Water Table
A Water Table in Slide3 is a type of Water Surface which represents a phreatic surface. A Water Table is created by setting the Water Type = Water Table, when you add a water surface using the Add Water Surface or Add Water by Location options.
A Water Table is used primarily for pore pressure calculation but also has several other possible uses. A Water Table can be used for the following purposes in Slide3:
- Pore Pressure - if the Groundwater Method = Water Surfaces then you can assign a Water Table to calculate the pore pressure for a material. Pore pressure is proportional to the vertical distance from the water table.
- Ponded Water - if a Water Table or a Drawdown Surface is defined above the slope surface, then Ponded Water is automatically created. The weight of ponded water is accounted for in the stability analysis.
- Unit Weight - if the Saturated Unit Weight checkbox is selected for a material, then different unit weights will be applied above and below a Water Table.
- Rapid Drawdown analysis - if you are using the Rapid Drawdown Analysis option then a Water Table must be defined, and an optional Drawdown Surface.
- Strength above water surface - if the Alternate Strength Above Water Surface checkbox is selected for a material, then you can assign a different strength criterion above a Water Table.
- Tension Crack - a Water Table can be used to define the water level in a tension crack
Pore Pressure Calculation
In order to use a Water Table for pore pressure calculation for a material, you must choose the Groundwater Method = Water Surfaces in the Material Properties dialog.
Ponded Water
For any Groundwater Method (i.e. Water Surfaces, Ru, Water Grids) a Water Table can be used to define Ponded Water. When you define a Water Table with elevation above the ground surface, ponded water is automatically created and used in the stability analysis, regardless of the Groundwater Method or water surface material assignment.
Tension Crack
For any Groundwater Method (i.e. Water Surfaces, Ru, Water Grids) a Water Table can be used to define the water level in a Tension Crack. This is used to calculate the hydrostatic force in a tension crack.
Number of Water Tables
Only ONE Water Table entity can be defined for a Slide3 model. If you have defined a Water Table, you will notice that Water Table can no longer be selected as the Water Type for any new water surfaces. If you already have a Water Table defined and you wish to define a new water table, then you will first have to delete the existing water table or use a Piezometric Surface.
If you require more than one Water Surface for modelling groundwater you will have to use Piezometric Surfaces.
Water Table versus Piezometric Surface
For pore pressure calculation, a Water Table is equivalent to a Piezometric Surface in Slide3. However, there are several additional features associated with a Water Table (e.g. Ponded Water) which are not available for a Piezometric Surface - see the Piezometric Surface topic for details