On the Groundwater page of the Project Settings dialog, the following advanced groundwater options can be enabled:
Excess Pore Pressure
To enable one of the advanced groundwater options, select the Advanced checkbox and choose an option. Only ONE option can be selected, it is not possible to run more than one advanced groundwater option simultaneously. The advanced groundwater options are summarized below.
The Transient Groundwater option allows you to carry out transient (time dependent) finite element groundwater seepage analysis. You can define multiple stages at different times with changing groundwater boundary conditions at each stage. To carry out a transient groundwater analysis:
Select the Transient Groundwater option on the Groundwater page of Project Settings.
Select the Transient page in Project Settings, and define the number of stages and times. See the Transient Groundwater topic for details.
You will then be able to define groundwater boundary conditions at each time stage, and carry out a slope stability analysis at any or all stages.
See the Slide Tutorials for detailed tutorials describing how to set up a transient groundwater model.
NOTE: with Transient Groundwater analysis you may choose any Groundwater Method to define the initial pore pressure distribution (e.g. Water Table, Water Pressure Grid, Steady State FEA). You do not necessarily have to use Steady State FEA to define the initial conditions for Transient groundwater analysis.
Excess Pore Pressure
The Excess Pore Pressure option allows you to use the B-bar method to calculate excess pore pressure due to undrained loading. The B-bar method allows you to account for sudden increases in pore pressure due to rapidly applied loading conditions. These loading conditions may include:
added material weight
vertical seismic loading
vertical external loading
When you select the Excess Pore Pressure option, you will be able to define B-bar coefficients for materials in the Define Material Properties dialog. Excess pore pressure is equal to the B-bar coefficient multiplied by the change in vertical stress. The change in vertical stress can be due to any of the above loading conditions. See the Excess Pore Pressure topic for more information.
NOTE: with Excess Pore Pressure analysis you may choose any Groundwater Method to define the initial pore pressure distribution (e.g. Water Table, Water Pressure Grid, Steady State FEA).
Rapid Drawdown Analysis
The Rapid Drawdown option allows you to analyze the stability of earth dams under rapid drawdown conditions, using one of four methods:
Duncan, Wright, Wong, 3 stage (1990)
Army Corps of Engineers, 2 stage (1970)
Lowe and Karafiath (1960)
Effective Stress using B-bar
For all methods, an initial water level is specified by defining a Water Table. A second water table defining the drawdown level can also be specified, or you can assume complete drawdown. The pore pressure is then calculated according to the drawdown method, and the safety factor for rapid drawdown conditions is calculated. For tutorials which demonstrate these options, see the Slide Tutorials page.
NOTE: with Rapid Drawdown analysis you must choose Groundwater Method = Water Surfaces, because the initial and final water elevation must be defined using a Water Table. You cannot use the Rapid Drawdown methods with any other Groundwater Method in Slide (e.g. Ru Coefficient, Water Pressure Grid, Steady State FEA).