Basic Blasting Patterns.ppt

7/21/2019 Basic Blasting Patterns.ppt

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Basic Blasting Patterns

©Dr. B. C. Paul 2000

Note – The concepts contained in these slides represent the author’s view of

information commonl held amon! those well studied in the field. "ome of the

fi!ures contained in these slides were ta#en from or prepared with inspiration from the

Blaster’s $and%oo# pu%lished % DuPont.



Blasting Nomenclature

& 'ree 'ace ( open area at the roc# air interface (

essential that %ro#en roc# has a place to !o to avoid

ener! turnin! to %ad vi%rations& )ow ( a line up of holes runnin! parallel to the 'ree

'ace

& "pacin! ( the distance %etween holes in a row

& Burden ( the distance from a row of holes to the

free face ( the roc# that must %e %ro#en up and

moved % the e*plosive



Drilling Patterns

"+uare Pattern ( ease of drillin! ( easil e*plained to la%or ( not a

lot of ,ud!ement to la out ( ,ust one num%er to remem%er

"pacin! - Burden improves fra!mentation ( %ut not availa%le here



Rectangular Pattern

Provides for spacin! - Burden ( mproves fra!mentation if ou can

!et our drillers to put one down



Staggered Pattern

Provides "pacin! - Burden % a considera%le amount

Pro%lem of leavin! stumps on +uarr floor ( ne*t row ta#es them

out

/nd our People Can Drill it Too1



Firing Patterns

& /ll shots need a free face for roc# to move to

– ith several rows must wait for material in front

to move to create a free face

& 3ac# of a free face turns throw ener! in

vi%ration

– causes crac#in! %ehind holes ( called %ac# %rea#( can ma#e future faces hard to support

– 24 to 50 ms would %e common



Plough Cut



Properties of the Plough Cut

& 6ives lon! linear muc# pile alon! the face

& 7pen 'ree 'ace $elps to /void Confinement

Pro%lems& 8ovement Perpendicular to 'ace Can 8a*imi9e

forward throw which ma %e pro%lematic for narrow

%enches

& Needs a )ectan!ular drill pattern to !et spacin! -

%urden

– /lso used with sta!!ered drill pattern



Peculiar Edge Delays on Plough

Cut & Plou!h Cut 7ften 'ires the :ntire )ow at

7ne Time

& Note That :d!e $oles "eem to 'ire 3ater

& :*plosive /ction 8ust Tear the )oc# /wa

of ; sides ( more open space eases the

%urden to %e pushed

– B delain! ed!e holes provides 2 free faces to

throw to



Considerations in Firing

& "tarts at 7ne :nd of "hot and "preads /cross

& Can "ee $ole nitiate on "urface Before Brea#(up

%e!ins at face& Primer is !enerall placed in toe ( Note That heave

%e!ins at %ottom

& Top ill "well

– <suall causes top to slump down

– n =uarr the timin! will %e set to heave clear of face

& )oc# Pile ma have lar!er pieces from stemmin! 9one





The V Cut



Properties of the V Cut

& 'irin! Pattern )ips out a > "hape ed!e

& 'irin! Pattern /lters the Position of the 'ree

'ace for 3ater 'irin! $oles

– Provides a 2?@ "pacin! to Burden )atio with a

"+uare Pattern

& Tends to Throw 8aterial into CentrallCollected 8uc# Pile

– Can %e !ood for limited %ench room



ore !"out V Cuts

& Central Collection Tends to Create 8ore

Potential Confinement

& )eal Caps don’t !et the Dela Times

Perfect ( called cap scatter

– f hole at ape* of > doesn’t fire ( confinement

for ne*t row %ac# will %e severe



odifications of the V Cut

& 'latten the ape* of the > ( fire two ma%e

three holes in a row at top of the >

– "pread the pile out a %it more

– 8ore for!ivin! of a cap misfire

– Can see at some point Plou!h and > cuts ma

melt into each other

& 'ire 7nl 7ne "ide of the > at two free

faces ( Called )ow :chelon 'orm



Ro# Echelon Firing Se$uence



Ro# Echelon in the Field

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Basic Blasting Patterns.ppt