CASE STUDY ON VERTI CAL CRATER RETREAT MI MI NI NG
BY: SUJAN DALBEHERA DEVGAN SINGH 1
ABHAYA MISHRA
VCR MI NI NG Vertical crater
retreat (VCR) mining is a method originally developed by the Canadian mining company INCO.
To Today, day,
VCR is an established mining method used by b y mines all over the orld o rld that have competent, steeply dipping ore and host roc!.
VCR is based on the crater blasting techni"ue in hich poer#ul e$plosive charges are
placed in large%diameter holes and #ired.
&art o# the blasted ore remains in the stope over the the production cycle, serving as temporary
support #or the stope alls. 2
VCR MI NI NG Vertical crater
retreat (VCR) mining is a method originally developed by the Canadian mining company INCO.
To Today, day,
VCR is an established mining method used by b y mines all over the orld o rld that have competent, steeply dipping ore and host roc!.
VCR is based on the crater blasting techni"ue in hich poer#ul e$plosive charges are
placed in large%diameter holes and #ired.
&art o# the blasted ore remains in the stope over the the production cycle, serving as temporary
support #or the stope alls. 2
COMP ARI SON FOR THE APP L I CABI L I TY OF VCR METHOD TO GI VEN CONDI TI ONS: CHARACTERSTICS
REQUIREMENTS
GIVEN CONDITIONS
Ore 'trength
oderate to 'trong
oderately 'trong
Roc! 'trength
airly 'trong to 'trong
oderately 'trong
*ip o# *eposit
airly steep(+-)
/ degree
*epth
'hallo to *eep
-//%0///m
Ore 1rade
oderate
Ore 2ni#ormity
airly 2ni#orm Other 1iven Conditions are3 0. Thic Thic!n !nes ess3 s34/ 4/%%-/ /m
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METHOD OF WORKI NG: It starts with a geoogi!a se!tio" that#s $ee" %i&i%e% i"to 'i"i"g $o!(s with regar% to geoogi!a reser&es) *he $o!(s are the" %i&i%e% i"to sto+es) •
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*he "e,t ste+ is to i"!-%e the 'ai" a"% s-$e&e %e&eo+'e"t that is "ee%e% to a!!ess a"% e,tra!t the sto+es) Geoogi!a a"% s-r&e. %ata %eter'i"es the gra%es a"% to""ages /or the sto+es) 0a""i"g the sto+es aso i"!-%es %e&eo+i"g the %ri a.o-ts a"% i"!-%i"g %ata s-!h as %rii"g +ositio"s %ire!tio" %e+th a"% hoe sie) 4
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METHOD OF WORKI NG:
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MI NE DEVEL OPMENT AND LAY OUT: The se"uence o# development o# VCR stopes is 7 8 haulage dri#t is e$cavated along the ore body at the drapoint level. 7 8 dra point loading arrangement is created underneath the stope, 7 The stope is undercut. 7 8n overcut access is e$cavated #or drilling and charging.
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CROWN PI L LARS: •
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*he ast te" 'eters o/ the sto+e a!ts i(e a te'+orar. !row" +iar a"% is "or'a. $ro(e" -si"g !ho(e $asti"g ) *he 'i"i"g se=-e"!e ha&e $ee" !ha"ge% /ro' %ow" %i+ to -+ %i+ a"% i"tro%-!e% $a!(>i"g $e!a-se o/ gro-"% !o"tro +ro$e's)
*his !ha"ge was 'a%e to ei'i"ate the sta$iit. +ro$e's that o!!-rre% $e!a-se o/ the !row" +iars that were e/t $ehi"% whe" 'i"i"g %ow" %i+ there are "o !row" +iars e/t $ehi"% whe" 'i"i"g -+ %i+
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ACCESSTO DEPOSI TS •
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*he a!!ess to the 'i"e is 'a%e thro-gh two &erti!a sha/ts at gro-"% e&e o"e /or ore a"% o"e /or +erso""e a"% 'a!hi"er.) *he two -++er sha/ts go %ow" a"% the" thro-gh a s-$9&erti!a sha/t %ow" to 1') *hese sha/ts are aso -se% /or &e"tiatio" +-r+ose) Ra'+s are aso %ri&e" whi!h !o""e!ts two e&es)
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MACHI NERI ES USED: •
a9or machineries used in VCR mining are •
IT: *rill machine
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Remote control ;:*
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'mall agon
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CROSSCUTS •
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A +assagewa. %ri&e" $etwee" the e"tr. a"% its +arae air !o-rse or air !o-rses /or &e"tiatio" +-r+oses) Aso a t-""e %ri&e" /ro' o"e sea' to a"other thro-gh or a!ross the i"ter&e"i"g 'eas-res so'eti'es !ae% !ross!-t t-""e or $rea(thro-gh)
or ea!h sto+e three 3)8 ' wi%e , 3)8 ' high %raw +oi"t !ross !-ts are %ri&e" /ro' the /ootwa oa%er %ri&e) oa%er !ross !-ts are the" %ri&e" thro-gh the ore $o%. to the ha"gi"gwa)
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SI L LS •
*he e"gth o/ the si is -s-a. ? to 1 ' )
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*he 'ost !riti!a o"e whe" the >"a o&er !-t si is $aste%)
DRAW LEVEL •
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Le&e where ore !a" $e oa%e% a"% re'o&e%) A %raw e&e is o!ate% $e"eath the sto+i"g area a"% gra&it. Cow tra"s/ers the ore to the oa%i"g e&e) *he %raw +oi"t !o"sists o/ a oa%er %ri&e two or three %raw +oi"t !ross9!-ts ) a ti+ a"% a &e"tiatio" ret-r" airwa.) Ea!h +ro%-!tio" sto+e i" the retreat has o"e LHD assig"e% to it) 11
STOPE DEVEL POMENT •
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*he sto+e %e&eo+'e"t /or V6R 'i"i"g !o"sists o/ two +ri'ar. e&es the to+ %rii"g e&e a"% the %raw +oi"t e&e) here the sto+e %rii"g heights e,!ee% 8 ' a" i"ter'e%iate e&e is aso esta$ishe% i" $etwee" the %rii"g a"% the %raw e&e) A three e&es are a!!esse% $. %ri&es /ro' the ra'+ o!ate% i" the /ootwa) he" %e&eo+'e"t rea!hes the ore $o%. the height o/ the roo/ o/ the !ross !-t is i"!rease% to 3)8 ') *wo %iere"t a.o-ts are -se% /or V6R i" the >rst o"e a si"ge V6R %rii"g !ha'$er with a wi%th o/ ?) ' a"% two 2)4 , 3)8 ' !ross !-ts) I" the se!o"% o"e two s'aer V6R %rii"g !ha'$ers are e,!a&ate% to a$o-t ;) ' wi%th whi!h res-ts i" i'+ro&e% sta$iit. /or the !ha'$er 12
DRI L L I NG P ATTERN
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BLAS T HOL E ARRANGEMENT:
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BLASTI NG •
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E"erge, !artri%ge s-rr. e,+osi&e is -se% it &er. resista"t to water a"% has a %e"sit. o/ 1)3g7!!) I" or%er to e"s-re >i"g o/ the hoe a"% to a&oi% %e!o-+i"g the !artri%ges are sit so that the. !a" easier e,+a"% i" the hoe) *he e,+osi&e +ower is !o"!e"trate% to a e"gth o/ si, ti'es the hoe %ia'eter to /or' a +oi"t !harge) *he te!h"i=-e -se% /or $asti"g the sto+es is ("ow" as the !rateri"g te!h"i=-e a"% ea!h $ast $rea(s a$o-t 2)8 ' to 3' o/ the sto+e $a!() *he hoes are +-gge% -si"g 11 '' %ia'eter , 48 '' e"gth woo%e" s+it +-gs) or ste''i"g %r. a"% -"i/or' sa"% is -se% ) Ea!h V6R $ast gi&es a" a&erage o/ 2)8 ' $rea( a"% gi&es a$o-t 2 t o/ ore) I" 'ost sto+es /rag'e"tatio" o/ ore is &er. goo% gi&i"g a" a&erage o/ )8 ' , )4 ' , )3 ') A/ter ea!h $ast the e"gth o/ the hoes are 'eas-re% to i%e"ti/. where the gro-"% e&e i" the sto+e is a"% to %e!i%e whi!h hoes sho-% $e $aste% "e,t) 18
BLASTI NG P ATTERN……
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SPECI FI C PROBLEMS HAVE BEEN ENCOUNTERED DURI NG STOPE BLASTI NG •
Hoe !os-re $e!a-se o/ +oor gro-"% !o"%itio"s i" so'e areas)
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sa"% $a(i"g $e!a-se o/ too '-!h ste''i"g a"% wet"ess)
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Bow o-ts $e!a-se o/ i"s-!ie"t ste''i"g or +oor +a!e'e"t o/ the !harge)
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!o"i"g o/ the hoe whi!h 'a(es it %i!-t to +-g the $otto' o/ the hoe)
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SUPP ORT: •
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Roo/ $ot: 2)4' o"g 12914 to" !a+a!it. 8'' 'i"i'-' threa% e"gth 18'',18'',4'' thi!( %og9eare% /a!e +ate i"stae% o" s=-are gri% )
Ma,i'-' aowa$e $ot +rotr-sio" is 8 91'' /or $oth roo/ $ot a"% threa%e% !a$e $ots a"% 8'' /or +ai" !a$e $ots)
A shaow %i+ hoes sho-% $e Cashe% o-t o/ !hi++i"gs $e/ore gro-ti"g roo/ $ot)
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VENTI LATI ON
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*he &e"tiatio" s.ste' i" V6R MINING ME*H5D is $ase% o" a te!h"i=-e that !reates a +ress-re %iere"!e $etwee" the 'i"e a"% the s-r/a!e $. s-!(i"g air o-t o/ the 'i"e a"% etti"g /resh air i") *he reaso" /or the high te'+erat-res is that air is heate% $. $oth a-to!o'+ressio" whi!h is a /-"!tio" o/ s-r/a!e te'+erat-re a"% %e+th a"% $. ther'a ra%iatio" /ro' the host ro!()
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ANAL Y SI SOFGI VEN CONDI T I ON The ore in a stope bloc! is drilled ith IT: drill rigs positioned in the overcut. :oles are drilled donard until they brea! through into the undercut. Vertical
holes
are pre#erred herever
possible.
:ole diameters vary #rom 0/ to 0=- mm, although
holes 5/- mm in diameter have been tried in a #e mines. or a 0=-mm dia hole , hole pattern o# by m is typical. :oles are charged #rom the overcut using poer#ul charges contained in a short section o# blast hole. The ore is muc!ed #rom stopes through the undercut using remote%controlled ;:*s or recovered by a
drapoint system underneath the stope as in sublevel stoping. The poer#ul VCR charges involve higher ris!s #or damaging the surrounding roc! than sublevel open
stoping.
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BLASTI NG ANAL YSI S…. •
'pherical charges should be placed to obtain the ma$imum cratering e##ect. 1ravity enlarges the crater dimensions
8ssuming hole diameter>0=- mm and ?last hole pattern o# by m •
;et the stope o# operation has length(along stri!e)>/m
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@idth o# stop is assumed to be /m (4/%-/m)
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8s e can control no. o# blasts in a shi#t rather than depth o# blast hich depends upon drilling machine.
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'o assume drill depth to be 0//m.
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'o volume o# blast>(/$/$0//)>0=////cubic meter
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8ssuming speci#ic gravity o# ore>5,
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Total output per round o# blast>0=////$5>45////!g(45/ ton)
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This is close to per shi#t production(0///A4>444.44tn)
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'o e re"uire 0 blasting in the stope per shi#t.
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PRODUCTI ON ANAL YSI S: •
1iven &roduction Target is 0///tnAday
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8suming 4 shi#ts per day, production per shi#t>0///A4>444.44tn
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8ssuming Capacity o# Remote control ;:* is 4tn
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'o no. o# cycles>444.44A4>005(assuming 0;:*) per shi#t
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8ssuming no. o# cylces by 0;:* is 55, no. o# ;:* re"uired is 005A55>=
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PRODUCTI ON ANAL YSI S:
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8ssuming in one day avg. 5 cycle is completed in 4 shi#ts and or!ing on drilling over B m5
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On charging o# 0m o# hole, let 0.-m retreat ore is produced by a single blasting.
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Volume o# ore produced in one cycle>BB0.->5 m4
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Volume o# ore produced in one day > 5B5>5 m4
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8ssuming some e$tra production o# 6m4, total production per cycle is -/ m4
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8ssuming -/ m4 are produced by development o# drives and crosscuts.
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'o in one stope>-/D-/>0//m4 per day
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;et in one day - stopes are depillared then0//B->-// m4 per day
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8ssuming copper ore hich has speci#ic gravity 5 24
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'o total production per day>-//B5>0///m4
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ine Rules
VENTI LATI ON ANAL YSI S:
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8ir velocity should be /.-%4 mAsec and recommended is 0.5 mAs
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5.- m4Amin per tn o# production
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=m4Amin per employee or!ed in mine
'o #or per shi#t production 444.44 tn(0///A4) re"uired "uantity o# air should be 5.-B444.44>6444.5- m4Amin>046.66 m4Asec
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8ssuming =// men are or!ing in a shi#t so re"uired "uantity o# air should be =//B=>4=//m4Amin
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To have e##icient ventilation •
Resistance should be minimiEed 28
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2se o# control devices should be reduced
8ssuming in one crosscut •
Fuantity o# air re"uired>5/m4Asec
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;ength o# air ay>4//m
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Cross section o# air ay>5.-mB4m
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Resistance coe##icient>/./0 N'5m%
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&ressure re"uired G &oer o# ventilationAair poer re"uired>
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BA CK FI L L I NG: It is done #or #urther e$traction o# ore in ne$t stope. It should be done in such a ay that it should su##icient enough such that it act as sel# supporting during the e$traction o# other.
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2pon completion o# the ore e$traction, the stope is o#ten bac!#illed #rom the top dri#t, providing roc! stability #or upcoming blasts.
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It can be bac!#illed ith cemented #ill to provide all support #or the blasting o# successive stopes.
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This process is repeated until the ore body is mined.
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ADVANTAGES:
:igher tonnage per day and loer stoping cost.
;oer development cost since it eliminates raise boring and slot%cutting. Increased sa#ety o# operations because drilling and blasting are carried out #rom above and
there is no need #or the miner to enter the actual stope. Improvement in #ragmentation (the method yields loest poder #actor). Reduced labour re"uirements and drilling and charging time. Reduced dilution and over brea! . Hlimination o# up%hole drilling and up%hole loading o# e$plosives 2?
CONCL USI ON
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or the gi&e" +ro%-!tio" target •
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Hoe %ia'eter sho-% $e 1;8'' 1 $asti"g is re=-ire% +er shi/t i" o"e sto+e No) o/ LHD re=-ire% ; 8 sto+es !a" $e e,tra!te% +er %a. -a"tit. o/ air sho-% $e 13?)?? '3 +er se! S-++ort !a" $e %o"e with roo/ $oti"g a"% wire 'esh At ast s-++orts !a" $e $a!(>e% with !e'e"te% > 2@
