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A OPEN PIT MINING AÇIK OCAK MADENCİLİĞİ

A OPEN PIT MINING AÇIK OCAK MADENCİLİĞİ

A OPEN PIT MINING AÇIK OCAK MADENCİLİĞİ

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product that must be produced from the<br />

mine.<br />

MaximizeT<br />

X<br />

bx<br />

b<br />

(2)<br />

bB<br />

Subject to:<br />

gb<br />

Gmin x<br />

b<br />

0<br />

(3)<br />

bB<br />

<br />

<br />

i i<br />

imb<br />

immax x<br />

b<br />

0, i 1,...,<br />

nim<br />

(4)<br />

bB<br />

<br />

<br />

x<br />

b<br />

0,1 , b B<br />

(5)<br />

In this model, T is the total tonnage of<br />

final blended material to be maximized, b is<br />

the block identifier, and B is the set of<br />

potential ore blocks in the block model. X<br />

b<br />

is the tonnage of material in block b, and x<br />

b<br />

is the decision variable. If x<br />

b<br />

is equal to 1,<br />

then block b is included in the blended<br />

product, and if x<br />

b<br />

is equal to 0, then block b<br />

is not included in the blended product and it<br />

will be treated as a waste block. g<br />

b<br />

and G<br />

min<br />

are the grade of material in block b, and<br />

minimum allowable grade of final blended<br />

i<br />

i<br />

product respectively. n<br />

im<br />

, im<br />

b<br />

, and im<br />

max<br />

are<br />

the number of impurities in the ore deposit,<br />

grade of impurity i in block b, and maximum<br />

allowable amount of impurity i, in the final<br />

blended product respectively.<br />

The aim of the model is to maximize the<br />

total tonnage of the blended product<br />

(Equation 2). Equation 3 guaranties that the<br />

grade of the final product is greater than the<br />

minimum required. Equations 4, is used to<br />

make sure that the amount of impurities<br />

(contaminants) in the final product is lower<br />

than the maximum allowed. Equation 5,<br />

make sure that the decision variables are<br />

binary.<br />

The model presented in equations 2-5,<br />

selects a sub set of potential ore blocks that<br />

meets the blending requirements, and it does<br />

not consider the final outline of the mine (pit<br />

limit). The set of the selected potential ore<br />

blocks is the input of the pit optimization<br />

algorithms. The values of the potential ore<br />

blocks are assigned to be equal to the value<br />

of the final product, and those ore blocks that<br />

are not selected for blending are treated as<br />

waste blocks. Then it is possible to determine<br />

BEVs and the ultimate pit limit. In the next<br />

section the approach to combine pit and<br />

blend optimization is presented.<br />

4 <strong>PIT</strong> AND BLEND OPTIMIZATION<br />

There are a number of pit design algorithms<br />

which is discussed in section 2. These<br />

algorithms require that the BEV of each<br />

block to be determined prior to applying the<br />

algorithms. In order to determine the BEV of<br />

the blocks, one needs to first select the set of<br />

blocks that can be blended. Then the BEV of<br />

these blocks is set to be equal to the value of<br />

final product. After this, one could apply any<br />

available methods to determine the ultimate<br />

pit limit (UPL). Figure 1 presents the<br />

procedure of determining the ultimate pit and<br />

blend limit according to Osanloo and<br />

Rahmanpour (2012).<br />

Figure 1. The procedure of determining the<br />

ultimate pit-blend limit<br />

According to figure 1 the steps of<br />

determining the ultimate pit-blend limit is as<br />

follow.<br />

Step 1) The potential ore blocks are<br />

selected from the block model based on<br />

characteristics such as rock type and ore<br />

grade. The set of these blocks are named S.<br />

Step 2) Set S is fed into the blend<br />

optimizing model to identify and select those<br />

block which satisfy the blending<br />

requirements. The set of those blocks that<br />

meet the blending requirements are called<br />

122

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