FLAC3D is an analysis package developed by Itasca Consulting Group, Inc. This software utilizes explicit finite difference formulation to simulate a multitude of geotechnical problems in the geotechnical, civil and mining industries.

The UCSD soil models UCSDSAND3BETA and UCSDCLAY have been integrated into FLAC3D as user-defined constitutive models (UDM). These material models are capable of simulating the essential dynamic response characteristics of cohesionless and cohesive soils respectively. Additional references can be found here.

Example of 1D site response analysis which utilizes the demo versions (demo versions are specific for 1D site response analysis) of the soil models is provided below (for illustration purposes). For 3D full version of the soil models, please contact Prof. Ahmed Elgamal (E-mail: elgamal AT ucsd DOT edu).

1D Seismic Site Response Examples

(UCSDSAND3BETA sand model demo version for FLAC3D ver. 5.01 32-bit: modelucsdsand3demo005.dll; please upload this .dll file to the "models" folder under the FLAC3D installation folder "\Itasca\Flac3d500\Exe32\plugins\models")

Example 1

Example 1 is a 10-m deep saturated medium sand soil stratum subjected to base shaking (El Centro motion).

Example 2

Example 2 is a 10-m deep saturated medium sand soil stratum subjected to base shaking (scaled Rinadi motion).

Example 3

Please follow the steps below to download, install, and run the FLAC3D example. For additional information, please reference the user manual.

Step 1: Download and Installation

    1) If you do not have FLAC3D 5.01 installed, please visit to download a 32-bit installation file. A demo version is available which allows UDM. This installation may require a restart.

    2) Download FLAC3D_Example.rar (10 MB, updated 9/13/2017)

    3) Unzip all files in the FLAC3D_example.rar to a desired location. The zip file includes the material models (modelucsdclaydemo005.dll, modelucsdsand3demo005.dll), and an excel sheet interface (1D_Seismic_Site_Response_Example.xlsm).

    4) Please move files modelucsdclaydemo005.dll and modelucsdsand3demo005.dll (contained in the above Example file) to the "models" folder which can be found in the FLAC3D installation folder "\Itasca\Flac3d500\Exe32\plugins\models".

    5) Update FLAC_location.txt with the location of the FLAC3D installation.

Step 2: Run 1D_Seismic_Site_Response_Example

    1) Open 1D_Seismic_Site_Response_Example.xlsm. If prompted please enable macros. This Excel sheet makes use of macros to generate input files for FLAC3D and run the analysis.

    2) Update the material and analysis parameters shown on the Excel sheet and then click "Create Input and Run" to start the analysis in FLAC3D.

    3) "View Results" can be used to load the output for previously completed runs.

Model Performance

Below are some sample responses using the UCSD soil models. Click images to see full sized versions.

UCSDSAND3BETA - Saturated:
Soil Column Model in FLAC3D
Pore Pressure Time History
Shear Stress vs. Shear Strain
Shear Stress vs. Confinement

Soil Column Model in FLAC3D
Shear Stress vs. Shear Strain

Soil Column Model in FLAC3D
Shear Stress vs. Shear Strain


For information on how to use the soil models UCSDSAND3BETA and UCSDCLAY in FLAC3D, please click here.