Equipment Alternatives for Stoping in Gold Mines

8/10/2019 Equipment Alternatives for Stoping in Gold Mines

1/8

J. S.

Atr Inst Min Metal/

vol. 89 no. 12

D ec. 1989 . pp. 387 -39 4.

quipment alternatives for stoping in gold m ines

by A .G . D U P L E S S IS t D.G . W YM ER t a n d N .C . JO UG HIN t

S Y N O P S I S

T he use of a dense hangingw all-support configuration extending right up to the face w ould enable greater levels

of safety and productivity to be achieved in stopes and becom es a practical proposition if w ater jets are used for

stope cleaning. S uch an arrangem ent opens the way for extending the use of w ater hydraulic power to the w hole

stoping operation. T flis in tum can provide further productivity benefits and significant savings in w orking costs.

W ith all the necessary equipm ent being available s uch a system could be introduced im mediately although the

designs of props and rockdrills are not yet ideal.

S A M E V A T T I N G

D ie gebruik van

n

digte dakstutkonfigurasie w at tot aan die front strek s al dit m oontlik m aak om n grater m ate

van veiligheid en produktiw iteit in afbouplekke te bereik en dit w ord

n

p ra ktie se p ro po sis ie as w ate rs tra le g eb ru ik

w ord om afbouplekke skoon te m aak. S o

n

reeling baan die w ag vir die uitbreiding van die gebruik van hidrouliese

w aterkrag na die hele afboubew erking. D it kan w eer verdere produktiw iteitsvoordele en beduidende besparings

van bedryfskoste inhou. M et al die nodige toerusting reeds beskikbaar kan so n s te ls el o nm id de llik in ge vo er w ord

hoewel die ontw erp van stutte en rotsbore nog nie ideaal is nie.

Introduction

C urren tly o ne of the m ajo r im ped im en ts to th e a chieve-

m ent of significant im provem ents in safety and produc-

tivity in gold-m ine stoping operations is the degree to

whic h g oo d h an gin gw all su pp ort is p ossib le w ith e xistin g

s toping equ ipmen t and con figura tio ns . Th is is p ar ti cu la rly

true for deep, narrow stopes and for those with a weak

stratum in the hangingw all. T he m ain problem is that the

attainm ent of the desired support density at the face is

c ompromise d b y d iffic ultie s in main ta in in g su pp ort c lo se

to the face and in cleaning blasted rock from around m ore

c lo se ly s paced s uppo rt.

In c onsiderin g the use of im prove d sto ping eq uipm en t

and m ethods, therefore, the em phasis should be placed

on approaches that facilitate, rather than detract from ,

g oo d su pp ort. A lte rn ativ e sto pin g e qu ipment a nd su ita ble

powering system s that can now m ake this possible are

becoming avai lable.

Panel Layout and Equipm ent

A pa nel layo ut is d ep icte d in F ig. 1. A n essen tial feature

is th e u se o f c lo se ly sp ac ed b la st-re sista nt h yd ra ulic p ro ps

extending to w ithin 1 m of the face before the blast. A fter

the blast, the front row of props would be almost 2 m

from the face, allow ing a scraper to be run along the face.

Once the face has been cleaned, and prior to the drilling

of blastholes, props w ould be advanced to within 1 m of

the face. A t n< ;>im e, th ere fo re, w ou ld peo ple be w orkin g

in an area not adequately supported. Interlinked head-

boards w ould be used to increase the area of hanging sup-

po rted directly a nd to help prev ent dislod ging du ring th e

.

Presented at a colloquium entitled Equipm ent A lternatives in

U nd erg ro und M in in g, w hich w as o rg an ize d by T he S ou th A frican

In stitu te o f M in in g a nd M eta llu rg y a nd h eld in Jo ha nn esb urg d urin g

S ep temb er 1 98 8.

t

COM RO Chamber of M ines Research O rganization), P.O . Box

9 123 0, A uc klan d P ark, 2 00 6 T ran sv aal.

@

T he South A frican Institute of M ining and M etallurgy, 1988. S A

IS SN 0038-223X / 3.00 + 0.00.

b la st. F or a de qu ate p ro te ctio n a ga in st ro ck fa lls, a su pp ort

resistance of up to 50 kN/m2 would be aimed for.

Face cleaning would be carried out using hand-held

w ater jets to mov e the blasted ro ck fo rw ard from betw ee n

the props into the path of a scraper running along the

face, as illustrated in Fig. 2. T his m ethod facilitates the

use of closely spaced props, and has proved to be m ore

v ersa tile a nd la bo ur p ro du ctiv e th an c on ve ntio na l c le an -

ing. A further benefit is that the footw all is com pletely

cleaned in this operation, and no additional sw eeping of

fi ne s is n ec es sa ry .

Use could be made of blast barricades mounted

d ia go na lly b etw ee n rows o f p ro ps, th ere by c on ta in in g th e

b la ste d ro ck while still a llowin g a cc ess fo r w ate r je ttin g.

A lte rn ativ ely , b ac kfill m ain ta in ed re la tiv ely c lo se to th e

face could provide confinem ent of the blasted rock.

Face rock drilling equipm ent would have to be light-

weight, compact, and easily manoeuvred in order to

operate w ithin the confines qf space dictated by the sup-

po rt con figu ra tio n. H an d-held roc kdrills an d thru stleg s

are therefore proposed. The use of rigs or self-steered

veh ic le s fo r d ri lli ng would not b e f ea si ble in t his s it ua tio n.

The adoption of an underhand face configuration,

rather than a breast face configuration as show n in Fig. 1,

could be advantageous, in that it could assist the w ater-

jet cleaning operation and, if back fill w ere used, w ould

keep the water used in the panel away from the fill.

C hoice of Stoping E quipm ent

Ideally, the hydraulic props w ould be Jightweight to

fa cilitate h and ling an d installatio n, and w ou ld be su ffi-

c ie ntly b la st-re sista nt to a llow fo r in sta lla tio n c lo se to th e

face without having to be removed before the blast.

Preferably, the hydraulic props should be powered by

p la in w ate r. E xistin g h yd ra ulic p ro ps re qu ire a h yd ra ulic

pressure of 20 to 40 M Pa for setting. Depending on the

ty pe o f h yd ra ulic p ow er so urc e u se d, a p re ssu re in te nsifie r

m ight be required to enable this pressure to be attained

JO UR NA L O F TH E S OU TH A FR IC AN IN ST IT UT E O F M IN IN G A ND M ET ALLU RG Y

D EC EM BE R 1 98 9

38 7


2/8

0

0

0

0

0

0

0

0

~

L ig h tw e ig h t b la s t r e si st an t

h ydraulic prop s in stalled at

a d ensity o f app roxim ately

one pro p per square m etre.

Face scrap er

F ig. 1-P anel layout w ith dense

h yd ra ul lc -p ro p s up po rt s ho w n a ft er a

blast

B ackfill or other back area

support

0

0

0 0

P acks for gully supp ort

F ig . 2 -W ater-je t a ssisted face scrap in g

38 8

D EC EM BER 1989

at the prop. S uitable com pact intensifiers for insertion

in the hydraulic supply line to the prop have been

d ev el op ed f or t hi s p ur po se . W a te r- po w er ed b la st -r es is ta nt

p ro ps a re a va il ab le c om m e rc ia ll y b ut t he s m al le st v er si on

h as a 2 00 k N s ettin g fo rc e m ak in g it re lativ ely he avy an d

of unnecessarily high force for the dense support con-

figuration proposed. In order to achieve the required

su pp ort res ista nce it is co nsid ered tha t a se tting fo rc e o f

as little as 50 kN w ould be sufficient w ith a configura-

tion of one prop per square m etre. T his w ould enable

m uch lighter props to be used w hich w ould be m ore

easily handled than those available at present. B eing of

s ma ller v olu me th es e p ro ps w ou ld re quire les s w ate r for

s ettin g. T he re fo re th e in te ns ifie r if re qu ire d c ou ld b e

e ven m ore co mp ac t th an th e v ersio n cu rre ntly a vaila ble .

In addition to being designed for w ater pow ering the

props w ould need to exhibit sufficient resilience and

JO U R N A L O F TH E S O U T H A F R IC A N IN S TITU TE O F M IN IN G A N D M E TA LL U R G Y


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Average Average

Steel Bit

penetration

drilling

Production No. in

length

rate rate rate

site

crew

m

mm m/min holes/h

A 2

0,9

31 to 38

0,53 24,2

B 2 1,2 38 to 42 0,63 23,0

C

1*

1,2

27 to 38

0,57 19,0

ro bustness to av oid being dislodg ed d uring th e b last. Few

problem s are foreseen in the developm ent of such units,

becau se the requ ired techn ologies a re w ell esta blish ed.

T he adoption of the dense support configuration pro-

posed w ould greatly reduce the incidence of rock falls at

the face, and w ould facilitate im proved productivity of

th e sto pin g a ctiv itie s. H owev er, fo r se ve re ro ck bu rst c on -

ditions, it w ould still be necessary to use heavier props

with setting forces from 200 kN upwards, possibly in

combination w ith lighter, low er-fo rce p ro ps.

H and-held w ater jets for face cleaning have been the

sub ject of a certain amou nt of en gin eering d evelopm en t

to rend er them suffic iently safe, ru gge d, an d reliable for

use in stopes . Suitable jetting guns are now available

for use w ith w ater at pressures ranging from 9 to 18 M P a.

A side from m aking it possible to carry out face cleaning

w ith the roof support system described above, the use of

w ater jets enables m uch higher face-cleaning rates to be

ach ieved . In trials con duc ted at K loof g old m ine o ver th e

past three years, average monthly cleaning rates of

typically 20 t/h scraper delays included) have been

re co rd ed u sin g th is c le an in g meth od , a pp ro ximate ly tw ic e

the average rate achieved elsew here on the m ine, w here

only face scrapers are used. The precise cleaning rates

achievable obviously depend on panel length and on the

condition and inclination of the footw all but, generally

speaking, an im provement of at least 50 per cent can be

expected. Labour productivity is also m uch im proved

because the scraper does not have to be rerigged during

the cleaning operation, and because a separate activity

to sweep fines is no longer necessary.

Conven tiona ll y, h and-h eld r ockd rill s and thr us tl eg s a re

pow ered by com pressed air, but hydraulically pow ered

versions operating on em ulsion 98 per cent water) are

now available com mercially. T hese hydraulic drills are

com parable in size and m ass w ith com pressed-air drills

b ut, b ec au se th eir p en etra tio n ra te s a re much g re ate r, th ey

are capable of achieving m ore than tw ice the num ber of

holes drilled per hour. They are particularly effective in

heav ily fractu re d groun d, a nd are en viron me ntally much

m ore acceptable because of reduced noise and elim ina-

tion of fog.

The drilling perform ance of the em ulsion-pow ered

rockdrills has been m easured exhaustively, and T able I

shows som e typical results obtained on various m ines

du ring a six-m onth p eriod un der a v ariety of produ ction

conditions2.

The drilling rates given in Table I are m ore than twice

thos e typic ally a ch ieved w ith comp re ss ed -a ir d ri lls . If f ul l

advantage is taken of this. high perform ance, drilling

labour productivities of up to 100 holes per shift can be

ach ieved con sisten tly w ith o ne drill. In p rac tice, v alu es

as high as 160 holes per shift w ith one drill have been

re co rd ed o n o cc asio ns.

T he hy draulic emulsio n fo r the se drills n eeds to b e sup -

plied at a pressure of 14 to 18 M Pa. Emulsion pumps

c ap ab le o f g en era tin g th ese p re ssu re s a re a va ila ble e ith er

in a conv ention al fo rm , p ow ered electrically , o r in a form

kn ow n as the h ydro-transform er in w hich high -p ressure

w ate r is u se d a s th e d riv in g med ium . H an d-h eld ro ck drills

and thrustlegs po wered b y p lain w ater are u nde r deve lop -

ment. A prototype version is shown in Fig. 3, and ver-

sions are expected to becom e available com mercially

TAB LE I

PERFORM ANCE OF EM ULSION-POW ERED ROCKDRILLS USED FOR

STOPING

*

The large stoping width at this site 2 to 2,5 m) made it possible to

drill w ith a single operator

d uring 199 1. W ith th ese, it w ill bec om e p ossib le to po wer

the drilling operations directly from the sam e supply of

h igh -p ressu re w ater a s tha t used fo r prop s and w ater jets.

F ig . 3 -P ro to ty pe wate r-p owere d ro ck drlll a nd th ro stle g

A common fe atu re o f a ll h yd ra ulic ally p owere d d ev ic es

h an dle d manua lly in sto pe s, in clu din g p ro ps, ro ck drills,

and w ater jets, is that they have to be powered through

flexib le h igh -p ressure ho ses co nn ected to th e po wering

in sta lla tio n. S ta nd ard h yd ra ulic h ose s d o n ot su rv iv e w ell

in the stoping en viron men t ow in g to the su sceptibility o f

the rubber cover to cutting and abrasion, and of the rein-

fo rcing w ire to corro sion . H oses o f im proved design and

ma te ria ls h ave been developed e sp ec ia lly f or t hi s app li ca -

tion, and are rea dily available co mmercially .

In any consideration of the equipm ent and its m ethod

of powering for the face layout show n in Fig. 1, the type

of eq uip men t to be used in the gullie s shou ld also be bo rn e

in m ind. G ully equipm ent is essentially concerned w ith

ro ckh and lin g; co nve ntiona lly , th e scraper w inch is used

for this purpose, but the continuous scraper and load-

haul-dump vehicle LHD) are alternatives3. A ll the

options are fully compatible with the proposed face

layout. A lthough scrapers are electrically powered at

present, it is quite feasible to power them with high-

pressure w ate r, an d a suitable scraper-w in ch driv e based

on a Pelton turbine has already been developed and

proved, and is available com mercially. If face scrapers

are also powered in this way, the possibility then exists

of po werin g the entire stope w ith w ater hyd rau lic s. W ith

th is in m ind , a ran ge of an cillary devices in clu din g item s

such as ventilation fans, watering-down guns, w inch

s igna ll in g bell s, a nd b la sthole c le an er s) h as b een develop-

JOURNA L O F TH E SOU TH A FR IC AN IN ST ITU TE O F M IN ING AND META LLURGY

DECEMBER 9 9

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ed for operation on high-pressure w ater, enabling all

ex tern al su pp lie s o f comp ress ed a ir, ele ctricity , a nd low-

pressure service w ater to be elim inated from the stope if

desired.

Sources of W ater H ydraulic Pow er for Stoping

In reco gnition o f th e desirab ility of po werin g stop in g

m ach inery h yd rau lically , tw o altern ative w ater-b ased

h yd rau lic-p owerin g tech no lo gie s h av e b een d ev elo ped :

e le ctr o- hydr au lic s a nd hyd ro -powe r.

I n a n e le ctr o- hydr au lic power in g s ys tem , h igh- pr es su re

w ater o r em ulsio n for th e p ow ering of sto pin g m ach inery

is g en erated by electrically driv en p um ps. T hese pu mps

can com prise centralized installations that m ay serve a

n umbe r o f p an els, o r m ay c on stitu te a d istrib uted sy stem ,

w here they are located close to the w orking areas and are

each sized to serve perhaps only one panel. The choice

of system to be im plem ented w ill depend largely on the

specific site and m ine layout under consideration. A

diagram matic representation of a m ine w ith a conven-

tional com pressed-air system is show n in Fig. 4, w hile

Fig. 5 depicts an equivalent situation where electro-

hydraulic pow er is used instead. It can be seen that the

use of electro-hydraulics allow s a sim plification of the

m ine services infrastru ctu re th rou gh th e elim in ation of

com pressed-air reticu latio n to th e stop es.

S ince h ydraulic ro ck d rills p ow ered b y plain w ater are

n ot y et av ailab le co mm ercially, any electro -hy draulic

powering system for stopes will have to supply high

p re ss ur e emuls io n f or th is pur po se a t p re se nt. Conver se ly ,

w ater jets w ould be pow ered by plain w ater only. Props

can be operated from either medium , although plain

water is p refe rab le . S ep arate ele ctro -h yd ra ulic p umpin g

in sta lla tio ns , s upply ing wa te r o r emuls io n a s a pp ropr ia te ,

cou ld be pro vid ed fo r the variou s item s o f equ ipm en t b ut,

although technically viable, this would introduce

u nn ec ess ary d up lica tio n o f eq uipmen t.

A n alternative approach w ould be to provide a single

pum ping installation operating on plain w ater, supply-

in g p rops a nd wate r- je ts d ir ec tly , a nd s upply ing emuls io n-

p owered ro ck drills th ro ug h h yd ro -tran sfo rm ers. Again ,

this is a technically viable approach, but the hydro-

tr an sf ormer s c on stitu te a n a dd itio na l e qu ipmen t r equir e-

ment.

A third option, considered to be the m ost attractive,

is to provide one pumping installation that can be

switched from water to emulsion as necessary, using

a pp ro priate ch an geo ver v alv in g. In its simplest fo rm , th is

approach is feasible only if rockdrilling and w ater jet-

ting do not take place sim ultaneously. For the larger

p umpin g in sta llatio ns th is a pp ro ach may n ot b e p ossib le ,

but the difficulty can be overcom e by the installation of

tw o or m ore sm aller pum ps instead of one large pum p,

and arranging for each to be operable independently on

w ater or em ulsion as required.

T he altern ativ e techn olog y o f h yd ro -po wer is b ased o n

th e ex plo ita tio n o f th e d iffere nc e in elev atio n b etw een th e

su rface an d u ndergro un d work in gs o f a m ine to g en erate

an underground supply of w ater at high pressure. This

is then reticulated to the m ining areas, w here it is used

to pow er stoping equipm ent directly, as w ell as to pro-

v id e lo calized co olin g an d su pp ress du st. V ersio ns o f all

th e eq uipme nt n ec essa ry fo r th e sa fe a nd reliab le re tic ula -

39

DECEMBER 9 89

JOURNA L OF THE SOU TH A FR IC AN IN STIT UT E OF M IN ING AND META LLURGY

tion of hydro-pow er are available com mercially, and

sy stem d es ig n p ro cesse s h av e b een d ev elo pe d4 .5 . Hyd ro -

po wer, because of its in herent sim plicity , rep resen ts an

id eal p ow ering so urce for th e op eration o f th e eq uip ment

required to im plem ent the m ining layout show n in Fig. 1.

A hydro-powered m ine is show n diagramm atically in

Fig. 6, and it can be seen that a m ajor sim plification of

the m ine services infrastructure can now be achieved.

Sin ce, for eco no mic reaso ns alo ne, it is no t feasible to

add appreciable am ounts of additives to the water in a

hy dro-p ow er sy stem , p lain w ater is the o nly m ediu m that

can be con sidered . T hu s, u ntil w ater-po wered h yd rau lic

rock drills beco me av ailab le in 19 91 , it w ill be n ecessary

to u se h ydro -tran sform ers for d rilling op eratio ns, bu t all

other equipm ent can be pow ered directly.

Equipment that can be powered by a hydro-power

system has been developed to operate over a pressure

ran ge o f 14 t o 1 8 M Pa, w hich co rresp ond s ap pro xim ately

to the head available in a 1400 t o 1800 m colum n of w ater.

In m any m ines, only a low er pressure head m ay be avail-

ab le. In s uc h cas es, th e te ch nica l feas ib ility an d e co nomic

d esirab ility o f b oo stin g th e static p res su re h ead a va ila ble

through electrically driven boost pumps has been

established.

In th e op eratio n of a w ater h yd rau lically po wered m in -

in g s ys tem , th e imp lic atio ns f or h andlin g was te wa te r both

in stopes and m ine wide are of obvious concern.

Howev er, th eo retica l stu die s4 .5 h av e in dicate d th at co n-

v en tio nal sto pin g o peratio ns p owered b y h ig h-p res su re

water would require between approximately 0,6 and

1,8 ton s of w ater p er ton o f ro ck m ined. T hese th eo retical

figures have been confirm ed by m easurem ents taken in

a sto pe o perated en tirely from h yd ro -po wer at K loo f go ld

m in e. T he w ater co nsum ptio ns m easu red at K loo f fo r th e

item s of equipm ent required for the im plem entation of

the panel layout depicted in Fig. 1 are given in Table 11.

TABLE I I

M EA N W AT ER CO NSU MPTlO NS M EA SU RE D IN T HE

HYDRO-POW ERED STOPE AT KLOOF GOLD MINE

Activity

W a te r c on su mp tio n

t/ t of rock m ined

Hydr au li c d ri ll in g

Wa te r j ett in g

W a terin g d ow n

Blas th ol e c le an in g

P ro p s et ti ng

0,22

0,28

0,03

0,07

0,01

0,61otal

It is therefore apparent that the quantity of water

required for hydraulically pow ered stoping is not very

d iff eren t from th at n orm ally req uire d in co nv en tio nally

pow ered stopes for cooling and dust suppression, and in

fact w ill in m an y in stan ces be con sid erab ly less. T here-

fo re, an y special p rov isio n fo r add ition al w ater su pp ly,

or for waste-water handling equipment and system s,

w ould norm ally not be required.

S ev eral ec on om ic fea sib ility stu dies in which th e co sts

o f w ater hy draulically p ow ered stop ing w ere com pared

w ith th ose o f co nvention ally po wered stop ing have b een

conducted on various m ines. The installation costs

of


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Equipment Alternatives for Stoping in Gold Mines

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Transcript of Equipment Alternatives for Stoping in Gold Mines