Pavement-Design Package in PFC

The pavement-design package (Potyondy, 2019) for the Particle Flow Code in 3 Dimensions (PFC3D) supports creation and triaxial testing of a synthetic unsaturated granular material containing geogrid.* The geogrid provides lateral restraint to the granular material as a result of interlocking and friction between the geogrid and the granular material, and this is believed to be the primary structural benefit of adding geogrid to the aggregate base layer of a pavement structure. The package can be used to study and quantify the effect of microstructural properties on macroscopic response, which includes the stress-strain curves produced during triaxial tests. The microstructural properties of the granular material include: grain size distribution of spherical or clumped grains, grain material type, moisture content and initial specimen porosity. The microstructural properties of the geogrid include: geometry, structural stiffness and grid-grain interface behavior. The package is being used to improve pavement-design methodology in Minnesota by estimating geogrid gain factors (defined as the ratio of resilient modulus of the aggregate base with geogrid to resilient modulus of the aggregate base without geogrid) for typical geogrid-reinforced aggregate roadway configurations in which the grain-size distribution, initial specimen porosity, moisture content and confining stress are varied (Potyondy et al., 2016; Siekmeier et al., 2016; Siekmeier and Casanova, 2016). The package could be extended to investigate the behavior of other aggregate-geogrid systems such as a geogrid pull-out or wheel-load test.

* [The pavement-design package is provided in the form of a consistent set of FISH functions that operate within PFC3D version 6.0. FISH is a programming language embedded within PFC3D. The PFC3D code can be obtained from {}, and the pavement-design package is provided below --- you must be signed in to see the file.] For the PFC3D 5.0 pavement design package, visit


Potyondy, D. (2019) "Pavement-Design Package for PFC3D [pdPkg6.1]," Itasca Consulting Group, Inc., Technical Memorandum ICG16-8528-15TM (April 17, 2019), Minneapolis, Minnesota. DOWNLOAD LINK

The additional references cited above are defined in the references section of the pavement-design package memo, and the documents themselves are provided in the pdPkgN/Documentation directory.


pdPkg6.1 (ZIP, 216 MB)
PavementDesignPkg[pdPkg6.1].pdf (24 MB)

Pavement-Design Package Software Update Revisions

pdPkg Release fistPkg Release PFC3D RELEASE Date / Description
6.1 6.5 6.00.12


Release of pdPkg for PFC3D 6.0. The package for PFC3D 5.0 uses the naming convention pdPkgM, where M is the package version number. The package for PFC3D 6.0 uses the naming convention pdPkg6.N, where N is the package version number. The syntax of commands and FISH items has been modified to be compatible with PFC3D 6.0. The package is ready for use. pdPkg6.1provides the same capabilities as pdPkg15, with the following exception.

The example project MatGen-HillGrid_C5Q is not included. This is the realistic example in the pdPkg memo. A better realistic example is provided by the example project MatGen-HillGrid_5Q of a typical roadway model (see ModelValidationTests.pdf).

15 26 5.00.39


Complete final pdPkg for PFC3D version 5. This package will be ported to operate with PFC3D version 6. Add magazine article (Siekmeier&Bittmann(2019)-MN_UseOfGrid.pdf) to Documentation directory. This article describes the work that has been recognized by the University of Minnesota Center for Transportation Studies 2018 Research Partnership Award to Geogrid Reinforced Aggregate Base Pavement Design.

Add report (Siekmeier(2018)-GeogridAggBase.pdf) to Documentation directory. This report utilizes the pavement-design package to provide a performance specification consisting of DCP and LWD target values for geogrid reinforced aggregate base.

14 25 5.00.35


Provide report (PFC_PavementDesign-Phase2.pdf) and associated documents in Documentation directory. This report summarizes the work for the MnDOT project "Geogrid Specification for Aggregate Base Reinforcement." The pdPkg14 is the deliverable of the project.

13 25 5.00.32


The package has been provided to John Siekmeier of MnDOT as a deliverable for the project "Geogrid Specification for Aggregate Base Reinforcement." The work is summarized as follows, with documentation listed in square brackets after each item --- see REFERENCES section below for abbreviations.

  1. Extend the geogrid representation to allow different geogrid types to be modeled. Create beam contact model, and verify that a string of spherical balls joined by beamed contacts provides the behavior of a structural beam of rectangular cross section with properties of Young's modulus and Poisson's ratio. Enhance geogrid representation via beamed grids, add ability to create triaxial beamed grids, and determine grid properties to match Tensar SS20 Single Rib Tensile (SRT) and Aperture Stability Modulus (ASM) grid tests. [pdPkg & BCM]
  2. Add Multiple Aperture Tensile (MAT) grid test. [pdPkg]
  3. Enhance hill material to include general grain shapes via clumped grains. [fistPkg, example of use in MV]
  4. Add typical roadway model, used to map out the modulus-porosity-grid-grain shape relationship. [MV]
  5. Add Dynamic Cone Penetrometer (DCP) and Light Weight Deflectometer (LWD) probes. [MV]
  6. Did not investigate ideas to improve material genesis. Did not investigate behavior during large-strain triaxial tests; however, PFC3D modeling of railway ballast by Mahmud (2017) suggests that matching the triaxial shear strength (maximum deviator stress that can be sustained by the material) requires polyhedral grains, because clumps are not sufficiently angular. It is not yet known if resilient modulus can be matched by clumps or polyhedral grains.


Mahmud, S.M.N. (2017) "Effect of Particle Size Distribution and Packing Characteristics on Railroad Ballast Shear Strength: A Numerical Study Using the Discrete Element Method," M.S. Thesis, Boise State University [advisor: Deb Mishra].

REFERENCES (in Documentation directory)

[fistPkg] Potyondy, D. (2017) “Material-Modeling Support in PFC [fistPkg25],” Itasca Consulting Group, Inc., Technical Memorandum ICG7766-L (March 16, 2017), Minneapolis, MN.

[pdPkg] Potyondy, D. (2018) “Pavement-Design Package for PFC3D [pdPkg13],” Itasca Consulting Group, Inc., Technical Memorandum ICG16-8528-15TM (March 9, 2018), Minneapolis, MN.

[BCM] Potyondy, D. (2018) “Beam Contact Model [version 1],” Itasca Consulting Group, Inc., Technical Memorandum 2-3558-01:17TM07 (March 9, 2018), Minneapolis, MN.

[MV] Potyondy, D. (2018a) "Model-Validation Tests," Itasca Consulting Group, Inc., Technical Memorandum 2-3558-01:17TM52 (March 9, 2018), Minneapolis, MN.


  1. Add memo ModelValidationTests.
  2. Add typical roadway model (see ModelValidationTests).
  3. Fix minor typoes in pdPkgMemo.
  4. Move grid tests to ExampleProjects\GridTests.
  5. Add Multiple Aperture Tensile (MAT) test to \GridTests.
  6. Rename grid-set parameters (grid-grain => grid-surface):
    • gd_ggemod => gd_gsemod
    • gd_ggkrat => gd_gskrat
    • gd_ggfric => gd_gsfric
  7. Add capability to perform resilient-modulus tests, and to perform DCP and LWD probes to ExampleProjects\MG-HillGrid.
  8. Provide additional Documentation items (see pdPkg-Documentation.pdf in Documentation directory).
12 25 5.00.30



  1. Create PFC3D beam contact model (see Potyondy [2017a] for model description and verification problem). The beam contact model matches the response (within 3%) of a tip-loaded cantilever beam subjected to axial, flexural and twisting deformations. The model is provided as a DLL that must be installed when installing the pdPkg.
  2. Enhance grid generation to provide biaxial and triaxial beamed grids in addition to existing biaxial parallel-bonded grids. The biaxial beamed grid has been calibrated to match SRT and ASM tests on Tensar SS20 geogrid. The triaxial beamed grid has been calibrated to match SRT and ASM tests on Tensar TX160 geogrid. The grids are symmetric --- i.e., there is no differentiation between TD and LD directions.
  3. Demonstrate that there are two offset curves of resilient modulus versus porosity for grid and no-grid models, with the grid curve lying above the no-grid curve. The effect of the grid on material stiffness is found by comparing the resilient moduli for the grid and no-grid cases at the same material porosity. This behavior is described at the end of the realistic pavement design example (see Figure 41).
  4. Use updated PFC3D executable (5.00.30) and fistPkg25.
  5. Clumped grains can be generated for both no-grid and grid models. For the no-grid case (in file MatGen.p3dvr), replace the call to mpParams-AG.p3dat, with a call to mpParams-AG_clumped.p3dat. For the grid case (in file MatGenGrid.p3dvr), replace the call to mpParams-AG_grid.p3dat, with a call to mpParams-AG_grid_clumped.p3dat.

Potyondy, D. (2017a) "Beam Contact Model [version 1]," Itasca Consulting Group, Inc., Minneapolis, MN, Technical Memorandum 2-3558-01:17TM07 (April 6, 2017).

Potyondy, D. (2017b) "Pavement-Design Package for PFC3D [pdPkg12]," Itasca Consulting Group, Inc., Minneapolis, MN, Technical Memorandum ICG16-8528-15TM (April 6, 2017).

11 24 5.00.27



  1. Pavement-Design Package [pdPkg10] made available to general public by posting to Itasca web page {} on Sep09_2016.
  2. Added citation of, and inclusion of, MnDOT pdPkg report {Siekmeier&Casanova(2016)-pdPkg.pdf}. Also add the technical summary of this report {MnDOT_TS(2016)-GeogridsIncrBaseStiff.pdf}.
  3. Fix bug that occurred when adding a grid to a cylindrical or spherical vessel. The bug caused the code to stop execution with an error message after generating the grains.
  4. Use updated PFC3D executable (5.00.27), and updated fistPkg (24).
10 23 5.00.24



  1. Use updated fistPkg (23).
  2. Rename master project directories to remove the "my" designators.
  3. Complete the realistic example in the pdPkg memo.

The first column of this table lists the Pavement-Design Package revision number; the second and third columns list the PFC 6.0 FISHTank and PFC3D 6.0 release, respectively, against which the Pavement-Design Package has been tested; and the fourth column describes the Pavement-Design Package revision. Note that each revision of the Pavement-Design Package is expected to operate with a PFC 6.0 FISHTank and PFC3D 6.0 release that is current or newer than that listed. Since newer revisions of the Pavement-Design Package may use features available only in newer revisions of the supporting software, they may not be compatible with older revisions of the supporting software.

Latest News
  • 3DEC 7 is officially released! Enhanced user interface with new automated block and zone generation tools, and new structural elements....
    Read More
  • Open Pit Dewatering: Dewater, Derisk, Deliver Learn more about developing an effective strategy for open pit dewatering and avoiding common pitfalls...
    Read More
  • Tutorial Series: Analyzing a Homogeneous Embankment Dam using FLAC 8.1 This is a three part tutorial series to calculate the total and effective stresses and...
    Read More

Upcoming Events
21 Sep
71st Highway Geology Symposium
Better highways through applied geology... Read More
12 Oct
CANCELED -- Focused Seismic and Liquefaction Training 2020
... Read More
18 Oct
Geothermal Resources Council Annual Meeting & Expo
Advancing the global geothermal industry through transfer of robust research, knowledge and guidance.... Read More