Numerical Modelling

OHMS has the capability to perform numerical modelling at any point in a mine’s life cycle or project study phase for open cast or underground mines.

Geological structures, anisotropy, heterogeneous rock masses, stress models, excavation geometries, constitutive behaviour, backfill and support elements can be incorporated in the assessments.

The numerical methods that is employed by the OHMS Modelling Division include finite element, boundary element (displacement discontinuity or fictitious force methods), and discrete element.

The numerical modelling packages and methods, which we use are based on the (i) finite element, (ii) boundary element (displacement discontinuity/fictitious force), (iii) discrete element, (iv) limit equilibrium, (iv) keyblock , (v) Monte-Carlo simulations, (vi) Point Estimate (vii) Rigid Body Fall Dynamic methods and codes, respectively.

The specific software packages include:
  • Map3D
  • Slide
  • RS2/Phase2
  • Unwedge
  • Dips
  • GEM4D (interpretation)
  • Trajec3D

Expertise & Experience

The OHMS Modeling Division has the expertise and resources to perform stability analysis, probabilistic risk analysis and simulation of astress and strains around underground mine structures and surface excavations at any point in a mine’s life. Geologic structures, differing rock properties, unique stress states, rock strengths, excavation geometries, elastic and elasto-plastic materials, backfill, and support elements can be incorporated into the models that we build.

We have the capability to perform probability of failure calculations on support systems and strength factors using Monte-Carlo and other methods. Problems of a mine wide scale can be solved in a cost-effective manner.

Our experience base includes commodities such as gold, coal, platinum and chrome and mining methods such as tabular (scattered and longwall), open cast slopes and board-and-pillar.

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Numerical Modelling capabilities and experience

Routine modelling (on- and off-reef)

  • Derive rock engineering parameters for input into the panel rating system on a monthly and quarterly basis.

Shaft pillar design and anticipated pillar behaviour

  • Optimizing extraction sequence based on criteria such as induced strain, critical stress levels and seismicity (potency and ride) on structures.

Room-and-pillar stability

  • Optimizing extraction ratio and risk profiles and design pillar sizes.

Longwall stability and Scattered Mining simulations

  • Determine rock engineering parameters such as critical strength, ERR and APS that drive ground conditions and seismicity around mine workings.

Rock reinforcement

  • Simulate support elements such as liners, anchors and elongates

Slope stability

  • Determine the Critical Factor of Safety (Shear strength reduction method), extent of the failure surface and stability parameters such as shear strain bands & total displacement.

Joint behaviour

  • Simulate joints in mine workings.

Water migration

  • Assess water flow in open pits and defunct mine workings.

Multi-seam mining

  • Simulate effects of multi-reef (seam) mining on another.

Tunnel stability and squeezing

  • Assess parameters such as overstressing and RCF for support design, optimizing extraction sequences and positioning of critical abutments. Simulate alternative positions for siting planned excavations.

Business Plan Risk assessment using Probabilistic Methods

  • Determine the utility levels (probabilities of exceeding critical thresholds) of tunnels, on-reef excavations and geological structures on a mine-wide basis. The utility levels can be translated to risk for input in the rock engineering risk matrix which will be used for input in business plan and life-of-mine documents.

Remnant Modelling

  • Assessment of bracket pillar sizes vs. induced ride on structures around remnants. Optimizing of extraction sequences. Quantifying historic seismic hazard and anticipated seismic hazard using seismic data and modelling data.

Geological Structure stability

  • Modelling of ride and potency on structures to assess seismic risk given certain planned extraction options.

Seismic back analysis and hazard assessment

  • Back analysis of seismic events on structures using the seismic system and numerical modelling.

Monte-Carlo analysis, Point Estimate method and the Area of Overlap method

  • Determining Probability of failure of a specific support system, critical pillar strength.