Groundwater

On the Groundwater page of the Project Settings dialog, you can choose the Groundwater Method used to model groundwater conditions. The following options are available:

• None
• Phreatic Surfaces
• Steady State (finite element analysis)
• Transient (finite element analysis)

Phreatic Surfaces

If the Groundwater Method = Phreatic Surfaces then RS3 will allow you to model a phreatic surface or water table. The phreatic surface or water table can be defined using water surfaces, pore water pressure points sets, and hydraulic parameters.

See the Phreatic Surfaces topic for more information.

Negative Pore Pressure Cutoff

For static method, if the pore water pressure at any nodes of the model is less (more negative) than the Maximum Cutoff Value then the pore pressure at those nodes will be limited to the cutoff value. For steady and transient analysis, the suction that used in calculation of effective stress will be limited at the value. The pore pressure is not limited. The Negative Pore Pressure Cutoff is important for models where matric suction (negative pore pressure) above the water table is high (negative), which can lead to unrealistic increases in strength particularly for slope models.

Steady State (Finite Element Analysis)

If the Groundwater Method = Steady State then RS3 will allow you to model a steady-state finite element seepage analysis to determine the pore pressure distribution, based on the groundwater boundary conditions which you define for your model.

• The hydraulic boundary conditions are defined with the Add Groundwater Boundary Conditions option in the Groundwater menu.
• The hydraulic material properties are defined with the Define Hydraulic Properties option.

The seepage analysis can be used in conjunction with the stress analysis capability of RS3, or you may use the seepage analysis as a standalone groundwater analysis option, without necessarily computing a stress analysis.

See the Steady State Groundwater topic for more information.

Transient (Finite Element Analysis)

If the Groundwater Method = Transient then RS3 will allow you to model a transient finite element seepage analysis.

The input required for a Transient seepage analysis is the same as a Steady State analysis, with some additional parameters required to define Transient time staging, boundary conditions and material parameters.

See the Transient Groundwater topic for more information.

DEFINE INITIAL PWP METHOD BY STAGE

If this checkbox is selected, then you can define the initial pore water pressure at any stage, using any of the available groundwater methods (phreatic surfaces, steady state, or transient) on the Stages page of the Project Settings dialog.

ADVANCED GROUNDWATER OPTIONS

For Steady State or Transient groundwater, the following advanced analysis options can be customized by selecting the Advanced button.

Tolerance

The Tolerance represents the convergence criterion for the finite element seepage analysis. The solution is considered acceptable, when the difference in hydraulic head between iterations, at all nodes of the mesh, is less than the Tolerance.

Maximum Number of Iterations

The Maximum Number of Iterations allowed for the finite element seepage analysis. If the Tolerance is not achieved within the Maximum Number of Iterations, then the analysis will be terminated at the Maximum Number of Iterations.

Pore Fluid Unit Weight

The Pore Fluid Unit Weight is used for the calculation of pore pressure if the Groundwater Method is set to one of the following options:

• Phreatic Surfaces,
• Steady State,
• or Transient

The default value of the Pore Fluid Unit Weight is determined by the Units selected under the Units tab in Project Settings. The default value may be changed as required.