater Seepage (Overview)

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Groundwater Analysis Overview

Introduction

Within the Slide program, Slide has the capability to carry out a finite

element groundwater seepage analysis, for saturated / unsaturated,

steady state flow conditions.

The Groundwater Analysis in Slide allows the user to define and analyze

a groundwater problem, using the same model as for the slope stability

problem. The boundaries of the problem only need to be defined once, and

will be used for both the groundwater analysis and the slope stability

analysis.

After a groundwater analysis is performed, the results (pore pressures),

can be automatically utilized by the slope stability analysis engine in

Slide .

NOTE:

• The groundwater analysis capability in Slide can be considered a

completely self contained groundwater analysis program, and can be

used entirely independently of the slope stability functionality of

Slide .

• You may perform a groundwater analysis in Slide , without

necessarily performing a slope stability analysis.

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• Although the Slide groundwater analysis is geared towards the

calculation of pore pressures for slope stability problems, it is not

restricted to slope geometry configurations. The groundwater

modeling and analysis capabilities in Slide , can be used to analyze an

arbitrary, 2-dimensional groundwater problem, for saturated /

unsaturated, steady state flow conditions.

Groundwater Modeling

The groundwater modeling options in Slide are all contained within the

Slide Model program.

In order to enable groundwater modeling, it is first necessary to set the

Groundwater Method in Project Settings to Finite Element Analysis .

When you do this:

• an Analysis Mode option will be available in the toolbar, which allows

you to select either Slope Stability analysis mode, or Groundwater

analysis mode.

• When you are in Groundwater analysis mode, the menu and toolbar

will present all of the necessary groundwater modeling options.

The following general procedure is required, in order to use the Slide

program for a groundwater analysis.

Project Settings

In order to perform a groundwater analysis, the first thing that must be

done, is to set the Groundwater Method in Project Settings to Finite

Element Analysis .

1. Select Project Settings from the toolbar or the Analysis menu.

2. Select the Groundwater tab, and set the Groundwater Method =

Finite Element Analysis .

3. You may configure the Groundwater Analysis parameters in Project

Settings as necessary (i.e. Tolerance or Maximum Number of

Iterations )

4. Select OK .

The Slide toolbar will now display an Analysis Mode option, as described

below.

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Enabling groundwater analysis with Slide .

Groundwater Analysis Mode

When you set the Groundwater Method = Finite Element Analysis in

Project Settings, you will notice that a drop-down selection box will

appear in the Slide toolbar. This option allows you to switch between two

different analysis modes of the Slide Model program – Slope Stability or

Groundwater .

• The Slope Stability analysis mode allows you to define the elements

of your model which are relevant to the slope stability analysis.

• The Groundwater analysis mode allows you to define the elements of

your model which are relevant to the groundwater analysis.

When you switch between Slope Stability analysis mode and

Groundwater analysis mode, you will notice that the menus and toolbars

are automatically changed.

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Boundaries

The SAME boundaries are used in both the groundwater and slope

stability analysis. However, the model boundaries can only be defined

when the Analysis Mode = Slope Stability .

• You MUST create the model boundaries, when Analysis Mode = Slope

Stability .

• You CANNOT create or edit the model boundaries, when Analysis

Mode = Groundwater .

For details about defining boundaries in Slide , see the previous tutorials,

or the Slide Help system.

Meshing

The groundwater analysis in Slide is a finite element analysis, and

therefore a finite element mesh is required in order to solve the problem.

To create the finite element mesh:

• the user can do this with a single mouse click, by selecting the

Discretize and Mesh option. This will automatically create a

graded finite element mesh within your model boundaries.

• If the mesh requires customization, several options are available in

the Mesh menu, which allow the user to customize the mesh as

necessary.

Finite element mesh for groundwater analysis.

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Boundary Conditions

Once the finite element mesh is satisfactory, the user must then set up

the boundary conditions which define the groundwater problem they

wish to solve. This is done with the Set Boundary Conditions option,

which allows the user to define all of the necessary pressure and flow

boundary conditions along the model boundaries, or at any other node(s)

of the mesh.

Dialog for assigning boundary conditions.

Hydraulic Properties

The permeability (hydraulic conductivity) characteristics of each material

are defined with the Define Hydraulic Properties option. You may

define a saturated permeability for each material. In addition, various

models are available for defining the unsaturated permeability, or the

user may create a user-defined permeability function.

Dialog for defining hydraulic properties.

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