Groundwater

The Groundwater tab in the Project Settings dialog includes the following groundwater setup options:

• Default Groundwater Method
• Default Joint Water Pressure Method
• Water Unit Weight

Default Groundwater Method

The Default Groundwater Method allows you to pre-select the desired Groundwater Method for your model. Choosing the Default Groundwater Method simply sets the Groundwater Method for each material in the Define Materials dialog, to the selected method. There are three Groundwater Methods:

• Water Surfaces
• Ru Coefficients
• Water Grids

The purpose of the Default Groundwater Method is to allow you to pre-set the Groundwater Method for all materials to the most common method which is applicable to most or all materials in your model so that you do not have to select it for each material.

Example

If most of the materials in your model use Water Surfaces to calculate pore pressure, but you also have some materials for which Water Grid data is available, then you should do the following:

1. In Project Settings, set the Default Groundwater Method = Water Surfaces
2. In the Define Materials dialog, enter the Water Surface for the applicable materials.
3. For the material(s) which require a water grid, set the Groundwater Method = Water Grids and choose the Water Grid for the applicable materials.

Default Joint Water Pressure Method

Water Pressure in the Joints are modeled as Material Dependent by default which means that the Water Pressure computed within the Joints depend on the Groundwater Method and associated information specified in the Define Materials dialog. There are also other options for defining Joint Water Pressure Method, which are independent of material properties:

• Water Surfaces
• Water Grids
• Dry
• Uniform
• Peak at Toe

Like the Default Groundwater Method, the Default Joint Water Pressure Method allows you to pre-set the Joint Water Pressure Method for all joint properties (Joints > Define Joint Properties) to the most common method which is applicable to most or all joint properties in your model so that you do not have to select it for each joint property.

Water Unit Weight

The Water Unit Weight is used to determine:

• The calculated water pressure (depends on the chosen Groundwater Method and Joint Water Pressure Method)
• The unit weight of ponded water defined by a Water Table. See the Ponded Water topic.
• The unit weight of water used to calculate the hydrostatic force in a water-filled or partially water-filled Joint.

The calculated water pressure at any given point is directly proportional to the Water Unit Weight if the Joint Water Pressure is set to:

• Water Surfaces
• Water Grids and grid type is Total Head or Pressure Head
• Material Dependent and if the Groundwater Method is Water Surfaces or Water Grids
• Peak at Toe

The Water Unit Weight does NOT enter into the water pressure calculations if the Joint Water Pressure is set to:

• Water Grids and grid type is Pore Pressure (pore pressure determined directly from the grid data)
• Material Dependent and if the Groundwater Method is Ru Coefficient (pore pressure determined from vertical earth pressure)
• Material Dependent and if the Groundwater Method is Water Grids and grid type is Pore Pressure (pore pressure determined directly from the grid data)
  
• Dry (no water pressure is applied)
• Uniform (a uniform water pressure is specified by the user, not computed)

The default value of the Water Unit Weight is determined by the Units of Measurement selected in Project Settings (9.81 kN/m3 for metric units, 62.4 lbs/ft3 for Imperial Units). However, you may change this value if necessary.