This lecture reviews the most important properties of mined materials
1. Material Density
The mass (weight) per unit volume of material.
a. The denser the material, the more weight there is per unit of equal volume.
b. Density of mined material varies greatly:
* iron ore insitu @ 6,000 lbs/BCY or 3 t/Bm3
* coal insitu @ 1,800 lbs/BCY or 1 t/Bm3
c. Sources of information
* field measurements
* handbooks for rough estimates only
2. Material Swell
a. When broken, material swells
b. Swell results in lower density of broken (loose) material
NOTE: loose density is always less than insitu (bank)
c. Swell depends on the type of material and on its size (how well broken)
d. Where to get the values from :
* field measurements
* handbooks for rough estimates
Typical swells: from 15% (sand) to 50% (rock)
Note This:
When describing the quantity of material
ALWAYS STATE IF LOOSE OR BANK
* loose cubic yards, LCY
* bank cubic yards, BCY
* loose cubic meters, LCM or lm3
* bank cubic meters, BCM or bm3
10% penalty for not following this rule in class assignments
Swell Factor (SF)
a. Defines the change of density or volume when material is broken (fragmented)
b. Defined in two different ways:
* based on change of density per unit volume; thus SF<1; sometimes used in America
(note CAT “load factor”)
* based on change of volume per unit of mass; thus SF>1; common elsewhere
c. Where to get the values?
Field measurements Handbooks?
Swell factor: density change
SF = 1 / (1 + % swell)
for swell of 30%
SF = 1 / (1 + 0.3) = 0.77
that means:
lbs/LCY = SF x lbs/BCY
lbs/BCY = (lbs/LCY) x 1/SF
Swell factor: volume change
SF = (1 + % swell)
for swell of 30%
SF = (1 + 0.3) = 1.3
that means:
lbs/LCY = (1/SF) x lbs/BCY
lbs/BCY = SF x lbs/LCY
Angle of Repose
a. The property of loose material that is related to its cohesion
b. Defines the free piling angle if the material is heaped
c. It is not a pit slope angle, unless the slope is excavated in loose material
d. It is a dump slope angle, a stockpile slope angle
e. Where to get the values from:
* insitu measurements
* handbooks for rough calculations
Fill Factor
a. We seldom load the equipment to its nominal volumetric capacity
* loading/hauling equipment match
* material properties: angle of repose/surcharge
* digging forces, material fragmentation @ the like
b. Fill factor needs to be defined for each job & material
c. Typical values:
* insitu job studies
* handbooks for rough estimates only
SF & AR: Mining Implications
a. Mine dump volume (LCY) is LARGER than the excavated pit (BCY)
* Know swell to properly plan and design mine dumps, waste disposal facilities, etc.
* Know swell to plan/design material stockpiles
b. Volume of transported material is more than either that excavated or dumped
* Know swell to properly size the mining equipment
Buzzwords
a. Bucket, bowl, box, tray, other?
b. Swell factor
c. Angle of repose or angle of surcharge?
d. Bank volume, loose volume
e. Bucket fill factor
Sources of information:
a. Local experts
b. CAT Performance Handbook
c. SME Mining Engineering Handbook