Explosives used in underground coal mines and method of drilling and blasting adopted explained in simple way.

1. K D PRASAD
GM(Min)/(Vig)

2.  Definition of Explosives : Explosives is a
chemical compound or mixture, when exploded
by action of heat, impact, gives large volume of
gases in a very short time at high temperature &
pressure.

 Classification : All commercial Explosives are
broadly divided in two categories.

 Low Explosives
 High Explosives

3.  Low Explosives : The chemical reaction in
low Explosives is called deflagration which is
a rapid process of combustion without
accompanying any shock wave but gives a
heaving effect.
 Example : Gun Powder
 Chemical Composition :
 Sodium Nitrate - 72%
 Sulphur - 12%
 Coal - 16%

4.  High Explosives : Reaction in High Explosives
is characterised by an associated shock wave
initiated by a detonator, basically contains.

 Oxidisers - Such as Ammonium Nitrate Fuel
Oil
 Sensitizers : MethyleAmino Nitrate, Per
chlorate Salt Physical Sensitizer : Entrapped
Air Bubbles

5.  Various important Explosives Characteristics
are
 Velocity of Detonation (VOD)
 Weight Strength
 Fume Characteristics
 Thermal Stability
 Sensitivity
 Density
 Water Resistance

6.  Velocity of Detonation : It is the speed at which
detonation wave travels through the media, it
depends upon Explosive type. VOD is measured
by, some electronic means or by Dautriche test.
Average VOD varies form 2500 M/Sec - 5800
M/Sec.

 Weight Strength : Weight strength is the energy
generated by an Explosive relative to that
produced by an equal weight of 94 AN 6 FO
(94%) Fuel Oil.

7.  Bulk Strength : It is the energy released per unit volume
of Explosive as compared to ANFO. Bulk strength can be
calculated from weight strength using the equation
 Relative Bulk Strength =
 Relative Wt. Strength x Density
 ------------------------------
 Density of ANFO
 Water Resistance : Explosives differ widely in resistance
to water and moisture penetration. Some Explosives
deteriorate rapidly under wet conditions, but others are
designed to withstand water for long periods. When
blasting is to be done under wet conditions, a water
resistant Explosive is preferable.

8.  Sensitivity : An Explosives is required to be
insensitive to normal handling, shock and
friction, but must remain sufficiently sensitive to
be satisfactorily detonated, and capable of
propagating satisfactorily, cartridge to cartridge,
even over gaps such as may occur in practice.

 Fume Characteristics : Explosives, when used
under stipulated ventilation conditions, should
liberate a minimum of harmful gases in the
products of detonation.

9.  Density : The density is important when selecting an
Explosive for a particular use. With a high density
Explosive the energy of the shot is concentrated a
desirable feature in tunneling and mining operations
in hard ground. On the other hand when the output of
lump coal from a mine is important, it is advisable to
use a low density Explosive, which distributes the
energy along the shothole.

 Thermal Stability : Explosives compositions should
be such as to be stable under all normal conditions of
usage.

10.  The DGMS stipulates that no blast hole shall be
charges if the temperature in the borehole
exceeds 80oC when blasting in hot ground.
Sometimes Explosives have to be used in sub
zero conditions in which some explosives
become insensitive. Explosives compositions of
M/s. Solar Explosives Ltd. are designed to be
stable and safe, under all conditions of use.
When blasting in hot ground, precautions as
stipulated by the DGMS should be adhered to.

11.  Properties of NG & AN :

 Nitro Glycerine (NG) - it is a liquid, insoluble in water,
highly sensitive to stock, friction and heat. In all Explosives
of N.G. based on nitroglycol is mixed for lowering the
freezing point, used for hardest rocks and metals and for
shooting oil wells.

 Ammonium Nitrate (AN) :

 It is a weak Explosives base. Difficult to initiate, so a
sensitizer like NG or TNT is used. It is Oxygen positive,
Hygroscopic, soluble in water. Tendency to form hard
cakes.

12.  A SPECIAL EXPLOSIVES FOR CONTOUR
BLASTING

 It is known as pipe charges or Gruit charge. Consist of
a plastic pipe (PVC) of dia 11mm & of length 460mm,
containing Explosives within it at concentration 0.11
Kg/m & 1.24 Kg/m respectively. Rate of detonation
4000 m/Sec. These are used in presplitting, smooth
blasting and when blasting close to buildings.
Advantages being saving in handling & charging time,
over charging is eliminated, less over break, less
cracking & less vibration.

13.  BULK EMULSION :
 Solar Explosives Ltd. has geared up for supply of
Bulk delivered system. This Emulsion technology
has been developed indigenously and
engineered a plant, which can manufacture
refined & reliable product. Emulsion technology
comes in the following categories :

 Repumpable Emulsion
 Site Mix Emulsion with Support Plant
 Augered Heavy ANFO
 Pumped Doped Emulsion

14.  To deliver the product down the borehole,
company is offering initially repumpable type
and Pumped Doped Emulsion. For this
company has designed special pump, truck
capable of pumping Bulk Emulsion after
mixing with density control agent on site.

15.  The system, which we are offering now, is named as
Repumpable Bulk Doped Emulsion, Solar BE 101. For
this system the emulsion of oxidiser and fuels is
prepared at location, where this facilities are
available. The emulsion can be stored in ambient
conditions and is non-explosive. This non-explosive
emulsion matrix after doping with Prilled Ammonium
Nitrate is mixed with gassing agents are charged into
bore hole by pump truck. The mixture becomes
sensitive only after the same is delivered in to the
blast hole and the gassing reaction completed in
above 15 minutes.

17.  Various important blasting accessories are as
under :
1) Safety Fuse
2) Plastic Ignitor Cord.
3) Detonators.
 Plain Detonators
 Electric Detonators
 Instantaneous Electric Detonators
 Long delay Detonators
 Short Delay Detonators
 Non Electric Detonators

18. 4) Cord Relay
5) Detonating Cord
6) Magnadet
7) Anodet
8) Ohm Meter
9) Exploder

19.  Safety Fuse :
 A cord of special black powder wrapped in envelope made
up of various layers of textile yarn & water proofing
material. Used for directly igniting low Explosive of
initiating high Explosive through plain detonator. Burning
rate 100-130 sec/m.

 Plastic Ignitor Cord :
 Used for ignition of several fuses in quick succession in any
desire sequence. It is 1.8-2.5 mm dia fuse, which gives
intense flame at uniform rate. Rates 3.3 S/M of 33 S/M.
slower one contains a core of a cu wire coated with plastic
incendiary composition and an iron wire added for
strength, with plastic covering.

20.  PLAIN DETONATORS :

 Used for initiating high explosives but are them selves
ignited by safety fuse consist of 6mm dia Al. Tube
partly filled with detonating charges. Modern
detonators have a base charge of PETN (Penta
Erithetetrol Tetra Nitrate) with a priming charge of
A.S.A. (Lead Azide, Lead Styphnate and Al. Powder)
strength depends upon amount of base charge.

 No.6 & No.8, No.6=0.22gm. of PETN & 35mm long.
No.8=0.45gm. PETN & 48 mm long both contains 0.2
gm ASA.

21.  These are fired electrically.

 INSTANTTANEOUS ELECTRIC DETONATORS :
 Comprises of Cu of Al. Tube of 7mm dia and a little longer
than the plain detonator so as to accommodate the fuse
head and the neopren plug. Copper Detonators are for
gassy coal mine where highly incendiary Al. is prohibited.
Explosive charges are ignited by an electric fuse head of
Nickel-Chromium-Iron alloy bridge wire soldered to the
ends brass foils separated by an insulating piece of card
board.
 Fuse Head Composition : Potassium Chlorate, Nitro
Cellulose, Charcoal (See Sketch)

23.  ELECTRIC DELAY DETONATORES :

 Special use in shaft sinking tunneling, drifting where
successive rounds are better fired in a certain sequence with
adequate time interval in between rounds so that each round
breaks into clear free face. In delay detonators a time lag is
deliberately introduced between the firing of the fuse head
and the explosion of the detonator.

 LONG DELAY DETONATORS :

 These are also known as half second delay detonators
having nominal delay interval of around 300 to 500 ms for
each. These are widely used for tunneling work and
generally from 1 to 10 Nos. are available.

24.  SHORT DELAY :

 Short Delay electric detonators are same as long delay in
construction and strength and above nominal delay interval
of 25 ms. for each delay.

 Delay composition of long delay detonator comprise of
antimony and KMNO while it is Red Lead & Silicon for short
delay.

 NON ELECTRIC DETONATORS :

 Earlier mentioned plain detonator also fall under this but due
to its restricted use it is explained under separate heading.

25.  Non-electric delay detonator basically consist of a length
of plastic single tube to which is fitted a powerful delay
detonators.
 The single tube is made of a special plastic material. The
outer dia being 3 mm and inner dia 1.0 mm. Its inner
surface is lightly coated with a mixture of reactive
powders which provide the energy transmitting medium
with in the tubing on initiation by a detonator cord or by a
detonator a shock wave propagates along inside the tube
at a velocity of about 2000 M/sec. without bursting the
tubing and therefore having no effect on any Explosives
through which is passes.
 The resulting flame front ignites the top of the delay
element with in the detonator tube.

26.  CORD RELAY :

 These devices permit short delay to be introduced into trunk
lines of detonating cords. A cord relay consists of two delay
detonators mounted inside a resilient plastic shell. They are
bi-directional in operation, Cord Relays are available in the 15
Ms, 17 Ms, 25 Ms, 50 Ms, 75 Ms, 100 Ms, delay time. The
shorter delay intervals are generally required for small (65-
90mm) dia blast holes drilled on close spacing whereas the
longer intervals are suited to larger blast holes drilled on
wider spacing.

 Cord Relays are designed for use with detonating cords,
which have core loads of 10 gm/M. No special connecting
tool is needed.

27.  DETONATING FUSE :

 It serves the same purpose as detonators and
directly initiates the high Explosives while them
needing a detonator for initiation. Useful in
simultaneous multiple shot firing minimising the
use of several detonators. Advantageous in
blasting long hole. It comprises of PETN (Penta
Erithetetrol Tetranitrate) train enclosed in a tape
wrapped in textile yarn and whole thing covered
by plastic. Finished dia 5 mm for the D.F., which
contain 10 gm PETN meter (See Sketch).

29.  OHM METER :
 Used for testing the continuity and resistance of blasting
circuits.These are of two types.
 Powered by low voltage hand operated generator.
 1.5v dry battery type.

 EXPLODER :
 Used for firing shots electrically, these are of two types:
 i) Generator type :- Magneto of dynamo (for large capacity)
operated by a quick twist of strong down ward push of
handle.
 ii) Condenser discharge type :- Can be battery of dynamo
powered.

31. No. of Charge Total
Holes Per Hole Charge
Per Ring (Kg) Per Ring (Kg)
Ring 5 1.40 7.00
Sumpers 8 1.12 8.96
Inner Easers 12 0.98 11.76
0.98Quter Easers 16 15.68
Trimmers 41 1.05 43.40

32. 
 Tunneling in rocks is currently performed mainly by blasting,
as this method only is capable of providing sufficiently high
effectiveness and economics in the construction of tunnel in
tough rocks.

 Tunneling by tunnel borers is considered to be less effective
especially as regards the construction of tunnels of large
cross sectional areas.

 Drifting /Tunnel Driving Methods in Rocks :
 The shot holes in a stone drift or tunnel are arranged in a
particular form or pattern. The drifting pattern, holes are
generally divided into three groups, e.g. Cut holes, Easer and
Trimmers.

33.  Cut holes : Shot holes in this group are generally longer
(approx. 15 cm) than the shot holes of other group. These
holes are fired first to created free face for the shots of
easers. Since these holes first make the opening in the face,
they are prime responsible for the depth of pull.

 Easers : The shot holes of this group are placed in the drift
around the cut holes in two or more rings depending on the
cross - sectional area. These holes ease the burden between
the succeeding shot holes to enlarge the excavation area of
the drift.

 Trimmers : The shot holes of this group are place around the
easer which are fired at the last to make the final shape of
the drift.

34.  The following type of cuts commonly use in Drifting /
Tunneling :
 (A) Cone / Pyramid / Diamond cut : Four or Six cut holes are
driven at the middle of the face which converge at the end to
form either a Cone or a Pyramid or diamond shape.
Maximum concentration of charge is at the apex of these cut
holes, which are fired first to create a free face for the rest of
the shot, which are fired next with the help of delays.

 (B) Wedge Cut : Horizontal cut holes are driven in inclined at
an angle less than 45 degree to the face towards the centre.
Like Cone / Pyramid cut maximum concentration of charge
at the apex of these cut holes, which are fired first to create a
free face for the rest of the shot, which are fired next with
the help of delays.

35.  (C) Parallel holes cut (Burn Cut, Cylinder Cut,Coromant Cut ) :
 A cluster of parallel shot holes are drilled at perpendicular to
the face to blast out a cavity in the centre of the heading.
Some of the holes are heavily charge with explosives while
others are kept empty to provided free face for reflection of
shock waves. There is specific geometrical relationship
between the diameter of empty hole and spacing between
the centres of empty hole and charged holes in a given rock,
which gives the essential condition of free breakage.

 (D) Drag Cut / Draw Cut : These type of cut is most suitable
for the laminated rocks for "controlled blasting " in drivage of
smaller cross-sectional area to brake the rock along the
cleavage planes.

37. 1. Making of blast hole: It should be made as accurately as
possible, particularly the line holes. This can be effected by
template, or marking use of spray paint as convenient. A
very efficient procedure of pointing holes on the working
face with a light projector with an optical attachment
consisting of metallic casing, lenses and a frame that
receives a metallic plate carrying the location of the blast
holes. Each hole is represented on the plate as an orifice
1mm in dia. The projector is placed at a distance from the
working face equal to 1.5-3 times the height of the working.
Source of the light is a lamp of 1000W. The apparatus is
located using two marks. Spotted on the face is an advance
light spot projected through the plate on the face
correspond to the holes to be drilled.

38. 2. Charging and shooting of blast holes: To reduce
the charging time it is possible to employ composite
explosive charges consisting of several cartridges
placed whether in paper shell or PVC pipes. The use
of composite charge, which is 5-10 times the carting
length, shortens the charging time by 50-60%.
3. Parallel wiring is generally used for firing shots from
an electric power mains and series for a blasting
machine. In case of NONEL use of D-cord and
electrical instantaneous detonators is fired with
exploder.

39. 4. Periphery holes: To control over break,
effective decoupling is required. It can be
done by,
 By using 25mm dia. Cartridge in 38mm dia. Hole.
 By using comparative weaker explosive
 By keeping air gap between two explosives
cartridges by using hollow bamboo spacer of
150mm long.

40. Thumb rules for u/g coal
blasting:
A) Cut face blasting:
1. No. of holes
For each 1 square meter area =
1 hole
2. Depth of hole 15cm less than cut length
3. Charge per hole 40% of hole length
4. Stemming 60% of hole length
5. Explosive
P1 type (Solarcoal-1) for degree
1 mines
P3 type (Solarcoal-3) for degree
2/3 mines

41. 1.
a)No. of holes a)For normal conditions,0.7 sq.mt = 1
hole
b)Tougher conditions, 0.5 sq.mt = 1 hole
2. Maximum depth of cut holes 0.7 x height of gallery
3. Depth of other holes = 0.8 x cut hole length
4. Charge per hole = 40% of hole length
5. Stemming = 60% of hole length
6. Explosive = P-5 type
7. Max. Possible pull = 0.8 x cut hole length
. No. of holes a)For normal conditions,0.7 sq.mt = 1 hole

42. 1. 'Freedom to Move : Insitu Coal needs free
passage to move out during blasting, i.e. Free
face to be created either by
1. CCM - Cut face blasting
2. Creating wedge opening by drilling and blasting a
few additional holes preferably at centre of face.
2. Cut Face Blasting : Holes need to be shorter by
15 cm from cut depth because explosives
energy released during blasting hits in a crater
shape and the point of concentrated energy is
15 cm beyond the end of cartridges, where free
face should be available for breakage of coal.

43. 3. Solid Blasting :
a) To create an initial cut, holes need to be drilled in
inclined position so as to provide direction and force
for coal to move outwardly, to create free face for
other holes. (Lever action theory)
b) Wider the opening (i.e. Free face) easier it would be
for other holes to perform better. It is advisable to give
zero delay for 6 cut holes in the centre.
c) Considering Beam theory, hole length beyond 70% of
seam height would not bring expected result. Rather
long sockets will be left and explosive energy will be
wasted and P.F. will be reduced.

44.  Solid Blasting :
d) Stemming less than 60% of hole length or un
proper packing may not be able to sustain
the volume / pressure of gases generated
during blasting and explosive energy will be
wasted in form of a blown out shot.
e) Cut holes should be charged more as
compared to other holes.
f) Initiation sequence should be maintained so
as that cut holes give way first, nearest hole
next and farthest holes last.

46. (Numbers show sequence of firing rounds)
Depth of Hole - 1.5 Meters
No. of Holes - 8
Charge /
Holes - 300 g
Total yield of Coal - 14 tones
Yield per kg - 6.00 tones

47.  The technique of blasting off-the solid (BOS) has been
found to be simpler, more economical and less
hazardous that the conventional method of breaking
coal with machine cutting and blasting. Mechanised
methods using BOS with scraper loaders and side
loaders have already proved successful. Several long
wall mining faces employing BOS are also tired out.
The hazards associated with blasting off the solid in
gassy coalmines, are such that the usual permitted
explosives of the category P1 and P3 are not
considered safe. Solarcoal-5 belongs to P5 category
and has been designed to meet the exacting safety
requirements in blasting coal off-the solid.

48.  The delay detonators, required for use with this
type of explosives, must be non-incentive.
Typical rounds of shot holes wedge cut and fan
cut patterns, and a schematic diagram indicating
blasting pattern and initiation sequence in long
wall faces are shown on the following pages. For
effective blasting off-the solid, full face firing in a
heading is necessary both form safety as well as
productivity point of view indigenously available
Schaffer type 350 and Rhino 25 shot exploders
are designed to meet this requirement of BOS.

50. Type of Number Depth of Explosive / hole Delay Stemming
Holes Holes Number
Cut Holes 6 1.7 m (5.6) 3 555 Z 60-65%
Other 6 1.6 m (5') 3 555 I 60%
Holes 3 1.6 m (5') 3 555 II 60%
Total Explosives
per
Expected
Pull
Expected
Coal Powder Factor
Detonato
r
Round (Insitu) T/Kg. Factor
8.32 Kg. 1.27 m (4') 19.74 M.T. 2.37 1.31

52. Degree of Classification of Gassiness Type of Permitted
Gassiness of Coal Explosives
seam
I < 0.1% of gas in the general body of air and P1 / P3 / P5
rate of emission of such gas is less than 1 cu.
m/t of coal production
II > 0.1% of gas in the general body of air and P3 / P5
rate of emission of such gas is greater than
but less than 10 cu. m/t of coal production
III Rate of emission of the gas is greater than 10 P3 / P5
cu. m/t pf coal production

53. 1. Explosives:
Types of Explosives
Degree of gassiness /
Type of Max
Application
Permissible charge
per
Shot hole (gms)
P1 Degree 1 mines, 800
P3
Cut face
1000Degree I, II & III mines,
P5
Cut face
1000Degree I-‘BOS’,
P5 Degree II &III-‘BOS’ 565

54. 2. Delay Detonator :

a) While using non-incentive delay detonators in ‘BOS’ application,
the maximum delay period between the first and last shot in a
degree I and II Gassy coal seams will not exceed 150 ms.

b) While using non-incentive delay detonators in ‘BOS’ application
the maximum delay period between the 1st & last shot in Degree
III gassy coal seams will not exceed 100 ms.

c) The delay period between 2 consecutive shots with different delay
numbers will not exceed 60 ms.
3. Distance between 2 adjacent shots with different delay
numbers will not come closer than 0.6 m at the
explosives charges ends.

55. 1. Explosives are also used for a variety of other
applications some of which are listed below :
2.
3. Agriculture.
4. Breaking blast furnace hearths / salamander blasting.
5. Cutting dimensional stones.
6. Demolitions.
7. Metal breaking.
8. Metal forming.
9. Salvaging scraps and wrecks.
10. Seismic prospecting.
11. Presplitting, smooth wall blasting etc.
12. Underwater blasting.
13. Roads & railway Construction.

56. 1. While storing transporting of handling explosives, do
not smoke or have in your possession matches, naked
light or apparatus of any kind capable of producing
flame or spark.
2. Do not keep explosives and detonators in the same
container or magazine. Explosives and detonators
must be transported separately to the blasting site.
3. Do not use tools made of iron or steel for opening
cases or for making holes in primer cartridges. Use
implements of hard wood, brass or other non-sparking
material.
4. Do not break an explosives cartridge.
5. Check the condition of shot holes with a
scraper/stemming rod before inserting cartridges.

57. 6. Do not force a detonator into a cartridge.
7. Do not try to soften hardened explosives by heating
over fire or by rolling cartridges on the ground.
8. Do not fire a blast until you have made sure that all
surplus explosives have been removed, and all
persons, vehicles and equipment are at a safe
distance.
9. Post guards with red flags around the site to prevent
persons approaching the danger area inadvertently
while the shots are being fired.
10. Keep primed cartridges separately and away from
other explosives until they are loaded into the holes.

58. 1. Test the exploder before use.
2. Stop all blasting work during an electrical storm and clears the
working area of all men.
3. While straightening the lead wires, do not hold the electric
detonator by the tube. Grip the wires about 10cm from the
detonator with one hand and smooth them out with the other. This
will avoid any pull on the fuse head.
4. While charging and stemming, take care to avoid damaging the
insulation of the lead wires of the electric detonator, which may
cause misfires.
5. Twin-core cables have top conductors and care should be taken to
make sure that the stands of one conductor are mot in contract with
those of the other. It is good practice to have the exposed ends of
the conductors staggered in relation to each other.
6. While making connections, the bare ends of the conductors should
be twisted together tightly for a length of about 3 cm. The
conductors should be thoroughly cleaned since greasy of dirty wires
give a poor connection and may cause misfires.

59. 7. To ensure good insulation and avoid short circuits in wet
conditions use insulating tape.
8. The key of the exploder should always be in the possession of
the shot fire.
9. All connections should be made by the shot fire himself; this
work should be not entrusted to any other person.
10. Before returning to the blast site, remove the exploder key,
disconnect the cable form the exploder and short circuit the
cable by twisting together the bare ends of the two
conductors.
11. Keep the exploder in a dry place.
12. Do not leave bare conductors on wet ground.
13. Take precautions against stray currents while blasting near
electrically operated machines or high voltage power lines.

60.  There are many circumstances under which a misfire
can occur and there are official regulations covering the
treatment of misfires. These should be strictly adhered
to and nothing in this chapter should be construed as
altering or amending such regulations. All misfires
should be treated with greatest care and all operations
dealing with them should be entrusted only to
experienced conscientious and careful men.

 No person should be allowed to approach a misfire until
either it has exploded or a sage period has elapsed. This
period should be at least 30 minutes with safety use
initiation and at least 5 minutes with electric shot firing.

61. 1. Misfires with Safety Fuse Initiation :
 In safety fuse firing faulty cutting of safety fuse, loose
crimping, use of non-waterproof fuse in watery conditions
can lead to misfires.

2. Misfires with Electric Shot Firing :
 In electric shot firing faulty connections, detonators left-
off unconnected, lead wires becoming bare during
stemming internally shot-circuited cable / damage in the
insulation, inadequate firing current due to failure of the
exploder toreach the rated output or the number of
detonators being greater that that can be fired by the
exploder, current leakage and other factors can cause
misfires.

62. 3. Misfires with Detonating Fuse :
 While firing with detonating fuse incorrect
method of limiting the detonating fuse, loop
cross-over, approach of a different branch of
detonating fuse, improper joints and branch-line
failure, use of detonators with too long a delay
interval, wrong sequencing of shots and
improper handling / use if delay detonator-relays
could lead to cut-offs of detonating fuse.

63. 4. Misfire with Exploders :

 A large number of misfires are generally caused by the
use of faulty exploders and use of wrong type of
exploder for a given purpose; Maintenance of
exploders is very essential to obtain the output.
Following are the causes of misfires with exploders :

a) Inadequate exploder capacity
b) Faulty exploder-defective generator/conductor
c) Poor contact in rotating crank type exploders
d) Exhausted cells
e) Faulty indicator

64.  Wherever possible, it is safer to fire the
explosives using a fresh primer than to
attempt to dislodge it and recover the
cartridges from the debris. However, before
deciding on the repriming of the explosives,
consideration should be given to the
possibility of excessive cracks in rocks, which
may occur because of the relief of the burden
of the misfired hole, by adjacent shots.

65.  (Cir.Tech. 11/1979)
 Use of L.O.X. in opencast Coal Mines :
 Recently, there was an incident of fire with the use of L.O.X. under
the following circumstances.

 Blasting was done with L.O.X. in the overburden of the opencast
workings if a coalmine. Old developed coal pillars were being
quarried. One of the shot holes in the overburden punctured into the
underground working and as such it could not be stemmed properly
before blasting. L.O.X. cartridges in the inadequately stemmed hole
were thus blasted without sufficient confinement. In all probability, a
part of the charge which had not blasted, communication down
below and configurated to set the coal debris lying belowground in
the gallery on fire.

 In order to avert such situations, you are advised that L.O.X. shall not
be used for blasting in overburden within 15 m of ug workings in the
coal seam immediately below or in the vicinity.

66.  Managements are requested to furnish
DGMS with a list of the shot fires in service at
their respective
 1. Name in Full :
 2. Father's Name :
 3. ResidentialAddress :
 4. Home Address :
 5. Number and kind of certificate he holds for
firing shots :

67.  A copy of the list should be sent to the
Superintendent of Police having jurisdiction
in the area, which the mine is situated.

 Managements are also advised to enforce
strict check or kind of personal search by the
attendance clerks at the mine entrance at the
time the unspent balance is brought to the
surface by shot fires.

68. THANK
YOU !!!