test 2 Flashcards
Explosives release energy as
gas, shockwave, heat
explosives initiated by
heat, impact, friction, or shock
RoR
rate of reaction
Detonation
RoR is higher than the speed of sound, creates shockwave
shock
rapid change in attributes such as density, temp, etc
detonation velocity
1500-8000 m/s
deflegration
slow RoR, no shockwave
3 types explosives
high, low, blasting agents
blasting agents
cannot be detonated by #8 cap, insensitive
detonator sensitive
high explosives set off by #8 cap
free face
volume being blasted that has air as neighbor
blast hole length
longer than bench height
cheapest way to break rocks
blasting
how explosives break rocks
shockwave creates micro fractures, gas pressure extends fractures radially to free face, pressure pushes out broken rocks
tensile strength of rock
10% of compressive strength
compressive wave becomes _ after reflection on free face
tension wave, further breaks rocks
confinement balance
too much=too large rocks, too little=fine rock/thrown material
most common explosive
ammonium nitrate fuel (ANFO)
emulsion
mixtures of two liquids that do not normally mix, droplets of one (discontinuous phase) suspended in another continuous phase. AN dissolved in water and mixed with oil.
why is emulsion heavier than water?
difficult to load light explosives in watery holes
what are emulsions used for?
wet holes
3 types of initiation
chem, mech, electrical
how detonator works
primary expl sets off secondary (like PETN)
PETN
pentaerythritol tetranitrate
why explosive timing is important
fragmentation depends on delay from neighbor, multiples of 25 MS
percussive drilling
breaks by hammering, best for hardest rocks
rotary drilling
breaks rocks by twisting+downward pressure
type of rock consumes most bits
abrasive rocks
burden
distance to free face, aspect used for spacing example: (S=1.4B)
subgrade drilling amount
1/3 burden
powder factor
ratio of explosives used per ton of rock broken
stemming material size
ideally 1/8 hole diam
bench height to burden
3-4 times burden
less burden means
more holes per sq area
things to change particle size distribution (PSD)
B, S, stemming, explosive type/quantity
why control grade?
- meet metal production target 2. meet mill grade target
grade sample linked to
particle size of blasthole cuttings
bad sample means
holes near cutoff grade get misclassified
choke
muck from previous blast not loaded and prevents movement of freface
features of strip mines
shallow dipping bedded deposits
spoil volume
space for overburden (cross sectional area based on angle of repose) should be `1.35 times what dragline removes based on expansion
width of drag line strip
depends on truck/shovel, reach of dl, narrow pros: shortens cycle for dl, spoil peaks easily leveled for reclamation.
2 types of production loaders
rope shovels and hydraulic excavators (front loading and back hoe)
rope shovel toughness
heavier and more protected buckets, can handle abrasive material
mobility of rope shovel
requires electric cable, managing power supply can be prohibitive
rope shovel vs h excavator
HE has higher production rates, RS have higher capitol cost but lower service cost. become cost effective in 5 years
of passes to load
3 to 4
productivity measured via
truck cycle time
time to load truck is a
kpi
guide to slope stability
design slopes properly, execute design, monitor slopes, maintain health of slopes
linear feature description
trend/ plunge
planar feature description
dip/strike
planar failure
dip direction similar to slope but flatter dip, greater than friction angle, due to structure
wedge failure
structure controlled, 2 structures intersect, intersection line is less than dip of slope but more than friction angle, rapid/slow
toppling failure
structure controlled, strike within 20 deg of face, steeply dipping, slabs form with large height to thick ratio, cog must shift to hapen
circular failure
not structure controlled, low soil strength
raveling failure
basic weathering, rain, freeze/thaw, usually minor
slope failure leads to
equilibrium
slopes dont fail without
reason
tension cracks
material is moving into pit leaving cracks, visit bench crest
scarps
material is moving vertically, material unstable
abnormal water flow
can be sign of slope failure, more/less
bulges/creep
slow failure indication, veg can be a clue, live trees grow with abnormal curve
rubble at toe
indicates failure
EDM
electronic distance measuring, robotic total station, control point, monitoring beacon, first 2 must not move
point clouds
area scanned periodically for movement, radar for about to happen failure
gps monitoring
in pit may not have coverage all day
pre splitting
use to minimize back break of explosives for final pit wall, not effective in closely jointed rock
line drilling
last row of holes uncharged to promote splitting, line of weakness, holes close together, construction/stone
vegetation must
achieve 70% reveg and survive 3 growing seasons since last seeding
5 themes of reclamation
dealing with lefotvers/harmful material, erosion/sed control, gentle/stable slopes, veg, appropriate land use
4 parts of topsoil reclamation
ID, salvage, stockpile, replace
pedestals
top soil reference, dozer rip after salvage to verify
topsoil stockpile
dont mix with OB, prevent erosion/loss, less than 5H:1V angle
drainage goals
reduce speed/erosion, control seds, water flow as should be
water/sed control structures
sed basin, diversion ditch, drop structures, backfill impound
sed basin design
2:1 L:W and L:D, 2-3 ft of permanent pool above storage,
check dams
internal dams like wall of rock in sed basin o catch big particles and slow water
turbidity curtains/baffles
slow water and increase distance it must flow, help drop sed from suspension
flocculants
chemical that help drop seds
diversion ditches
prevent mixing of runoff from undisturbed area with mine runoff
diversion stability
rock rip rap, grass lined, check dams
drop structures
used in ditches through steep gradients to protect channel
alternative sed control
straw/hay bales, water not supposed to flow over, not ideal for steep/narrow, catch seds, degrade
rock check dams
for steep and defined drainages
weir
built to monitor water flow, uniform cross section
backfill settling
3 to 10 ft
in situ leaching
for uranium/copper/etc, metal leached w/ lixiviant, 5/7 spot patterns
ISU deposit requirements
deposit is porous and saturated, chemistry good for leaching, impermeable layers above/below, economic value
excursion
escape of solutions outside mining layer, unplugged exp holes, excess pressure, blocked aquifer
controlling leach
more solution pumped out than in, neg pressure, up to 5%
well patterns
overlapping flows
monitoring wells
closely spaced, above/below mine layer
restore mining layer phases
- stop inj/pump out solution/h2o enters, 2. pumped out solution is treated w/ rev osmosis and injected, 3. pump out aquifer and chemically remediate solution and inject, 4. pump out and in to mix it all
mining layer restoration times
- 7 months, 2. 9 months,
ISU recommended best pract
compreh understanding of aquifer/subsurf enviro, strong disposal plan, demonst of capability
placer mining
mining on streams or shallow beds, artisinal scale common, soft alluvial sands, grav separation
