Groundwater
There are three groundwater analysis options in Settle3. You can define the water level using either of the following two options:
Alternatively, with the Pore Water Pressure Function option, you can define pore water pressures with depth.
Under the Groundwater tab in the Project Settings dialog, you can include the effect of pore pressure in the consolidation analysis, by selecting the Groundwater Analysis checkbox.
- This allows you to define one or more piezometric lines, one or more groundwater grids, or one or more pore water pressure profiles.
- If your model is multi-stage, then you can specify the depth of the water table, assign a water grid, or define a new pore water pressure function at each stage (i.e. you can raise or lower the water table).
- You can assign different, staged, piezometric lines, water grids, or pore water pressure functions to different materials.
When the Groundwater Analysis checkbox is selected, this enables all other groundwater modelling options in Settle3. For an overview of groundwater modelling options in Settle3, see the Groundwater Overview topic.
- If you are modelling a time-dependent consolidation analysis, then you MUST select the Groundwater Analysis checkbox, because the modelling of pore pressure is essential for the time-dependent consolidation analysis (i.e. you must define the groundwater conditions, this is NOT optional).
- If you are NOT modelling time-dependent consolidation, then you do not necessarily have to define groundwater (e.g. if you are only interested in immediate settlement or long-term consolidation).
- In order to carry out a liquefaction analysis, you MUST select the Groundwater Analysis checkbox, since the modelling of pore pressure is necessary in order to carry out a liquefaction analysis. Liquefaction analyses can be done with either the Piezo Lines or Grid options.
Water Unit Weight
The water unit weight is used to calculate the initial pore pressure. The initial pore pressure at any point below the water table is equal to the water unit weight multiplied by the vertical distance to the water table.
Generate Excess Pore Pressure above Water Table
By default, the soil is assumed to be dry above the water table, so an applied load does not generate excess pore pressure above the water table.
If you want the soil to behave as if it were saturated above the water table, then you can select the Generate excess pore pressures above water table checkbox. If this checkbox is selected, applied loads will generate excess pore pressure above the water table, as if the material were saturated with B-bar = 1.
This option does NOT affect initial pore pressure calculations, only the calculation of excess pore pressure above the water table. Initial pore pressure above the water table is ALWAYS zero, regardless of the setting of this option.