Hydrogeological modeling improvements


Source: SoilVision Systems Ltd.

SoilVision Systems Ltd. is pleased to announce the addition of regional flow modeling capabilities to SVFlux as well as our other bundled 3D products. SoilVision Systems Ltd. has worked with a number of hydrogeologists in order to enhance the abilities of our SVFlux, ChemFlux, and SVHeat software to model regional groundwater scenarios. Traditionally, such models have been created through the use of finite difference legacy codes. Such codes have received widespread use for groundwater models. Even though these finite difference codes are common, the use of the finite element method offers a number of advantages when solving specific cases involving regional modeling. Advantages include:

  • Finite element code allows modeling of more complex geometries and boundaries than with their finite difference counterparts
  • Significantly greater control over mesh
  • Handling of pinch-out zones
  • Sub-division of elements vertically within layers is possible

Our 3D software makes use of tetrahedral elements which are generated in a true and comprehensive 3D manner. The use of tetrahedral elements allows elements to be wedged into pinch out zones to allow more complex numerical models to be generated. The mesh is also not extruded in the 3D zone as in some other software. This advantage means that soil layers can be represented with multiple layers of mesh which has the potential to significantly improve the accuracy of calculated flows. Automatic mesh refinement is also fully enabled in 3D applications. This means that the tetrahedral elements can refine themselves in any direction based on the required accuracy levels for the model. This has the possibility to significantly reduce convergence problems as it becomes easily apparent to the user which zones of the model may require additional mesh density. Mesh refinement within any model can be triggered by any model variable. Manual controls over the mesh density also allow significant user control over the mesh.

Several years ago, SoilVision decided to put research effort into enhancing the ability of SVFlux for handling complex 3D regional groundwater models. The basic mesh generation of the software and mesh refinement allowed it greater potential for modeling than any other package currently available. Our company has since collaborated with a number of consulting firms and hydrogeologists in order to enhance the ability of the software to handle these types of scenarios. This close collaboration with industry has resulted in many improvements to the software. Specifically the following improvements to the software are relevant to regional numerical modeling:

  • PEST analysis
  • Rigorous climatic coupling for recharge calculation
  • Innovative representation of wells, tunnels, and rivers
  • Import of ESRI shape files and AutoCAD files
  • GIS compatibility
  • Unsaturated flow
  • Fully automatic 3D tetrahedral mesh generation
  • Fully automatic mesh refinement
  • Database of over 6200 unsaturated hydraulic properties
  • Piezometer calibration statistics
  • Advanced coupling (ChemFlux, SVFlux, SVAirFlow, SVSlope)

These additional features compliment the already powerful mesh generation, automatic mesh refinement and coupled climatic analysis which have made the software popular. The software package allows new tools for the analysis of complex models and situations never before possible.

The PEST integration was implemented as a result of close collaboration with John Doherty and work continues with setting up additional example models which make use of the PEST interface.

Significant work was performed in the implementation of well, tunnel, and river objects. The river objects allow an unlimited number of rivers to be specified in a numerical model. The rivers act like surface boundary conditions on the numerical model. The difficulty with wells and tunnels is that there are often steep gradients next to such a model feature. This results in steep gradients for which additional mesh density is often required. Even though our software supports automatic mesh refinement the steep gradients can still create difficulties in certain numerical models. Therefore a new approach was taken which makes the implementation of wells and tunnel objects more stable in the majority of numerical modeling scenarios. The result is increased accuracy in the modeling of wells and tunnels.

The tunnels feature is particularly useful in modeling of mine shafts for which a pumping dewatering scenario needs to be designed. Any number of arbitrary “tunnels” can be placed in the numerical model. Such tunnels can cross any number of geo-strata definitions. Standard head, flux, or review-by-pressure boundary conditions can be placed on such internal boundaries and the resulting flows in or out of such tunnel structures can be computed.

The software also implements true and rigorous unsaturated flow through a number of nonlinear soil water characteristic curves such as van Genuchten, Fredlund & Xing, Brooks & Corey, and others. Inclusion of the SoilVision software also provides access to an extensive database of hydraulic unsaturated soil properties on over 6200 soils.

The coupling of additional processes to the groundwater flow process is simple in the SVOffice software. Additional processes are each handled through a separate view of the same numerical model. For example, all thermal properties would be assigned to the numerical model through the SVHeat package. There is no need to duplicate geometry in a coupled package and the user may switch between processes (i.e., SVFlux, ChemFlux, SVHeat, SVAirFlow, or SVSlope) dynamically during building of the model. This design allows the user to create coupled numerical models which remain simple to set up. The user will not be overwhelmed with multiple inputs from different processes but can focus on inputs such as material properties or boundary conditions from a single process at a time.

The additions to the software make it ideal for applications in the following areas:

  • Calculation of pumping rates for mine shaft dewatering scenarios
  • Evaluation of groundwater remediation systems
  • Evaluation of soil-vapour extraction systems
  • Simulate natural attenuation of contaminated groundwater
  • Predict salt-water intrusion from over-pumping in coastal regions
  • Detailed and rigorous calculation of recharge rates through the unsaturated zone
  • Determine contaminant fate and exposure pathways for risk assessment
  • Delineate well capture zones for municipal drinking water supplies

Our company continues to have interest in working collaboratively with hydrogeology firms. If your firm is interested in increasing their numerical modeling capabilities please contact us here. Complimentary trial versions of SVFlux 3D will be provided to collaborating firms.

SoilVision is a registered trademark of SoilVision Systems Ltd.

SVSlope is a registered trademark of SoilVision Systems Ltd.

About SoilVision Systems Ltd.

SoilVision Systems Ltd. was formed in 1997 by Murray Fredlund, PhD, PEng to provide high level, software tools to meet the needs of geo-professionals attempting to model the behavior of complex saturated and unsaturated soil systems.

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