Piezo Lines can be used for calculating pore pressure when the Groundwater Method in Project Settings is set to Water Surfaces. A Piezometric Line in Slide can represent an actual Piezometric surface obtained from piezometer measurements, for example.
To add a Piezometric Line to your model:
Select Add Piezometric Line from the Boundaries menu.
Enter the vertices of the Piezometric Line as described in Entering Coordinates.
IMPORTANT NOTE: the Piezo Line MUST BE DEFINED ACROSS ALL MATERIALS for which pore pressure is to be calculated using the Piezo Line. If it is not, then the analysis will not be able to calculate the pore pressure for slip surfaces where the Piezo Line is not defined, and a safety factor will NOT BE CALCULATED. Therefore, always make sure that a Piezo Line spans all relevant material zones of the model, or the slope will not be analyzed where the Piezo Line is undefined
When all vertices are entered, right-click and select Done, or press Enter with nothing in the prompt line.
You will now see the Assign Piezo Line dialog. Select the checkbox for each material for which pore pressure is to be calculated using the Piezo Line. NOTE:
A Piezo Line can also be assigned to materials using the Define Material Properties dialog. The Assign Piezo Line dialog is simply a shortcut, which allows you to quickly assign a Piezo Line to all desired materials at once.
For more information about the Assign Piezo Line dialog, see the Assign Water Surfaces topic.
When you are finished with the Assign Piezo Line dialog, select OK.
The Piezometric Line will appear on the model as a blue line, with an automatically assigned ID number (see below for details).
Piezometric Line ID Number
Piezometric Lines are automatically given an ID number, which will appear at the mid-point of the first and last segments of the Piezometric Line. This ID number is used to identify Piezometric Lines with the corresponding soil region(s) of the model, in the Define Materials dialog. The Piezometric Line ID numbers range from 1 to 20, and are assigned in order, according to how many Piezometric Lines are already defined. A maximum of 20 Piezometric Lines can be defined for a model.
Pore Pressure Calculation
Pore pressure calculation for a Piezo Line is exactly the same as for a Water Table. For details, see the Water Parameters topic.
Piezometric Lines vs. the Water Table
For the purposes of pore pressure calculation, a Piezometric Line and a Water Table are interchangeable in Slide. However, the Water Table has a number of additional features which are not available when using a Piezo Line. See the Add Water Table topic for the differences between using a Water Table or a Piezometric Line in Slide.