Hydraulic Statistics Overview
In general, the majority of the features and functionality in Hydraulic Statistics are similar to Material Statistics. We recommend first reviewing the Material Statistics page and its features. This section will highlight the unique aspects of Hydraulic Statistics.
The hydraulic properties available to set as random variables are specific to groundwater analysis and are defined in Define Hydraulic Properties in the “Groundwater” tab. As such, the groundwater analysis method must be FEA steady state or transient stages must be ON and defined in order to define hydraulic properties. The dialog can be displayed by selecting the hydraulic option from the statistics menu.
The Hydraulic Statistics dialog allows you to do the following:
- Choose the hydraulic properties that you wish to define as Random Variables.
- Enter the statistical parameters of hydraulic property Random Variables.
- (Optional) - For advanced users, the Equate and Cross-Correlation options are also available.
- (Optional) - Define spatial variability for random variables.
The hydraulic properties that can be randomly varied are the following:
Common hydraulic properties:
- Saturated Permeability (Ks)
- K2/K1 ratio
- K1 angle
- Saturated Water Content (WC Sat) – Requires Transient Analysis
- Residual Water Content (WC Res) – Requires Transient Analysis
- Coefficient of Volume Compressibility (mv) – Requires Transient Analysis
Parameters specific to permeability models:
- Brooks and Corey Bubbling Pressure
- Brooks and Corey Pore Size Index
- Fredlund and Xing A Parameter
- Fredlund and Xing B Parameter
- Fredlund and Xing C Parameter
- Gardner a Parameter
- Gardner n Parameter
- Van Genuchten alpha Parameter
- Van Genuchten n Parameter
- Van Genuchten m Parameter
- All statistical-based data such as pore pressures for each sample and hydraulic query data are a component of the slope stability analysis. Computing the groundwater directly without slope stability will not yield any statistical-based results
- A significant amount of statistical hydraulic data are saved to files during and after computation. Deletion or movement of these files will likely cause unintended behavior/analysis results.
- Should any sample not converge to a solution during groundwater analysis, the result is not included in probability of failure and reliability calculations
Sensitivity
Similar to Material Statistics, Hydraulic Statistics can define parameters to use in a Sensitivity analysis.
Cross-Correlation
Similar to material statistics Cross-Correlation and Equate Materials, Hydraulic Statistics can correlate and equate hydraulic properties between materials. Hydraulic properties can correlate between other randomly varied hydraulic properties for any material including itself.
Spatial Variability
Similar to spatial variability for soil strength parameters, hydraulic parameters can also vary spatially. You can select which materials are spatial for hydraulics as well as their correlation lengths.
The following properties can be spatially varied:
- Saturated Permeability (Ks)
- Saturated Water Content (WC Sat) – Requires Transient Analysis
- Residual Water Content (WC Res) – Requires Transient Analysis
Note that setting a material as spatially variable in the hydraulics dialog means that all hydraulic properties cannot be random variables and must all be spatial. Due to these restrictions, any property that is not one of the aforementioned spatial properties will be removed and unable to add as a spatially random variable.
Each spatial sample data can be viewed in the property viewer similar to soil strength parameters.
Pore Pressure Viewer in Property Viewer
For each sample, the pore water pressure data can be viewed in the property viewer in interpreter. Similar to spatial data, you can change which sample you’re viewing to see the pore pressure data for the current stage. This option is available for both random and spatial inputs.
The only available unique groundwater data viewable in the property viewer (being saved for all transient stages and all samples) is the porewater pressure. For other parameters relevant to groundwater, the results can be saved as query points using the Hydraulics Query option.
- Pore pressure data can still be viewed in the property viewer even if the transient stage does not calculate FS.
- Sensitivity analysis data is not viewable in the property viewer
Hydraulic Statistics Tutorial
For an overview of Hydraulic Statistics and its features in Slide2 and a step-by-step tutorial example, see Tutorial 31 - Hydraulic Statistics.