Excavation in hard rock

Rock excavation tools disintegrate and remove the rock from boreholes and tunnels by four basic mechanisms: thermal spalling, fusion and vaporization, mechanical stresses, and chemical reactions

1. EXCAVATION IN
HARD ROCK
PrabhanjanThorat
prabhanjanthorat@gmailcom

2. EXCAVATION IN HARD ROCK

Machines are used for excavation in hard rock includes
1.Rippers
2.Jackhammers
3.Drills
4.Compressors and
5.Pneumatic equipments

3. Ripper

Theripperisthelongclaw-likedeviceonthebackofthebulldozer.

Ripperscancomeasasingle(singleshank/giantripper)oringroups
oftwoormore(multishankrippers).

Usually,asingleshankispreferredforheavyripping.

Therippershankisfittedwithareplaceabletungstensteelalloytip.

Rippingrockbreaksthegroundsurfacerockorpavementintosmall
rubbleeasytohandleandtransport,whichcanthenberemovedso
gradingcantakeplace.

4. Rippers

Crawlertractorscanbefittedwithrearmountedripperswithvarious
configurationsandlinkagedesignsfordepthcontrolandadjustment
ofthetip’sattackangle.

Becauseofthepowerandtractiveforceavailablewithlargetractors,
penetrationdepthofarearripperonsuchmachinescanbeasgreat
as4to5ft.

5. Parts of Ripper

Theverticalmemberoftheripperthatisforceddownintomaterialto
berippedisknownasshank.

Arippertoothisfixedlower,cuttingendoftheshank.

Thetipisdetachableforeasyreplacement,asitconstitutesthereal
workingpartoftheripperandreceivealltheabrasiveactionfromthe
rock.

6. Types of Rippers

Therearethreetypesofripperattachmentsavailable:
1.FixedRadial
2.FixedParallelogramand
3.Parallelogramlinkagewithhydraulicallyvariablepitch.
 Curvedandstraighttypesofshanksareavailablefortheripper.
 StraightShanksareusedformassiveorblockyformations.
 Curvedshanksareusedforbeddedorlaminatedrocks,orpavements,wherealiftingactionwill
helpshatterthematerial.

7. Types of Rippers
1.FixedRadial:
Withradialtyperipperlinkage,the
beamoftheripperpivotsonlinkarmsabout
itspointofattachmenttothedozer;
thereforetheangleoftipattackvarieswith
thedepthofshankisdepressed.
Thismaymakeitdifficulttoachieve
penetrationintoughmaterials.

8. Types of Rippers
1.Parallelogram:
Theparallelogramtyperipper
maintainstheshankinaverticalpositionand
keepsthetipataconstantangle.

9. Types of Rippers
1.Parallelogramwithvariablepitch:
Theparallelogramwithvariablepitch
typerippertheoperatorcancontroltip
angle.

10. Factors affecting
effectiveness of Ripper

Down pressure at the ripper tip

Thetractor’susablepowertoadvancethetip;a
functionofpoweravailable,tractorweight,and
coefficientoftraction.

Propertiesofthematerialbeingripped;laminated,
faulted,weatheredandcrystallinestructure.

11. Percussion Drills

Percussion drilling accomplishes disintegration of the rock by hammer
impacts to the bit at the same time a rotating motion is applied to
the bit.

The percussion drill bit is literally hammered into the rock, it smashes
the rock to pieces.

These drills may vary in size from handheld units such as
jackhammers to large crawler mounted rigs.

12. JACK HAMMER

13. Jack Hammers

Alsocalledaspneumaticdrillordemolitionhammer

Itisa pneumaticorelectro-mechanicaltoolthatcombinesa
hammerdirectlywithachisel.ItwasinventedbyCharlesBradyKing.

Hand-heldjackhammersaretypicallypoweredby compressedair,butsome
useelectricmotors.

Largerjackhammers,suchasrigmountedhammersusedon construction
machinery,areusuallyhydraulicallypowered.Theyareusuallyusedtobreak
uprock,pavement,andconcrete.

14. 
Ajackhammeroperatesbydrivinganinternalhammerupanddown.

Thehammerisfirstdrivendowntostrikethebackofthe bitandthenback
uptoreturnthehammertotheoriginalpositiontorepeatthecycle.

Thebitusuallyrecoversfromthestrokebymeansofa spring.

Theeffectivenessofthejackhammerisdependentonhowmuchforceis
appliedtothetool.

16. Types

Pneumatic

Electromechanical or electropneumatic

Hydraulic

17. Pneumatic

Alsoknownasapneumaticdrillorpneumatichammer

Itisjackhammerthatusescompressedairasthepowersource.

Airsupplyusuallycomesfromaportableaircompressordrivenbyadieselengine.

Reciprocatingcompressorswereformerlyused.

Theunitcomprisedareciprocatingcompressordriven,througha centrifugalclutch,
byadieselengine.

Theengine'sgovernorprovidedonlytwospeeds:
1.idling,whentheclutchwasdisengaged
2.maximum,whentheclutchwasengagedandthecompressorwasrunning

Modernversionsuserotarycompressorsandhavemoresophisticatedvariable
governors.Theunitisusuallymountedona trailerandsometimesincludes
anelectricalgeneratortosupplylightsorelectricpowertools.

Additionally,someusersofpneumaticjackhammersmayusea pneumatic
lubricatorwhichisplacedinserieswiththeairhosepoweringtheairhammer.

Thisincreasesthelifeandperformanceofthejackhammer.Specificlubricantis
filledinthepneumaticlubricator.Furthermore,aircompressorstypically
incorporatemoistureintothecompressedairleadingtofreeze-upsofthe
jackhammerorairhammerincoldweather.

18. Electromechanical or electro pneumatic

Varietyofsizesfromabout12lbs-65lbs.

Requireanexternalpowersource,butdonotrequireacompressor.

Althoughinthepastthesetoolsdidnothavethepowerofanairorpneumatic
hammer,thisischangingwithnewerbrushless-motortoolscomingclosetothe
powerofapneumatictoolandinsomecasesevenmatchingit.

Electricpoweredtoolsareusefulforlocationswhereaccesstoacompressoris
limitedorimpractical,suchasinsideabuilding,inacrowdedconstruction
site,orinaremotelocation.

Electropneumatictoolsuseavarietyofworksforattachingchisels.

Theconnectionendsizeisalsorelatedtothebreakingenergyofthetool.

19. Hydraulic

Ahydraulicjackhammer,typicallymuchlargerthanportableones,maybefitted
tomechanicalexcavatorsorbackhoesandiswidelyusedforroadwork,quarrying
andgeneraldemolitionorconstructiongroundwork.

TheselargermachinemountedbreakersareknownasRigMounted,orMachine
MountedBreakers.Suchtoolscanalsobeusedagainstverticalwalls(orceilings
forthatmatter),sincethevehiclesinvolvedaremassiveenoughandpowerful
enoughtoexerttheforcesinvolvedwithoutneedingthehelpofgravityin
operatingthetool.

Pneumaticorhydraulictoolsareparticularlylikelytobeusedin mineswhere
thereisanexplosionrisk(suchasunderground coalmines),sincetheylackany
high-powerelectricalcircuitrythatmightcauseatriggeringspark.

Hydraulicbreakersusuallyuseahydraulicmotordrivingasealedpneumatic
hammersystem,asahydraulichammerwoulddevelopalowstrikespeedand
transferunacceptableshockloadstothepumpsystem.

Advancesintechnologyhaveallowedforportable hydraulicbreakers.The
jackhammerisconnectedwithhydraulichosestoaportablehydraulicpowerpack:
eitherapetrolordieselenginedrivingahydraulicpump;ora mini-
excavatororskid-steerviaapowertake-offdriveshafttothemachine'shydraulic
system.

Hydraulicpowersourcesaremoreefficientthanaircompressors,makingthekit
smaller,cheaperormorepowerfulthanacomparablepneumaticversion.

20. Glossary of terms

Bit–Thisisaportionofdrillwhichcontactwithrocksanddisintegrates
it.

Burden–Horizontaldistancefromarockfacetothefirstrowofdrill
holesorthedistancebetweenrowsofdrillholes

Coupling–ashort,hollowsteelpipehavinginteriorthreads.Couplingis
usedtoholdthepiecesofdrillsteeltogetherortotheshank.Percussion
energyistransferredthroughthesteel;notthecoupling.Therefore
couplingmustallowthedrillsteeltobutttogether.

Cuttings–Thedisintegratedrockparticlesthatareremovedfromahole.

Drifter–Itisanairoperatedpercussiontypedrillsimilartojackhammer;
thatisrequiredmechanicalmounting.

21. Bits (chisels)
Bit types include:

Spade-providesflatfinishforconcreteoredginginasphaltordirt

Flattip-allowsdirectioncontrolorfineredgefinish

Point-generalbreaking

Stakedriver-drivesconcreteformstakes

Scabbler-finishessurfacesmoothorforcleaningpriortobonding

Flexchisel-flexiblemetalblade(attachedtoshankwithbolts)fortile
removalandscraping

Bushingtool-multiplecarbidepointsforcleaningupseamsandknocking
downroughspotsinconcrete

22. Working of jackhammer

When the valve is in the
position shown here, air enters
through the thick yellow hose
at the top and follows the
thinner paths shown in yellow,
pushing the piston (red)
downward and smashing the
hammer (green and gray) into
the ground.

As the piston moves down, air
flows back up through one of
the pipes and pushes the blue
valve over to the right, so the
air now follows the brown paths
and exits.

23. Working of jackhammer –Cont….

Drillingunitconsists–Hammer,drillsteelandbit

Compressedairflowsthroughahammer,itcausesapistontoreciprocateata
speedupto2200blows/minute.

Energyofpistonistransmittedtoabitthroughadrillsteel

Airflowsthroughaholeinthedrillsteelandthebittoremovethecuttings
fromtheholeandtocoolthebit.

Drillsteelisrotatedslightlyfollowingeachblowsothatthecuttingedgeof
thebitwillnotstrikeatthesameplaceeachtime.

24. Suitability of jackhammer

Withorwithoutpusherleg(Pneumaticpowered)forholelengthupto3.5mand
dia.32-38mm–Mediumhardrocktohardrocks,smalloutput,smallsize
horizontalmineopeningsandpinholesforservices.

Handheld–Funnelchamberexcavation,shaftsinking,winzinginallandtypes
ofrocks

ElectricbreakersfromKennardscomein10kg,15kgand33kgmodels.-They
canbeusedforsmalltomediumdemolitionprojectsliketilelifting,bitumen
cuttinganddiggingclay.

The10kgoptionislightenoughtoworkhorizontallybutstillbreakupconcrete
withathicknessof50mm.

Thelargestmodelwillbreakconcreteofupto100mminthickness,andhas
theequivalentimpactofa28kgpneumatichammer.

25. Suitability of jackhammer –cont…..

Ajackhammertrolleyisidealforeasyremovaloflinoandfloortiles,andhas
built-inshockabsorptionandananti-vibrationdevicetoensurethejobisn't
harderthanitneedstobe.

Pneumaticjackhammersaresuitableforalldrillingpurposesinunderground
andopen-pitminingduetotheirlowweightandhighstability,however,they
needexpensivepowersupply.(SmallScaleMining)

Theelectrichammershouldbeconsideredasanalternativetopneumatic
systemsinsmallmineswithonlyfewworkingplaces.ItslowInputofprimary
energyneededandenvironmentalsoundnessaremarksoftheelectric
hammer,however,highcostofinstallationofelectricpowersupplyshouldbe
consideredinthecasethatitisnotavailable.

26. Jack hammer drill bits

27. AIR COMPRESSORS

Aircompressorsaredevicesusedtoprovideefficient
powertoconstructiontoolsandmachinery.

Aircompressorscanbeoperatedbyinternalcombustion
enginesandtheirabilitytopressurizeairenablespower
tobetransmittedviapipesorhoses.

Aircompressorsarecommonlyusedfortransmitting
powertorockdrills,jackhammers,airmotors,pumps,
andmanymoretypesofconstructionequipment.

Theuseofcompressorsenableworkerstoboreholes,
cutmaterials,crushrock,pourvibratedconcrete,and
areconstantlyusedincountlessotherconstruction
applications.

28. Features/How it Works

In order for air to transmit power, it needs to be compressed or increased
to a higher pressure. When air is compressed it is given energy that can
provide power for machinery, usually through the use ofpistonspushing
the compressed air back and forth.

Boyle’s lawindicates that the volume ofgas(such as air) increases when
the pressure is decreased at a constant temperature. Because of the
nature of compressed air, it is inevitable that some energy will be lost in
the process.

This loss of pressure is caused by the friction of air as it travels through
pipes or hoses, therefore making the size of the pipe/hose a primary
factor in maximizing energy.

Several air compressors are usually used in conjunction with one another
to create a distribution system that carries the compressed air as power to
different points. The air is then conceived as energy for a mechanical
tool.

29. Types of Compression
Temperatures

Adiabaticcompressionoccurswhenthevolumeofairchangeswithouta
necessarychangeinheattemperature.

Isothermalcompressionoccurswhenthetemperaturedoesnotchange
butthereisachangeinthevolumeofair.

Intercoolersareusedinbetweenthestagesofcompressiontohelp
reducetheairtemperatureandremovemoisturefromtheair.

Aftercoolersallowcompressorstocooltheairafteritisdischarged.If
moistureisnotremovedfromtheair,itrunstheriskoffreezinginthe
processofexpanding,sometimescausingtheoilusedtolubricatetoolsto
washawayandbecomelesseffective.

AirReceiversarealsousedtoequalizethepulsationsbeingproduced
fromthecompressor.Thisremovesanywaterandoilvaporsthathave
accumulatedduringtheprocess.

30. Distribution System

A distribution system is installed to make the most of compressed air for
large-scale construction applications.

When compressed air travels from its point of origination to the tool in
question, the pressure drops, causing a loss of power. The distribution
system aims to reduce the loss of power using pipes that are large enough
so that pressure does not extend more than 10 percent of the original
pressure amount. Shorter hoses can be used, which means less pressure
escaping.

When a project requires a significant amount of compressed air per
minute, anair manifoldcan assist with this.

Air manifolds have pipes that are much larger in diameter and allow
compressed air to pass through different systems without the fear of
“friction-line loss”.

31. Types

Compressorscancomeinmanydifferenttypeswithselectfeatures.They
canbeeitherstationaryorportable.

Stationarycompressorsarebestusedforapplicationsthatendurelong
periodsfromafixedsite,whereasportableonesareusedonsiteswhere
thereisconstantmovement.

Portablecompressorsaremadesowiththeuseofrubbertires,steel
wheelsorskidsandarepoweredbygasordieselengines.Themost
commontypeofportablecompressorusedforconstructionprojectsisthe
rotaryscrewcompressor.

Compressorscanprovideaflowofpowerthatisintermittent,alsoknown
aspositive-displacement,oracontinuousflowofpower,whichisseen
incentrifugalandaxialflow(forfluids).

32. Positive-displacement
Compressors

Rotary Screw Compressors
Rotaryscrewcompressorsarethemostcommoncompressionsystemsused
forautomobiles.Theyconsistoftwohelicalrotorscrewstopushgas(air)
intoasmallenvironment.Theairiscompressedwhenitenterstheconfined
spaceallottedforit.Theadvantagesofthistypeofcompressorareitslight
weight,compactness,andlowmaintenance.Itisbestsuitedfor
applicationsthatinvolveair-poweredtoolsthatrequireamoreuniform
flowofpower.

ReciprocatingCompressors
Reciprocatingcompressorsachievecompressionwithpistonsthat
reciprocateinsidetandemcylinder(s).Thistypeofcompressorisusedwhen
highcompressionratiosareneededwithoutahighflowrate.Reciprocating
compressorsusuallypowerdevicesthatrequirelowerspeeds.

33. 
RotaryVaneCompressors
Rotaryvanecompressorshavebladeslocatedinsidethe
rotorthatslideinandoutofpockets.TheRotorblades
arewhatachievecompression.Rotaryvanecompressors
canhavemulti-stages,wherethepreferredpressureis
producedafterseveralstages.Itcanalsocomein
portableorstationarycompressors.

ScrollCompressors
Scrollcompressorshavespiralvanestocompressair.In
thisscenario,oneofthevanesarestationarywhilethe
othermoves,creatinganenergyofcompressedair.

34. DRILLING
EQUIPMENTS
DRILLS
PERCUSSION
DRILLS
ABRASION
DRILLS
FUSION
PIERCING
DRILL BITS
DETACHABLE
BITS
FORGED BITS

35. DRILLING

DEFINITION-The process of making a
hole in hard materials such as rocks and
earth.

COMPONENTS –

Drill-Type of tool which holds the drill
bit and rotates it to provide axial force
to create a hole.

Drill bits-Cutting tools used to create
cylindrical holes.

36. TYPES OF DRILLS

PERCUSSION DRILLS
1.JACKHAMMER OR SINKERS 2.TRIPOD DRILLS
3.STOP HAMMER 4.DRIFTERS
5.CHURNS OR WELL DRILLS 6.PISTON DRILLS
7.WAGON DRILLS

ABRASION DRILLS
1.BLAST-HOLE DRILLS 2.SHOT DRILLS
3.DIAMOND DRILLS

FUSION PIERCING

37. PERCUSSION DRILLS

Jackhammer or Sinkers-Air operated drill,
mainly used for drilling vertical holes.

Tripod drills-Mounted on tripod to provide
sufficient stability,used for very hard rocks.

38. 
Stop hammers-Thrust end to hold the drill against the work and usually
used for “up” holes.

Drifters-Similar to jackhammer, but so large that it requires
mechanical mounting.

39. 
Churns or Well drills-Reciprocating
Drill consisting of a long steel bit
mechanically lifted and dropped
to disintegrate the rock.

Piston drills-Drill rod is securely
fastened to the piston and travels
the full length of the piston stroke.

Wagon drills-Drifter mounted on a
mast supported by two or more
wheels used to drill holes at any
angle from down to slightly
above horizontal.

40. ABRASION DRILLS

DEFINITION-Grind rock into small
particles through abrasive effect of bit
that rotates in hole.

TYPES-
1.Blast-hole drills
2.Shot drills
3.Diamond drills

Blast hole drills-Rotary drill consisting of
steel pipe drill stem on bottom of which
is roller bit that disintegrates the rock as
it rotates over it.

41. 
Shot drills-Rotary drill whose bit consists of a steel pipe with a
roughened surface at bottom.

Diamond drills-Rotary drill whose bit consists
of metal matrix consisting a large number of
diamonds disintegrating the rock while rotating.

42. FUSION PIERCING

Recent development in drilling holes for blasting purpose.

Produced by burning a mixture of oxygen and flux bearing fuel, such as
kerosene at the end of a blow pipe.

43. DRILL BITS

TYPES OF DRILL BITS-

Detachable bits-Removable from the drill when required.

Forged bits-Made up of single length of drill steel and are available
at several shapes.

44. DRILLING PATTERNS

Selection of drilling pattern varies with the type
and size of the drill’s used, depth of hole, kind of
rock, quantity, rapidity of the explosive & amount
of steaming.

45. BLASTING

DEFINITION-The process of
breaking rocks into smaller
pieces by use of explosives.

TYPES OF EXPLOSIVES-

Explosives based on chemical
nature

Explosives based on availability

46. EXPLOSIVES BASED ON CHEMICAL NATURE

High or detonating explosives-
Process is extremely rapid, almost
instantaneous.

Low or deflagrating Explosives-Low
velocity of burning and produce
pressure by progressive burning.

47. EXPLOSIVES BASED ON AVAILABILITY

Powder explosives-
Slow burning , slow acting and low strength
explosives made either from potash nitrate or sodium nitrate.

Disruptive explosives or Dynamites-Available in various sizes and
strength. Approximate strength
is specified as a percentage of
ratio of weight of nitroglycerine
to the total weight of a cartridge
.

48. DETONATORS

DEFINITION-Cylindrical metal shells close
at one end having 6.8 mm dia& 50 mm
height.

The ignition of detonator is done by
blasting fuse or electric ignitors.

Following is required for electric
ignition:
1. Detonator.
2.Power source-dynamo.
3.Circuit line-iron or copper wires.
4.Electric ignitor-comprising 2 supply wires
detonator shell and priming charge.
5.Line testing apparatus-galvanoscope or
measuring bridge.

49. FIRING CHARGE

common practice to fire several holes using
parallel circuit,seriescircuit or combined parallel
and series circuit

50. FUSES

Fuses are required to ignite
explosives.

They are in the form of a small rope
of cotton with core of continuous
thread of gun powder.

The rate of burning is about 1
cm/sec.

They enable the person firing the
charge to move to a safe distance
before the explosion takes place.

51. BLASTING CAPS

DEFINITION-Small explosive
device used to detonate a
larger, more powerful explosive
such as dynamite.

52. TOOLS FOR BLASTING
1.Dipper 2.Jumper
3.Priming needle 4.Scraping spoon
5.Tamping bar

Dipper-Used to drill hole to the required depth.

Jumper-Used to make blast hole & more effective in boring a nearly
vertical hole.

Priming needle-Used to maintain the hole while tamping is done & is in
the form of a thin copper rod with a loop at one end.

Scraping spoon-Used to remove dust of crushed stone from blast hole.

Tamping bar-Used to tamp the material while refilling a blast hole.

53. PROCESS OF BLASTING
1.The blast holes are made and
cleaned by using the tools.
2.The charge of explosive placed
at the bottom.
3.Remaining portion is filled
with clay and tamped.
4.Fuse is inserted, kept
projecting 15-20 cm above the
rock surface.
5. Thereafter free end of fuse is
fired by detonator.

54. Transporting and handling of explosives
1.Dynamite and detonators should be
kept separately when storing and
transporting.
2.Vehicle carrying explosives should
carry a warning sign and operated with
care.
3.The smoking or the carrying of
matches and lighteners etc., should
not be permitted on or around a
vehicle transporting explosives.
4.Wiring on motor-truck used for moving
explosives should be heavily insulated.
5.Explosives should be stored in dry
ventilated bullet proof and fire
resistant magazines, away from
buildings and roads.

55. Thank you