3. 2 | P a g e
Introduction
The aggregatessectorin the UK is showingstronggrowthcoupledwithrise ininfrastructure
projects.Manycompanies
WestCountryAggregates(WCA) have beenaskedtoforma comprehensivedesignforthe blasting
and productionsequence fora proposedlimestone quarryonbehalf of the Camborne school of
Mines(CSM). Provisional projectionsshow areserve of material toa depthof 900m withplanning
permissionlimitingthe depthof the site to90m below surface elevation.2mof overburdenhas
alreadybeenstrippedawaytobeginproduction.Regulationspermitthatbenchheightbe nogreater
than 15m andfor safetyoverall slopeangle mustnotexceed47degrees. Benchwidthsare set10m
to accommodate the widthof one ADT, withall levelshaving anaccessramp to the next.Any
changesto accessramp designcan be plannedandconstructedduringproduction.
The geologyof the depositisa limestonewiththree jointsetsconfirmedthroughlogging(See Table
1). A horizontal zone of weaknessof 1.5m thicknesswasinterceptedthroughinvestigationworkata
depthof 36m. Investigationworkanticipatesthatthe workingswill be belowthe watertable.
Table 1: Geotechnical data for joint sets from site investigation
To the North-Westof the site there isa domesticpropertyapproximately250mfrom the proposed
workings.The excavationwill be predominatelyoval shaped.
The quarry has beenaskedtoproduce 20,000 tonnesof limestoneaggregate permonthforthe
aggregatesindustry.Thisresultsinanannual productionof 240,000 tonnes.The quarryissmall to
mediumscale. Rockpile muckingwillbe achieved throughone 35 tonne track mountedswing
shovel feedingintothe primaryinpitmobilecrushingunit.The crushedpilewillbe muckedbyone
frontendloaderand fedintoa 45 tonne ADT to be transferredtothe secondarycrushingplant.
500m is the approximatedaverage distance the ADTwill coverinone cycle.
The rock masspropertiesforthe site are as follows:
UCS = 170 MPa
SpecificGravity= 2.65 t/m3
Jointset Dip° Direction Persistence Spacing(m)
1 32° NNE High 0.9
2 89° SSE Medium 2.5
3 18° WSW Low 6.0
4. 3 | P a g e
Quarry Parameters
1.1 Bench Height
Regulationsimpose alimitof quarryingtoa depthof 90m. A 2m overburdenstriphasalreadybeen
completed.Thisleaves88mof mineral depthtobe quarried.Witha maximumallowable bench
heightsetat 15m itis proposedthatthe quarry be splitinto6 bencheswiththe firstbeing13mand
the followingbenches15minheight.
BenchNo. 1 2 3 4 5 6
Benchstart height
fromsurface (m)
0 -13 -28 -43 -58 -63
Benchheight(m) 13 15 15 15 15 15
Benchfinishheight
fromsurface (m)
-13 -28 -43 -58 -63 -88
1.2 Bench Angle
Most UK quarriesoperate abenchangle between5-15 degreesdependingonthe rocktype and
stability (assumedvaluethroughworkexperience).Vertical benchespresenttoomanyissueswith
drillinganddonotsupportslope stability. WCA recommenda10 degree benchangle asthe most
efficientfordrillingblastholesandaidingslope stability. For6 benchesthisgivesanoverall slope
angle of 37 degrees.
Figure 1: 2D side view for quarry bench parameters
5. 4 | P a g e
Vibration Prediction
Before the timingsforthe holescanbe established,firstitisimportanttopredictthe vibrationof the
blast.A domesticpropertyissituated 250 metersfrom the quarry boundary. BS 6472 part 2 dictates
that no blast should exceed a peak particle velocity (PPV) of 6mm/s. PPV can be affected by the
geology, the Maximum instantaneous charge (MIC) and the amount of explosive detonating at the
same time. The main cause of increased PPV is the MIC. MIC is the square of separation distance
betweenblastandreceiveri.e.the propertydividedbythe scale distancecorrespondingthevibration
level required. The equation is shown below:
𝑀𝐼𝐶 = (
𝑠
𝑠𝑑
)
2
To work outthe scaleddistance inmKg-0.5
requiresthe followingequation:
𝑃𝑃𝑉 = 𝛼( 𝑠𝑑) 𝛽
α andβ representdimensionlesssite factors.Theypermitforthe use of local geologyinfluencingthe
attenuationof blastvibration.Theyare the resultof specificsite investigationandare resultantfrom
the leastsquaresregressionmethod. [4]
No data hasbeenprovidedforthe dimensionlesssite factors.WCA assumesthatfurthervibrational
analysiswill be conductedatthe site inorderto change the blastdesigntofitwithinthe allowable
limitsof vibration.Usingpreviousexperience workinginlimestonequarries,WCA assumes thatthe
valueof α for thislimestone quarryata 95% confidence levelis180.00 (forprogrammable
detonation) and βhas a value of -1.1.
With this information calculated it’s possibleto determine the scaled distance.
6.0 ( 𝑃𝑃𝑉) = 180.00( 𝛼) × ( 𝑠𝑑)−1.1( 𝛽)
Therefore scaled distance=22.02 m
From this MIC can be calculated:
𝑀𝐼𝐶 = (
250
22.02
)
2
This gives an MIC of: 128.9 Kg
Blast Parameters
The following section outlines the key parameters for every blast to be undertaken at the quarry.
A breakdown for individual benches can be seen in Chapter 4.
3.1 Number of Blasts per Month
As there isa limitationonequipmentavailabilityit’sthe recommendationof WCA thatthe quarry
operatesone blastpercalendarmonth.Thisshouldmaximise the utilisationof the equipmentand
ensure minimal overbreakandback breakthroughlargerscale blasting.
6. 5 | P a g e
3.2 Hole Diameter
Hole diameterischosentosuitthe blastratio forthe rock type andto supplysufficientyield.Inthe
UK it iscommon to findquarriesblastingwitha110mm drill hole.WCA recommendsa110m drill
hole withnumerical calculationinthissectionprovidingevidence forthe choice.
3.3 Burden
Burdeniscalculatedthroughthe followingequation:
𝐵 = (30 𝑡𝑜 45)𝐷
Where:
B= Burdeninmeters
D= Hole Diameterinmeters
30 to 45 is a value representsthe type of rock.Where 30 is hardrock and 45 is softrock.
For lime stone the value istypicallychosenas37.
Withthisinformationthe burdeniscalculatesas:
37 × 0.110 = 4.07 𝑚
3.4 Spacing
Spacingiscalculatedthroughthe followingequation:
𝑆 = 𝐵 × (1 𝑜𝑟 1.25)
Where:
S = Spacinginmeters
1 or 1.25 is the multiplierchosenbaseduponthe geologyof the rock.If the jointingpreferable then
the spacingcan calculatedwitha 1.25 multiplierbutinmostcasesthe multiplieris1 resultingina
square pattern.For thisdesignandgeologyamultiplierof 1is sufficient.
Therefore spacingisalso: 4.07 𝑚
3.5 Sub Drill
Subdrill iscalculatedas: 𝑈 = 0.3𝐵
Thiswouldgive asub drill of: 0.3 × 4.07 = 1.221 𝑚
Thisisn’ta practical value forsubdrill forthe drill operator.Toensure a cleanbench floorand
removal of the toe it isrecommendedthatthe subdrill value be roundedto1.0 meters.
3.6 Stemming
Stemmingatthe top of the hole isusedtoavoidflyrock by ensuringthe gaspressure of the blast
doesnotventout the top of the hole.Stemmingwillbe made of 6-10mm gradedaggregate.The
stemmingvalue isequal tothe calculatedburdenforthe hole diameterwhichis4.07mpractically
thisisharder to achieve therefore valuesbetween4.0and 4.2 metersare allowed.
7. 6 | P a g e
3.7 Hole Volume
The volume allocatedtoone hole isequal tothe burdenmultipliedbythe spacingandthe heightof
the hole.The heightof the hole includessubdrill,thereforeeachhole willbe 15+1 whichis16
meters.Forthisdesignthatwouldresultin:
4.07 × 4.07 × 16 = 265.04 𝑚3
3.8 Column Charge
The columncharge isthe heightof the explosiveinthe hole.Thisisequal tothe hole heightminus
the stemmingheight.Forthisdesignitisequal to16m – 4.07 m whichis11.93 m.
3.9 Blast Ratio
There are typical blastingratiosforhardrock, softrock and mediumstrengthrockbasedonANFO.
These are:
Hard rock – 4t/Kg
Mediumrock – 6t/Kg
Softrock – 10t/Kg
Explosive Parameters
The followingsectionoutlinesthe explosivesanddetonationsystemusedforall blasts.
2.1 Explosive properties
The chosenexplosive isOrica’sCentraTM
Gold70 bulkemulsion.The technical dataforthisexplosive
isoutlinedin Table2.
Product CentraTM
Gold 70
Density(Kg/m3
) 1200
MinimumBlasthole Diameter(mm) 45
Hole Type Wet & Dry
Delivery System Pumped
Typical VOD(m/s) 3600
Relative WeightStrength(%) 70
Relative BulkStrength 102
Gassingtime 20 minutesbetweenloadingandstemming
Table 2: Explosive technical data [1]
2.2 Primer
The chosenprimerisBrexco’sT-500 Booster.
Colour Red– outersleeve
VOD 6800 m/s
Mass 500g (+/- 20g)
Density 1500 kg/m3
Sensitivity –impact/friction 14.7 J / >353 N
Table 3: Primer technical data [2]
2.3 Detonation system
WCA recommendsandwill calculatethe blastingschedule baseduponaprogrammable system
providedbyOrica.The systemisknownas IKON.Ithas beenusedbyNordkalkinFinlandand
8. 7 | P a g e
Glendenninginthe UK.The systemhasa highaccuracy withdelaysprogrammedaslow as1ms. The
optimumdelaytime isconsidered8ms.
Figure 2: Simple layout of programmable detonator [3]
Calculation Results
Takingthe informationabove WCA hascreateda table foroptimumblastdesignsforthislimestone
quarriesbenchblasts.
Burden (m) 4.07 4.10 4.20 4.30
Spacing(m) 4.07 4.10 4.20 4.30
Total columncharge for
16m hole length(incsub
drill) (m)
11.93 11.90 11.80 11.70
Volume (m3
) 265.04 268.96 282.24 295.84
Hole tonnage (t) 662.60 672.40 705.60 739.60
Requiredexplosive(based
on 6t/Kg ratio) (kg)
110.43 112.07 117.60 123.27
Explosive BulkStrength
(%)
102 102 102 102
Explosive Density(t/m3
) 1.2 1.2 1.2 1.2
Loadingrate (Kg/m) 9.83 9.83 9.83 9.83
Loadedhole (Kg) 117.28 116.98 116.00 115.02
Table 4: Blast design parameter calculation results
From the table it’sthe recommendationof WCA thatthe parametershighlightedinblue be
implementedinthe general blastdesign.The holesare slightlyoverchargedby4.91 Kg butthisis
manageable withthe slightexpansionof Burdenandspacing.Eachhole theoreticallywill yield672
tonnesof rock. For 20000 tonnespermonthtarget thiswill meanone blastwith30 holes. The total
yieldwill be 20172 tonnespermonth.The extratonnage can be stockpiledorusedforconstruction
of ramps.Each blastwill consistof three rowswith10 holesperrow ina square pattern.(See figure
3)
9. 8 | P a g e
Burden 4.1m
Burden
4.1m
4.1m stemming
Column Charge 11.90 m
Sub Drill 1.0 m
Spacing 4.1 m
Drill hole diameter
110mm
Toe
Bench face
Crest
Figure 3: Design drawing not to scale
FREE FACE
Figure 4: Blast Design for starter bench, Delay timings and blast
direction
10. 9 | P a g e
Timing Design
Bench1 will have the same designas benches2,3,4,5and 6 despite beingshallower.The design
calculationsshowthatthe same burdensandspacing’sandall the holeswill containlessexplosive
whichwill notaffectthe MIC calculation. The blastingpatternforthe starterbench will beginfrom
the middle andpropagate outward. The designisderivedfromDynoNobel’sshotfiringguide [5]
.
The designsincorporatesacentral startingblastwiththe 5th
hole fromthe leftinitiatingafter0ms
delay.Fromthere the blastfiresfromthe leftfirstwitha8ms delay,tothe rightthere isa delayof
16ms forthe 3rd
hole. There are a total of 15 delaysforthe 30 hole blast.There are 10 holesperrow
and eachrow will initiate16msafterthe firstblastfrom the previousrow. See figure 4.
For the all otherblaststhat aren’tstarter benchblaststhe designwill be showninfigure 5.
Figure 5: Blast pattern for Nonstarter blasts
Thispatternis double rowtominimise riskof backbreak.The starterhole firesfromthe middle
similartothe starter benchdesign.Howeverthisdesignhasevenholeseitherside of the middle.
The resultingthrowwill be similartothe startingbenchesbutovera greaterdistance inwidth.The
blastis basedoff informationpasseddownviaOrica.Timingsbetweenholesare setat 8ms as thisis
shownto be optimumtime delay.16msdelaysbetweenrows.
11. 10 | P a g e
Production
Thissectionwill outline the productionschedule forthe quarrywithrecommendedinpitvehicles
and crusherchoice.
6.1 Fragmentation (KUZ RAM)
It ispossible tomodel the fragmentationusingthe crushedzone model (definedfromKuz-ram).This
wouldgenerate apredicteddistributioncurve forthe blast. WCA isinterestedinlookingatthe 80%
average size fromthe blastcalculatedthroughspreadsheetsoftware.Assumptionsonblockspacing
and otherfactorshave been made [9]
.Figure 6is a table showingthe percentage oversize and
undersize baseduponamaximumoversize aloudbythe jaw crusherselected.
Figure 6: Kuz Ram predicted fragmentation
Figure 7: Fragmentation distribution predicted by Kuz Ram for blast parameters.
6.2 Excavator
The chosenexcavatoristhe KomatsuPC360LC-10 HydraulicExcavatorwitha 2.66 cubic meter
bucketattached. The operatingweightis35.6 tonnes. [6]
6.3 In-Pit Crusher
The chosencrusherwill be a 200 t/hMC 100 R EVOKleemanprimaryjaw crusher.Thiscrushersis
mobile trackmounted. [7]
Maximumsizefeedis0.9mX0.5m.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 0.2 0.4 0.6 0.8 1 1.2
PercentPassing
Size (m)
12. 11 | P a g e
6.4 Front end Loader
The chosenfrontend loaderwill be aCAT926 M witha 5 cubicmeterbucket.
6.5 ADT
Cat’s745C isthe ADT of choice witha rated payloadof 41.0 tons.
6.5 Productivity Cycle
Assumptionsmade:
- 2.5% moisture contentinrock
- 25% swell factor
- 4 daysa weekoperating,1day maintenance andhammeringoversize
- 9 to 5 workingdaywith1 hour lunchbreak.
- 60 secondcycle time
For a 7 hour shift,the crushercan process1400 tonnespershift.Assuminga90% utilisationof the
crusherthiswouldresultin1260 tonnescrushedpershift. 4 daysa weekoperatingequatedto5040
producedperweek.Permonththisproduces20160 tonnesof crushedmaterial.
The buckethas a capacity of 2.66 cubicmeters.The followingequationworksoutthe tonnesper
cycle of the excavatortocrusher.Where 2.65 is the specificgravityof the rock,1.25 representsthe
swell factorand0.9 representsthe 90%fill factor.
(
2.65
1.25
× 2.66) × 0.9 = 3.96 𝑡𝑜𝑛𝑛𝑒𝑠 𝑝𝑒𝑟 𝑐𝑦𝑐𝑙𝑒
A shiftlengthis420 minutesor25200 seconds.Withone cycle taking60 secondsthiswill resultina
total of 420 cyclesper shift.Thisworksoutas 60 cyclesperhour.
Maximumthroughputtothe crusher worksoutas: 3.96 × 60 = 237.6 𝑡𝑜𝑛𝑛𝑒𝑠 𝑝𝑒𝑟 ℎ𝑜𝑢𝑟
Thisis slightlylargerthanthe 200 tonneshourthat the crushercan achieve butassuming some
downtime inthe day and extendedbreaksthiswill matchup.
The CAT 926M withits 5 cubic meterbucketwill take 4passesto loadthe 41 tonne CAT 6745C. it will
take 7 minutesforthe ADT to loadand travel 500m to the secondaryplantwitha20kmh average
speedanda 60 secondcycle per passfor loading.Thismeansthat the loadercan load200 tonnesin
35 minutesthiswill leave 25minutesperhourwhere the loaderisn’toperating.Howeverfactoring
inthe time ittakesto getthe pile large enoughtobeginloading(takenas3 hoursto gaina pile of
600 tonnes).The loaderdriver’sshiftcanbe cutto 4 hours a day.A 4 hourshiftwill resultin1400
tonnesanhour beingtransportedtothe processingplant.Withthe lasthourjustremovingthe final
endsof the crushedpile of 840 tonnes.
