Piezo Surface

A Piezo Surface in Slide3 is a type of Water Surface which might represent pore pressure in a confined aquifer for example. A Piezo Surface is created by setting the Water Type = Piezometric Surface, when you add a water surface using the Add Water Surface or Add Water by Location options.

A Piezometric Surface is used primarily for pore pressure calculation.

• Pore Pressure - if the Groundwater Method = Water Surfaces then you can assign a Piezometric Surface to calculate the pore pressure for a material. Pore pressure is proportional to the vertical distance from the piezo surface.

Piezometric Surface versus Water Table

For pore pressure calculation, a Piezometric Surface is identical to a Water Table. If you only require a Water Surface for pore pressure calculation then a Piezometric Surface and a Water Table are interchangeable.

However, a Piezometric Surface cannot be used for the following purposes:

• Ponded Water
• Saturated Unit Weight
• Strength Above Water Surface
• Rapid Drawdown
• Water in Tension Crack

For modelling, these options you must define a Water Table.

In general, a Water Table refers to a Phreatic Surface (e.g. a water table in an unconfined aquifer) which represents a surface of zero pore pressure within the material.

A Piezometric Surface could represent pore pressure in a confined aquifer. In such cases, a piezometric surface might have an elevation above the ground surface. In this case, you would NOT want Ponded Water created by the Piezo Surface. This is why a Piezo Surface in Slide3 does NOT generate Ponded Water.

Number of Piezometric Surfaces

There is no limit on the number of Piezometric Surfaces which can be defined in a Slide3 model.

This is in contrast to a Water Table - only ONE Water Table is allowed in a Slide3 model. If you require more than one Water Surface for modelling groundwater you will have to use Piezometric Surfaces