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FracMan Applications: Mining

Mining rock mechanics has long recognized the importance of faults and fractures in controlling mine stability. Despite this, continuum approaches which ignore discrete features effects are commonly used for a wide range of mining issues. Kriging is widely used in ore reserve estimation, and continuum flow models are used to provide pressures for rock wedge stability analysis. This inconsistency results in inaccurate analyses and less than optimal designs.

FracMan brings mining into the 21st century with a consistent set of geologically based discrete feature approaches for stability, ore reserve estimation, and hydrogeology. FracMan allows mining engineers to the use their extensive knowledge of mine structural geology to simultaneously improve mineral resource estimation and mine design.

The advantages of FracMan for mining applications include:

• Integrated discrete feature data analysis
• Leveraging of borehole structural data for stability, hydrology, and reserve estimation
• Ore reserve estimation for vein deposits reflecting the vein geometry
• Use of a single consistent discrete feature geological model for both stability and flow analysis

Golder Associates is a recognized world leader in geological, environmental, and engineering support to the mining industry. Golder Associates provides proven and state of the art technologies such as FracMan to mining clients worldwide.

FracMan applications in the mining industries include:

• Mineral Resource Estimation
• Geomechanics
• In Situ Leaching Design and Analysis
• Hazardous Waste Disposal and Remediation Technology
• Hydrologic and Solute Transport Testing and Design
• Geologic Investigation and Data Collection

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Mineral Resource Estimation

Ore reserve calculations for disseminated deposits can be treated effectively using continuum approaches such as Kriging, which produce a smoothed contour of mineral concentration. However, many minerals such as gold, silver, and copper occur in vein based deposits. For these deposits, the most accurate way to estimate reserves is through a 3D model of the geological structure of the veins which contain minerals.

FracMan/FracWorks directly models the geometry of fractures, faults, and other discrete features which contain minerals. For each feature, FracWorks can assign an ore grade and vein thickness, reflecting both the geology and the spatial structure of the deposit. FracOre then calculates the total ore contained in a specified mine layout.

The advantages of this approach are as follows:

• Vein structural geology use used directly for quantitative ore reserve calculations
• FracMan/FracWorks provides realistic 3D visualization of the vein geometry
• Both known veins and undiscovered veins can be considered through stochastic and conditional simulation
• Results can be compared directly with continuum assumptions based on Kriging and indicator Kriging

Geomechanics

The mechanical and hydrologic properties of fractured rock masses are controlled by interaction between stress, strain, and flow fractures and in rock pores. FracMan provides an integrated suite of rock mechanics tools which bring FracMan's accurate, realistic 3D structural models to mining.

FracMan discrete fracture models are used in mining for:

• Open pit slope stability analysis, using the same discrete features for water pressure and wedge stability calculations
• Design in situ leaching
• Analysis of grout injection
• Key block stability analysis
• Design of rock bolt supports
• Calculation of surface subsidence due to mine development
• Interface to UDEC and DDA for distinct element stability analysis
• Slope depressurization design

In Situ Leaching Design and Analysis

Design of in situ leaching depends upon an accurate understanding of the pathways taken by injected leachate, and the as it flows within the ore body and the potential pathways for leachate out of the mine region. In many cases the flow of leachate is controlled by a system of interconnected fractures.

Golder Associates' discrete fracture modeling and analysis technology has the potential to greatly improve the evaluation of in situ leaching feasibility and design of in situ leaching systems. The benefits of the FracMan discrete feature analysis approach for in situ leaching mine design include:

• The use of FracMan data analysis (FracSys) to maximize the information extracted from geological and hydrological tests
• 3D discrete feature visualization (FracWorks, FracView) to better understand the flow system
• Pathway analysis (PAWorks), connectivity analysis (FraCluster), flow and transport modeling (MAFIC), and ore reserve estimation (FracOre)

Applications include:

• Recoverable ore estimation by calculation of leachate/mineral contact area in fracture networks
• Optimization of well placement by pathways analysis through fracture networks recovery
• Design of monitoring systems based on pathways analysis
• Prediction of leachate loss
• Support for environmental licensing
• Design of hydraulic fracturing for optimization of leachate recovery

Hazardous Waste Disposal and Remediation Technology

Hazardous waste disposal and remediation is an increasing concern in the mining industry. Golder Associates has over 20 years experience in design, performance assessment and remedial action (RCRA/CERCLA) for hazardous wastes including:

• Environmental site investigations and assessments including design of drilling programs and sampling programs, on-site real time chemical analysis, and soil gas surveys
• Remediation design, cost estimation, construction supervision/quality control, and facility permitting
• Monitoring well network design and evaluation
• Feasibility studies including pathways analysis for dose calculations
• Source analysis and cost allocation modeling for PRPs

FracMan provides unique capabilities for design of remediation technologies which directly take advantage of the connectivity provided by fracture networks. These include:

• Pathways analysis (PAWorks) and tributary drainage volume (FraCluster) analysis for design of pump and treat system
• Simulated borehole investigations (FracWorks) for design of site characterization programs
• Flow and transport modeling (MAFIC) to assess the spatial pattern and extent of pollution
• Graphical visualization of waste plumes (FracView)
• Dose calculations based on discrete fracture transport pathways (RIP)

Flow and Solute Transport Analysis

Continuum models are adequate for flow and solute transport analysis where the connectivity pattern of discrete features such as faults, fractures, and solution features is unimportant. For many mine sites, however, groundwater is controlled by discrete feature networks. For these mines, FracMan provides a more reliable, cost effective alternative to conventional continuum groundwater flow and solute transport modeling. With over 20 years experience in continuum groundwater approaches and 10 years experience in FracMan groundwater flow and transport modeling, Golder Associates is able to provide the best solution with the best technology.

Mining applications of FracMan flow and solute transport modeling include:

• Design and implementation of packer and tracer testing programs
• Prediction of mine inflows and design of mine drainage and ventilation systems (MAFIC)
• Analyses of groundwater pressure for mine design (MAFIC)
• Groundwater resource assessment
• Solute transport modeling for environmental management (MAFIC, PAWorks)

Geologic and Hydrological Site Characterization and Testing

Golder Associates' 30 years experience in the design of geologic investigations allows us to design and execute efficient site characterization studies which collect only the information needed for mine assessment, design, and development.

FracMan supports geological investigation through the FracSys suite of data analysis procedures for

• Orientation (ISIS)
• Size (FracSize)
• Shape (FracSize)
• Spatial pattern (HeterFrac, Fractal)
• Well test interpretation (FlowDim, Flare)
• Conductive fracture (OxFilet, Flare)
• Tracer test (Moench)

FracMan/FracWorks includes a complete facility for simulated site characterization and testing. This provides us with the capability to evaluate the effectiveness of alternative testing strategies before proceeding to the field program. Simulated boreholes are much less expensive than real boreholes.