Openpit fundamentals

1. Venkat

2. 2
Terminology
BENCH:Ledgethatformsasinglelevel
ofoperationabovewhichmineralor
wastematerialsareminedfromthe
benchface.

3. 2
Terminology
BENCHHEIGHT:Verticaldistancebetweenthe
highestpointonthebench(crest)andthelowest
pointorthebench(toe).Itisinfluencedbysizeof
theequipment,miningselectivity,government
regulationsandsafety.

4. 2
Terminology
BENCHSLOPEorBANKANGLE:
Horizontal angleofthelineconnecting
benchtoetothebench crest.

5. 5
BERM:Horizontalshelforledgewithintheultimatepit
wallslopelefttoenhancethestabilityoftheaslope
withinthepitandimprovethesafety.Berminterval,
bermwidthandbermslopeanglearedeterminedbythe
geotechnicalinvestigation.
Terminology

6. 5
OVERALLPITSLOPEANGLE:Theanglemeasured
fromthebottombenchtoetothetopbenchcrest.Itis
theangleatwhichthewallofanopenpitstandsandit
isdeterminedbyrockstrength,geologicstructuresand
waterconditions.
Terminology

7. 5
Theoverallpitslopeangleisaffectedbythewidthand
gradeofthehaulroad.
Terminology

8. 8
HAULROADS:Duringthe
lifeofthepitahaulroad
mustbemaintainedfor
access.
HAULROAD-SPIRAL
SYSTEM:Haulroadis
arrangedspirallyalongthe
perimeterwallsofthepit.
Terminology

9. 9
HAULROAD–SWITCHBACKSYSTEM: Zigzagpatternon
onesideofthepit.
HAULROADWIDTH:
Functionofcapacityof
theroadandthesize
oftheequipment.Haul
roadwidthmustbe
consideredinthe
overallpitdesign.
Terminology

10. 10
HaulRoadEffectonPitLimits

11. 11
ANGLEOFREPOSE:Maximumslopeofthe
brokenmaterial.
SUBCROPOROREDEPTH:Depthofwaste
removedtoreachinitialore.
PRE-PRODUCTION STRIPPING:Stripping
donetoreachinitialore.
Terminology

12. 12
ULTIMATEPITLIMITS:Verticalandlateralextendof
theeconomicallymineablepitboundary.Determinedon
thebasisofcostofremovingoverburdenorwaste
materialvs.themineablevalueoftheore.
PITSCHEDULING:Materialmaybeminedfromthepit
eitherin:
1)sequentialpushbacks
2)conventionalpushbacks.
Terminology

13. STRIPPINGRATIO:Expressedintonsofwastetotons
oforeinhardrockopenpitoperations.Criticaland
importantparameterinpitdesignandscheduling.
AVERAGESTRIPRATIO:Totalwastedividedbytotal
orewithintheultimatepit.
CUTOFFSTRIPPINGRATIO:Costsofminingatonof
oreandassociatedwasteequalstonetrevenuefromthe
tonofOre.
Terminology

14. 14
SingleWorkingBench

15. 15
ShovelinWorkingBench

16. 16
TwoWorkingBenches

17. 17
Final
Pit
Limit

18. 18
Example Mine
2001 2007 2011

19. 21
Pit
Sequence
(1)

20. 22
Pit
Sequence
(2)

21. 23
Pit
Sequence
(3)

22. 24
Pit
Sequence
(4)

23. 25
SectionofPitSequence

24. 25