Ing Civil

17* International Mining Congress and Exhibition of Turkey- IMCET2001, © 2001, ISBN 975-395-417-4

Open Pit Optimization - Strategies for Improving Economics of Mining
Projects Through Mine Planning
K.Dagdelen
Mining Engineering Department, Colorado School of Mines. Golden, Colorado, USA

ABSTRACT: The open pit design and scheduling problem is a large-scale optimization problem that hasattracted considerable attention during the last 40 years The development of the "know-how" to improve
economics of open pit mining projects through the use of mathematical optimization techniques goes back to
early 1960's. Unfortunately, up until recently, many of these "optimizing algorithms" could not be
implemented due to the limited capacity of the computer hardware used in many miningoperations. During
the last 10 years, advancements in the computer hardware technology along with developments in software
technology allowed open pit mines to have powerful desktop computers that can solve complex optimization
problems on site. Due to applications of optimization techniques developed in the early 1960*s, for example,
Chuquicamata Open Pit Mine in Chile re-evaluated their cutoffgrade strategy and improved Net Present
Value (NPV) of their ' operations by USS800M. Newmont Gold Corporations in Nevada, USA has
implemented large scale Linear Programming Model mat was developed in early I980's to schedule their
entire mine and mill production in the Carlin District, resulting in significant process costs savings. This
presentation will outline open pit optimizationtechniques that are available today and how they can be used
to improve overall economics of projects that are being planned or in production.

1 INTRODUCTION
The current practice of planning of hard rock open
pit mine begins with a geologic block model (see
Figure 1) and involves determination of: 1) Whemer
a given block in the model should be mined or not;
2) If it is to be mined when it shouldbe mined; 3)
Once it is mined then how it should be processed.
The answer to each of these questions, when
combined within the whole block model, define the
annual progression of the pit surface and the yearly
cash flows that will be coming from the mining
operations during the life of mine. There can be
many different solutions to the scheduling problem
depending on how the decision ismade for each of
the blocks. Decision as to which blocks should be
mined in a given year, and how they should be
processed (i.e. waste, run of mine leach, crushed ore
leach or mill ore etc.) defines not only the cash flows
for that year but also impacts the future annual
schedules. What is decided today has long-term
implications as to what can be done in the future and
all these decisionslink together in defining the
overall economics of the a given project. The
objective of the planning process for an open pit
mine is usually to find optimum annual schedules
that will give the highest Net Present Value (NPV)

while meeting various production, blending,
sequencing and pit slope constraints.
Traditionally, the scheduling problem described
above is solved by dividing theproblem into sub
problems similar to one shown in Figure 2. The
solution step starts with the assumption of initial
production capacities in the raining system and the
estimates for the related costs and commodity prices.

Figure I 3-D geologic block model representation of a copper
deposit.

117

Once the economic parameters are known, the
analysis of the ultimate pit limits of the mineİs
undertaken to determine what portion of the deposit
can economically be mined. Within the ultimate pit
limits, pushbacks are further designed so that deposit
is divided into nested pits going from the smallest pit
with highest value per ton of ore to largest pit with
the lowest value per ton of ore. These pushbacks are
designed with haul road access and act as a guide
during the...