Download Open Pit Planning and Design - Supplemental Teaching Resources

Open Pit Planning and Design
The Standard Approach for Open
Pit
©2007 Dr. B. C. Paul
The Ajo Open Pit in Arizona
They mined around the
barren core
Lacks Clear Steps and Has A Lot of
Interaction – Computers Almost a
Necessity
 In general need to know
you have a large ore
reserve close enough to
the surface to be open pit
mined
 Generally comes from
geologic data
– Open pit designs normally
represent ore reserves and
geology as a block model
 Slice and dice the ore
reserve up into small blocks
that sit end to end and on
top of each other
Building Block Models
 Start by specifying block dimensions
 Look at drill and sampling data for how
continuous the mineralization is
– Use computer routines to estimate the ore
grade of the blocks using samples
– One of the most popular is Kriging (also
polygonal and IDS)
 Most going to study how interpolation is done in this
class. (You’ll be given a block model to work with)
Determine the Minable Ore Reserve
 Assume economics for material removal
 Look at geology for how steep the pit slopes can
stand without sliding in
 Have the computer analyze the largest set of
blocks that can be removed without taking stuff
that looses money
– This set measures the size of the pit that can ultimately
be mined (called the Ultimate Pit)
 Too complex to visualize
– Done with either a Floating Cone Miner or LearchGrossman computer routine
Sequencing
 Considering the need to work from top down
and the grade of the ore
– Calculate a series starting with richest ore and
working down in grade over time
 Usually accomplished with modified
computer routines
 Getting best ore early in life greatly
improves the NPV of the project
Developing a Practical Layout
 With a series of nested pit shells as a guide
design a set of pits that follows the guides
but has benches, and roads required for
practical mining.
 Pick Equipment Fleets
 Work on intermediate and short term
equipment schedules to execute the over-all
plan