In your role as a new engineer in training at ABC mines \'he mine manager asks y
ID: 159278 • Letter: I
Question
In your role as a new engineer in training at ABC mines 'he mine manager asks you to evaluate a section from a new pit they are planning. She gives you the information received from the geology department that contains grade information for each block in that section of the block model. The mineral in questions is cuprite, a copper oxide ore and the grade values are tor pure contained copper. Each block in the model is 15 metres high (the height of a bench), 15 metres wide and 15 metres deep. The density of both the waste and the ore is 2,265kg/m^3.The mine manager tells you that the ore will be processed using a heap leach pad, meaning that costs will be- low, but recovery will be only 30%. Processing costs arc S1 .03 per tonne and excavation (mining) costs are S4.00 per tonne. The cut-off grade is given to you as 0.05% and the price of copper is $3.1187/lb (lb = pound). The mine manager requests that you prepare a brief memo detailing the value (if indeed there is any) of this pit section including details of the method you used to solve the problem on her desk In Monday, November 2^nd. Based on the above information, and using your knowledge from section 10.2 of the SME handbook, construct a similar 7xl5 matrix containing the value of each block (positive or negative) based on the mining and processing costs relative to the potential revenue of the block. Using this as your 'original' matrix, solve for the- value of this pit section using the Lerchs-Grossmann method discussed in class. Verify your result by using t he- floating cone method. Report the value of the pit and illustrate/identify the final pit shape (which blocks arc- mined and which are- not). You can solve this by hand, however it may be simpler in Excel or some other computer program. Show your work (or examples of your excel code/program) for full marks. This assignment is worth 5% of your final grade. You are to complete it alone; collaboration is NOT permitted for this assignment. Since this mine is in Canada, please use SI units. For extra credit: If the price of copper were to change, at what price would the pit shape begin to change? Show this both for a drop in price and for an increase in price.Explanation / Answer
Lerch Grossman method requires two values
1. one for the block location
2. one for the value to be used in the optimization calculation
Some guide lines for eatablishing the cost structure for an optimization study
1. only operational costs are included in any optimization study
2. If the mine can afford to pay for them, then good, if not then the ore body does not generate enough profit to support them.
3. Any block that is at or above the mill break even grade and is within the profitable pit will be added to the value of the operation and extend the mines life.
4. Reducing the amount of tonnes that are available to be processed, which will increase the capital allowance, which will increase the break even grade, and so on.
5. cost of mining is the cost of filling truck up with rock (rock includes both ore and waste). All normal operational costs such as loading, haulage, drilling, blasting, day works and supervision are all included in the cost structure for mining.
6. Any difference in mining ore from waste is assigned to the cost of processing.
Firstly establish the vertical section through a block model of the deposit. Each square represents the net value of a block if it were independently mined and processed.
Secondly, add the values down each column of the blocks and enter these numbers into the corresponding blocks.
Thirdly, start with the top block in the left column and work down each column. Put an arrow in the block pointing to the highest value.
Calculate the bottom value for the block by adding the top value to the bottom value of the block the arrow points to. The bottom value in each block represents the total net value of the material in the block, the blocks in the column, and the blocks in the pit profile to the left of the block.
At last, scan the top row for the maximum total value. This value is the total net return of the optimal pit.
Now use your exel sheet