Overview of ATC Williams Numerical Modelling Expertise

ATC Williams is a leader in developing and applying numerical modelling techniques to simulate the behaviour of tailings, soil and rock materials to predict the response of geo-structures such as tailings and water-retaining structures to various types of loading and groundwater conditions.

– Groundwater Modelling (MODFLOW-USG)


The behaviour of geomaterials is modelled in two ways. The first is as a continuum by implementing material constitutive models and/or fluid flow equations commonly incorporated, in finite element and finite difference based software programs such as FLAC, Abaqus, Modflw USG, Plaxis and RS2. The second method is modelling materials as discrete bodies by implementing the laws of motion at particle-particle contact levels in discrete element software programs such as PFC (Itasca Group).

Outcomes from these analyses predict the deformation or movement of complex geo-structures, assess pore water pressure and stress states, predict groundwater flow, and determine Factors of Safety (FoS) and failure mechanisms.

Our numerical modelling team consists of a highly experienced and specialised group of engineers with postgraduate degrees with select specialty areas and skill sets.

– Numerical Testing of Rockfill (PFC)



ATC Williams has provided advanced numerical solutions for analysing and designing geotechnical structures and groundwater modelling for over two decades. Our expertise is founded on the successful application of various numerical analysis techniques, including finite element, finite difference, finite layer, finite strain, and discrete element methods, to challenging geotechnical and civil engineering problems.

Over the last twenty years, we have been involved in a diverse portfolio of local and global projects. We are committed to advancing the practice of numerical modelling and have contributed to numerous technical publications, lectures, and presentations.

– Earthquake Induced Deformation (FLAC)



The primary scope of our numerical modelling team is to provide a tailored set of services to cover all aspects of numerical modelling, from obtaining model input parameters via field and laboratory investigations and basic studies to performing advanced static and dynamic analyses and interpretation of the results.

Our ever-expanding capabilities include:

Field and Laboratory Investigation and Model Calibration

  • Field testing for determination and calibration of model input parameters.
  • Advanced laboratory testing framework (static and dynamic) for determining constitutive model parameters.
  • Calibration of constitutive model parameters using laboratory test results and single element (numerical) analyses.

ATC Williams utilises the experts of its in-house NATA accredited laboratory to tailor specialised test programs to support its numerical modelling team. Our engineers use an iterative process to calibrate numerical models against observed site conditions to refine the input parameters and maximise the accuracy of the assessment.

– Liquefaction and Deformation Analysis (FLAC, ABAQUS)


Advanced Numerical Analyses

  • Saturated and unsaturated seepage analyses
  • Hydrogeological and contaminant transport modelling
  • Advanced liquefaction constitutive models, the critical state framework, and bounding surface analyses of geo-structures
  • Simulating coupled and uncoupled staged construction of geo-structures
  • Assessment of static liquefaction triggering mechanisms such as construction, excavation and ground water fluctuations
  • Capture embankment static deformations:
    • Short-term static (during construction and staged filling)
    • Long-term static (consolidation, creep deformation)
    • Small-strain and large-strain deformations
  • Non-linear dynamic simulations under various and complex seismic loadings and determining the post-seismic deformation and stability of structures
  • Seismic liquefaction assessment of tailings, embankments, and foundation materials
  • Tailings large-strain consolidation and evaporative drying (vadose zone) modelling
  • Large-scale numerical strength testing (triaxial, simple shear, etc.) for rockfill materials using the Discrete Element Method (PFC 2D/3D software) instead of physical laboratory testing, which is considered scarce, time-consuming, expensive, and requires a significant amount of materials
  • 3D numerical analyses where the boundary effects should be carefully considered (e.g. excavations, natural/fill slopes)
  • Slope stability analyses using strength reduction and limit state techniques


Our in-house services can be engaged at any point, from the geotechnical investigation to the detailed design stage, to provide numerical solutions to assess and enhance the design or cost of structures.

Our advantages include:

  • Our in-house NATA accredited laboratory can determine and properly evaluate soil and tailings behaviour under different conditions
    Details on our laboratory capabilities are featured in the related article here.
  • Extensive knowledge and application of constitutive models, the critical state framework, and associated parameters (more details here)
  • Proper interpretation and review of numerical simulation results by our numerical modelling team
  • Our in-house hydrogeology team can determine the groundwater and environmental impacts of tailings storage facilities, waste rock dumps and water-retaining dams
  • Our in-house seismology team can provide site-specific seismic hazard analyses and establish design earthquake and ground motion parameters
  • We actively engage in research and development with leading universities to enhance our numerical modelling capabilities. ATC Williams has a track record of supporting successful PhD students with current research projects evaluating the mechanical behaviour of rockfill materials using the discrete element method.

– Factor of Safety Calculation (FLAC)


ATC Williams has formed a strategical group of numerical modelling experts available to address the most complex geotechnical problems that cannot typically be solved using conventional methods. Our numerical modelling team have developed specialised computer codes, techniques, and processes capable of simulating sophisticated problems.

The key members of our numerical modelling team are:

Dr Behrooz Ghahreman-Nejad
is ATC Williams Chief Technical Officer and the team director with over 28 years of experience on a broad scope of projects in the civil, geotechnical, and mining engineering fields. His expertise encompasses the application of a comprehensive range of experimental (physical) and theoretical (numerical) modelling techniques in geomechanics.

Freeternity Rusinga
is a Senior Associate Engineer with over 19 years of experience in hydrogeology and surface water hydrology and leads the groundwater modelling team.

ATC Williams hydrogeology modelling is supported by Dr Gideon Steyl and Jeremy Haynes, Principal Hydrogeologists with extensive experience in the mining, energy, transportation, manufacturing and waste management industries.

Meri Sadeghipour is an Associate Engineer with a bachelor’s degree in civil engineering and a master’s in geotechnical engineering with over 14 years of experience in the design of oil, gas, and mining projects. She has extensive experience undertaking advanced numerical analyses for large dams under different loading conditions using FLAC and ABAQUS software programs.

Dr Michael Munro
, Senior Associate, has extensive experience working on projects that focus on the civil and geotechnical design aspects of tailings storage facilities. Michael’s pertinent expertise includes advanced seismic numerical modelling, material characterisation and constitutive model calibration through advanced laboratory testing, as detailed further in this article.

Dr Mahdi Naeini
is a Senior Engineer with significant practical and research experience in geotechnical engineering, focusing on the dynamic behaviour of soils and tailings using numerical simulation and laboratory testing. He has several publications in peer-reviewed journals.

Dr Yuqi Tan
is a Senior Engineer with ten years of experience in tunnelling and dams. Yuqi has completed his bachelor’s and master’s degrees in mining engineering and his PhD in geotechnical engineering.

Dr Mojtaba Karami
is a Senior Engineer with over twelve years of experience in geotechnical engineering of tailings and water-retaining dams with extensive experience undertaking advanced numerical analyses of geo-structures under both static and seismic loading conditions.

Please contact the ATC Williams head office on (03) 8587 0900 or email us to discuss how we can assist you with your numerical modelling or laboratory testing requirements.