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Presented:

Date:

Location:

© SRK Consulting (UK) Ltd 2011. All rights reserved.

Mining Project Essentials: Integrated Geo-Technical Studies for Cost Effective Mine Design

31 March 2014

Allan McCracken

• Integrated Technical Aspects • (Geology)

• Structural Geology

• Mining Geotechnics

• Hydrogeology

Minex Central Asia Forum, Astana, Kazakhstan

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Integrated Geo-technical Studies

Cost Effective Mine Design

Missed opportunIties I

to combiNe early stage N strucTural geology, T

geotEchnical & E hydroGeological G

woRk R

can cost A A

loT of mon€y T

and timE! E

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Joint pacing

Masterclass Objectives

• Understand and explain – Goals of integrated Geo-Technical design

– The integrated design process

– What data is needed for different types of mines

– Organising cost effective integrated data gathering

– Integrating the evaluation and analysis

– Integration at different stages of projects

• Result – Integrated design

– Optimised design

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Integrated Geotechnical Mine Design

• Stages to the integration – Preliminary assessment of the deposit

• Defines the more critical technical aspects and constraints to the project

– Mining Method Selection • Defines the targets of the data gathering

– Mine Design Parameters • Assesses the data and defines the mine design criteria

– Optimisation for Maximum IRR/NPV and Safety • Phased approach:

– Adding necessary data,

– Improving confidence,

– Mitigating risk.

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Integrated Geotechnical Mine Design

• Key Drivers in Mine Design/Slope Stability/Instability

• Key Success factors in Slope Design optimisation

– Geology

– Structure

– Rock mass GT properties

– Hydrogeology

• Groundwater related pore pressure: a critical role in pit slope stability;

• Representation by simple phreatic surface often not sufficient

• Pore pressure can be directly input to stability analysis

• Majority of Failures - stability controls related to: – Hydrogeology

– Structure

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Mine Design: Common Requirements for ALL Mining Projects

• Geological and mineralisation controls

– Lithology, Ore Genesis, Orebody geometry, Grade distribution: – Fundamental to

• Geological Structure – Regional deformation; Local structure; Rock fabric; Controls on

mineralisation; Influence on GT

• Mining Geotechnics – Strength: Intact; Discontinuity shear; rock mass – Structure: Faults; joint orientation; – Water: Water levels; Pressures;

• Mine Hydrogeology – Hydro Regime; Water inflows; Dewatering requirements; Ground

water management; (water supply potential).

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Mining Method Selection: – Predominantly based on GT Criteria

• Geology and Structure: Orebody geometry; depth; grade distribution; Resource Recovery; • Geotechnics and Water: RMR; Rock strength • Geotechnics: Surface Constraints: Subsidence/Non-subsidence • Geotechnical related Costs: Stripping ratio; Development sizes; Support; backfill/No backfill

Orebody Characteristics Mining Method Rankings

Geometry and Grade Distribution General Shape: Undefined/Massive/Platy-tabular/Irregular Ore Thickness: Very narrow <3m/Narrow 3-10m/moderate 10-30m/ Thick 30-100/>100m Ore Plunge: Undefined/flat <200/intermediate 20-550/steep >550 Grade Distribution: Undefined/uniform/Gradational/Erratic Depth: Shallow <100m/intermediate 100-600m/deep >600m

(best) Open Pit (30)

Cut and Fill Stoping (30)

Square Set Stoping (28)

Sublevel Caving (26) Block Caving (24) Shrinkage Stoping

(14) Top Slicing (13)

Longwall Mining (-24) Sublevel Stoping (-27) Room and Pillar (-43)

(worst)

Rock Mass Rating (after Bieniawski 1973) Ore Zone: Very weak <20/ weak 20-40/ medium 40-60/strong >60 Hanging Wall: Very weak <20/ weak 20-40/ medium 40-60/strong >60 Footwall: Very weak <20/ weak 20-40/ medium 40-60/strong >60

Rock Substance Strength (unconfined compressive strength / principal stress) Ore Zone: Very weak <5/Weak 5-10/Medium 10-15/strong>15 Hanging Wall: Very weak <5/Weak 5-10/Medium 10-15/strong>15 Footwall: Very weak <5/Weak 5-10/Medium 10-15/strong>15

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Mining Method Selection

Orebody Characteristics Mining Method Rankings

Geometry and Grade Distribution General Shape: Tabular Ore Thickness: Thick 30-100m Ore Plunge: Steep >55degrees Grade Distribution: Erratic Depth: Deep >600m

Rock Mass Rating (after Bieniawski 1973) Ore Zone: weak 20-40 Hanging Wall: Medium 40-60 Footwall: Medium 40-60

Rock Substance Strength (unconfined compressive strength / principal stress) Ore Zone: Weak 5-10 Hanging Wall: Very Weak <5 Footwall: Medium 10-15

(best) Sublevel Caving (35) Block Caving (31) Sublevel Stoping (30) Cut and Fill Stoping (30) Square Set Stoping (20) Top Slicing (17) Open Pit (-19) Shrinkage Stoping (-28) Longwall Mining (-70) Room and Pillar (-89)

(worst)

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Mine Design Parameters: Open Pits Data gathering and the design process

– Open Pit methods and design • Likely pit geometry: Possible Footprint, possible depth • Based on Preliminary pit shells; • Derived from experience based Conceptual Level parameters

– Geotechnical Model/Design Domains • From geology, lithologies, structure, rock mass strength, water conditions. • Based on mapping, orientated BH data, index testing, lab testing, down hole packer testing

and flow tests • Spatial domains of similar geotechnical properties • Input values of parameters derived per Design Domain

– Stable Slope Configurations • Derived from analysis of the design domains • Overall slope angles • Inter-ramp slope angles • Berm-Bench Configurations • Ramp routes • Excavatability/Trafficability

– Water Management: • Pre-dewatering/depressurisation/Drainage/Quality/Pumps/Disposal

– Input to Mine Design Engineers • Updated Pit shell and engineered pits

– Check analysis to ensure Required FoS achieved • Modifications back to Mine Design engineers

– Monitoring

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Open Pits: Integrated Design Process

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Mine Design Parameters: Underground Mines Data gathering and the design process

• Data required is dependent on Potential Mining Methods Selected – Subsidence method/Non-subsidence Method

• Geotechnical Model/Design Domains – From Geology, lithologies, structure, rock mass strength, water conditions.

– Based on mapping, orientated BH data, index testing, lab testing, down hole packer testing and flow testing

– Design Domains: Upper Hangingwall/Immediate Hangingwall/Ore Zone/Footwall

• Design Criteria – Shaft/Decline Access: locations (avoid major structures), sinking conditions, sinking

methods (D&B, Bore, Freeze), water control; rock support; lining design.

– Main development: Development methods; water management; spans; support classes.

– Stoping: Stope dimensions; Spans v Support; Pillar designs; access/remote loading

– Resource recovery and Dilution:

– Backfill: Economic case for Backfill: Subsidence prevention; backfill designs; reticulation

– Water Management: Inflows; sumps; pumps; quality; disposal

– Input to Costs:

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Underground Mines: Integrated Design Process

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Integrated Mine Design Data requirements

• What Data is Needed/How is it integrated?

– Geological Structure

– Geotechnical Data

– Hydrogeological Data

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Integrated Mine Design Data Requirements

Structural geology – Regional geology and structure – Published data – regional maps and

mapping; neighbouring mines • Constraints to mineralisation • Compartmentalisation of GT and Hydro conditions • Influences macro scale mine design parameters

– Local structure • preliminary models from initial exploration

– Ground truthing – mapping and core assessment • Remote imagery • Map outcrops • Core Data

– Visual assessment of fault zones and deformation – Orientated structural data

– Output of structure to integrated model: • Improved 3D Model • Deformation of the orebody/Control on mineralisation • Rationalising GT data sets (fractures into types of joint system); • Ductile fabric/later stage brittle fractures • Interface with Geotechnics re:

– Discontinuity orientations – Kinematic interpretation inputs – Late stage brittle fractures likely to cause instability

• Interface with Hydrogeology re: – Hydraulic flowpaths/Compartmentalisation

INTEGRATED

GEO-TECH

DESIGN

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Geological structure is more complex at some projects when compared with others

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Importance of understanding structural geology

• Angouran Zinc Mine

• One missed major structure below the face caused the failure of the whole slope.

• ~40% of the reserves were sterilised

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Integrated Mine Design Data Requirements

Geotechnics – Geological and structural geology model

• Source: Geology and Structural Geology teams • Influences macro scale design parameters

– Rock Mass Model: Ore and Waste horizons • Targets

– Open pits: Weathering profile; Pit wall areas for slope design; ore for excavatability and interim slopes

– Underground: Hangingwall/roof, ore and footwall/floor for spans, support, pillar (crown, sill, rib) design.

• Sources: – Mapping of outcrop – Neighbouring Mines – Geotechnical Drillholes specifically designed to intesect domains of interest; orientated core

by ori-devices or ATV/OTV : Geotechnically logged and sampled for testing:

• Material testing: – Depending on material and mine function: including:

» UCS, UTS, TXL, shear, moduli, time-creep, cuttability, abrasion

• In-situ testing /Monitoring: In-situ/mining induced Stress

– Output to integrated model: • Rock Mass Classification • GT Domains • Domain parameters for analysis • Mine design Criteria

INTEGRATED

GEO-TECH

DESIGN

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Integrated mine design

• Good design can save $100m’s

Unexpected problems can cost dear

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Integrated Mine Design Data Requirements Hydrogeology

– Inputs: • Geological and structural geology model

– Source: Geology and Structural Geology teams

• Geotechnical model

– Hydrogeology Model: Local to mining area • Targets

– Open pits: Weathering profile; areas surrounding open pit; faults; springs – Underground: General rockmass; potential inflow features intersected by mining – Both: Surface hydrology –rivers traversing/in proximity to mining area

• Sources: – Catchment areas – River hydrology – Neighbouring Mines – Drillholes specifically designed to intesect domains of interest; orientated core by ori-devices or

ATV/OTV, : Drillers logs- water strikes/losses; Geotechnical logs; – Packer tests, flow tests, falling head tests, blow out and recovery tests in BHs – Conversion of cored holes to standpipe piezometers (water levels) and vibrating wire holes (pore

pressures).

• Material testing: – In soils: particle size distributions – Rocks and soils: triaxial permeability

• Output to integrated Model: – Water level/phreatic surface profile – Hydrogeological model – Design to dewater/depressurise/drain – Inflow/Pumping requirements

INTEGRATED

GEO-TECH

DESIGN

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Incomplete depressurisation in weak materials caused the loss of life and loss of a mine

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In many projects the hydrogeology model and ability to depressurise the slopes is key to stability

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Presented:

Date:

Location:

© SRK Consulting (UK) Ltd 2011. All rights reserved.

Talk 2: Integrated Data Gathering

31 March 2014

Astana, Kazakhstan

Allan McCracken

• Exploration Drilling Programmes o Collect as much geo-technical data from all holes o Ensure specific holes are included for specific purposes

• Structural Geology o Core orientation and structural logging

• Mining Geotechnics o Rock mass characterisation: Combined BH geophysics & GT

logging

• Hydrogeology o Investigations for mine dewatering and slope stability

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Organising an Integrated Geo-Technical Data Gathering Programme

• Missed opportunities to integrate early works cost money and time later! • Integrate the Scope of Work

– Structural Geology, Geotechnical and Hydrogeological teams and Developer should co-operate

• at the proposal stage or at the outset of the commission

• Co-ordinate the drilling programme – Co-ordinate at as early a stage as possible to address the needs of the different disciplines. – Exploration drilling programmes should double up for GT and Hydro data as well as geology

and structure. – Different disciplines need holes in different places from the resource geologists

• Geotechnical holes are often targeting the waste rocks • The resource team should always be consulted. They too will be interested in the limits of the

mineralised body

• Co-ordinate and schedule the fieldwork – Undertake the structural and GT mapping and core logging assessment together – Provides invaluable insights to the deformation history and latest stage fabric – Hydrogeological and geophysical testwork needs to be fully co-ordinated with the drilling

programme to ensure hole availability • Liaise during the fieldwork

• Liaise during the evaluation and design – Ensure input parameters are compatible with envisaged model

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Integrated Geo-Technical Mine Design at successive Project Stages • Integrated Geo-Tech Mine design can be applied at ALL Levels

and Stages of Projects – Conceptual – Order of Magnitude – Pre-feasibility – Feasibility – Final Engineering design

• The levels of knowledge of each discipline should be compatible at each stage – Imbalance of understanding can lead to uncertainty and wrong

outcomes

• The level of knowledge should be commensurate with the level of impact of each discipline – The different disciplines can have greater or lesser degrees of

importance in different projects – The relative importance of each discipline should be assessed at the

early stages of the project and reassessed as the project develops