Explosive compositions and method utilizing bulking and gassing agents

This invention relates to a method of preparing an explosive composition which comprises adding an inert bulking agent to said explosive composition, so as to increase the weight and density thereof, and thereafter introducing gas into said composition, so as to decrease said density to at least 1.1 g/cc. The invention also provides an explosive composition which comprises an inert bulking agent which is added to the composition to increase the weight and density thereof, and further includes gas which is thereafter added to lower the density to a predetermined or desired level.

This invention relates to explosive compositions including watergel, slurry 
and emulsion compositions, and to methods of forming and using same. 
In many forms of explosive compositions used up until this time, both 
active and inert ingredients have been mixed together and inserted or 
loaded into bore holes. Thereafter the explosive compositions have been 
detonated. 
In using exposives, bore holes are often drilled in strata or rock, such 
bore holes being drilled for example vertically or inclined. The bottom of 
the bore hole is referred to and known as the `toe` of the hole. The 
generally central or elongate part of the bore hole is generally known as 
the `body` of the bore hole. The upper area or top of the bore hole is 
known as the `collar`. 
It is generally accepted in the explosives industry, and among those using 
explosives such as for example, in the mining and excavation industries, 
that the work done by an explosive at the `toe` of the bore hole is 
greater than the work done in the `body` and `collar` areas of the bore 
hole. 
At this point in time, it is known at relatively common for the same 
explosive composition to be loaded into the `toe` of a bore hole as is 
loaded into the `body` of the bore hole. Thus, on detonation, more energy 
is supplied to the `body` of the hole than is necessary to break the 
middle and top of the bore hole. Thus, in order to achieve a better 
distribution of energy from the detonation and explosion in such 
situations, it is known to load a higher energy composition in the `toe` 
area, than in the `body` area of the bore hole. This mode of loading 
explosive compositions into bore holes is known as `combination loading`. 
In order to achieve relatively successful `combination loading`, various 
methods have been used for adjusting or varying the energy at different 
parts of the bore hole. For example, in some cases high energy additives 
have been used. This has been done relatively successfully. Further, 
methods have been successfully used which employ the use of high density 
explosives in the `toe`, with separate low density explosives in the 
`body`. 
The result of such `combination loading`, allows for a relatively high 
energy conventional blast in the `toe` of the bore hole, such as to break 
the burden in the `toe` of the bore hole. The lower energy top loading, 
caused by the reduced density in the `body` of the bore hole lowers the 
bulk energy on detonation; that is to say, the explosive fills and acts 
over more of the bore hole than does a comparable weight of explosive in 
the bottom load at the `toe` of the hole. 
In conventional blasting which does not employ `combination loading`, and 
where the same explosive has been used throughout the hole, (that is in 
both the `toe` and over the `body`), the explosive energy at the `toe` was 
sufficient and desirable, whereas the explosive energy in the `body` of 
the bore hole was greater than required. Detonation of such loads results 
in over-fragmentation at the top of the hole coupled with `back break` 
into new material causing instablity in the high wall area. Further, such 
use of explosive energy is inefficient where the greater energy provided 
over the `body` of the bore hole is unnecessary. The use of less 
explosives in the bore hole does not of itself reduce the overbreak in the 
`body` of the hole, but does cause oversize material on the top of the 
blast. 
It is an object of the present invention to provide an explosive 
composition and methods of forming and/or using an explosive composition 
which overcome or at least minimise one or more of the problems outlined 
above. 
It is a further object of this invention to provide a straightforward and 
efficient explosive composition and a straightforward and efficient method 
of forming and using an explosive composition. 
Other objects of this invention will become apparent from the following 
description. 
According to one aspect of this invention there is provided a method of 
preparing an explosive composition, comprising adding an inert bulking 
agent to said composition so as to increase weight and density thereof and 
thereafter introducing gas so as to decrease said density. 
According to a further aspect of this invention there is provided a method 
of preparing an explosive composition, comprising adding an inert bulking 
agent to said composition so as to increase the weight and density 
thereof, and thereafter introducing gas so as to decrease said density to 
at least 1.1 g/cc. 
According to a further aspect of this invention there is provided a method 
of preparing an explosive composition, comprising adding an inert bulking 
agent to said composition so as to increase weight and density thereof, 
and thereafter adding or introducing gas, so as to decrease the density of 
said composition to between 1.1 g/cc and 1.3 g/cc. 
According to a further aspect of this invention there is provided an 
explosive composition comprising an inert bulking agent added to increase 
weight and density of said composition and further including gas to 
thereafter lower said density to a predetermined or desired level. 
According to a further aspect of this invention there is provided an 
explosive composition comprising an inert bulking agent added to increase 
the weight and density of said composition and further including gas 
introduced to thereafter decrease said density to at least 1.1 g/cc. 
According to a further aspect of this invention there is provided an 
explosive composition comprising an inert bulking agent added to initially 
increase weight and density of said composition and further including gas, 
thereafter introduced to lower said density to between 1.1 g/cc and 1.3 
g/cc. 
This invention will now be described by way of example only but it should 
be appreciated that improvements and modifications may be made to the 
invention without departing from the scope or spirit thereof. 
The present invention has application to watergel slurry and emulsion 
explosive compositions, although it should be kept in mind that when the 
invention applies to compositions to be used in wet bore holes, the 
density of the resultant composition should be greater than at least 1.1 
g/cc to ensure that the composition has sufficient weight and will not 
float in the bore hole water. 
The explosive composition of the present invention, formed by the method of 
the present invention, allows for detonation resulting in a substantially 
low density top load, the results being that fragmentation of rock is more 
uniform because of better energy distribution, and `back break` being 
reduced at the `collar` of the bore hole due to reduced bore hole 
pressure. Detonation of the explosive composition of the present 
invention, within bore holes, results in reduced bore hole pressure. 
Further, environmentally, lower bore hole pressure lowers the noise from 
the blast on decimation. 
In a preferred form, the explosive composition of the present invention is 
used in an essentially `combination load` manner, with a standard 
explosive being loaded into the `toe` of the bore hole, while explosive 
composition according to the present invention is loaded into the 
remainder of the bore hole. If desired however, the explosive composition 
of the present invention could be used over the whole length of the bore 
hole. 
The present invention essentially sets out to provide an explosive 
composition whereby the density of the composition can be lowered so as to 
modify the detonation characteristics of the composition, and additionally 
be loaded into a bore hole under water. 
The lowering of the density of the explosive composition will result in the 
explosive column being higher in the bore hole, so that the explosive can 
act over a greater length of the bore hole. The lower density will also 
lower the bore hole pressure, reducing the `back break`, stabilising the 
high wall and lowering adverse environmental factors such as noise, which 
result from blasts using compositions available at this point in time. 
It should be appreciated that when the present invention is used in wet 
holes, the composition must be adjusted so that the density is at least 
1.1 g/cc and preferably higher (for example between 1.1 g/cc and 1.3 
g/cc), to ensure that the composition will not float in the bore hole 
water. 
The present invention has application to all known commercial slurry 
watergels and emulsion and emulsion-containing products. Explosive 
compositions may for example be mixtures of oxidisers, fuels and 
sensitisers, which may include for example bulking agents, finely divided 
metals and liquid or solid molecular explosives (such as for example TNT, 
smokeless powder, methyl amine nitrates, ethanol amine nitrite and the 
like). 
In the present invention slurry watergel explosives and emulsions would 
include normal compositions containing ammonium nitrate, calcium nitrate 
and sodium nitrate, and perchlorates of sodium and ammonia. By way of 
example, these oxiders and sensitisers could be solid or dissolved in a 
solvent such as, but not limited to, water and alcohols. The fuels and 
fuel sensitisers may include for example fuel oil and other distillate 
products, paraffins, waxes, resins and pitches, water soluble fuels such 
as glycols, alcohols, amines and amine salts. Also if desired organic 
thickeners such as starches, gums, polyacrylamides, sawdust, wood pulp and 
wood extracts or by-products. Additionally, they may use emulsifiers which 
are used to stabilise water-in-oil emulsion or crystal habit modifiers. 
The above are by way of example only. 
In the method of the present invention, the composition is formed by adding 
to an explosive composition an appropriate inert material or combination 
of inert materials, which may for example be styrene beads, glass beads, 
sand or other mineral fillers or the like. The above are by way of example 
only. 
In the preferred form of the invention the inert material, being added as 
inert bulking agents, have a bulk density of from 1.1 to 4.0 g/cc. 
The inert bulking agent is added to the composition to increase the weight 
and density thereof, so that in particular the composition has sufficient 
weight to avoid floating in wet bore holes. Following the addition of the 
inert bulking agent, gas is introduced or added to the composition so as 
to thereafter reduce the density of the composition as a whole and to 
increase the volume thereof. The gas is introduced so as to reduce the 
density to at least 1.1 g/cc and preferably between 1.1 g/cc and 1.3 g/cc. 
The reduction of the density of the composition, (and the increase in the 
volume thereof), by the introduction of gas, lowers the density so as to 
meet the objects of the present invention and to allow the composition, on 
detonation, to have a lower bore hole pressure and results in a more 
evently distributed explosive force over the length of the bore hole.

There now follow, by way of example only, examples of explosive 
compositions according to the preferred form of the invention. 
EXAMPLE NO. 1 
In this example a watergel explosive was taken such as that knnown as GX-20 
(trade mark). Further, approximately 3 mm glass beads were taken, the 
glass beads having a bulk density of approximately 1.51 g/cc and a 
particle size of approximately 2.48 g/cc. Approximately 80% (by weight) 
explosive composition and 20% (by weight) glass beads were mixed together, 
this resulting in the bulk density and weight of the explosive composition 
being increased. For example being increased to between approximately 1.30 
g/cc and 1.40 g/cc. Thereafter gas was introduced to the composition 
including the glass beads, and the density of the composition was reduced 
to approximately 1.2 g/cc. 
EXAMPLE NO. 2 
In this example the watergel explosive GX-20 (trade mark) was again taken. 
Further, glass beads of 650-800 microns were taken, these beads having a 
bulk density of approximately 1.49 g/cc and a particle size of 
approximately 2.50 g/cc. The glass beads were added to the explosive 
composition so that the resultant composition comprised of approximately 
80% (by weight) watergel explosive and approximately 20% (by weight) glass 
beads. This increased the weight of the composition and the density 
thereof to between approximately 1.38-1.40 g/cc. Gas was then introduced 
into the composition to reduce the density of the composition to 1.2 g/cc. 
EXAMPLE NO. 3 
In this example the same watergel explosive GX-20 (trade mark) was taken. 
To this explosive composition was added a bulk filler or inert building 
agent in the form of Ilminite. The resultant composition was 80% (by 
weight) watergel exposive and 20% (by weight) Ilminite. The Ilminite had a 
bulk density of 2.54 g/cc. In this example, the addition of the Ilminite 
increased the density of the composition to approximately 1.38 g/cc to 
1.43 g/cc. Thereafter gas was introduced to the composition to reduce the 
density to approximately 1.2 g/cc. 
EXAMPLE NO. 4 
In this example an emulsion explosive composition was used. To the emulsion 
composition was added an inert bulking agent in the form of glass beads of 
650-800 microns. The resultant composition was 78% (by weight) emulsion 
composition and 20% (by weight) glass beads. The addition of the glass 
beads increased the density of the composition and thereafter gas was 
introduced to lower the density of the composition to approximately 1.25 
g/cc. 
The above examples are by way of example only and it should be appreciated 
that this invention has been described by way of example only and that 
modifications and improvements may be made thereto without departing from 
the scope or spirit thereof as defined by the appended claims.