Groundwater Overview

Within the Slide program, Slide has the capability to carry out finite element groundwater seepage analysis for saturated / unsaturated, steady state flow conditions. NOTE:

• The groundwater analysis engine in Slide is completely separate from the slope stability analysis engine. You may perform a groundwater analysis in Slide, without necessarily performing a slope stability analysis.

• However, after a groundwater analysis is performed, the results (pore pressures), can be automatically utilized by the slope stability analysis engine in Slide.

In order to use the Slide program for a groundwater analysis, the following general procedure is required.

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 Finite Element Analysis parameters in Project Settings as necessary (e.g. Tolerance or Maximum Number of Iterations)

4. Select OK.

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

Groundwater Analysis Mode

When you set the Groundwater Method = Finite Element Analysis, you will notice that a drop-down list in the Slide toolbar, will allow 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 parts of your model which are relevant to the slope stability analysis.

• The Groundwater analysis mode allows you to define the parts 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.

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 CANNOT create or edit the model boundaries, when analysis mode = Groundwater.

• You MUST create the model boundaries, when analysis mode = Slope Stability.

See the topics in the Boundaries section of this Help system, for full details about defining and editing model boundaries in Slide.

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:

• you 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 total number of finite elements and the element type (in the Mesh Setup option), customize the discretization of the model boundaries (Custom Discretize option) and more advanced mesh refinement options (see the Mesh Refinement topic)

Groundwater Boundary Conditions

Once the finite element mesh is satisfactory, the user must then define the boundary conditions which define the groundwater problem they wish to solve. This is done with the Set Boundary Conditions option, which allows you to define all of the necessary pressure and flow boundary conditions along the model boundaries, or at any other node(s) of the mesh.

Groundwater Material 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, and various models are available for defining the unsaturated permeability.

Groundwater Compute

When all of your groundwater boundary conditions and material properties have been defined, then you are ready to run the groundwater (seepage) analysis. To run the analysis:

• Select the Compute (Groundwater) option from the toolbar or the Analysis menu. This will run the Slide Groundwater Analysis engine.

• You will see a Compute dialog while the analysis is running. When the analysis is finished, you will be returned to the Slide Model program.

After you have computed the groundwater analysis, you should view the results of the groundwater analysis, by selecting the Interpret Groundwater option.

If the groundwater analysis results are satisfactory, then you can return to the Slide Model program, switch the Analysis Mode = Slope Stability, and proceed with your slope stability analysis.

When you select the slope stability Compute option, the slope stability analysis will automatically use the pore pressures calculated from the groundwater analysis.

Groundwater Interpret

The Groundwater analysis results are viewed in the Slide Interpret program, and can be viewed simultaneously with the slope stability analysis results. For information, see the Groundwater Results Overview topic.

After you perform a groundwater analysis with Slide, it is always a good idea to first use the Interpret program, to check that the groundwater analysis results are reasonable. If not, then you should go back to the Slide Model program, and check that you have defined your model correctly.