Cradle to grave
Planning and operating an opencast mine is both intricate and tough.
Optimising an
opencast mine
T
he planning and management
of an opencast mine is a
complex and challenging
task, particularly for mines that have
extended mine lives. Optimisation
techniques can be applied to resolve
any issues that might arise during
the mine planning process.
Pit optimisation is a vital part of
the mining process and is often one of
the first steps carried out by engineers
in opencast mine design. A pit
optimisation analysis is conducted to
determine the most profitable opencast
design and given a mineral resource
and a set of economic and metallurgical
parameters. These parameters typically
consist of commodity prices, process
recoveries, and operating costs.
The first outcome of pit optimisation
is to determine the ultimate pit that
gives the highest possible undiscounted
surplus between net revenue and total
operating costs, without considering
scheduling constraints or discounting.
Mining software plays a critical
role in this process and equips mining
engineers with the tools to design
optimal mine plans that ensure a
profitable operation. Micromine 2016
[38] MINING MIRROR FEBRUARY 2018
offers integrated tools for modelling,
estimation, design, optimisation,
and scheduling and as a scalable
solution, it provides users with the
flexibility to choose the specific
functionality when required.
A key differentiator for Micromine
over other general mine planning
software is the fact that pit optimisation
is fully integrated into the Micromine
product, which means users do not
need to manually import and export
files to exchange data with other
applications. This presents considerable
efficiency gains for mine planners.
Micromine Pit Optimisation
uses the industry-standard Lerchs-
Grossma n (LG) algorithm. Given
an ore deposit represented as a block
model containing ore grades or block
revenues, the LG algorithm determines
the pit shape by identifying the blocks
that can be removed to contribute
to a positive discounted surplus.
A nested pit shell analysis is then used
to determine the discounted optimal
pit. Nested pit shells are a sequence of
ultimate pits generated by incrementing
the commodity price across a range
of values around the base price. The
optimal pit gives the highest possible net
present value, considering all operational
scheduling constraints (annual
mining and processing productivity),
discounting, and recurring capital costs.
Benefits of Micromine’s Pit
Optimisation module:
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Fully integrated within
Micromine, with all parameters
in one place, saving time and
money by eliminating the
need for data exchange.
Internal and external 32- or 64-bit
engines provide the flexibility to
adjust the optimiser to suit the
available computing resources.
Up to four times faster than
competing applications.
Widely regarded as being the
most intuitive and easy-to-use
pit optimisation application.
Supports any combination
of sub-blocked and rotated
models, and DTM surfaces.
Input parameters for mining
costs and element prices can be
set up as functions instead of
constants, adding greater flexibility
to the optimisation process.