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Examination of alternative mining methodologies that have the

potential to increase productivity at the mine site

Keith Whitchurch

PT SMG Consultants

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SMGC has been consulting

internationally for over 44 years

with a staff of highly experienced

and accredited full-time

professionals. Consultants cover a

comprehensive range of disciplines,

and their international experience

covers most types of mining and

minerals

Founded 1966

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Independent Jakarta Headquartered Consulting group

Examination of alternative mining methodologies that have the

potential to increase productivity at YOUR mine site

A slight change in Title

THE FOCUSING QUESTION

“which mining options on the basis of improved costs and productivities and reduced risks should be applied to your project”?

Mining Methods – Focus on Overburden

• Conventional Loader and Truck

• Excavator to Semi Mobile crusher

• Excavator to Mobile Crusher

• Bucket wheel to Conveyor

• Dozer to conveyor

• Dozer to Final spoil

• Dragline

Loader and Truck

Mining Technique - Truck Shovel

Trucks can haul from anywhere in pit direct to waste

Dimension

1

2

Type of Excavator

Bench layout

• Large excavator (26 cu m) • Large electric shovel (48

cu m)

• Bench height • Panel dimensions

• Cat 777 / Komatsu HD785 (100t)

• Cat 785 (136t) • Cat 789 (177t) • Cat 793 (218t)

CONVENTIONAL HYDRAULIC EXCAVATOR OR ELECTRIC SHOVEL

/ TRUCK ON WASTE Options

2

3 Size of Truck

Dependent qualities

• Diesel power • Trailing cable; ground pressure

• Time between minor relocations

• Time between major relocations

• Ground pressure • Tyre availability

•Large fleet size for high production rates

•No leverage to reduce operating costs

CONVENTIONAL LARGE EXCAVATOR / TRUCK

•Known methodology •Minimum Capex by Client •Contractor owns

equipment •Ease of changes in

production rate •Expected production = ~ 9

Mbcmpa per fleet

•Uncommon methodology to Indonesia

•Ground conditions – shovel prone to bogging – ramification of wiping out cable reeler

•Needs larger trucks to realise produciton gains – again ground conditions

•Electric shovels require operational discipline – respect for cables; correct gradients on benches; correct blasting

•Limited leverage to reduce operating costs

ELECTRIC SHOVEL / TRUCK

•Larger bucket size •Larger bench height (20m) –

for decreased bench moves •Minimum Capex by Client •Contractor owns equipment •Ease of changes in

production rate •Expected production = ~18

Mbcmpa per fleet

Excavator to Semi Mobile Crusher

Excavator to Semi Mobile Crusher

Spreader Generation 1 & 2

Generation 2 – Mae Moh, Thailand

20,000tph

Generation 1 – Goonyella

7,000tph?

Spreader Generation 3 and 4

Generation 4 – RAHCO system

Fully mobile spreader conveyor (MSC)

Generation 3 – Low Profile Spreader

With track shiftable conveyors

Mining Technique - Truck to Crusher

Trucks can haul to crushers from anywhere in pit or haul direct to waste

Dimension

1

2

Type of Excavator

Bench layout

• Large excavator (26 cu m) • Large electric shovel (48

cu m)

• Bench height • Panel dimensions

• Semi-mobile crusher • Mobile crusher

EXCAVATOR OR SHOVEL TO IN-PIT CRUSHING (ON WASTE)

Options

2

3 In-pit crusher system

Dependent qualities

• Diesel power • Trailing cable; ground pressure

• Time between minor relocations

• Time between major relocations

• Bandwagon to feed pit conveyor

• Crusher rates • Conveyor rates • No. of pit conveyors • No. of spreaders

Loading Type

•Dictated by design capacity •Same as for Loader/Truck

• Degree of Capex by Client • Initial installation locks in production

rate • High Capex to increase production • Optimum for large working area • Requires balance of upper / lower pit

production • Failure of one component in

continuous system stops upper pit production

• Less flexible than total truck system • Geotechnical failure = catastrophic

DIGGER TO TRUCKS TO SEMI-MOBILE CRUSHER TO CONVEYOR

• Proven methodology in tropics (e.g. Mae Moh)

• Multiple installations give high production rates

• Expected production of 2 x 5000 tph crushers = ~ 25 Mbcmpa

• Potential to reduce operating costs • Flexibility in trucks feeding from RL

of +/- 20 to 30m from crusher level • More flexible than full conveyor

system • Able to divert diggers to alternate

work areas while coal / IB being extracted

• Able to divert trucks to lower levels when system is out-of-action

Mobile Crusher Generation 1 & 2

Generation 1 – Ulan

Generation 2 – Goonyella

Tertiary Overburden

O&K

MMD / P&H

Mobile Crusher Generation 3

Generation 3a – China

Generation 3b – Clermont

Krupp

Mantakraf / Abon

Excavator to Mobile Crusher

Excavator to Mobile Crusher

Mining Technique - Combination System

System can only operate efficiently in large interburdens

• Unproven methodology in tropics • Degree of capex by Client • High capex (incl. 4 x conveyors) • Initial installation locks in production rate • No flexibility • Needs large working area • Unable to work system in coal / IB zones • Requires balance of upper / mid-level / lower

pit production • Needs mid-level system such as semi-mobile

crusher fed by trucks • Failure of one component in continuous

system stops production • Bogging of tracks of mobile crusher • Geotechnical failure = catastrophic

DIGGER TO MOBILE CRUSHER TO CONVEYOR

• Multiple installations give high production rates

• Expected production of 1 x 5 000 tph crusher = ~ 12 Mbcmpa (fed by L996 excavator)

• Potential to reduce operating costs by eliminating trucks

Bucket wheel excavator to Conveyor

Bucket wheel excavator to Conveyor

Bucket wheel excavator to Conveyor

Mining Technique - Combination System

System can only operate efficiently in large interburdens

Dimension

1

2

Type of Excavator

Bench layout

• Compact unit • Design to specific site

• Bench height • Panel dimensions

• 4 x conveyors • Bandwagon to feed pit

conveyor • Spreader

BUCKET WHEEL EXCAVATOR TO CONVEYOR

Options

2

3 Materials handling system

Dependent qualities

• Dig rate – anything to 3 000 bcm/hr • Ground pressure

• Time between minor relocations

• Time between major relocations

• Conveyor rates • No of pit conveyors • No. of spreaders

• Degree of capex by Client • High capex (incl. 4 x conveyors) • Initial installation locks in production rate • No flexibility • Needs large working area • Unable to work system in coal / IB zones • Requires balance of upper / mid-level /

lower pit production • Needs mid-level system such as semi-

mobile crusher fed by trucks • Failure of one component in continuous

system stops production • Suited to material – blasting? stickiness? • Geotechnical failure = catastrophic

BWE TO CONVEYOR

• Proven methodology in tropics (e.g. Jorong; Bukit Asam)

• Single installation for high production rates

• Expected BWE production up to 1 x 3 000 bcm/hr = ~ 18 Mbcmpa

• Potential to reduce operating costs by eliminating trucks

Push Dozer to Mobile Crusher

Push Dozer to Mobile Crusher

Mining Technique - Combination System

System can only operate efficiently in large interburdens

Dimension

1

2

Type of Excavator

Bench layout

• Dozer D11R – Carry Dozer

• Komatsu 575 Super Dozer • Bench height

• Panel dimensions

• Size & capacity of Stammer breaker / feeders

• 4 x conveyors

DOZER TO FEEDER TO CONVEYOR (ON WASTE)

Options

3 Materials handling system

Dependent qualities

• Dig rate – est. 450 to 500 bcm/hr per dozer

• Time between minor relocations

• Time between major relocations

• Bandwagon to feed pit conveyor

• Spreader • Conveyor rates • No of pit conveyors • No. of spreaders

• Unproven methodology in tropics • Degree of capex by Client • High capex (incl. 4 x conveyors) • Initial installation locks in production rate • No flexibility • Needs large working area • Unable to work system in coal / IB zones • Requires balance of upper / mid-level / lower

pit production • Needs mid-level system such as semi-mobile

crusher fed by trucks • Failure of one component in continuous system

stops production • Suited to material – able to increase face height

beyond 25m? • Geotechnical failure = catastrophic

DOZER TRAP TO CONVEYOR

• Single installation for high production rates

• Expected dozer trap production of 2.5 to 3 Mbcmpa per dozer

• Potential to reduce operating costs by eliminating trucks

• Relatively cheap capex and opex of dozers compared to other continuous systems

• Dozers may be used on other tasks during system outages

Push Dozers – To Final spoil

Push Dozers – To Final spoil

Example Dozer Method X Section

Dozer

Truck Shovel

Mined out Dozer Spoil

Truck Spoil

Dozer

Truck Shovel

Mined out Dozer Spoil

Truck Spoil

Blast Dozer Pass and Then Truck Shovel Pass

Example Dozer Method X Section

Dozer

Truck Shovel

Mined out Dozer Spoil

Truck Spoil

Dozer Pushes Ramp through Blast at Panel

Prestrip mined and hauled cross pit

Dozer

Truck Shovel

Mined out Dozer Spoil

Truck Spoil

Example Dozer Method X Section

Dozer

Truck Shovel

Dozer Spoil

Truck Spoil

Dozer Push to Final – Leaves Highwall Wedge

Shovel Truck Clears Highwall Wedge and Low wall rehandle

Highwall Wedge

Truck Shovel

Dozer Spoil

Truck Spoil

Rehandle Wedge

• Unproven methodology in Indonesia • Needs large working area • Requires highly disciplined approach • Unable to work system in coal / IB zones • Requires truck/loader support • Geotechnical failure • Application limited by deposit

geometry/geology • Bulk dozer push requires specially rained

operators

DOZER PUSH TO FINAL

• Expected dozer production of 2.5 to 3 Mbcmpa per dozer

• Relatively cheap capex and opex of dozers compared to other systems

• Dozers may be used on other tasks

Dragline

Dragline

Truck Shovel Prestrip

Blast Top Pass

Dozer Push Top Pass to Form Bench

Dragline to bench

Dragline Removes First Pass Truck Shovel mines Coal

Blast Second Pass

Dragline chops Highwall and extends bench

Dragline sits on bench and removes remainder of second pass

• Unproven methodology in Indonesa • Degree of capex by Client • High capex • Initial installation locks in production rate • No flexibility • Needs large working area • Limited application by deposit

geometry/geology • Unable to work system in coal / IB zones • Generally needs a prestrip system • Exposure to failure of a single unit • Modern high productivity spoil side operations

unlikely due to geotechnical constraints • Geotechnical failure = catastrophic

DRAGLINE

• Single installation for high production rates

• Expected 14Mbcm to 25Mbcm pa • Potential to reduce operating

costs by eliminating trucks • Very low opex • Not impacted by Rain • Very long asset life > 30 years

WHICH ONE IS FOR YOU?

“which mining options on the basis of improved costs and productivities and reduced risks should be applied to your project”?

HOW DO WE DECIDE WHAT IS BEST IN YOUR DEPOSIT

• Capital Cost

• Operating Cost

• Exposure to escalation of Operating Costs

• Practicality – degree of compatibility with this site

• Mining complexity

• Risk of technical failure

• % of production applicable to the method

• Operating hours per year

• Material conditions (as applied to impact on method)

• Timing of implementation (lead time)

• Availability of technology and parts

• Local Skills

• Geotechnical stability / consequences of failure

• Acceptability to international banks for finance

• Hydrology – consequences of water inflow

Decision Criteria – Starting List by consensus

Weightings determined independently and pooled

Weighting 1 = unimportant, 10 = important

SMGC Contractor SMGC Client Average

Description of Criteria weighting weighting weighting weighting Weighting

Capital cost (size of capital cost) 10 7 10 5 8.0

Operating cost (indicative relativity for method) 10 10 10 10 10.0

Exposure to escalation of Operating Costs 6 5 7 5 5.8

Practicality - degree of compatibility to TOP site 10 10 10 10 10.0

Boxcut (implications of external dumps) 2 2 8 5 4.3

Mining Complexity 7 7 8 2 6.0

Risk of Technical Failure 7 7 7 5 6.5

% of Production Applicable to method 2 5 6 1 3.5

Operating hours per year 5 4 7 1 4.3

Material Conditions (as applied to impact on method) 8 3 7 2 5.0

Timing of Implementation / lead time 4 2 2 1 2.3

Availability of Technology and Parts 6 1 6 1 3.5

Local Skills (degree where lack of skill = high probability of failure?) 3 2 7 2 3.5

Geotechnical - Consequences if geotech failure 7 5 7 1 5.0

Acceptability to International Banks 10 2 9 5 6.5

Hydrology - Consequences on method of water inflow 7 2 8 1 4.5

• Capital Cost

• Operating Cost

• Exposure to escalation of Operating Costs

• Practicality – degree of compatibility with this site

• Mining complexity

• Risk of technical failure

• % of production applicable to the method

• Operating hours per year

• Material conditions (as applied to impact on method)

• Timing of implementation (lead time)

• Availability of technology and parts

• Local Skills (degree whereby lack of skill = high probability of failure

• Geotechnical stability / consequences of failure

• Acceptability to international banks for finance

• Hydrology – consequences of water inflow

10

5.8

3.5

10

6.0

3.5

6.5

4.3

5.0

2.3

8

3.5

Decision Criteria – Rank From 1 to 10 – average of

participants

5.0

4.5

5.0

Raw Scores per Option Determined by technical analysis

(SMGC)

HE / shovel HE / shovel Dozer to Dozer push;

Hydraulic Electric Front End to Truck to to fully Bucket feeder Dragline; combination

Excavator Shovel Loader Semi-mobile mobile Wheel to breaker to proportion excavator

Description of Criteria to Trucks to Trucks to Trucks Crusher Crusher Conveyor Conveyor of waste & trucks

Capital cost (size of capital cost) 3 2 3 1 1 1 1 1 3

Operating cost (indicative relativity for method) 1 1 1 3 3 3 3 3 1

Exposure to escalation of Operating Costs 1 1 1 2 3 3 3 3 1

Practicality - degree of compatibility to TOP site 3 2 1 3 3 1 3 2 2

Boxcut (implications of external dumps) 3 3 3 1 1 1 1 3 3

Mining Complexity 3 2 2 2 1 1 2 1 1

Risk of Technical Failure 3 2 2 3 2 1 2 1 2

% of Production Applicable to method 3 3 2 3 3 2 2 1 3

Operating hours per year 3 3 3 3 2 2 2 3 3

Material Conditions (as applied to impact on method) 3 2 1 2 2 1 3 2 3

Timing of Implementation / lead time 3 2 3 1 1 1 1 1 3

Availability of Technology and Parts 3 2 2 2 2 2 3 2 3

Local Skills (degree where lack of skill = high probability of failure?) 3 2 3 2 2 2 2 1 3

Geotechnical - Consequences if geotech failure 3 2 3 1 1 1 1 1 3

Acceptability to International Banks 3 2 3 1 1 1 1 1 3

Hydrology - Consequences on method of water inflow 3 2 2 1 1 1 1 1 3

Raw Scores per Option Determined by technical

analysis (SMGC)

HE / shovel HE / shovel Dozer to Dozer push;

Hydraulic Electric Front End to Truck to to fully Bucket feeder Dragline; combination

Excavator Shovel Loader Semi-mobile mobile Wheel to breaker to proportion excavator

to Trucks to Trucks to Trucks Crusher Crusher Conveyor Conveyor of waste & trucks

24 16 24 8 8 8 8 8 24

10 10 10 30 30 30 30 30 10

5.75 5.75 5.75 11.5 17.25 17.25 17.25 17.25 5.75

30 20 10 30 30 10 30 20 20

12.75 12.75 12.75 4.25 4.25 4.25 4.25 12.75 12.75

18 12 12 12 6 6 12 6 6

19.5 13 13 19.5 13 6.5 13 6.5 13

10.5 10.5 7 10.5 10.5 7 3.5 3.5 10.5

12.75 12.75 8.5 12.75 8.5 8.5 8.5 12.75 12.75

15 10 5 10 10 5 15 10 15

6.75 4.5 6.75 2.25 2.25 2.25 2.25 2.25 6.75

10.5 7 7 7 7 7 10.5 7 10.5

10.5 7 10.5 7 7 7 7 3.5 10.5

15 10 15 5 5 5 5 5 15

19.5 13 13 6.5 6.5 6.5 6.5 6.5 19.5

13.5 9 9 4.5 4.5 4.5 4.5 4.5 13.5

234 173 169 181 170 135 177 156 206

1 5 7 3 6 9 4 8 2

Comments on Ranking

• Ranking 1: Conventional hydraulic excavator and trucks has been ranked as the highest or equal highest in 14 of the 16 categories. Such systems benefit from flexibility and simplicity, low total capital cost and acceptability to international banks. The only negative aspects are high operating cost and likelihood of future increases in those costs.

• Ranking 2: The second choice is a variation of the top ranking, with dozer assist to conventional hydraulic excavator and trucks. This system scored similarly in most categories as the conventional use of hydraulic excavator and trucks; but lost points from the additional complexity and probability of technical failure.

• Ranking 3: The third choice is the loading mechanism of an hydraulic excavator or electric shovel dumping to a semi-mobile crusher. This system gains in terms of operating cost criteria; but loses against capital costs, size of boxcut to establish, the degree of complexity added by a conveyor spreader system and the related issue of acceptance to international banks.

• Ranking 4: The fourth option is waste moved by a fleet of dozers pushing to a low-capital cost but high throughput feeder-breaker to a conveyor system. Such a system scores well on operating cost and practicality to the thick overburden task at this project. The dig side of a dozer operation is not affected by rain; the dozer faces could be designed in excess of 20m to decrease the frequency of system moves, and the method handles poor material conditions. The downside would be the high capital cost of conveyors and spreader, size of boxcut to establish and the degree of complexity added by a conveyor spreader system.

• Ranking 5: Waste mining up to 50Mbcm per year with a fleet of large front-end-loaders is a poor option on both practical and technical grounds. These machines would not be able to match the superiority of hydraulic excavators for production time or ability to handle the soft ground conditions

• Ranking 6: The ranking of the waste systems has eliminated the concept of the fully-mobile MMD-style crusher being fed directly by an hydraulic excavator or electric shovel. Again this option scored highly on the operating cost factor. It suffered on non-suitability to the pit geometry due to high inherent system capacity (to match peak production later in mine life); need for frequent moves down 20m high benches and resultant low work hours per year; high capital costs; size of boxcut to establish; the degree of complexity added by a conveyor spreader system and the related issue of acceptance to international banks.

• Ranking 7: The option of electric shovel to trucks loses against the hydraulic excavator in the two aspects of complexity (relating to the need to design, plan and maintain procedures associated with the electric cables and substation) and in material conditions (being the consequences of machine bogging with resultant damage to rear cable reel).

• Ranking 8: The dragline option has been ruled out on the basis of poor technical application. The concept of a single large and unique (to Indonesia) dragline operation with the responsibility of all coal exposure task would be a high risk option with multiple areas for failure (such as high degree of complexity; poor material stability under the machine; lack of local skills and discipline vital to successful dragline application).

• Ranking 9: The ranking of the waste systems has eliminated the BWE which scored highly on one factor only (cost). It scored badly on material conditions (due to the likely presence of soft sticky material in small buckets); and on all other criteria.

Conclusions

• These conclusions are for this example project only

– Options 1 to 3 are

• Conventional Hydraulic excavator to truck

• Dozer assist of Conventional Hydraulic excavator to truck

• Hydraulic excavator or Electric shovel to fully mobile in pit crusher/conveyor

• These 3 options require further detailed study

Conclusions

• A range of options are open

• The best option depends on a wide range of factors

• The best option for someone else's project is not necessarily the best option for your project

• There is no substitute for in country experience in guiding this decision making process

Thank You