Ponded Water Load

The distributed loading due to Ponded Water (e.g. impounded water against a slope or dam) can be applied with the Add Load option and Ponded Water Load selected as the Load Type. This allows you to easily define hydrostatic loading due to Ponded Water by specifying total head boundary conditions on user-selected boundary segments.

To apply a Ponded Water Load:

1. Select the Loads workflow tab
2. Select Faces Selection as the Selection Mode.
3. Select the face(s) on which to apply the load.
4. Select Add Loads to Selected from the toolbar or the Loading menu.

TIP: with the face(s) selected, you can also right-click on the viewing screen and select Add Loads from the Loading sub-menu.

5. You will see the Add Load dialog. In this dialog:
   1. Select the Load Type = Ponded Water Load
   2. Enter a value of Total Head. This value should be numerically equal to the z-coordinate of the water level you are modeling.
   3. The load Orientation for a Ponded Water Load is always Normal to boundary.
   4. In a multi-stage model, the water level can be changed at different stages
   5. In a multi-stage mode, the Staging options allow you to specify the stage at which the Ponded Water Load will be installed and the stage at which the load will be removed. Loads can be staged by selecting the Stage Factors checkbox, and entering the Total Head at each stage. If you do not stage the load on a multi-stage model, then the load will be applied with the same total head at all stages.

See below for details about the load magnitude, orientation, and staging.

6. When finished specifying the load properties, select Apply. The Ponded Water Load will be applied to all selected surfaces (i.e. faces). RS3 will automatically create a series of distributed loads on the boundary that are equivalent to the hydrostatic force of the ponded water, as indicated by the display of blue arrows and the magnitudes.
7. Check the direction of the arrows and the magnitude, to make sure that this is the load you wished to apply. If there is a mistake, you can repeat the above steps to apply the correct load, or select and edit the load using the Properties Pane to change the load parameters.

PONDED WATER LOAD MAGNITUDE

When a Ponded Water Load has been added to a model, the load magnitude is defined in terms of the equivalent distributed load values (i.e. force per unit area), applied normal to the boundary (i.e. surface). The values of the equivalent load magnitude are derived from:

• the value of Total Head (entered in the Add Load dialog)
• the elevation of each boundary vertex (relative to the water level)
• the value of the Pore Fluid Unit Weight entered in the Groundwater page of the Project Settings dialog.

STAGING PONDED WATER LOADS

On a multi-stage model, Ponded Water loads can easily be staged by selecting the Stage Factors checkbox in the Add Load dialog (Step 5 above). You will see Total Head Stage Factor in the expanded dialog. Select the Add Stage button for each stage and enter a Total Head Stage Factor for the Ponded Water Load at each stage.

PONDED WATER LOADS AND TOTAL HEAD SEEPAGE BOUNDARY CONDITIONS

It is important to note that defining a Ponded Water Load does not define the Total Head conditions for a finite element groundwater seepage analysis. This must be done independently with the Set Boundary Conditions option in the Groundwater menu.

And conversely, defining the Total Head boundary conditions for a finite element seepage analysis does not automatically define the loading due to the weight of the ponded water. The weight of the ponded water can only be defined with the Add Load option and selecting the Load Type as Ponded Water Load, as described above.