This document discusses short delay blasting in underground mining. Short delay blasting involves detonating explosive charges in a specified sequence over milliseconds to increase blast efficiency. It allows for a free face for subsequent charges and increases rock fragmentation. Short delay blasting is used with delay detonators arranged in single or multi-row patterns. Examples of typical arrangements for short delay blasting in underground mining contexts like vertical crater retreat are provided.

1. SHORT DELAY BLASTING
IN UNDERGROUND MINING
113MN0493
M BALA SUBRAHMANYAM

2. CONTENTS
 INTRODUCTION
 ARRANGEMENT OF DELAY DETONATORS
 WHY WE ARE DOING
 MOVEMENTOF ROCKS WITH AND WITH OUT DELAY DETONATOR
 WHERE SHORT DELAY IS USED
 PERFORMANCE OF SHORT DELAY
 PATTERNS USED IN OPEN CAST AND UNDERGROUND MINING
 A typical arrangement for blasting in VCR methods of mining
 REFERENCES

3. SHORT DELAY BLASTING
 A method of blasting in which the detonation of
several explosive charges takes place in a specified
sequence over certain intervals of time, usually
measured in milliseconds.
 The idea of short delay blasting was put forth and realized in the
USSR.
 By the engineer in 1934 during
the sinking of mineshaft; later, it was introduced in
the USA (1945) and Great Britain (1949).

4. DELAY DETONATOR
FIG 1: SOURCE
http://www.kayakujapan.co.jp/en/sale/denkiraikan.html

5. ARRANGEMENT OF DELAY DETONATORS
FIG 2:source
http://gsi.ir/General/Lang_en/Page_25/DataId_2485/Action_BodyView/Drill,.blast.prac
tices.to.improve.blasting.efficiency.at.Murgul.copper.mine.html

6. WHY WE ARE DOING THIS ?
 Reduced consumption of explosive as blasting is
more efficient due to availability of a free face for
each row of round of shots . (i.e. blasting due to
No.1 delay detonator gives a free face for the
blasting effect of shots fired by No.2 detonator)
 In short delay blasting, the initiation of each
subsequent charge or group of charges occurs in
an area of the rock mass that is under stress as a
result of the preceding explosion, thus increasing
the useful blast effect

7. .
 The use of shortdelayblasting increases intensity of
fragmentation of the medium by the blast
 Reduces disruption of the rock mass outside the
crushing zone,provides localized disintegration of the
rock mass, and decreases the seismic effect of the
blast.
 In addition, short delay blasting makes possible
control of the direction of movement of the crushed
rock providing collision and additional crushing of
the fragments.

8. With out Delay detonator
 If the delay between the rows is too short, the rock from the back
rows tends to take an upward direction instead of a horizontal.
FIG 3: https://miningandblasting.files.wordpress.com/2009/09/discussion-on-firing-pattern-in-
blasting.pdf

9. With Short delay detonator
 control of the direction of movement of the
crushed rock is achieved.
FIG 4: https://miningandblasting.files.wordpress.com/2009/09/discussion-on-firing-pattern-in-
blasting.pdf

10. CONDITIONS WHERE SHORT DELAY IS
USED
 In shafts withhazardous gas and dust conditions,
shortdelay blasting makes possible the firing of an
entire set of blast holes in one stage instead of
several, with instantaneous blasting (charging an
d blasting of sumper holes and ventilation, chargi
ng, and blasting of auxiliary holes).

11. PERFORMANCE OF SHORT DELAY
 Short-delay blasting is performed by means
of shortdelay electric detonators or, when blasting with a
detonator fuse, by means of
pyrotechnic delay mechanisms (relays).
 Singlerow and multirow shortdelay blasting arrangements are use The
principal singlerow shortdelay blasting arrangements are sequential
row blasting in which the charges are detonated one by one from
one end to the other.

12. Single row and Multi row short delay
 And consecutive-counter blasting
in which the detonation proceeds from the centre
of a row toward its flanks.
 Providing head-on collision of the
fragments and formation of a pile against the
centre of the face.
 In cases of a large face, the method can be repeate-
d, forming several collision centres along the front
(wave arrangement)

13. DRILL PATTERNS WITH SHORT DELAY BLASTING
FIG5 : https://miningandblasting.wordpress.com/

14. MULTI ROW SHORT DELAY
 The principal types of Multi row short delay blasting are
sequential row blasting in which the charges are
detonated consecutively
(for example, 20 milliseconds between charges and, so
that the moments of detonation of adjacent charges do not
coincide, 30 milliseconds between rows).

15.  Short Delay Series detonators are designed for opencast and
underground mines, for driving tunnels, shaft sinking and in quarries
where multi shot rounds are required.
 Long Delay Series detonators are designed for underground mining
for driving shafts and tunnels, blasting raises and shaft sinking. They
are used for stopping in metal mines, trenching and other blasting
applications.
 The longer delay period allows sufficient rock movement before
firing the consecutive shot.

16. Patterns used in open &
underground mines for short delay
blasting
FIG 6: https://sites.google.com/site/copperminingphotofromindia/explosives-andblasting-in-
mines/blasting-principles-for-open-pit-mining

17. FIG 7: BENCH
BLAST PATTERN
In open cast mines
we use this pattern for
Short delay blasting

18.  Under ground Blasting provides a good over view for a
Varity of underground blast design
 A typical arrangement for blasting in VCR methods of
mining.
FIG 8: http://technology.infomine.com/reviews/Blasting/welcome.asp?view=full

19. Vertical crater retreat
 Vertical crater retreat (VCR), also known as Vertical retreat mining, is
an open stoping, bottom-up mining method that involves vertically
drilling large-diameter holes into the ore body from the top, and
then blasting horizontal slices of the ore body into an undercut
 A system of primary and secondary stopes is often used in
VCR mining, where primary stopes are mined in the first stage and
then backfilled with cemented fill to provide wall support for the
blasting of successive stopes.

20. FIG9:
https://queensminedesign.miningexcellence.ca/index.php/File:Pic44
88.jpg
Holes are drilled vertically from the top drift through to the bottom
drift. Holes are charged such that blasting of horizontal slices of the
ore body occurs, progressing from the bottom drift to the top drift.

21. Vertical crater retreat
 The most common drill hole diameter used in VCR mining is 165mm
 Blasted ore is collected at the draw points using LHD vehicles, and
then transported to ore passes, sometimes to be crushed, before it is
transported to surface for processing
 Upon completion of the ore extraction, the stope is often backfilled
from the top drift, providing rock stability for upcoming blasts.
 This process is repeated until the ore body is mined.

22. VCR is a suitable mining method for ore bodies that exhibit
the following characteristics
Characteristics Requirements
' 'Orebody Dimensions
 Steeply-dipping orebodies (>45º), with widths of no less
than 12-15m, OR
 Very large both vertically and horizontally [2]
Grade
 VCR is not a selective mining method, therefore the ore
grade should be low to medium, and it should be
relatively uniform throughout the entire orebody [2]
Depth  VCR mining can occur at any depth.

23. REFERENCES
 www.encyclopedia2.thefreedictionary.com/short-delay +
blasting
 Deshmukh D.J(2012),Elements of Mining Technology, Vol-
1,Denett & co, Nagpur,
Pg 8.24-8.27.
 Samir Kumar Das, EXPLOSIVES & BLASTING PRACTICES IN
MINES, Lovely Prakashan, Dhanbad, Pg. 42-45
 www.msha.gov/S&HINFO/TECHRPT/BLAST/SHORTDEL.pdf
 https://miningandblasting.files.wordpress.com/2009/09/discus
sion-on-firing-pattern-in-blasting.pdf
 http://www.researchgate.net/publication/237723752_SHORT-
DELAY_BLASTING_IN_UNDERGROUND_COAL_MINES

24. REFERENCES
 http://gsi.ir/General/Lang_en/Page_25/DataId_2485/Action_BodyVi
ew/Drill,.blast.practices.to.improve.blasting.efficiency.at.Murgul.cop
per.mine.html
 http://www.kayakujapan.co.jp/en/sale/denkiraikan.html
 https://queensminedesign.miningexcellence.ca/index.php/Vertical
_crater_retreat
 https://queensminedesign.miningexcellence.ca/index.php/File:Pic4
488.jpg

25. THANK YOU