Assignment #6 Stripping
Ratios by Planimeter
©Dr. B. C. Paul Summer 2003
Assignment
• Stripping Ratios can be done by average end
•
•
area on pit cross sections
You will find an autocad file showing 4 cross
sections
Determine the area of the overburden in each
cross section
– Assume each cross section covers 400 feet
– Get the volume of overburden in each cross section
More Assignment
• Use autocad to get the area of the mined ore
body in the 4 cross sections
– Assume each cross-section covers 400 feet
– Get the total volume of ore
• Using the volume of waste and the volume of
•
ore, calculate the volumetric stripping ratio for
the pit
Assuming ore weight 4900 lbs/cubic yard and
overburden is 4100 lbs/cubic yard calculate the
weight based SR for the pit
Get Ready to Load Your File
• You will need to get an e-mailed or disk copy of
the autocad file
Go to File to load
The needed drawing
You are viewing Cross-Section 1
Using Autocad
The Layer
Is turned
on
Enter the Area Command
Note that the
Word “Area”
Has been
Typed in
Specify that you want the area of
an Object (in this case the hatched
Overburden)
After pushing Enter
After the Area
Command, the
Program is asking
For you to trace
Something or select
An object.
You specify an
Object by typing “o”
You Select Your Object
I placed the curser
On the edge of the
Overburden.
The Machine
Immediately spits
Out the area of the
overburden
Issue the Area Command and
Select the Ore
Curser
Answer
Go to Cross Section #2
Note that a pull down
Menu is activated.
The light bulbs by the
Three other
Cross-sections are dark
(meaning they are not
On for viewing)
Click on the light bulbs
Click the Cross Section #1
Light bulb to turn it off
Now click the Cross
Section #2 light bulb to turn
It on.
The Drawing Switches to the
Second Cross Section
Use this Procedure to Obtain Areas
for Each Layer in Turn
• You now have the areas of Ore and Overburden
•
•
in each of the 4 cross-sections
We are assuming equal weight for each cross
section so simply take the average overburden
and average ore areas
Multiply the average ore or overburden area by
1600 ft (400 ft * 4 sections) to get a volume for
ore and a volume for overburden
– Do note that the drawing units are in feet so your
answer is in cubic feet
Getting Volumetric Stripping Ratio
• Volumetric Stripping Ratio is just the
Overburden volume divided by the ore
volume
• To get the weight based stripping ratio
you must convert cubic feet to cubic yards
(or convert you densities which are
expressed in lbs per cubic yard)
– There are 27 cubic feet in a cubic yard