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 EXPLOSIVES AND

BLASTING IN

UNDERGROUND COAL

M INING

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INTRODUCTION

 All seams in underground coal mines areconsidered gassy, the degree of gassiness

may vary from I to III.Methane gas that is released from duringecavation !hen mied in the "ro"ortions#et!een $%&'( forms an e"losive miture.

In underground coal mines, there is also anadditional ris) as coal dust !hich undergoesa dust e"losion !hen suita#ly ignited !ithair.

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Methane ignition is )no!n to ta)e "lace dueto follo!ing reasons*

⇒Direct action of shoc) !ave from thee"losive.

⇒ Indirect action of the shoc) !ave after ithas #een re+ected from solid surfaces in thevicinity of e"losives.

⇒ot gaseous "roducts of detonationmiing !ith the methane%air miture.

⇒ot reacting solid "articles of e"losivesgetting e-ected in to the methane%air

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ence , s"ecially designed e"losives anddetonators are reuired for use inunderground coal mines.

/0RMITT0D 01/2O3I403

Only those e"losives, !hich are included inthe o5cial list of authorised e"losives issued#y the Chief Controller of 0"losives in India,may #e used for #lasting in mines.

Only on "assing the tests in an e"losivea""roved as a 6"ermitted7 e"losive. 

In India there are 8 ty"es of "ermitted

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/%& Ty"e /ermitted 0"losives* Thesee"losives can #e used for drifting or ri""ingand simultaneously 9ring in anundercut:middlecut:overcut and in de"illaringfaces, in coal seams of 9rst degree ofgassiness.

/%8 Ty"e /ermitted 0"losives* These are0uivalent%to%3heathed 0"losives used fordrifting or ri""ing and simultaneously 9ring an

undercut:middlecut:overcut and in de"illaringfaces, in coal seams of 9rst degree ofgassiness.

/%$ Ty"e /ermitted 0"losives* These are

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NON /0RMITT0D 01/2O3I403

=or certain o"erations such as shaft sin)ingand stone drifting, !here there is no gas or

coal dust "resent, e"losives other than "ermitted e"losives can #e used, su#-ect tosuch conditions as may #e laid do!n #y theD>M3 in s"eci9c instances.

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D0TONATOR3 In con-unction !ith /ermitted 0"losives,only a""roved detonators may #e used for

coal #lasting.Only electric detonators !ith co""er tu#e are

 "ermitted for use in coal #lasting.There are ? ty"es of detonators*  @ Instantaneous Co""er 0lectricDetonatorsBC0D  @ Co""er Non%Incendive 3hort Delay

DetonatorsBCDD

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  /RINCI/203 O= IN

COA2

Underground coal mining o"erations could

#e divided into t!o categories , namely,Develo"ment and De"illaring.

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ON A /R0%CUT =AC0

In many mines coal%cutting machines areused to "rovide an additional free face for#lasting. hile this may #e under , over,middle or side cut, the most common "ractisein Indian mines is to have undercut face. =or#lasting on cut faces the follo!ing conditionsmust #e com"iled !ith*

⇒The length of the shot hole should #e atleast &$cm BE inches less than the de"th ofthe cut.⇒ The detonators in a round should #e 9red

simultaneously , "refera#ly in series.

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3O2ID O= COA2B

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COD0 O= >OOD /RACTI303 INUND0R>ROUND

4elocities of Air Current BD>M3

sti"ulations*

  The velocity of air current measured

in metres "er minutes at the "lace sho!n incolumn B? shall not #e less than that sho!nin columnB8 for the dierent seams sho!n incolumnB& of the ta#le

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Degree ofGassiness

Place where the velocity of air isto be measured

Velocity ofair

First, Second or Third Degree

Intermediate out by ventilation connectionfrom the face 3

First, second

degree

!i"#$% mts from any face whether wor&ing or

discontinued on the inta&e side of thebrattice or 'artition

3

!ii"($% mts out by the discharge end of anair 'i'e )%!iii" *t the ma+imum s'an of a ongwallface -

 Third Degree !i"#$% mts from any face whether wor&ing ordiscontinued on the inta&e side of thebrattice or 'artition

#%

!ii"($% mts out by the discharge end of an

air 'i'e .%!iii"*t the ma+imum s'an of a ongwall face (%

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  TANJ KOU