Blasting Fundamentals

7/24/2019 Blasting Fundamentals

1/17

Blasting Fundamentals

Dr. B. C. Paul 2000

Note The slides that follow present the authors summary of knowlede !ommonly

held "y people well studied in the field. #hile information found here$in !an "e

found in a %ariety of pu"lished sour!es this material does not "y desin or intention

follow any one sour!e of information.


2/17

The Role of Fragmentation in

Mining& 'o!k masses must enerally "e redu!ed into

small dis!rete pie!es to ena"le materials

handlin and pro!essin

& 'edu!tion is usually a!!omplished

me!hani!ally "y rippin or s!rapin if

softness permits& By "lastin usin e(plosi%es to a!!omplish

si)e redu!tion


3/17

Explosive Types

& *ow +(plosi%es $ proress of the rea!tion

front throuh the e(plosi%e !hemi!al

mi(ture is slower than the speed of sound

+(ample $ Bla!k Powder

& ,ih +(plosi%es $ rea!tion front is faster

than speed of sound

+(ample $ TNT and Dynamite


4/17

Blasting Agents

& Popular e(plosi%e formulation today

& -ade of !om"inations of !hemi!als that are

themsel%es not e(plosi%e

d%antae in transportation

Takin hih e(plosi%es o%er pu"li! hihways is

a ma/or permittin issue

-ay pro%ide for storae of non$e(plosi%es

e(plosi%es re1uire spe!ial powder maa)ines


5/17

Blasting Agents Continued

& -ost !ommon e(ample is N34

Com"ination of prilled mmonium Nitrate a

fertili)er a"out 567

Diesel 3uel a"out 87

& 95:0s put N34 mi( in !ans and used as

!heap dynamite& *ate 9580s early ;0s redis!o%ered as a "ulk

e(plosi%e $ Te(as City< Te(as


6/17

Formulation of an Explosive

& Com"ination of a 3uel and an 4(idi)er

& 3uel that is prone to fast rea!tion and

usually produ!es lare num"er of fumes and

a hih enery yield

& 4(idi)er pro%ides for fuel to "urn without

kineti! limitations of atmospheri! e(!hane

Can "last under water


7/17

Elements of an Explosive

Detonation& =nitiation eneryusually in form of heat

or sho!k e(ample $ Nitroly!erine

& 4(idi)er

most hih e(plosi%es "uild it in

& Confinement and Pressure

heat< !onfinement< and pressure are needed to "oostrea!tion kineti!s and make fuel "urn with a rea!tion front

faster than sound

& Can you see what happened at Te(as City


8/17

Initiation of a Blasting Agent

& -eant to "e safe $ o off only when %ery

spe!ifi! desin !onditions are met

& Cap >ensiti%ity

Deals with amount of sho!k enery to initiate

& Chare in a "lastin !ap is not enouh sho!k enery

enerally heat alone will not pro%ide enerythreshold

& Drillin into !hare or ettin !auht in a fire enerally

not enouh


9/17

Classic Blasting Initiation ystem

& >eries of ele!tri! "lastin !aps

& Burst of ele!tri!ity throuh the !ir!uit initiates

"lastin !aps& +a!h "lastin !ap !ontains a "ride wire similar to

the element of a liht "ul"

The ele!tri! "urst !auses the "ride wire to "e!ome %ery

hot

& Below the "ride wire is a !olumn of "la!k powder

$ inited "y hot "ride wire


10/17

Classic Initiation

& Bla!k Powder Column fun!tions as a delay.

?aria"le powder !olumn lenths allow one

pulse of ele!tri!ity to !ause !aps to o off atdifferent pre$desined times

& t "ase of powder !olumn is a heat sensiti%e

hih e(plosi%e !hare !alled a "ase !hare& #hen the "la!k powder !olumn "urns down

the !ap e(plodes


11/17

Initiation from a Cap

& Cap is a"out the si)e of an o%errown 22 shell

$ !ould "low finers off your hand $ not "low

up ro!k

& Cap is inserted in a small hole !alled a !ap

well in a "ooster

& Booster is a !hunk of hih e(plosi%e su!h asTNT or PTN

is sho!k sensiti%e "ut limited heat sensiti%ity


12/17

Cap Initiation Continued

& Booster with a Cap inserted is !alled a primer

& The primer is !ap sensiti%e

#hen handled $ !an play 3ris"ee and Base"all

with it and it wont o off

#hen the !ap oes off a"out ; or 90 l"s of hih

e(plosi%e detonates& +nouh enery to shatter a person or a small

amount of ro!k


13/17

Blo!ing Things "p

& The primer sits in a !olumn of "lastin

aent

& >ho!k from ; l"s of TNT is enouh to

initiate the "lastin aent

& -ain e(plosi%e !hare oes off shatterin

the ro!k mass and any stupid su!ker

standin in the "last area


14/17

trengths of the Modern

Approach& ?ery limited amounts of hihly e(plosi%e

material used

& >taed initiation ensures that main

e(plosi%e !hare is almost impossi"le to set

off without desin and intent

& -a(imi)es performan!e of lare amounts of

powerful e(plosi%es


15/17

Initiation Alternatives

& Pro"lem of ele!tri! "lastin !aps is ele!tri!al sure

initiates

*ihtin strike !an !ause full detonation with people inarea

lare loops of wire a!t as antennas and !an indu!e !urrent

from radio wa%es

& 'emem"er radio silen!e re1uirements around "uildindemolition sites

& Detonatin !hord $ !ord filled with hih e(plosi%e

set off "y sinle !ap


16/17

Detonating Chord

& Cap is not eliminated "ut one person hooks up

at the ede of the shot area after the shot is

wired $ reatly redu!ed %ulnera"ility

& Produ!es a surfa!e hih e(plosi%e "last $

deafenin sound $ distur"s neih"ors

Can "ury the !hord "ut still noisy and !ould "reak

!onne!tion

& ,ih speed rea!tion throuh !hord eliminates

most opportunities for !ontrolled delays


17/17

#on$ El

& ,ollow plasti! tu"e with an e(plosi%e

!oatin inside

& Can "uild delay elements into !ir!uit

& >imilar to det !hord "ut slower rea!tion

&*imited e(plosi%e redu!es noise

& >till initiate with a sinle !ap

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