The present invention relates to a stemming plug augmenting resistance to stemming in
holes (SPARSH). The present invention particularly relates to a stemming plug
augmenting resistance to stemming in holes (SPARSH) essentially required for
engineering blasting operations in order to.enhance explosive energy utilisation
Stemming is an inert material used in holes to contain the explosive energy (particularly
the gaseous energy component) in the holes for effective explosive energy utilization
during engineering blasting operations in mines, tunnels, caverns and other engineering
structures involving removal of rock using explosives. The. desired prime objective for an
effective stemming for engineering blasting operations can be understood from the
meaning of the word stem itself, which is 'stop or restrict (flow or progress of
something)'. Uniform fragmentation, reduced noise, fly-rock and dust, and improvement
of fragmentation thereby increase in blasting economy are the end results if the stemming
is properly achieved. The objectives for effective stemming are achieved when the
stemming material provide enough resistance to escape of the gaseous explosive energy.
Seminal work on stemming is well documented by Sir John Burgoyne (John Burgoyne
(1849). Rudimentary Treatise on the Blasting and Quarrying of Stones. London) whereas
it had been stressed that stemming material shall be light in weight, angular in shape and
properly temped in the holes. Since then, drill cuttings and crushed stone materials are
preferred and widely used materials for stemming due to ease in availability. Application
of these materials, however, is not sufficient in most of the cases. Insufficiency of the
conventional stemming material led to development of devices, which are known as
stemming-plugs. The present invention relates to invention of a stemming device which
greatly enhances resistance to ejection of stemming. The invention can be used for any
engineering blasting operation irrespective of the place of its use, such as mines, tunnels,
caverns and other engineering projects involving removal of rock using explosives. The
invention can also be used to provide air-decking in holes, which is another method to
enhance explosive energy utilization for engineering blasting operations.
2
References to the prior art may be made to the following patent specifications. Majority
of prior art details related in public domain and literature is related to the applications of
hereinafter referred patent specifications and hence not referred here for brevity.
(1) US004754705 -Mechanical stemming construction for blast holes and method of
use by P.N. Worsey of July 5, 1988.
(2) US005936187- Blasting stemming plug by J.T.Miller and R.B. Brown of August
10, 1999.
(3) US005979327 -Method and apparatus for blast hole stemming by S. Thomson of
November 9, 1999.
(4) US006324980B1 -Conical plug for sealing blast holes in ope·n cut mining by
C.E. Bianchini ofDec. 4, 2001.
(5) US006386111B1 -Stemming arrangement and method for blast holes by P.C.
Shann of May 14, 2002.
(6) US006502631B I -Reinforced borehole plugs by D.F. Fitzgibbon of January 7,
2003.
(7) US007331291B2 Self-supporting air tube for blasting by D.W. Kang of
February 19, 2008.
(8) US007533721B2- Millable pre-installed plug by A.J. Sorhus of May 19,2009.
(9) US007690307B2 - Mechanical stemming apparatus for mining blasting
operations by G.L.G. Gonjalez of April 6, 2010.
(10) WO 97/17588- Method and apparatus for blasthole stemming by S. Thomson of
May 15, 1997.
(11) WO 03/060290Al -Activated stemming device by Van D.Y.K. Andre of July 24,
2003.
(12) WO 2004/023064A 1 - Stemming by G.H Harcourt and B.l. Eurich of March 18,
2004.
(13) WO 2006/042342A1 -Stemming plug by H.G . .Robert, G.G. Cooper and D.R.
Arthur of April 20; 2006.
(14) WO 2008/100347 A2- Self stemming cartridge by B. Carroll of August 21,2008.
(15) WO 2008/144846 A 1 - An inflatable void former for use in explosives boreholes
by M.M. John of December 4, 2008.
3
(16) WO 2009/037529 AI - ~last hole plugging apparatus by K.A.M. Dhooge of
March 26,2009.
The abo~e referred prior arts on the subject rely on a _single mechanism for work in the
hole for blasting, i.e., they try to emulate stemming column as a single unit to lift and
thus just delay the ejection process as it is more difficult to lift a heavy column than the
assemblage of discrete particles. The drawback in their functioning emanates from their
limitation in increasing resistance or stiffness to the stemming column. This limitation in
the prior art obviates possibility in substantially reducing the length of the stemming
column which remains very high since ages. This limitation restricts the application of
these prior arts and limits the possible advantages out of a proper stemming. Many of
these stemming devices ·of the prior art require elaborate arrangements for their
application in blast holes and thus are not a preferred technical and practical solution for
effective stemming. The prior art on the subject also increases cost of blasting as many of
them require special construction and application procedure which results in increase in
the cost. The prior art on the subject cannot function as independent device either to
create air-decking column in holes at specified locations and separated explosive columns
required under certain situations. Lack in capability of isolating explosive columns and
providing air-decking columns of the prior arts restrict their application as separate
measures will be required to achieve the purpose of the decking and the isolation thus
complicating the complete blasting process. Yet another disadvantage with the prior arts
on the subject is their restricted scope of application which is mostly in downward
direction holes in open cut mines.
Considering the requirements of an effective stemming and drawbacks of the prior art, a
stemming device is required which can augment resistance to ejection. An effective
resistance can only reduce the length of the stemming column. A stemming device is
required which is economical and simple in application yet raises effectiveness of the
stemming. It is also desired that a device is available which can provide air-decking or
isolation columns between explosive columns in a hole under certain conditions in
addition to its function as to improve stemming performance. It is further required that a
stemming device of a single design with same operational principals and simplicity in
·4
design is required which can work in all possible situations where blasting is to be ~one,
i.e. open cut and underground, downward, upward and horizontal direction holes, etc.
The main object of the present invention is to provide a stemming plug augmenting
resistance to stemming in holes (SPARS H) which obviates the drawbacks of the hitherto
known prior art as detailed above.
Another object of the present invention is to provide a stemming plug which is simple in
design and application, and which can work in all possible situations where blasting Is
required and it is desired that explosive energy utilization is efficiently utilized.
Still another object of the present invention is to provide a unique device for blasting
which can augment explosive energy utilization through air-decking technique without
disrupting routine blasting program such as hole charging and placement of explosives
restricted to specific locations.
Yet another object of the present invention is to provide a device for blasting which can
considerably reduce length and requirements for stemming while increasing efficiency
and economy of blasting operations and at the same time which reduces deleterious
impacts of blasting.
The present invention is illustrated in figures I to 5 of the drawings accompanying this
specification. In the drawings like reference numbers/letters indicate corresponding parts
in the various figures.
Figure I represents a complete assembly for the Stemming Plug Augmenting Resistance
to Stemming in Holes (SPARSH). Part 1 is the base plate which acts as emulator making
the complete stemming column as a single unit in the event of gas pressure exerted from
the bottom of the hole (Part 6) in rock ((Part 7). Part 1 can be made of any suitable
economically available material such as wood, plastic or rubber. A slit is provided in Part
1 to insert and position it at a specified location in the hole with a setting tool which is
Part 2. Part 2 has an arrangement similar to j-hook which is used to push the SPARSH in
5
the hole to a specified location, pull-back action to fix the SPARSH at the specified
location by tensioning spring anchors those are Part 3. Part 2 can be made of any suitable
materials having anti-static properties and can be screwed together when used in plurality
such as plastic, wood and metal. Part 3 is an expanding spring anchor made of spring
steel which significantly augments stiffness of the stemming column at the time when
action of detonation products expands the borehole. Part 3 is inserted into the hole in such
a manner that it exerts outward pressure on the walls of the hole at all the time while in
the hole. This outward pressure make the self-locking arrangement for SPARSH in hole
and the locking arrangements further tightens itself in the event of gaseous pressure tries
to eject the stemming material out of the hole and thus significantly augments stiffness of
the stemming. The combined action of Parts 1 and 3, i.e., emulating stemming as a
column of single material with significantly higher stiffness make SPARSH an unique
device which greatly improves blasting performance, significantly reduces deleterious
effects of blasting, improves blasting economy and reduces requirements of stemming
column to a minimal level. The non-obvious action of greatly augmenting
stiffness/resistance of stemming to ejection together with an emulator action making
stemming as a single unit column makes the present invention a unique and hitherto
unknown device or system.
Figure 2 represents Part 1 as a separate unit having plurality of holes for attachment to
Part 3 and a single slit to the centre of it to set the SPARSI-i at a specified location in the
hole as well as passage of wires required for blasting. Part 1 can be made of any suitable
)
material such as wood, plastic and rubber, etc. Part I can be made like a flexible bowl in
place of a disc as represented if so desired. Shape of the Part 1 has no much role to play
in its function due to rapid reaction rate of detonation process.
Figure 3 represents Part 2 as a single unit having two j-hooks type shapes at one end to
push the SPARSH to a specified location in the hole as well provide self locking to the
SPARSH at the specified location. Part 2 can be made of any suitable material having
anti-static properties such as wood, plastic, metal, etc.
6
.--------------------------------------------------- --
Figure 4 represents Part 3 as a single unit which is made of spring steel and total width at .
the two free ends of Part 3 is in excess to the hole diameter which makes it to behave in
such a manner that it exerts outbound pressure all the time while locked in the hole at a
specified location. This outward pressure significantly augments stiffness to the
stemming and increases the locking pressure of SPARSH while detonation products tries
to push the stemming and increases borehole diameter.
Figure 5, though not limited to, 'represents a typical step-wise procedure for mode of
operation of SPARSH. Figure 5(a) represents SPARSH ready to be inserted into a hole.
Figure 5(b) represents SPARSH pushed to a specified location in the hole. Figure 5(c)
represents SPARSH locked in the hole at a specified location. Figure 5(d) represents
SPARSH increasing locking pressure while detonation products are trying to fracture the
rock.
Accordingly the present invention provides a stemming plug augmenting resistance to
stemming in holes (SPARSH) in such a manner that it locks itself in the holes for blasting
at specified location thus prevents ejection of stemming and/or explosive material from
the specified location in the hole and the locking increases as the pressure of blasting
increases and the plug works in every situation of blasting irrespective of the diameter,
location and directi<-?n of the holes which comprises a base plate to emulate stemming as a
column of single unit material or base for the decking limit or the limit for the explosive
column separation zone and plurality of spring anchors those are provided in such a
manner that facilitates ease in application while inserting in holes but pose a stiffer path
against ejection of stemming and air-column and the spring anchors those can engage to
the hole walls in such a manner that the locking arrangement keeps the SPARSH at the
specified location and the locking pressure increases as the hole expands and walls starts .
to get fractured through piercing into the walls under such demanding situation.
In an embodiment of the present invention is a base plate as Part I which assists in
emulating the stemming column as a single unit material as opposed to a composition of
discrete material particles with a slit to the centre of the plate to facilitate application of
SPARSH to a specified location and passage of wires required for blasting. Material and
7
:e "E:. ~ "!.:- ~.· ..~. -~: ~·
..i; .&; - ;,!;.· . ..&;. - .i! ~'- ...&.:. r;,:;-
shape for this embodiment of Part 1 is irrelevant as the material can be wood, plastic or
rubber or any other suitable material and it can take a shape of a disc or cone or a bowl or
any other suitable shape.
In another embodiment of the present invention is plurality of spring anchors as Part 3
those provide a locking arrangement in such a manner that s:p ARSH engages itself to the
walls of the holes for blasting with a characteristics of locking arrangement which further
tightens/strengthens at the same location as the hole expands or rock starts to fracture due
to blasting.
In yet another embodiment of the present invention is a setting tool for SPARSH as Part 3
which has a j-hook type structure at one end and male-female threading arrangement at
another end to facilitate extension of the length ofthe setting tool as per the requirements·
to engage SPARSH at a specified location in the hole. The setting tool as Part 2 having
anti-static property can be made of wood, plastic and metal or any other suitable material.
In yet another embodiment of the present invention is a setting tool for the stemming plug
as Part 3 which has a j-hook type structure at one end and male-female threading
arrangement at another end to facilitate extension of the length of the setting tool as per
the requirements to engage the stemming plug at a specified location in the hole. The
setting tool as Part 2 having anti-static property can be made of wood, plastic and metal
· or any other suitable material.
Figure 6, though not limited to, represents a schematic of wider application
spectrum of the present invention, SP ARSH. The present invention comprising of Part 1
and Part 3 can be placed with the aid of Part 2, a setting tool, inside the blast hole, Part 6
which encompasses explosive column as Part 5 resting below the stemming column, Part
4. Part 6, blast hole, for engineering blasting is made within rock mass, Part 7 where with
the assistance of the present invention, SPARSH, comprising Part I and· Part 3, a
provision of air-decking, Part 8, can easily be provided under normal conditions or for a
8
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hole containing cavity, Part 9. The provision of air-decking is essentially required to
enhance the explosive energy consumption.
Various parts of the invention described as below;.
PART I - BASE PLATE of SPARSH (A component I entity of the complete product)
PART 2- SETTING TOOL for SPARSH (A tool required for application ofSPARSH)
PART 3 - SPRING ANCHORS for SPARSH (Novelty or Non-:-obvious components I
entities ofSPARSH. They are the only components other than a base plate)
PART 4 - STEMMING COLUMN (A section of blasthole filled up with generally drill
cuttings or other suitable inert material. Required to stop the premature ejection of
explosive energy from the blastholes)
PART 5 - EXPLOSIVE COLUMN (A section of blasthole filled up with the suitable
explosive)
PART 6- BLASTHOLE (A cavity made in the rockmass to place the explosive to extract
the rockmass)
PART 7- ROCKMASS (Compact rock material)
PART 8 - AIR-DECKING (A void section in the blasthole acting as air column. Void
maintained purposefully either to avoid explosive placement at undesired loose rockmass
I cavity or purposefully maintained so that the explosive energy reverberate in the
section for higher energy transmission. The air column acts as a spring during the
explosive energy transmission.)
PART 9- CAVITY (A void section in the bla~thole. Created purposefully for air-decking
or created from geological anomalies).
The novelty of the present invention SPARSH locks into the hole for the blasting
at a specified location in such a manner that the locking gets further strengthening
through piercing of the walls of the hole while detonation is in progress. This novelty of
locking arrangement which is non-obvious and absent from hitherto unknown prior art on
the subject effectively stem the stemming material against ejection by significantly
augmenting stiffness I resistance to the stemming column. Yet another novelty and nonobvious
inventive step of the SPARSH and its locking arrangement is that it facilitate
stiffness at a significantly higher level to stemming column in any situation of blasting
9
and irrespective of diameter and direction of the holes. Yet another novelty and nonobvious
inventive step of the SPARSH and its locking arrangement is its capability of
providing air-decking and separate explosive columns spaced to each other by a deck of
air column within a single hole for the blasting at any position without complicating
blasting process which is not possible with the hitherto known prior art on the subject.
Application of the present invention, a stemming plug augmenting resistance to stemming
in holes (SPARSH), is extremely simple and cost-effective. It is required that a unit of
SPARSH to be inserted and pushed in the hole using the setting tool in such a manner
that the plurality to spring anchors compresses and allows sliding along the wall of the
hole. Once SPARSH is placed at the specified position in the hole, whether for stemming
or decking or making separate decks for explosive columns,· it has to be gently pulled
back slightly with the setting tool which will result in forcing spring anchors into the .
walls of the hole by piercing and thus wiJI lock the SPARSH at the specified location.
The remaining process of the blasting can take place thereafter such as pouring of
stemming material or explosive material at the specified location to make a deck. The
process of pushing/inserting SPARSH to another specified location, if required, can be
repeated in a manner as described above to make a separate column or gap in the same
hole. Detonation can take once the remaining upper portion of the hole is filled with
stemming. The only care required for SPARSH is that it needs to be inserted/pushed in
such a manner that spring anchors compress themselves and allow the insertion. An
attempt in wrong/other direction for insertion will not permit SPARSH to be placed in the
hole, which also make simpler in decision making that how SPARSH to be used.
The following examples are given by way of illustration of the working of the invention
in actual practice and therefore should not be construed to limit the scope of the present
invention.
EXAMPLE-I
With reference to Figure 6, though not limited to, is one of the typical illustrations for the
use of the present invention, a stemming plug augmenting resistance to stemming in holes
(SPARSH). Part 4 is stemming column resting on Part 5 which is explosive column in the
10
hole, which is Part 6 made inside rock, a Part 7. In this illustration, the present invention
SPARSH is emulating stemming column as a single material with a significantly higher
stiffness/resistance to ejection. Figure 7 and Figure 8 illustrate a proof of field application
of SPARSH with a comparative evaluation. Figure 7 is showing the result of blasting
with application of SPARSH as illustrated in Figure 6 while Figure 8 is the result of
blasting without SPARSH in the holes while keeping all other blasting parameters same.
Bel).efits of uniform fragmentation without wastage of explosive energy as blown out is
self evident from Figure 7 while the blasting without SPARSH in Figure 8 suffered from
blown out holes and large boulders requiring secondary blasting.
EXAMPLE-2
With reference to Figure 9, though not limited to, is an illustration for another application
of the present invention SPARSH to be used as a medium to provide air-decking column,
Part 8, at the top of the explosive column, Part 5. This arrangement with the SPARSH is
aimed to enhance effectiveness of gaseous component of the explosive energy and
subsiding shock energy of the same explosive having inherently higher component for
shock energy.
EXAMPLE-3
With reference to Figure I 0, though not limited to, is an illustration for another
application of the present invention SPARSH to be used in holes with plurality of
purposes and directions as may be required in ring drilling for underground mining or
tunneling. Part 9 in Figure 10 can be a weak rock or inherent void which does not require
fragmentation from blasting. Figure 10 illustrates application of SPARSH in providing
air-decking and separation of explosive columns in a single hole and application of
SPARSH in any direction ofthe hole.
The main advantages of the present invention are:
1. It provides unique opportunity and method of significantly augmenting
stiffness/resistance to stemming in holes for blasting thus provide the best option for
proper utilization of the explosive energy.
2. It provides a simple, robust and cost-effective method and device to improve blasting
efficiency and economics for variety of blasting situations arid demands.
11
3. It provides unique opportunity and method of further augmenting the explosive energy
utilization through air-decking and separation of explosive columns in the same hole
through plurality of combination of the application ofSPARSH.
4. It provides a unique opportunity and method for safe blasting with lesser chances for
deleterious impacts of blasting such as air overpressure/noise, dust generation, fly rock,
etc. for demanding situations such as blasting near habitats, etc.
5. It provides the best procedure and method to significantly reduce length of stemming
column and thus saving in time. and material for stemming with further augmentation in
the effectiveness of the objectives for the stemming column. This advantage has potential
to further reduce back break or damage to par.ental rock mass left in-situ after blasting
and thus has great benefit in augmenting effectiveness for smooth wall blasting
techniques.
12

We claim:
1. A stemming plug augmenting resistance to stemming in holes (SPARSH) which
comprises a stemming plug augmenting resistance to stemming in holes in such a
manner that it locks itself in the holes for blasting at specified location thus
prevents ejection of stemming and/or explosive material from the specified
location in the hole and the locking increases as the pressure of blasting increases
and the plug works in every situation of blasting irrespective of the diameter,
location and direction of the holes consisting of a base plate (PART 1) to emulate
stemming as a column of single unit material or base for the decking limit or the
limit for the explosive column separation zone and plurality of spring· anchors
(PART 3) those are provided in such a manner that facilitates ease in application
while inserting in holes using a setting tool (PART 2) but pose a stiffer path
against ejection of stemming and air-column and· the spring anchors those can
engage to the hole walls in such a manner that the locking arrangement keeps the
SPARSH at the specified location and the locking pressure increases as the holes
expands and walls starts to get fractured through piercing into the walls under
such demanding situation.
2. A stemming plug as claimed in claim 1, wherein a base plate is employed w,hich
assists in emulating the stemming column as a single unit material as opposed to a
composition of discrete material particles with a slit to the centre of the plate to
facilitate application of SPARSH to a specified location and passage of wires
required for blasting, material and shape for this base plate is irrelevant as the
material can be wood, plastic or rubber or any other suitable material and it can
take a shape of a disc or cone or a bowl or any other suitable shape.
3. A stemming plug as claimed in claims 1 - 2, wherein plurality of spring anchors are
employed those provide a locking arrangement in such a manner that SPARS I I
engages itself to the walls of the holes for blasting with a characteristics of locking
arrangement which further tightens/strengthens at the same location as the hole ·
expands or rock starts to fracture due to blasting.
13
- --- --------------------------------------
4. A stemming plug as claimed in claims 1 - 3, wherein a setting tool for SPARSH is
employed which has a j-hook type structure at one end and male-female threading
arrangement at another end to facilitate extension ofthe length of the setting tool as
per the requirements to engage SPARSH at a specified location in the hole, ·setting
tool having anti-static prop~rty can be made of wood, plastic and metal or any other
suitable material.