4. rock characterization at el teniente mine.pdf

8/20/2019 4. Rock Characterization at El Teniente Mine.pdf

1/15

~

Synopsis

C av in g is th e lo west

cost underground

m in in g m eth od p ro vid ed

th at th e d ra wp oin t

s pac ing d raw po in t s iz e

and ore hand li ng

facilities are designed to

suit th e ca ve d m ateria l

an d th at th e d raw po in t

horizon can be

m aln ta ln ed fo r th e life

qfthe draw. In the near

future s everal open pi t

m ines that produce m ore

than 50 kt per dqy will

have to exam ine the

f ea sib ility q f c on ve rtin g

to low cost large scale

underground oper at ions.

S ev era l o th er la rg e

scale low grade

underground oper at ions

w ill e xp er ie nc e m q jo r

ch ang es in th eir m in in g

en viro nm ents a s larg e

d rop do wns a re

implemented

T he se c ha ng es

d em an d a m ore re alistic

a pp ro ach to m in e

planning than in the

past where exis ting

o pe ration s h ave b een

p rq je cte d to in cre ase d

d ep th s w ith little

co nsid era tio n q f the

ch ang e in m ining

en viro nm ent th at w ill

o cc ur. A s e co no mic s

fo rc e th e c on sid er atio n

q f u nd erg ro un d m in in g

qf large competent

.

p.a. Box

95 ,

Boesmansriviermond

6 19 0. C ap e P ro vin ce .


2/15

v e m ining-the state of the art

o re bo die s b y low- co st

m ethods, the role qf

cave m ining w ill have

to be dUined In the

past, caving w as

genera llY cons idered for

rockm asses that cave

a nd fra gm en t re adilY .

T he a bility to de fin e

c avab il it y a nd fr agmen -

t at io n, t he a va il ab il it y

q f la rg e, r ob us t

l oa d-h au l-d ump u nits ,

a b et te r und er st andi ng

q f draw-con tro l

r equi remen ts , improv ed

d rilli ng e qu ipme nt fo r

se co nda ry b la stin g, a nd

reliable cost data have

sh ow n th at c om peten t

o reb od ies w ith c oarse

fragmentation can be

exploited by cave

m ining at a m uch lower

c ost th an b y d rill-a nd -

b la st me thod s.

~ 280

It is com mon to find that old established

m ines, w hich have developed standards during

the course of successfully m ining the easy

tonnage in the upper levels of the orebody, have a

resistance to change and do not adjust to the

ground-control problem s that occur as m ining

proceeds to greater depths, or as the rock types

c ha ng e. M in es tha t ha ve ex perien ce d co ntinu ou s

problem s are m ore am enable to adopting new

techniques to cope w ith a changing m ining

situ ation . D etailed k no wle dg e of loc al an d

regional structural geology, the use of an accepted

roc km ass classifica tio n to ch arac terize the

rockm ass, and know ledge of the regional and

induced stress environm ent are prerequisites for

good m ine planning. It is encouraging to note that

these aspects are receiving m ore and m ore

attention.

The Laubscher rockmass c lass if ica ti on

s ys tem th at p ro vid es b oth ro ckma ss ra tin gs a nd

ro ckma ss s tre ng th is n ec es sa ry fo r d es ig n

p ur po se s. The ro ckma ss ra tin gs RMR d efin e

th e g eo lo gic al e nv iro nment, a nd th e a dju ste d o r

m in in g ro ckma ss ra tin gs MRMR con sid er th e

e ffe ct o f th e m in in g o pe ra tio n o n th e ro ckmass .

The r ati ng s, d eta ils o f th e mi ning env ir onmen t,

a nd the w ay in w hich th is a ffe cts th e roc km ass

a nd g eo lo gic al in te rp re ta tio n a re u se d to d efin e

th e cav ab ility , s ub sid en ce ang le s, f ai lu re zones ,

f ragmen ta ti on , undercu t- face shape , cave-f ron t

o ri en ta ti on , undercu tt ing sequence , overal l

m in in g s eq uenc e, a nd s up po rt d es ig n.

Factors f fec ting av ing Opera tions

Twen ty fiv e p arame te rs th at s ho uld b e

c on sid ere d b efo re th e imp lemen ta tio n o f a ny

c ave m in ing o pe ra tio n a re se t o ut in T ab le H . T he

p arame te rs in c ap ita l le tte rs a re a fu nc tio n o f th e

param eters that follow in the sam e box. M any of

th e p arame te rs are u niq ue ly d efin ed b y th e

orebody and the m ining system , and are not

d is cu ss ed f ur th er . The par ame te rs con sid er ed

la te r a re co mmon to a ll ca ve -m ining sy stems a nd

need to be addressed if any form of cave m ining

is contemplated.

OCTOBER 99

v bility

Monito rin g o f a la rg e n umbe r o f c av in g

op eration s h as sh ow n th at tw o ty pes o f c av in g

ca n o cc ur. T he se ha ve b ee n d efine d a s stre ss a nd

subs idence caving .

S tre ss c avin g o ccu rs in v irg in c ave b loc ks

w hen the stresses in the cave back exceed the

stren gth of the ro ckm ass. C aving c an sto p w he n

a stable arch develops in the cave back. T he

un de rc ut m ust b e in cre ase d in siz e, o r b ou nd ary

w ea ken in g must be u nd erta ke n to ind uc e fu rth er

caving.

S ub sid en ce c aving oc curs w he n a djac en t

m inin g h as remov ed th e la te ra l re stra in t o n the

blo ck b ein g c av ed. T his ca n re sult in ra pid

p ropaga tio n o f t he cav e, w it h lim it ed bul ki ng .

F ig ur e 1 illu stra te s th e e ffe ct o f removin g th e

la te ra l re stra in t from b lo ck 1 6 a t S habani. B lo ck

16 had a hydraulic radius of 28 w ith an M RM R

of 6 4 a nd a sta ble , a rch ed ba ck. T he ad ja cen t

block, no. 7, w as caved and resulted in a

reduction in the M RM R in block 16 to 56, at

w hic h sta ge ca vin g o ccu rre d. F or a ra ng e o f

MRMR,F igur e 1 illu str ate s wo rl dw id e cav ing

and s tab le s it ua ti ons.

T he stresses in the cave back can be

m odified to an extent by the shape of the cave

f ro nt. Numeric al mod ellin g c an b e a u se fu l to ol,

h elp in g th e e ng in ee r to d ete rm in e th e s tre ss

p atte rn a ssoc ia ted w ith s ev er al pos si ble min ing

s eq uenc es . An u nd erc ut fa ce , c on ca ve towa r~ s

th e c av ed a re a, p ro vid es b ette r c on tro l o f majo r

struc tu re s. In o re bo die s w ith a ran ge o f M R MR ,

the o nse t o f co ntin uo us c av ing w ill be b ase d o n

the lo we r ra tin g z one s if th ese are c ontinu ous in

p la n a nd s ec tio n. This is illu stra te d in F ig ure 2B,

where the class 5 and 4B zones are shown to be

c ontin uo us. In F ig ure 2 A, th e p ods of c la ss 2

r ock a re suf fic ientl y la rg e to in flu en ce cav ing,

a nd th e c ava bility sh ould b e ba se d on th e ra tin g

o f th es e p od s.

A ll ro ckm asses w ill c av e. T he m ann er of

th eir c av in g and th e re su lta nt fra gmen ta tio n s iz e

d is trib utio n n ee d to b e p re dic te d if c av e m in in g

is to b e implemente d s uc ce ss fu lly . The ra te o f

c av ing c an be slo we d do wn b y c ontrol o f th e

d raw sinc e th e c ave c an p ro pa gate o nly if th ere

is space into w hich the rock can m ove. T he rate

of caving can be increased by a m ore rapid

a dva nc e of the u nd erc ut, b ut p rob lems c an a rise

if this allow s an air gap to form over a large

a re a. In th is s itu atio n, th e in te rs ec tio n o f majo r

s tru ctu re s, h ea vy b la stin g, a nd th e in flu x o f

wate r c an re su lt in d amagin g a irb la sts . R ap id ,

u nc on tro lle d c av in g c an re su lt in a n e arly in flu x

of was te d il ut ion .

The r ate o f under cu tt in g

RV

s ho uld b e

c on tro lle d s o th at ra te o f c av in g RC i s f as te r

than the rate of dam age RD ;

RC>RU>RD.

T he J ouma l o f T he S ou th fr ic an n stitu te o f M in in g a nd M eta liu rg y


3/15

v e

m ining-the state of the art

T able

r m ete rs to b e con sid er ed b efo re the implem en t tion of c ve m inin g

P RIM AR Y F RA GM EN TA TIO N

R oc km ass stre ng th M RM R

Geo log ica l s tru ct ure s

Jo in t/ fr act ure spac ing

J oin t c on di ti on r at in gs

S tre ss o r su bsid en ce c av in g

I nd uc ed s tr es s

LAYOUT

Fragmentation

Drawpoint spacing and size

M ethod of draw

U ND ER CU TT IN G S EQ UE NC E

pre/advance/post

Regiona l s tr e ss es

R ockma ss s tr en gt h

Rockbur st po ten ti al

R ate o f a dv an ce

Ore requ ir emen ts

DEVELOPMENT

Layout

Sequence

Production

Dr il li ng and b las ti ng

P RA CT IC AL E XC AV AT IO N SIZ E

Rockma ss s tr en gt h

n s it u stress


Cavi ng s tr e ss es

S econ da ry b la st in g

D RA WP OIN T INT ER ACT IO N

D ra wp oin t s pac in g

Fragmentation

T im e fram e o f w orkin g d ra wp oints

S EC O ND AR Y B LA ST IN G B R E AK IN G

S e co n da ry f ra g me n ta ti on

D ra w m eth od

D ra wp oin t s iz e

Size o f e quip men t a nd g rizzly sp acing

S UP PO RT R EP AIR

Tonnage drawn

P oi nt a nd c ol um n l oa di ng

B ro w w e ar

Secondary blast ing

T he J ouma l o f T he S ou th fric an n stitu te o f M in in g a nd M eta llu rg y

OC TO BER 1994

28 1


4/15

7

~ 6

:: E

~ : : E

5

4

3

2

A

I

2

5

ClASS lA ,B

ClASS 2A,B ClASS 3A,B

~~1««1

Cavem ining-the state of the art

10 0

90

8

I

3

I

5

4 6

I

2

7

2

5

I

2 5 feet

Figure A s tabi li ty d ia gram for var io us m ines wo rldw ide

HYDRAULIC RADIUS

=

Area/perimeter

CRO SS SEC TIO N B LOCK 7/2

ST BLE Only lo ca l s up po rt r eq uir ed .

TR NSITION L S up po rta ble in u ppe r b and , w ith a rc hin g

in m iddle band and interm ittent caving/arching in low er

band depending on outside influences such as blasting,

water.

C VING P rogressive caving of cave back or w alls into

p re vio us ly c av ed a re as .

C av ab ility , f un ctio n o f:

R o ckmas s s tr en gt h

Geol og ic al s tr uc tu re

I n s itu stress

Water


]

MRMR

0 Stable

~ T ran sition al

. Caving

80metres

CROSS SE CTION BLOCK WEST/2

~

F igure 2 Geomechan ic s c la ss if ic at io n dat a

O CT OBER 1994

82

. ., ..

;

.

I

l O O m

C lA SS 4A ,B

C lA SS 5A ,B

I:;;~ ~ , :;; : I

~

T he J ou rn al o f T he S ou th fric an n stitu te o f M in in g a nd M eta llu rg y


5/15

a v e

m ining-the state of the art

INPUT D T

C VING

OPER TION

G o o d

geotechnicaIinformation,as well as

mon ito rin g o f th e ra te o f c av in g and ro ckma ss

d amage , is n eeded to f in e- tu ne th is r ela tio nship .

r g m e n t t io n

In c av in g o pe ra tio ns, fra gmen ta tio n h as a

b ea rin g on th e f oll ow ing:

> - D rawp oin t spa cin g

>- D ilution entry into the draw colum n

>- D raw control

> - Drawpo in t p roductiv ity

> - S ec on da ry b la stin g/b re ak in g cos ts

> - S ec on da ry blastin g d am ag e.

T he in put da ta ne ed ed for the ca lcu la tion of

th e p rimary fra gmen ta tio n a nd th e fa cto rs th at

d ete rm in e th e s ec on da ry fra gmen ta tio n a s a

fu nc tio n o f the ca vin g o pe ration a re sho wn in

F igur e 3 .

Cav ing r esults i n p rima ry f ragmenta tio n,

w hich ca n b e d efin ed a s th e siz e distrib utio n of

th e p artic le s th at se pa ra te from th e c av e b ac k

an d e nte r th e d raw c olumn. T he p rim ary

fr agmen ta tio n f rom s tr es s cav ing is g en er ally

fin er th an th at from sub sid en ce c av in g owin g to

th e ra pid p ro paga tio n o f c av in g in th e la tte r c as e,

w it h d is in tegr atio n o f th e r ockmass , p rima ril y

a long f avou rably o riented jo in t s et s, and li ttle

sh ea rin g o f in ta ct ro ck . The o rie nta tio n o f th e

ca ve fro nt or ba ck w ith re sp ec t to the jo int se ts

an d direc tion o f prin cip al stre ss ca n h av e a

s ign if icant eff ec t on the p rimary f ragmen ta ti on .

S ec on da ry fra gmen ta tio n is th e re du ctio n

in siz e o f th e o rig in al p artic le th at e nte rs th e

draw colum n as it m oves through the draw

column . The p ro ce sse s to whic h p artic le s a re

sub jected d ete rm in e th e f ragmenta ti on s iz e

d is trib utio n in th e p artic le s th at re po rt to th e

d rawpo in ts . A s tr ong, we ll- jo in ted ma te ria l c an

re sult in a sta ble pa rticle sh ap e at a low draw

height. Figure

shows the decreasein f ragmen-

ta tio n f or d if fe rent d raw heights and le ss -j oin ted

coar se t o well -j oint ed f ine rockmasses . A

ra ng e in roc km ass ratings w ill result in a w ide

ra ng e in fra gmen ta tio n s iz e d is trib utio n a s

c ompa red w ith tha t pro duc ed by ro ck w ith a

s in gle ra tin g, s in ce th e fin e mate ria l p ro du ce d b y

th e fo rm er te nds to c ushio n th e large r blo ck s an d

p re ve nts fu rth er a ttritio n o f th ese b lo ck s. This is

illustra ted in F igu re 2 B, in w hic h cla ss 5 a nd

c la ss 4 m ate rial is sho wn to c ushio n the larg er

p rim ary fra gm ents fro m c lass 3 . A slo w ra te o f

d raw a llows a h ig he r p ro bability o f time-

d ep en de nt failure as the ca ving stre sse s w ork on

p artic le s in th e d raw column .

F ra gmen ta tio n is th e ma jo r fa cto r

de termining drawpo in t p roducti vi ty . Experi ence

has show n that 2 m 3 is the largest size of block

that can be m oved by a 6 yd LHD and still allow

an a cc ep ta ble ra te o f p ro du ctio n to b e

main ta in ed . In F ig ure 5 th e p ro du ctiv ity o f a

layout using 3,5 yd, 6 yd, and 8 yd LHDs and a

g riz zly a re re la te d to th e p erc en ta ge o f fra gmen ts

la rge r tha n 2 m3. T h e usa ge of se co nd ary

e xp losiv es is ba se d on the amou nt o f ove rsize

that cannot be handled by a 6 yd LH D.

Orientation-Cave

Front/Joints

PRODUCTION

Seconda ry B l as ti ng

D am age a nd C osts

Op er at io na l C os ts a nd Ov er al l P ro du ct iv it y

F igure ~nput data for the calculation of fragm entation

The Joum al of T he South frican nstitute of M ining and M etallurgy

OCTOBER 994

28 3


6/15

C a v e

mining-the state of the art

350mm

14 Gr

5 0 0 m m

20' Gr

3yd IJID 6yd lJID

10 0

90

.S 80

f)

(f)

'

70

'

80

~ 50

~

40

.. 30

'

20

10

0,1

0.01

.

1 5 D r il le d a nd B l as te d

=

8 o f Op er at in g Co sl s

0. 1

SIZE m 3

*

1 0 5 m DrawHeight

Primary Fragmentation

- - - -

S ec on da ry F ra gm en ta ti on

1.0 2.0

F ig ur e 4 -S iz e d is tr ib utio n o f c av e fr agme nta tio n

1400

1300

1200

1100

1000

90 0

-- '

:a BO O

[; 700

0..

'

60 0

§

50 0

0

E-

40 0

30 0

20 0

10 0

0

'

....

0,1 1 5 10 2030 5070

P e r c e n t a g e

+

2m 3 - S econdary F ragm entation

10.0 100.0

35 0

.


7/15

iPlX

DII.IJBlU.

P D

DRAIBlU.

I T - - T I ~

C a v e m ining-the state of the art

Drawbell

Dranone

Drawpoinl

18m 22m 24m

11 1411.1 11111 11.111111 '11.111

jl12mljjl Illllljl8m lljlljl~m ll

I

I I

11

I I

I

j I I

I I

I I

I I

I I

I

j I I

I

1

/

1?~II

/

I?~jjlljlllll~~lj~~1

j

'11

'1IIIlllljllfl\III(l\1

I} \ riJ24m ll I I I Iloml...J2om ll I} \ [12m

W18l.J

I I \ I I L ~ I

j

I \ I

j

L ~ I I L ~ I I L ~

j

~~..l

:(

n ~1

en

W d W

W d ~ t j :

30m

Produclion

Level

F ig ure -Max imum and m in im um d rawzon e s pa cin g (is ola te d d rawzon e

=

1 0m a re a o f in flu en ce

=

2 25 m )

11

Lo r

Pressure

Zone

Vedl e. 1 S tr es s

Inere.sed by

. dj .eent wo rk ing

drorpoint

- - Vedle.t

R.dl.1

A . D IPs

@

2.2 X IDZ DIAM.

D IL . ENTRY 15

B. DIPs

@

1.5 X IDZ DIAM.

D IL . ENTRY 6 0

-- -

c. DIPs

@

1.1 X IDZ DIAM.

D IL . ENTRY 8 5

D. DPs

@

1.1 X IDZ WORKED

IN ISOLATION DIL. ENTRY 25

IT -

-TI~

Figure 7 - The r esul ts o f t hr ee -d imens iona l sand-mode l e xper iment s

F ig ure 8 -F low lin es a nd in fe rre d s tre ss es b etw ee n

ad jacen t work ing operat ions

T he J ouma l o f T he S ou th fr ic an n stitu te o f M in in g a nd M eta llu rg y

O CT OBER 1 994

285 ....


8/15

Loading Width

I a ximum /l li nimum Spa ci ng o f D r aYZon es

5m

= 24/14m

4m

=

15/Bm

20/llm

22/13m

3m = 10/5m 13/7m IB/IOm 21/12m

2m

=

9/4m 12/6m

16/9m

Areaof

ionuence

m

- -~

95

- -

~160

- -~ 290

--~360

a v e


R o c k m a s s Class

F F m

R o c k S iz e R an ge

L oa di ng W id th

5m =

4m =

3m =

2m =

5

50 7

0.01-0.3m

4

20 1 5

0.1-2m

3

5 0 4

0.4-5m

Iso la ted Drawzone Di ame te r

2

1 5 0 2

1.5-9m

6.5m

6m

9m

a.5m

am

13 m

12.5m

12 m

Figure 9-M axim um /m inim um spacing of draw zones based on isolated draw zone diam eter

INPUT D T

EFFECT OF

L YOUT

PRODUCTION

INFLUENCE

F ig ur e 1 o- Dra w- co ntr ol re qu ir em en ts

Ore Recovered + Dilution =

P ro du ctio n T on nag e a nd G ra de

~

28 6

It ha s be en e sta blishe d tha t th e d raw w ill

a ng le towa rd s le ss d en se a re as . This p rin cip le

c an be used to mov e th e m ateria l o ve rlyin g th e

m ajo r a pe x by the diffe ren tia l draw o f line s of

drawbe lls so tha t zo ne s o f va ry ing de nsity are

created.

i lu ti on n tr y

The p erc en ta ge o f d ilu tio n e ntry is th e

pe rce nta ge of the o re co lumn tha t ha s b ee n

d rawn b efo re d ilu tio n a pp ea rs in th e d rawpoin t,

and is a function of the am ount of m ixing that

occurs in the draw colum ns. T he m ixing is a

functi on of the fol lowing :

OCTOBER 99

T he J ouma l o f T he S ou th fd ca n n st tu te o f M in in g a nd M eta llu rg y


9/15

0 0

02 0.2

0.4

0.4

0.6 0.6

0.8 1.6

1.2

2.0

1.6

1.2

2.0 0.8

20 40

[

1

[

1

V a l u e of

A

1.9

1.4

Dra.

B

0.9

1.4

,

,

C

:-A-

,

B

4

80 60

40

20

RMR

RMR Range Curves Examples Ratings

0

-

14

NO.l A 50 - 60

15 - 29 NO.2

30 - 49

No.3

+5 0

No.4

B

5 - 60

20

40

60 80 90

120 140

HEIGHT O F IN TE RACT IONZONE IllZ

Range D.Z.Spacing

H.I.Z

10 21m 45m

55 21m

90m

C a v e


Application

Ca lcu la ti on of t onnage

R ec ord in g o f to nn ag es p ro du ce d

Con tr ol li ng t he d raw

A

U n p a y

7 0 % 1 0 0 %

1

% O ra . [

I 1

1 .0 % 0 .7 %

1 .4 % 1 .1 %

1 2 8 % 1 5 0 %

1

1

O r e R e c o ve r y

0 .5 % 8 5 %

0 .7 % 9 6 %

2 0 0

D r a w p o i n t s

A v e ra ge O r e G ra de

=

1 . 4 %

S hu t o ff G ra de

=

0 . 7 %

F ig u re 1 1 -G r a d e analysis

~ Ore draw height

~ Range in fragm entation of both ore and

waste

~ Drawzone spacing

~ R ange in tonnages draw n from draw points.

B

The r ange in f ragmenta tio n s iz e d is tr ib uti on

a nd the m in im um d rawz one sp ac in g a cross th e

ma jo r a pe x w ill g iv e th e h eig ht o f th e in te ra ctio n

z on e (H IZ ). This is illu stra te d in F ig ure 1 2.

T here is a volum e increase as the cave

p rop aga te s, so th at a ce rta in amou nt of m ate ria l

is d rawn b efo re th e c av e re ac he s th e d ilu tio n

z on e. The v olume in cre as e o r swe ll fa cto rs a re

b ase d on th e fragme nta tion an d a re ap plie d to

column height. The f ol low ing a re typi ca l swel l

fa cto rs : fin e fra gmen ta tio n 1 ,1 6, med ium 1 ,1 2,

coa rs e 1 ,08.

A draw -c ontrol fa cto r is ba se d o n the

v ar ia tio n in tonnages f rom wo rk ing d rawpo in ts .

Th is is ill us tr ated in F igur e 13. I f p roduct io n

d ata a re n ot a va ila ble , th e d raw- co ntro l e ng in ee r

mu st p re dic t a lik ely d raw p atte rn . A fo rmula

b ase d on th e ab ove fa ctors h as be en d ev elo pe d

to d et erm in e th e d il uti on entr y p er centage :-

Di lut ion entry =

A -B /A x C x 100,

where

A =Draw-column hei gh t x swe ll f ac to r

B

=

Heigh t o f int erac ti on

C= Draw-control factor.

The g ra ph fo r d ilu tio n e ntry was o rig in ally

d rawn a s a s tra ig ht lin e, b ut u nd erg ro un d

o bs erv atio ns sh ow th at, whe re th ere is e ar ly

d ilu tio n, th e ra te o f in flu x fo llows a c urv ed lin e

w ith a long ore tail , as show n in Figure 14.

F ig ure 1 5 sh ow s tha t d ilu tio n e ntry is a lso

a ffe cte d b y th e a ttitu de o f th e d rawzon e, whic h

c an ang le towa rd s h ig he r o ve rb urd en lo ad s.

,

R M R O F A L L M A T E R IA L IN T H E P O T E N T IA L D R A W C O L U M N T O B E U S E D IN C A L C U L A T IO N A S F IN E S F L O W M U C H F U R T H E R T H A N C O A R S E

M I N J }, {i l l S P A C I N G O F D R A 1 f Z O N E S

A C R O S S T H E M A lO R A P E X

IBm

15m

-- --

12m9m

V E R T IC A L L I N E ( ' L O C A T E D A T H IG H E S T R A T IN G O F M A T E R IA L I N D R A W C O L U M N

Figure 12-Height of the interaction zone (H IZ)

T he J ouma l o f T he S ou th fr ic an n stitu te o f M in in g a nd M eta llu rg y

OCTOBER 994 287


10/15

C a v e mining-the state of the art

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

2

ID 11

Standard Deviation x 100 of Tonnage of W orking Drawpoints

DiPs

Monthly

Tonnage

W ll

2000

E 4

1800

Ell

80 0

W12 E 2

1000 2500

w 3

600

E 3 w 4

1500 800

Mean

=

1375 Standard D eviation

= 682 100 =

7

D raw Con tro l F ac to r

=

0.6

F ig ure 1 3- T he dra w-c on tro l fa cto r

A-B

x C x 100A

A =

O re D raw C olumn H eig ht x Swe ll F ac to r

=

168m

B = Height o f I nteraction Zone = 90m

C

= D raw-control Factor = 0.6

= D ilu tio n E ntr y

168

- 90

x 0.6 x 100

168

= 28

0

100

C

9

0 80

M 70

P

60

0

S

50

I 40

T 30

I

20

0

N

10

0

20 0

25 0

D IL U T I O N W A S T E

0 20

25 0

0

60 80 100

Percentage Draw

20 0

F igu re 1 4-C alc ula tio n of dilu tio n e ntry

~ 28 8

OCTOBER 9 9 4

y o u t s

A f a c to r tha t needs to be resolved i s the co rr ec t

shape of the m ajor apex. It is considered that a

s ha ped p illa r w ill a ssis t in th e re co ve ry o f fin e

o re . Wh ere c oa rs e ma te ria l re su lts in majo r

a rc hin g, a sq ua re -to pp ed majo r a pe x (p illa r) is

p re fe ra ble in te rm s o f a rc h fa ilu re a nd b row

w ear, as show n in Figure 16. The m ain area of

b row wea r is immed ia te ly a bo ve th e d rawpoin t.

If the v ertica l he ig ht o f pilla r ab ov e the b row is

sm all, a s sh ow n in F ig ure 16A fa ilu re o f th e to p

s ec tio n w ill re du ce th e s tre ng th o f th e lowe r

s ec tio n a nd re su lt in a gg ra va te d b row wea r.

M ore thought m ust be given to the design of

LHD l ay ou ts in o rd er to p ro vid e th e maximum

amou nt of m ano eu vring sp ace for the m in im um

siz e o f drift o pe ning so tha t larg er m ac hin es c an

b e u se d w ith in th e o ptimum d rawzon e s pa cin gs .

Ano th er a sp ec t th at n ee ds a tte ntio n is th e d es ig n

o f LHD s to re du ce th e le ng th a nd in crea se th e

w id th . Whilst the use o f la rge m ac hin es m ig ht b e

a n a ttrac tio n, it is re commend ed th at ca utio n b e

e xe rc ise d a nd th at a d ec isio n o n m ach in e size be

b ase d o n the c orre ct a ssessm ent o f the re qu ire d

d rawzon e s pa cin g in te rm s o f fra gmen ta tio n. The

loss o f rev enu e th at ca n resu lt from h igh d ilu tio n

a nd o re lo ss fa r e xc ee ds th e lowe r o pe ra tin g

cos ts a ssoc ia ted w ith l ar ge r mach in es .

E ight d if fe rent hor izon ta l LHDl ayouts and

tw o in clin ed d rawpo int LHD la yo uts are in use a t

v ariou s op erating m in es. A n e xample o f an

in clin ed LHD l ayo ut is sh ow n in F igu re 1 7.

nder utting

Und erc uttin g is o ne o f th e mos t impo rta nt

a spe cts o f ca ve m ining sinc e, n ot o nly is a

comp le te under cu t n eces sa ry to induce cav ing,

b ut the u nd ercu t m eth od c an re du ce the

d amagi ng e ff ec t o f in duced s tr es se s.

The normal under cu ttin g s equence i s t o

d ev elo p th e d rawb ell a nd th en to b re ak th e

u nd erc ut in to th e d rawb ell, a s s hown in F ig ure 1 8.

In e nv iro nmen ts o f h ig h s tre ss , th e p illa rs a nd

b row s a re damag ed by th e a dva nc in g a butm ent

s tre ss es . The Hen de rs on M in e te ch niq ue o f

d ev elo pin g th e d rawb ell w ith lo ng h ole s from th e

u nd erc ut le ve l re du ce s th e time in te rv al a nd

exte nt o f d amag e a ss oc ia te d w ith p os t

under cu tti ng . I n o rd er t o p re se rv e s tabili ty ,

H end erson M in e ha s also fo un d it n ece ssa ry to

d ela y th e d ev elo pment o f th e d rawb ell d rift u ntil

the be ll h as to be b lasted (F ig ure 1 9).

The d amag e c au se d to p illa rs a ro un d d rifts

a nd d raw be lls by a bu tm en t stresse s is

s ig nific an t, b ein g th e ma jo r fa cto r in b row wea r

and excavatio n collaps e. Rockbu rs ts a re a ls o

loc ated in th ese a re as. T he so lution is to

c omple te th e u nd erc ut b efo re th e d ev elo pment o f

th e d rawpoin ts a nd d rawb ells . T he adv an ced

u nd erc ut te ch niq ue is s hown in F ig ure 2 0.

The Journal of The South African Institute of Mining and Metallurgy


11/15

C a v e mining-the state of the art

A.

v e r a g e L o a d in g b o v e D ra w p o in t s

t

t t t ~

t

f

.n

.. .

~ ::::

FOOTWALL

un

D RA W PO IN TS

B H ig h e r L o a d in g T o S id e O f D ra w p o in t s

SIMULATED HILL

FEATURE ffiGHER

O V E R B U R D E N

LOADING

~ ~

M O D E L

C O R N E R

E F F E C T

F ig ure 1 5-ln clin ed dra wpo in t la you t sh ow in g th e e ffec t of d iffere nt o ve rbu rd en loa din g thre e-dim ensio nal sa nd -m od el e xp erim en ts

M O R E S T B L E

R C H E S

F IR F I N E S

D R W

S T B L E R C H E S

H I G H E R

F ig ure 1 6-S ha pes o f m ajo r a pe x/p illa rs

T he J ouma l o f T he S ou th fric an n stitu te o f M in in g a nd M eta llu rg y

P O O R F I N E S

D R W

B E T T E R

R C H F IL U R E

OCTOBER 994

289


12/15

C a v e

m ining the state of the art

Inclination

4 0

S p a c i n g .

D IP

1 2

1 5

1 8

S T R I K E

1 0

1 2

1 2 / 1 5

V E R T I C A L

1 0

1 2 . 5

1 5

F i g u r e 17 An ex am ple o f th e lay ou t o f a n in clin ed d raw po in t

Production Leve l Layout De ta il

I~-

EI~

I I

I I

I I

--~--r r-~---

_ _ ~ _ _ L

L_~---

E

B Cro ss Sec tion

F ig u r e 8 L H D

l ayouta t E lTeniente

~

29

OCTOBER 994

C Isometr ic V iew o f

B lo ck caving w ith LHD

The Joum al of The South fncan nsm ute of M ining and M etallurgy


13/15

C . M e d iu m / L o w

~Stress Weak

G r o u n d

. ;

. :

P ro d u c t io n D r i f t

c ;

f; j

D r a w p o in t a n d

D r a w b e l l D r i f t

~ F u l ly ~ T e m p o r a r y

Full y - - -

S u p p o r t e d

S u p p o r t e d

S u p p o r t e d

C a v e m in in g - t h e s t a t e o f t h e a r t

I n th e p a s t i t w a s c o n s id e r e d th a t th e h e ig h t

o f t h e u n d e r c u t h a d a s ig n i f i c a n t in f lu e n c e o n

c a v in g a n d , p o s s ib ly , th e f lo w o f o r e . T h e

a s b e s t o s m in e s in Z im b a b w e h a d u n o e r c u ts o f

3 0 m w it h n o r e s u l ta n t im p r o v e m e n t in c a v in g o r

f r a g m e n t a t io n . T h e lo n g t im e in v o lv e d in

c o m p le t in g t h e u n d e r c u t o f te n le d to g r o un d -

c o n t r o l p r o b le m s . G o o d r e su lt s a re o b ta in e d w it h

u n d e r c u t s o f m in im u m h e ig h t p r o v id e d th a t

c o m p le te u n d e r c u tt in g is a ch ie ve d . W h e r e

g r a v i t y is n e e d e d f o r t h e f lo w o f b la s t e d u n d e r c u t

o r e , th e u n d e r c u t h e ig h t n e e d s t o b e o n ly h a lf

t h e w id t h o f t h e m a jo r a p e x . T h is r e s u l ts in a n

a n g le o f r e p o s e o f 4 5 d e g r e e s a n d a l lo w s th e o r e

t o f lo w f r e e ly .

upp or t equ ir emen ts

I n a r e a s o f h ig h s t r e s s , w e a k r o c k w il l d e f o r m

p la st ic a ll y a n d s t r o ng r o ck w il l e xh ib it b ri t t l e ,

o ft e n v io le n t , f a ilu re . I f th e r e is a la rg e d if fe re n c e

b e tw e e n th e R M R a n d M R M R , y ie ld in g s u p p o r t

s y s t e m s a r e r e q u ir e d . T h is is e x p la in e d in

F ig u r e 2 1 .

F ig u r e 1 9 - 1 s o m et r ic v ie w o f a p a n e l- c a v e o p e r a t io n

B la s t e d H o r . H o le s

- - -

A .

Very H i g h Stress

Production D r i f t

O n l y

~

-

= -

m - - -

~ = - ~

-

.~ ~

~ ly S u p p o r t e ~

N a r r o w

U n d e r c u t

P r o d u c t i o n

L e v e l

B . H ig h Stress

P r o d u c t io n D r i f t

a n d D r a w p o in t

- - =

m ~ - - -

~

F u l l y

S u p p o r t e d

N a r r o w

U n d e r c u t

P r o d u c t i o n

L e v e l

F ig ur e ~ iff er en t s eq ue nc es o f a d va nc ed u nd erc uttin g

T he Joum al of T he South frican nstitute of M in ing and M etallurgy

OCTOBER 99

N a r r o w

U n d e r c u t

291


14/15

v e mining-the state of the art

0

0

20

0

20

M

30

R

40

M

R

50

60

70

80

90

R

M

R

30

70 800 60

0

SYSTEMS

ilure

. RIGID SUPPORT SYSTEM S

. ..

i

. .

10 0

Figu re 21 -Suppo rt r equ ir ement s f or c av ing operat ions

Acknowledgements

This p p e r p re se nt s a n u pd at e

of the technology of cave

mining. It is not possible to

quote references since the

b ulk o f th e d ata s up po rtin g

the contents of this paper

have not been published and

the basic concepts are know n

t o m in in g e ng in ee rs .

H ow ever, it is appropriate to

a ck now le dg e t he c on tr ib ut io ns

from discussions w ith the

fo llo win g p eo ple in c an ad a,

C hile, S ou th A frica, a nd

Z im babw e: R . A lvarez, P .).

B artle tt, N .).W . B ell, T . C are w,

A .R . G ue st, C . P ag e,

D . S ta cey , an d A . S us aeta.

Thanks are due to

P.). B artlett for assisting in the

fin al p re paratio n of th e p ap er .

T he sim ulation program for

the calculation of prim ary and

se conda ry f r agment at ion

referred to in the text w as

writtenby

G .5 . E ste rh uiz en at P reto ria

University.

~

29 2

Table IV

upport te hniques

90 100

t

High

stress

=

1 m +

0,33 W x

F

=1 m

=

R ig id r eb ar

0,5 mm x 100 mm aperture

Cables

=

1 m +

1,5 W

M es h- re in fo rc ed s ho tc re te

R ig id s te el a rc he s

Mass iv e conc re te

L ar ge w as he rs tr ia ng le s

T en do n s tr ap s

25 m m rope-cable slings

P re -s tr es sed c ab le s have l it tl e app li ca ti on i n

u nd erg ro un d situ atio ns u nle ss it is to st ab ili ze

fra ctu re d ro ck i n a low-s tre ss e nv iro nm en t. T he

n ee d fo r e ffe ctiv e la te ra l c on stra in t o f th e ro ck

a nd o f lin in g su rface s su ch as co ncrete c an no t b e

to o h ig hly empha si ze d. S uppo rt t ec hn iq ue s a re

i ll us tr at ed i n Tab le IV.

on lusions

~ C av ability can be assessed provid ed

a ccur at e geo te chn ic al d at a a re ava il ab le

a nd th e g eo lo gic al v aria tio ns a re

re co gn iz ed . T he m in in g ro ckmass ra tin g

MRMR) sy st em prov ides t he nec es sa ry

d ata fo r th e emp iric al d efin iti on o f th e

u nd erc ut d im en sio n in term s o f th e

hydrau lic r ad ius .

~ N um erical m odelling can assist the

e ng in ee r in u nd ers ta nd in g a nd d efin in g

t he s tre ss env ir onmen t.

~ Fragmentation is a m ajor factor in an

a ss es sm en t o f t he fe as ib ility o f c av e

m ining i n l ar ge compet en t o rebodi es .

P ro grams a re b ein g d ev elo pe d fo r t he

d ete rm in at io n o f fra gm en ta tio n. a nd e ve n

the l es s s ophi st ic at ed p rog rams p rov ide

g ood d esig n d at a. T he e co nom ic v ia bil ity

o f c av in g in c ompete nt o re bo die s is

d ete rm in ed by LHDp ro du ctiv ity a nd th e

cos t o f b re ak ing l ar ge f ra gment s.

Low s tr es s

Bird cag e cables from un de rcut le ve l

In clin ed p ip es

Grouting

E xt ra bo lt s and cab les

P la tes , s traps , and arches

W is th e s pa n o f t he tu nn el a nd F is b ase d o n

MRMR

=

0-20: F

=

1,4 MRMR

=

21-30: F

=

1,30

M RM R=41-50: F=

1,1 MRMR=51-60: F= 1,05

O CTOBER 1994

MRMR

=

31-40: F

=

1,2

MRMR > 61 : F

=

1,0

The Joumal

of

The Sout h f ri can I ns ti tu te

of

Mini ng and Me ta ll ur gy


15/15

a v e mining the

state

of the rt

~ r a w p o i n U d r a w z o n e spacings fo r coarser

m aterial need to be exam ined in term s of

r ecov er y and impr ov ed m ining

env ir onmen ts Spacing s mu st n ot b e

in cre ase d to lowe r o pe ra tin g c ost s a t th e

exp en se o f o re r ecov er y

~ The interactive theory of draw and the

diam ete r of the isola te d d raw zo ne ca n b e

u se d in the de sign of drawzo ne spa cing

~ C om plications occur w hen the draw zone

s pa ci ng is d es ig ne d o n th e p rim ary

fra gmen ta ti on a nd t he s ec on da ry fra gmen

tat ion is s ign if icant ly d if fe ren t

4. rock characterization at el teniente mine.pdf

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