DRIEFONTEIN GOLD MINE

Mining Methods

Presented by: FJ Castelyn

Date: 15 September 2005

Content

•Introduction

•Tabular Deposits <350 dip:

•Longwalling

•Scattered

•Caving

•Wide reef

•Backfilling

Content

•Massive Mining >350 dip:

•Sub-level (open) stoping (blast hole stoping)

•Shrinkage stoping

•Cut and fill

•Sub-level caving

•Block caving

•Conclusion

IntroductionIntroduction

Considerations in the Choice of Mining Method

• Geometry of orebody

• Geological complexities

• Geotechnical properties of the country rock and orebody

• Depth below surface of extraction

IntroductionIntroduction

Considerations in the Choice of Mining Method

•Economic viability including:

• infrastructure

• value distribution

• Environmental aspects

• Engineering constraints

• Relevant legislation

Tabular deposits <35Tabular deposits <3500 dipdip

Considerations:

• depth > 2000m

• high grade – total extraction possible although not desirable

• geological complexity

Longwalling

Tabular deposits <35Tabular deposits <3500 dipdip

Advantages:

• Follow behind development

• Can be trackless

• Concentrated stoping

Longwalling

Tabular deposits <35Tabular deposits <3500 dipdip

Longwalling

Disadvantages:

• Inflexibility

• Variable geology

• Highly stressed abutments

Tabular deposits <35Tabular deposits <3500 dipdip

Scattered Mining

Considerations:

• Narrow reef 2-5m

• Depth intermediate

Tabular deposits <35Tabular deposits <3500 dipdip

Scattered Mining

Advantages:

• Advanced knowledge of geological complexities –pre-development

• Flexibility in choice of stopes - value

Tabular deposits <35Tabular deposits <3500 dipdip

Scattered Mining

Disadvantages:

• Less concentrated stoping

• Change in stress of tunnels as over –stoping takes place

• Highly stressed abutments

Tabular deposits <35Tabular deposits <3500 dipdip

Caving

Considerations:

• Application – weaker hangingwall than footwall

• Controlled bulking

Tabular deposits <35Tabular deposits <3500 dipdip

Caving

Advantages:

• Cost effective

• Face stresses lower

Tabular deposits <35Tabular deposits <3500 dipdip

Caving

Disadvantages:

• Back area support compromised typically gullies

• Controlled cave difficult to obtain

Tabular deposits Flat Tabular deposits Flat -- <35<3500 dipdip

Wide Reef – Bord and Pillar, Drift and fill

Considerations:

• Span between pillars

• Fill material availability

• Subsidence

• Geological weaknesses particularly jointing, potholes, triplets, smectites, etc

• Depth relatively shallow

Tabular deposits Flat Tabular deposits Flat -- <35<3500 dipdip

Wide Reef – Bord and Pillar, Drift and fill

Advantages:

• Mechanization

• Total extraction can be achieved

Disadvantages:

• Economies of scale – lower value ore

• Ore oxidation, groundwater control

Tabular deposits Flat Tabular deposits Flat -- <35<3500 dipdip

Wide Reef – Step Room and Pillar

Massive mining methods >35Massive mining methods >3500 dipdip

Sub-level (Open) Stoping

Considerations:

• Steep dip

• Favourable geotechnical characteristics

• Regular orebody geometry

Massive mining methods >35Massive mining methods >3500 dipdip

Sub-level (Open) Stoping

Advantages:

• Mechanization – drilling carried out in advance of stoping

• Extraction on retreat

Disadvantages:

• Extensive development prior to extraction

Massive mining methods >35Massive mining methods >3500 dipdip

Shrinkage Stoping

Considerations:

• Steep dip

• Favourable geotechnical characteristics

Massive mining methods >35Massive mining methods >3500 dipdip

Shrinkage Stoping

Advantages:

• Mechanization – drilling carried out in advance of stoping

• Only bulk of ore removed after every blast – provide stability for hangingwalls and footwalls

Massive mining methods >35Massive mining methods >3500 dipdip

Shrinkage Stoping

Disadvantages:

• Ore prone to oxidation and hydrolysis

Massive mining methods >35Massive mining methods >3500 dipdip

Cut-and Fill Mining

Considerations:

• Steep dip, thin

• Favourable geotechnical characteristics

• Fill material characteristics

Massive mining methods >35Massive mining methods >3500 dipdip

Cut-and Fill Mining

Advantages:

• Can be used in ore bodies with irregular contours

• Offers more mining selectivity

• Total extraction

• Working platform

Massive mining methods >35Massive mining methods >3500 dipdip

Cut-and Fill Mining

Disadvantages:

• Orebody is above mining – potential for fall-out if orebody not competent

Massive mining methods >35Massive mining methods >3500 dipdip

Sub-level caving

Considerations:

• Easy separation of waste from ore (magnetic)

• Orebody boundaries are vague

Massive mining methods >35Massive mining methods >3500 dipdip

Sub-level caving

Advantages:

• Pre-drilling

• Economies of scale

• Total extraction

• Little support required

Disadvantages:

• Extensive pre-development

Massive mining methods >35Massive mining methods >3500 dipdip

Block caving

Considerations:

• Steep dip or large vertical extension

• Orebody weak –susceptible to breakage

• Subsidence acceptable

Massive mining methods >35Massive mining methods >3500 dipdip

Block caving

Advantages:

• Economies of scale – cost effective

• Total extraction

Massive mining methods >35Massive mining methods >3500 dipdip

Block caving

Disadvantages:

• Extensive pre-development

• Time lag – slow build-up to production

• Hang-ups at drawpoints – costly secondary blasting

ConclusionConclusion

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