Practical Management of Quarry Development Constraints The Redlynch Experience

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Practical Management of Quarry Development
ConstraintsThe Redlynch Experience

• Travis Potts Project Development Manager

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Overview Redlynch Quarry is a hard rock site at
Cairns. The site has physical, regulatory and
commercial constraints which restrict
development. Redlynch is a useful example of
development planning and delivery.

• Creating a development plan Balancing competing
  constraints
• Resource Geology Geotechnical (PHYSICAL)
• Terrain Topography Climate (PHYSICAL)
• Environment Approvals, Impacts and Encroachment
  (REGULATORY)
• Costs Upfront Development Production Costs
  (COMMERCIAL)
• Delivering a development plan Practical lessons
  learned
• Scheduling
• Blasting
• Stripping
• Load Haul

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1. Creating a development plan
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The geology of the site restricts the potential
pit developmentto reserves within the steep
mountain ridge. There is limitedroom to quarry
deeper.
Resource
Room for 2 benches below free draining level
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The site has very complex geotechnical conditions
which influence the overall wall slope and
extraction methodology. Wide benches and shallow
batters are not possible because of the ridges
natural slope. Tropical rainfall and steep
terrain also inhibit development.
Future Workings 260 m High wall
Current Workings 160 m High wall
3 geotechnical domains have very different
characteristics
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Environmental constraints restrict development,
even within the approved extraction boundary.
Urban encroachment adds additional pressure on
environmental compliance.
Protected Vegetation
Breaching hill would expose the quarry (visual
impact noise)
World Heritage National Park
Watercourse
Watercourse
Receptor
Receptor
Receptor
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View of quarry from development
Houses constructed on ridge recently
View of development from quarry
House also in quarry amphitheatre
Equestrian Centre
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Developing the top of the hill requires a new 2.2
km long haul road. The top 3-4 benches have
extremely low yield but must be extracted to
create room below. Additional load haul
capacity is required for production and ongoing
stripping. The project is cost sensitive.
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Creation of a quarry development plan is an
iterative process of best fit to balance all
constraints. Final mine plans arerarely
final and each stage requires the same
iterative process.

• Define lateral boundary
• Geology
• Environmental constraints
• Tenure
• Determine mine plan parameters
• Geotechnical conditions
• Yield
• Annual requirements
• Develop haul road design parameters
• Fleet selection
• Safety considerations
• Confirm commercial viability
• Upfront costs (haul road, stripping, trucks)
• Production costs

High yield, impact and cost beneficial geotech
Moderate yield, impact and cost challenging
geotech,
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Scheduling is the most effective way to balance
competing constraints at Redlynch. This
practical approach to development planning may
have applications at other sites.

• Quarry Development Objectives
• Balance schedule by quarrying bottom while
  developing top of hill
• Seasonally work the pit (drop cut stripping
  during dry)
• Use a single fleet of small articulated trucks
  for load haul and stripping
• Feed from ROM while stripping (also blending)
• The mine plan must be delivered precisely there
  will be no second chance
• The philosophy of developing Redlynch is to
  balance competing constraints by accessing raw
  feed at the base of the hill whilst developing
  the top of the hill

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Initial Pit 2007
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Development Phase (2011)
Strip top of hill. Strip in 2011.
Raw feed from base of hill Stripped in 2009
80m high
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5 Year Plan (2017)
5 Year PlanNovember 2016
Strip top of hill recover some raw feed
Raw feed base of hill
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10 YearNovember 2021
10 Year Plan2022
Minor stripping and Recover most raw feed
Minor raw feed from Drop cut (dry season)
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20 Year PlanNovember 2031
20 Year Plan2032
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30 Year PlanNovember 2041
30 Year Plan 2042
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Final Pit DesignNovember 2051
Final Pit2052
260m high
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2. Delivering a mine plan
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In order to deliver the mine plan, blasting must
be precise. Blast optimisation is a critical
process of balancing environmental impacts, wall
stability and fragmentation.
Method Environmental Environmental Wall Stability Wall Stability Fragmentation Fragmentation Result?
Method Airblast Vibration Back Wall End Wall Oversize Feed Result?
Tight square pattern POOR GOOD POOR MOD VERY GOOD MOD -
Cushion blasting POOR GOOD GOOD POOR MOD MOD -
Presplit End wall VERY POOR GOOD GOOD VERY GOOD MOD MOD ?
Small blasts, staggered MOD GOOD MOD MOD MOD GOOD ?
Soft start larger blast ?
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Historical Blasting Tight Square Pattern Poor
environmental results walls
Cushion Poor end walls
Presplit Non Compliant
Staggered Pattern/Small Blasts Improvement
Overall
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Blast fragmentation has a direct correlation to
jaw throughput with variations of /- 20 t.p.h.
between blasts. Improved fragmentation was
correlated to slight increase in oversize.
Historical 195t/hour
Project 1 175t/hour Reduced Oversize
Project 2 ??? Integrated Approach
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A number of challenges were encountered during
stripping suchas unexpected outcrop and very
variable overburden thickness.

• Variable overburden thickness
• Need to leave terraces for drill access
• Impaired because of thin overburden in some areas
• Overburden left in place where thicker
• In-situ overburden has since tended to scour
  during rain
• Large outcrop boulders encountered
• Balance design criteria for development ramps
  versus haul road

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To minimise haul road risk construction costs,
a single-lane road will be built. A fleet of
small articulated trucks allow more aggressive
road design (width and gradient) and flexibility
to campaign strip. Long term feasibility is a
balance of upfront cost versus future production
cost.
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Emergency escape ramps and collision bunds will
be builtto arrest a runaway vehicle. Boral has
since built emergencystopping collision bunds at
sites with long or steep roads.
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Summary Development planning and delivery
requires balancing of many constraints which
often compete or contradict one another.

• Each constraint has potential to be a show
  stopper
• Prioritising one constraint above another may be
  impossible, impractical or unfeasible. This is
  demonstrated by todays examples
• Wide benches ideal for geotech Low yield
  unfeasible project
• Develop top of hill down ideal mine plan Low
  yield unfeasible project
• Pre-splitting ideal for geotech stability
  Environmental non-compliance unfeasible project
• Upfront stripping ideal mine plan Excessive
  upfront cost unfeasible project
• Large rigid trucks are efficient Impossible
  haul road required unfeasible project
• Underpinning all quarry development projects is a
  need to balance physical and regulatory
  constraints yet remain commercially viable.