Open-cast Mining Method

8/17/2019 Open-cast Mining Method

1/56

OPEN CAST MINING

METHOD


2/56

Open Cast Mining Method

• Open cast mining is a surfaceexploitation method, used mainlyfor coal It resem!les open pit mining

!ut di"ers in one uni#ue respect$

The overburden is nottransported to waste dumps for

disposal but cast or hauleddirectly into adjacent mined-out panels.


3/56

Continued%%

• OC Mining is su!di&ided into t'o methodsi Strip Mining

iiTerrace Mining

i. Strip Mining

• This method is ideal under the follo'ingconditions$

a)Relatively thin overburdenb)Extensive area of reserves

c)Regular horizontal/at topography and seams


4/56

Strip Mining) cont

• The deposit is mined in a series ofstrips


5/56

Strip mining) cont

• The o&er!urden from each strip iscast directl* into the &oid created !*the pre&ious coal e+traction

• Strip Mining is normall* a largetonnage operation using largemining machines such as Draglines

and Power shovels for Coal andOverburden strippingrespectively.


6/56

ii, Terrace Mining

a, This method is used 'here $

The overburden is too thick or

The oor is too steeply dippingto permit direct across the pit casting ofo&er!urden material- Theoverburden (spoil) must !e

transported !* other means andtipped back into the void left backby previous mining.


7/56

Cont

!,This is a multi !ench lateral ad&ance

method- the 'hole mine mo&ingacross the deposit- !ut not in asingle stage operation as with

strip mining


8/56

Cont

• c, .pper le&els are usuall* transported!* truc/ and sho&el- or !* acom!ination of !uc/et 'heel e+ca&ators

012E,- con&e*ors and stac/ersd, If a dragline is used in terrace mine

it can onl* operate on the bottom

benches 'here direct casting ofo&er!urden is possi!le


9/56

Terrace mining) cont


10/56

Terrace Mining)cont


11/56

Opening up into a coalseam3

• The initial opening into a coal seam iscalled a Bo cut. a trench or box cut4is made through the o&er!urden to e+posea portion of the coal seam This trench is

e+tended to the limits of the property 0Deposit, in the stri/e direction

• After coal removal- a second cut is made

parallel to the !rst one- and theo&er!urden material from this cut is placedin the void of the !rst cut


12/56

Position of !o+ cut

A bo cut is either made in the shallo"estpart of a pitching deposit, to mine to thedip or

1

bo cut

For a thick deposit a box cut may be madenear the center or at the highest part so thata series of benches may be ta!en out"ards


13/56

1o+ cut ) cont%


14/56

1o+ cut 5cont

• 6rom the !o+ cut coal miningproceeds down the dip or acrossthe mining lease O&er!urden isremo&ed from in front of thead&ancing high!all and thro'n intothe mined out area as in 7gure

!ello'


15/56

1o+ cut) cont Striping Dragline


16/56

1ac/ 7lling or 1ac/ Casting

• 2hen the dip angle# $, of a coaldeposit is less than the angle ofrepose of the spoil heaps plus a

factor of safet*- it is possi!le todump spoil8o&er!urden 'aste insidethe e+ca&ated area 01ac/7ll, Dip angleof coal seam 9:


17/56

Direct 1ac/ 7lling

• 2here possi!le the o&er!urden'aste is direct back%cast acrossthe cut 'ith a Dragline or stripping

Po'er sho&el


18/56

Indirect 1ac/7lling

• 2hen either the overburden orcoal seam is too thick the reachof the dragline or stripping sho&el

!ecomes small- and the o&er!urdenhas to go round the pit and !e 7lledin from !ehind


19/56

Indirect !ac/7lling)cont


20/56

Ma;or Open Cast Operations


21/56

Ma;or OC operations cont

i) &ush clearing and leveling This in&ol&es the remo&al of the &egetation to

ensure homogeneous topsoil A bulldo'er ortractor does this 'ith a ripper !ehind The area isthen graded to allo' smooth tra&eling of haul

Truc/s

ii, Top soil removal$???@ Topsoil is remo&ed separatel*- and ultimatel* re)

placed upon graded spoils 0o&er!urden 'astedumps,


22/56

Cont

Top soil can !e stoc/piled at the sideof the pit area for later redistributionor ma* !e hauled immediatel* to the

graded area for redistri!ution The method of redistri!uting the topsoil

is dictated !* economics considering

#uantit* and distance it ma* !e !*oader8Truc/ method or !* self)ele&ating scrapers- etc


23/56

cont.

iii) verburden stripping The overburden benches ma* !e one

or more depending on 3

) The thickness of the overburden andthe reach of the stripping euipment.

) In a !ench 'here a dragline is used-

cast or * bu+er blasting is used toloosen the roc/ !efore the dragline can'or/ on the material


24/56

Cont

• 2here the o&er!urden is &er* thic/-eg. -m. /t 0ankie colliery inBim!a!'e- o&er!urden stripping is

di&ided into )1enches1 m on top is "orked by a po"er

% shovel bench- or 0supplementar*

strip !ench, andThe bottom 21m. is 'or/ed !* a

Dragline hence called Dragline !ench


25/56

Cont

iv) 3oal 4xtraction• 3oal mining ma* !e !* $

• A single !ench or t'o depending onthickness or uality of the coal seam.

Eg at 'an/ie collier* in Bim!a!'e a 5 mthick seam is mined in t"o benchesbecause the top m is po"er coal andthe !ottom m is coking coal The maine#uipment here is the po'er sho&el


26/56

OC operations

&, 6egrading of Spoils• arge 1ulldoers and Graders grade

7lled mined out areas !efore topsoil is

re)placed

&i, Top Soil 6eplacement• Scrapers- doers- loaders and truc/s are

used in this operation A la*er of fertilesoil is spread on top of graded spoils

•


27/56

OC Operations

vii) 6e%vegetation orreplanting $

• ???@

• Planting of &egetation is accomplished !*a con&enient farm implement- and is doneas soon as practical Seed selection is!ased on post mining land use


28/56

deposits for open cast

mining.


29/56

Coal Open Cast machines

8ragline 4xcavators

• The dragline is a &ersatile attachmentcapa!le of a 'ide range of operations at

and !elo'ground le&el The dragline candig through loose to mediumcompacted soil

• The !iggest ad&antage of the dragline

o&er other machines is its long reach forboth digging and dumping Anotherad&antage is its high cycle speed


30/56

Cont

• The roc/s that is to !e handled must !e of lo"density of >) T8 MF and 'ith lo' abrasiveproperty.

• The machines are electricall* operated A

dragline !uc/et s*stem consists of a largebucket 'hich is suspended from a boom 0alarge truss)li/e structure, 'ith 'ire ropes The!uc/et is maneu&ered !* means of a num!er

of ropes and chains The hoist rope- po'ered !* large diesel or

electric motors- supports the !uc/et and hoist)coupler assem!l* from the !oom

http://en.wikipedia.org/wiki/Trusshttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Dieselhttp://en.wikipedia.org/wiki/Dieselhttp://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Truss


31/56

Cont

The dragrope is used to dra' the!uc/et assem!l* horiontall* 1*s/illful maneu&er of the hoist and the

dragropes the !uc/et is controlled for&arious operations ! schematicdiagram of a large dragline

buc"et system is sho'n !elo'


32/56

Dragline 5cont


33/56

Dragline operation•

9n a typical cycle of excavation$ the bucket is positioned above the material to !e

e+ca&ated The bucket is then lo"ered on the material The dragrope is then dra"n or pulled so that the

!uc/et is dragged along the surface of the material The buc"et is then lifted by using the hoist

ropeA swing operation is then performed to mo&e the

!uc/et to the place 'here the material is to !e

dumped The dragrope is then released causing thebuc"et to tilt and empt* This is called a dumpoperation


34/56

Draglines in mining 5sieand cost

• A large dragline s*stem used in the openpit mining industr* costs appro+imatel*.S )> million A t*pical !uc/et has

a &olume ranging from F to cu!icmetres- though e+tremel* large !uc/etsha&e ranged up to >J cu!ic metres Thelength of the !oom ranges from #$ to

%&& metres In a single c*cle it canmo&e up to K metric tonnes ofmaterial


35/56

Dragline L po'er source

• Most mining draglines areelectrically po"ered.. Their po'erconsumption is so great that the*

ha&e a direct connection to the high%voltage grid at &oltages of !et'een to / A t*pical dragline- 'ith

a cu!ic metre !uc/et- can use upto Mega'atts during normaldigging operations


36/56

Dragline po'er sourcemo&ement

• In all !ut the smallest of draglines-mo&ement is accomplished !*'al/ing using feet or pontoons- as

caterpillar trac/s place too muchpressure on the ground- and ha&egreat dicultl* under the immense'eight of the dragline

• Ma+imum speed is onl* at most a fe'hundred metres per hour since the feetmust !e repositioned for each step


37/56

imitation of .se ofDraglines

• The primar* limitations of draglines are $boom height andboom length-

'hich limits 'here the dragline can dumpthe 'aste materialdig depth- 'hich is limited !* the length

of rope the dragline can utilie Inherent

'ith their construction- a dragline is mostecient e+ca&ating material !elo' thele&el of their !ase can,


38/56

Draglines 5cont

• Despite these limitations- and theire+tremel* high capital cost,draglines remain popular 'ith man*

mines- due to their reliability, ande+tremel* lo" "aste removal cost


39/56

PO2E= SHOE

• A :o"er shovel 0also called a Stripping or;ront Shovel in some mar/ets, is a !uc/ete#uipped machine- usuall* electricall*po'ered- used for digging and loading earth

or fragmented roc/- and mineral e+traction• A po'er sho&el is second to the dragline in

sie- !ut is more po"erful 'hen it comesto digging hard coal or overburden

• arge machines are electricall* operatedSmall sie of sho&els ma* ha&e$ ac- dc-diesel- diesel h*draulic or diesel electric-transmission


40/56

:o"er Shovel 8esign

• Sho&els normall* consist of a revolvingdeck 'ith a po"er plant, driving andcontrolling mechanisms, usuall* acounter"eight, and a front attachment,such as a boom or crane 'hich supports ahandle 'ith a digger at the end Themachiner* is mounted on a !ase platform'ith tracks or "heels


41/56

Capacit* of sho&els anddraglines3

• measured in bucket volume. Theregular range of sho&el !uc/ets is '&.#-%() m* + popular si,es

• 6or truc/ loading in metalliferous openpits or #uarries% FQ)K mF

• 6or truc/ loading in opencast coalmines-large iron ore mines- and large coppermines >)>> mF

Po'er Sho&el digging


42/56

Po'er Sho&el diggingo&er!urden


43/56

Cont

• O&er!urden stripping in opencastcoalmines

0Not used for truc/ loading, up to >FJ mF

• 1uc/et 7ll factor for hard roc/ is a!outR- !ut small !uc/ets in soft roc/s canha&e o&er ?R 7ll factor

• A sho&el should 7ll a truc/ in K) passes-as a rule of thum!


44/56

Cont

• Normall* a sho&el runs on the oorle&el it digs for itself and 'or/s fromthat height up

• A !ulldoer is /ept for clean upduties and oor grading- the sho&elis not sucientl* mo!ile to performits o'n cleanup

Si f P


45/56

Sie of Po'ersho&el8Draglines

• Marion 1=>5 The Mountaineer % The Story• Imagine a machine that stood as high as a >%

story building that 'as still a!le to mo&e !* itso'n moti&e po'er A machine that had an

operating "eight of 21=5 tons- s'ung a >1cubic yard bucket that took 55 ton !ites ofearth and roc/- and mo&ed it over the lengthof a football !eld to place it on top of a giantspoil pile this stripping sho&el- 'as t*pe Qand 'as manufactured and erected !* the

Marion Po'er Sho&el compan* during >? 8 in .SA This sho&el 'as !etter /no'n under itsunocial name- the Mountaineer.

PO2E= SHOE 2O=ING


46/56

PO2E= SHOE 2O=INGP=INCIPE

• There are three to four motions onthe shovel+

• a, 8ig !* pulling on the rope that goes

o&er the end of the !oom to the !uc/et ordipper thus lifting it through the roc/ pile

• !, 3ro"d !* rolling the dipper do'n past

the !oom to the !uc/et this forces the!uc/et into the roc/ pile as it mo&esfor'ard


47/56

Cont

c) S"ing )to ta/e the !uc/et round and empt* itthrough its !ac/ doord) propel ) mo&ing the sho&el unit to di"erent locationsor dig positions

•A sho&elUs 'or/ c*cle- or digging c*cle- consists of fourphases$•digging•

s'inging•dumping•returning

•


48/56

Cont

• The cro"ding action of the dipper stic/and its hea&*- stiV*)mounted !uc/et- gi&ea sho&el a much stronger loading

breakout force than either a dragline ora front end loader- eg a -.> m? po"ershovel has a breakout force of @5T'hile a =.> m? loader has a breakout

force of ?1T A sho&el can break outshales or coal "ithout blasting andalso gi&e a smooth !ench surface

3h i b t 8 li


49/56

3hoice bet"een a 8raglineand a po"er shovel.


50/56

Cont

• There are other small machinesused in open cast mining for au+iliar*operations eg &ackhoes for

ditching etc- "heel loaders-graders- &ulldo'ers, scraperloaders- tractors etc

Oth hi th


51/56

Other machines) the1ac/hoe


52/56

)The 1ull doer


53/56

)The 2heel loder


54/56

Grader


55/56

Scraper loaders


56/56

Tractor

Date post:	06-Jul-2018
Category:	Documents
Upload:	ogala-oscar
View:	247 times
Download:	0 times

Open-cast Mining Method

Documents