AU2014203265B2 - Improved low energy breaking agent - Google Patents

Abstract

- 48 A breaking agent for use in boreholes and other rock or concrete breaking operations; said breaking agent operable 5 with commercial detonator initiation systems; said breaking agent comprising a cartridged or poured volume of an explosive formulation, so formulated as to maintain a low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; 10 characterised in that initiation of said low velocity detonation of one, or an interconnected series, or a poured column of said breaking agent, may be initiated by any one of, an electric detonator, a shock tube detonator or an electronic detonator. '302 Fig. 5/

Description

IMPROVED LOW ENERGY BREAKING AGENT

This invention relates to improvements in rock and concrete breaking and has particular but not exclusive application for excavation, mining, construction and demolition industries.

BACKGROUND

Conventional high explosive when placed in a borehole in rock or concrete and initiated by a commercial detonator, will detonate, producing a strong shock wave, shattering the rock or concrete in close proximity to the borehole, blasting high speed, shocked gas through cracks and micro-cracks radiating axially from the near borehole shattered zone, and breaking and throwing rock or concrete with great violence from the blast site.

The detonation of conventional high explosive in a borehole drilled into rock or concrete shatters the surrounding rock or concrete and supersonic gas from the detonation propagates through cracks emanating from the shattered zone of material immediately surrounding the detonation. The rock or concrete material is broken and displaced by a combination of shock action and heave imparted by the expanding gasses produced by detonation. A conventional, detonating high explosive needs no confinement to detonate, providing the initial shock stimulus is enough to initiate detonation, although confinement will generally increase detonation pressure and velocity. Examples of conventional, detonator sensitive high explosives are Dynamite, Detonator sensitive emulsion, Ammonium Nitrate/Fuel Oil (ANFO), T.N.T and Plastic Explosive. There are many other commercial and military high explosives known in the art. A conventionally detonating high explosive in commercial use will detonate at velocities generally between 2500 meters per second and 6200 meters per second, depending on column height, diameter and confinement conditions.

In contrast to the behaviour of a conventionally detonating high explosive as described above, an explosive formulated to undergo a very low velocity, low pressure detonation, will, when initiated, explode in confinement as described above, but will generate a very weak, low order shock wave during the low velocity detonation process, breaking and displacing the rock or concrete material surrounding the stemmed borehole containing the explosive by expansion of the explosion gasses and crack propagation induced by the hot, expanding gasses. There is little or no shattered zone around the bore hole, in contradistinction to the shattered zone produced by conventionally detonating explosives as a general rule. A weakly detonating material or, for the purposes of this explanation, a low order detonating material will, when initiated unconfined in small diameters, usually not support detonation, needing confinement to properly explode, whereas a conventional high explosive, as above described, will usually detonate without confinement provided the initiation stimulus is powerful enough. A low order detonating explosive may detonate at speeds between 1200 and 2000 meters per second, compared to the higher velocities of conventionally detonating explosives in common commercial use.

It is well known in the explosives art to lower the detonation velocity of, for example, ammonium nitrate fuel oil mixtures (ANFO) by admixing, for example, expanded polystyrene beads with the prilled ANFO. This explosive is known as ANFOPS (Ammonium Nitrate Fuel Oil Polystyrene).

By Way of example an Orica product " Amex LD " has three grades of ANFOPS, the 50 ANFO/50 Expanded Polystyrene Beads mix is quoted as detonating at between 2300 to 4000 meters per second, the 40 ANFO/60 Expanded Polystyrene Beads mix as detonating between 2100 and 3300 meters per second, and the 30 ANFO / 70 expanded Polystyrene Beads mix at between 2000 and 2900 meters per second. A minimum diameter for free poured Amex LD to detonate reliably is quoted as being 75 mm. ANFOPS requires a booster (a secondary, high velocity charge attached to a detonator which provides a very much more powerful shock impulse necessary to detonate many commercial ammonium nitrate based commercial bulk explosives).

In contradistinction, ANFO alone may detonate at between 2500 and 4800 meters per second (with a booster attached to the detonator providing adequate shock stimulus) depending on borehole diameter and column height and confinement conditions . A non detonating, deflagrating explosive has uses when vibration is an issue or excessive fly rock is a possibility. Deflagrating explosives, such as black powder or smokeless powder are usually described by those skilled in the art as having explosion velocities of below 1000 meters/second under severe confinement, although some very high velocity deflagrations can resemble low speed detonations in effect. As deflagrating explosives produce little or no shock wave, they impart reduced vibration to surrounding rock strata. This diminished vibration can be very important in inner city construction sites or near critical infrastructure for example, where excessive vibration can damage surrounding properties or equipment.

Another use of non detonating explosives is the production of dimensional stone. A low velocity non detonating explosive will enable the operator to win large unfractured blocks of dimensional stone without cracking or micro-cracking of the valuable rock.

It is known in the art that certain deflagrating materials are capable of detonation under sufficient conditions of confinement and with sufficient shock stimulus, for example those which are donated by a detonator. An example of such a material is smokeless powder, a common propellant used for the bullets and shells fired from rifles, handguns and shotguns.

Smokeless powder is composed of nitrocellulose, combined with stabilisers and anti static agents, and provided as small flakes or grains. This type of smokeless powder is called Single Base powder. Another common smokeless powder is called Double Base powder, and contains a proportion of nitroglycerine as well as nitrocellulose.

The nitrocellulose and nitro-glycerine form a solid colloid when combined which is safe to handle and use. Both types of powder do not detonate when used correctly for their intended purpose, that is, propulsion of projectiles from gun, rifle or handgun barrels.

Rather it is the case that these smokeless powders undergo a very fast, controlled burn, thus propelling the bullet or shot at a controllable velocity. If either type of powder was to detonate in a gun barrel, the results would be catastrophic, as the shock wave generated would shatter the breech of the weapon, probably killing or injuring the firer. The reason this does not happen is that the powder is ignited by a spit of flame from the cartridge or shot shell primer, and proceeds to burn, under the conditions of confinement existing within the breech and barrel, in a highly controllable and extremely rapid manner.

However it is also the case that both types of smokeless powder can be induced to detonate, given sufficient conditions of confinement and an adequate shock input, for example that provided by a commercial detonator, or detonator booster assembly, particularly in the case of double base smokeless powders .

By further way of example, there have been a number of bombing incidents where smokeless powder has been used as a high explosive. The Atlantic City bombing during the Olympics of 1996 was one such.

It is well known in the art that if a cartridge containing smokeless powder is placed into a borehole in rock or concrete, primed with a commercial detonator and well stemmed, the powder may detonate. This means that smokeless powder can perfectly well be used as a high explosive if initiated with a commercial detonator or booster.

If the same assembly is provided with an igniter, rather than a detonator, the confined smokeless powder will burn rapidly under confinement, thus breaking the rock in a non detonating manner as above described. An igniter is usually an electric igniter or a shock tube igniter that generates a hot flame and sparks, well known to those skilled in the art.

Igniters may contain, among many other compounds, lead mono nitro resorcinate, potassium chlorate, boron, lead dioxide, silicon. All being, in various combinations, igniferous and formulated to produce a hot flame and/or copious sparks.

In contrast with an igniter, a detonator contains a high explosive such as penta erythrytol tetranitrate, as well as a primary explosive such as lead azide and, when functioned, detonates, producing an intense localized shock wave, sufficient to detonate most substances capable of detonation. US Patent 57 65923 describes the use of the above described nitrocellulose based propellant powder in a rock or concrete breaking role; the powder is ignited rather than detonated. US application 2003/0015112 describes a deflagrating composition that may be composed of "a group consisting of nitrocellulose, nitroguanidine, sodium nitrate, ammonium nitrate and mixtures thereof" or "any suitable energetic material that deflagrates" housed in a cartridge and ignited by "a high energy igniter", and that this composition has a "burn rate ranging from about 100 to about 400mm/sec". US application 2005/0132921 describes "propellant coated with ammonium nitrate" as a deflagrating composition for use in rock breaking.

All the above cited patents claim deflagrating compositions ignited by an igniter. A disadvantage of igniters is that they are usually electrically initiated, and must be affixed to the cartridge containing the above described propellant in a manner that is secure and completely waterproof. A disadvantage of this system is that the above described electric igniters are instantaneous in action; each cartridge must be provided with an igniter, and there may be many cartridges required in any one rock or concrete breaking shot, and the cartridges are not interconnectable.

The operator therefore has to connect in series all the lead wires appending from the igniters embedded in the cartridges, wherever the cartridges may be in a series of boreholes. This leads to very complicated wiring procedures and frequently results in misfires. Because all the shots must be fired instantaneously the operator cannot avail himself of the wide range of delay shock tube and electronic detonators available from commercial explosives suppliers.

Another disadvantage of this product is that the deflagration of the smokeless powder, or other deflagrating compositions, under conditions of cartridge in borehole confinement is so slow that, unless all holes are fired practically simultaneously, flaming combustion products vent from cracks developed by other fired holes, thus wasting the energy developed by the smokeless powder, or other deflagrating composition, leading to poor breakage.

This means frequently sub optimal breakage patterns are common due to the lack of ability to control fragmentation through the skilled use of delays between explosive events.

Vibration can also become a problem due to the necessity to fire all the charges in a round simultaneously. Even if the charges are not detonating, the sheer mass of rock or concrete being moved can impart unacceptable vibration levels to a critical site.

There exist electro-mechanical or electronic delay systems for instantaneous igniters but they are complicated and very expensive. These types of delay systems are more usually encountered in the fireworks display industry, where precise timing of individual firework shots is critical. They are not suited to routine excavation and demolition operations .

It is an aim of the current invention to provide a system for those engaged in drilling and blasting rock or concrete that is amenable to the use of commercial detonating systems, for example Orica Exceldet products. Currently commercial nondetonating breaking agents must rely on the use of an igniter to initiate deflagration.

It is known in the art that gunpowder (black powder) is an explosive that is a reliable deflagrant, will not detonate, and has been used for centuries as a blasting explosive. It has long been supplanted by high explosives for most rock breaking tasks, but is still used for production of dimensional stone, particularly in Italy. A disadvantage of black powder is that it is not very powerful (about a fifth as powerful as ammonium nitrate/fuel oil, as above described) and does not produce much gas compared to other explosive materials. Another disadvantage is that it is also extremely sensitive to flame, sparks and friction, and will explode with a very hot fireball unconfined. It is regarded worldwide as an extremely dangerous substance, with good reason.

It is an object of the current invention to address or at least ameliorate the above mentioned disadvantages of the above described contemporary commercial products.

Notes 1. The term "comprising" (and grammatical variations thereof) is used in this specification in the inclusive sense of "having" or "including", and not in the exclusive sense of "consisting only of". 2. The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or part of the common general knowledge of persons skilled in the art in any country.

BRIEF DESCRIPTION OF INVENTION

In a first broad form of the invention there is provided a formulation of an oxidiser in prill form in combination with an effective amount of gasifier or fuel; the formulation when activated adapted to deflagrate.

Preferably, said prill is provided in granules in diameters ranging between 0.25mmm and 3.5mm.

Preferably, said prill is provided in granules in diameters ranging between 1mm and 3mm.

Preferably, said prill acts as a fuel or gassifier.

Preferably, said formulation further including a graphite or charcoal powder; said graphite or charcoal powder acting as a fuel and an antistatic agent.

Preferably, said formulation further including an aluminium powder; said aluminium powder acting as a fuel.

Preferably, said formulation further including aluminium fine turnings or aluminium swarf; said aluminium fine turnings or aluminium swarf acting as a fuel.

Preferably, said formulation further including a sodium carbonate; said sodium carbonate acting as an antacid.

Preferably, said formulation further including a nitrocellulose; said nitrocellulose acting as a fuel.

Preferably, said nitrocellulose acts as waterproofing agent.

Preferably, said formulation further including a Guar Gum; said Guar Gum acting as fuel.

Preferably, Guar Gum acts as a waterproofing agent and binder.

Preferably, said formulation further including water; said water acting as a working fluid enabling binding and Guar Gum gelling.

In a further broad form of the invention there is provided a method for the preparation of the formulation described above; said method including the steps of: (a) adding ingredients one by one or part premixed to an epoxy coated or stainless steel mixing drum or ribbon blender. (b) spraying in nitrocellulose lacquer and/or water, (c) letting the product dry by air circulation during rotation of the drum.

Preferably, said method includes the further step of packaging said formulation into plastic cartridges.

Preferably, said method includes the further step of packaging said formulation into chubs.

Preferably, said method includes the further step of transferring said formulation into bulk carrier dispenser units by means of an auger.

In still a further broad form of the invention there is provided a method of applying a low energy breaking agent to a bore hole; said method including the steps of: (a) providing a formulation according to the formulation described above in at least one cartridge, (b) providing said at least one cartridge with a detonator at one end of said cartridge, (c) lowering said at least one cartridge with detonator end first to the bottom of said bore hole, (d) Stemming an area of said bore hole above said at least one cartridge.

In a further broad form of the invention there is provided a method of applying a low energy breaking agent to a bore hole; said method including the steps of: (a) providing a formulation according to the formulation described above in the form of a chub or cartridge, (b) providing said chub with a detonator at one end of said chub or cartridge, (c) lowering said chub or cartridge with detonator end first to the bottom of said bore hole, (d) Stemming an area of said bore hole above said at least one cartridge.

In a further broad form of the invention there is provided a method of applying a low energy breaking agent to a bore hole; said method including the steps of: (a) Lowering a primer with a detonator into said bore hole, (b) pouring a formulation as described above or as claimed in any one of claims 1 to 11 into said bore hole, (c) Stemming an upper portion of said bore hole.

In a further broad form of the invention, there is provided a breaking agent for use in boreholes and other rock or concrete breaking operations; said breaking agent operable with commercial detonating systems; said breaking agent comprising a cartridged or poured volume of an explosive formulation, so formulated as to maintain a low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; characterised in that initiation of said low velocity detonation of one, or an interconnected series, or a poured column of said breaking agent, may be initiated by any one of, an electric detonator, a shock tube detonator or an electronic detonator.

Preferably, said formulation includes one or more oxidisers in powder or prill form in combination with an effective amount of gasification or fuel; said formulation when activated adapted to said low velocity detonation.

Preferably, said powder or prill is provided in granules in diameters ranging between 0.001mm and 3.5mm.

Preferably, said powder or prill is provided in granules in diameters ranging between 0.001 and 3mm.

Preferably, said powder or prill acts as a fuel or gasifier.

Preferably, said formulation further includes fuel oil or paraffin as a fuel.

Preferably, said formulation further includes a graphite or charcoal powder; said graphite or charcoal powder acting as a fuel and an antistatic agent.

Preferably, said formulation further includes an aluminium powder; said aluminium powder acting as a fuel.

Preferably, said formulation further includes aluminium fine turnings or aluminium swarf; said aluminium fine turnings or aluminium swarf acting as a fuel.

Preferably, said formulation further includes a sodium carbonate; said sodium carbonate acting as an antacid.

Preferably, said formulation further includes a nitrocellulose; said nitrocellulose acting as a fuel.

Preferably, said nitrocellulose acts as waterproofing agent.

Preferably, said breaking agent further includes fuel oil, preferably diesoline.

Preferably, said breaking agent further includes fuel oil, preferably paraffin oil.

Preferably, said breaking agent further including polyisobutylene .

Preferably, said breaking agent further includes a Guar Gum; said Guar Gum acting as fuel.

Preferably, said Guar Gum acts as a waterproofing agent and binder.

Preferably, said breaking agent further including water; said water acting as a working fluid enabling binding and Guar Gum gelling.

In still a further broad form of the invention, there is provided a method for the preparation of the breaking agent as described above or as claimed in any one of claims 1 to 11; said method including the steps of: (a) adding ingredients one by one or part premixed to an epoxy coated or stainless steel mixing drum or ribbon blender, (b) spraying in nitrocellulose lacguer and/or water, (c) letting the product dry by air circulation during rotation of the drum.

Preferably, said method includes the further step of packaging said breaking agent into cartridges.

Preferably, said method includes the further step of packaging said breaking agent into chubs.

Preferably, said method includes the further step of transferring said breaking agent into bulk carrier dispenser units by means of an auger.

In another broad form of the invention, there is provided a method of applying a low energy breaking agent to a bore hole; said method including the steps of: (a) providing a formulation as described above or as claimed in any one of claims 1 to 11 in at least one cartridge, (b) providing said at least one cartridge with a detonator at one end of said cartridge, (c) lowering said at least one cartridge with detonator end first to the bottom of said bore hole, (d) Stemming an area of said bore hole above said at least one cartridge.

In yet a further broad form of the invention, there is provided a method of applying a low energy breaking agent to a bore hole; said method including the steps of: (a) providing a formulation as described above or as claimed in any one of claims 1 to 11 in the form of a chub, (b) providing said chub with a detonator at one end of said chub, (c) lowering said chub with detonator end first to the bottom of said bore hole, (d) stemming an area of said bore hole above said at least one cartridge.

In a further broad form of the invention, there is provided a method of applying a low energy breaking agent to a bore hole; said method including the steps of: (a) lowering a detonator into said bore hole, (b) pouring a formulation as described above or as claimed in any one of claims 1 to 11 into said bore hole, (c) stemming an upper portion of said bore hole.

In a further broad form of the invention there is provided a breaking agent for use in boreholes and other rock or concrete breaking operations; said breaking agent operable with commercial detonator initiation systems without requiring a booster element; said breaking agent comprising a cartridged volume of a powdered explosive formulation, so formulated as to maintain a low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; characterised in that the explosive formulation comprises a dry mix of effective amounts of: a. Ammonium Nitrate b. Diesoline (with waxoline dye additive) c. Potassium Nitrate (Technical Grade) d. Urea Prill e. Guar Gum f. Potassium Perchlorate g. Aluminium Powder wherein tolerances by percentage volume of the components of the explosive formulation are: - Ammonium Nitrate Prill (Crushed) 56.4 +/- 10.0 - Diesoline (with waxoline dye additive) 3.6 +/- 0.3 - Potassium Nitrate (Technical Grade) 23.8 +/- 5.0 - Urea Prill 3.0 +/- 0.2 - Guar Gum 2.0 +/- 0.1 - Potassium Perchlorate 6.2 +/- 1.2 - Aluminium Powder 5.0 + /- 1.0 and wherein said non-detonating oxidizer and said aluminium act to decrease detonating pressure while maintaining reliable initiation sensitivity to commercial detonator systems .

Preferably said formulation includes at least a first nondetonating oxidizer and a second non-detonating oxidizer.

Preferably said first non-detonating oxidizer comprises Potassium Nitrate.

Preferably said second non-detonating oxidizer comprises Potassium Perchlorate.

Preferably components to decrease explosive pressure and maintain reliable initiation sensitivity to detonators further include effective amounts of one or more of Potassium Nitrate, Urea Prill, Guar Gum and Potassium Perchlorate.

Preferably said components comprise by percentage of batch volume : - Ammonium Nitrate Prill (Crushed) 56.4 - Diesoline (with waxoline dye additive) 3.6 - Potassium Nitrate (Technical Grade) 23.8 - Urea Prill 3.0 - Guar Gum 2.0 - Potassium Perchlorate 6.2

Preferably reliable initiation sensitivity to commercial detonators is maintained in said formulation applied to bore holes equal to or less than 50mm diameter.

Preferably said breaking agent in use is contained in a waterproof cartridge; said cartridge comprising a tubular element and first and second end caps.

Preferably the first end cap includes a projecting tubular element closed at an inner end; said tubular element adapted to receive therein a detonator.

Preferably said first and second end caps provides closures for respective first and second ends of said tubular element.

Preferably said tubular element, said first and second end caps are injection moulded in PVC; said first and second end caps secured to said tubular element by a PVC solvent to form a waterproof cartridge.

Preferably initiation of said low velocity detonation of one, or an interconnected series, or a poured column of said breaking agent, may be initiated by any one of, an electric detonatoignif shock tube detonator or an electronic detonator.

Preferably said formulation includes one or more oxidisers in powder or prill form in combination with an effective amount of gasification or fuel; said formulation when activated adapted to said low velocity detonation.

In yet a further broad form of the invention there is provided a method of formulating a dry powder breaking agent for low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; formulation of said dry powder breaking agent including at least Ammonium Nitrate, a Fuel and Aluminium; the method including the steps of: a. crushing Ammonium Nitrate in prill form in a hammermill, b. adding crushed Ammonium Nitrate to a drum mixer, c. combining said Fuel with said crushed Ammonium Nitrate in said drum mixer and rotating the drum of said drum mixer for a predetermined period, d. forming a premix including a non detonating oxidiser e. combining said premix with said Ammonium Nitrate and said Fuel and rotating said drum of said drum mixer for a further predetermined period, wherein said premix acts to decrease detonating pressure while maintaining reliable initiation sensitivity to commercial detonators .

Preferably said premix includes one or more of Potassium Nitrate and Potassium Perchlorate.

Preferably said premix includes one or more of Potassium Nitrate, Potassium Perchlorate, Aluminium swarf or powder, Guar Gum powder and Urea.

In yet a further broad form of the invention there is provided a method of formulating a dry powder breaking agent for low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; formulation of said dry powder breaking agent including at least Ammonium Nitrate, a Fuel and Aluminium; the method including the steps of: a. crushing Ammonium Nitrate in prill form in a hammermill, b. adding crushed Ammonium Nitrate to a drum mixer, c. combining said Fuel with said crushed Ammonium Nitrate in said drum mixer and rotating the drum of said drum mixer for a predetermined period, d. forming a premix of one or more of Potassium Nitrate, Potassium Perchlorate, Aluminium swarf or powder, Guar Gum powder and Urea, e. combining said premix with said Ammonium Nitrate and said Fuel and rotating said drum of said drum mixer for a further predetermined period, wherein said premix acts to decrease detonating pressure while maintaining reliable initiation sensitivity to commercial detonators.

Preferably percentage volumes and tolerances of ingredients of said formulation are: - Ammonium Nitrate Prill (Crushed) 56.4 + /- 10.0 - Diesoline (with waxoline dye additive) 3.6 + /- 0.3 - Potassium Nitrate (Technical Grade) 23.8 +/- 5.0 - Urea Prill 3.0 +/- 0.2 - Guar Gum 2.0 +/- 0.1 - Potassium Perchlorate 6.2 +/- 1.2 - Aluminium Powder 5.0 +/- 1.0

Preferably a predetermined volume of said dry powder breaking agent is poured into a cartridge; said cartridge comprising an assembly of a tubular element and a first end cap assembled to a first end of said tubular element.

Preferably said cartridge is formed into a waterproof cartridge by closing a second end of said tubular element with a second end cap.

Preferably outer diameter of said cartridge is equal to or less than 50 mm.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a cross section of an area of strata and a bore hole showing a first preferred embodiment of the invention using a cartridge form of the breaking agent,

Figure 2 is a cross section of an area of strata and a bore hole showing a second preferred embodiment of the invention using a chub form of the breaking agent,

Figure 3 is a cross section of a an area of strata and a bore hole showing a third preferred embodiment of the invention using a loose poured form of the breaking agent.

Figure 4 illustrates a cartridge arrangement according to a fourth preferred embodiment of the invention,

Figure 5 shows the cartridge of Figure 4 in use.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention comprises a cartridged or bulk series of formulations for the explosive breaking of rock or concrete that, when exposed to the shock of the detonation of a commercial detonator, will detonate only at a very low detonation pressure and velocity in the range of 1200 to 2000 meters per second, generating a very weak shock wave through the material to be blasted, not shattering rock or concrete in close proximity to the borehole, but generating gas at high temperature and pressure to aid break up, heave and throw of the rock or concrete.

The present invention is of particular utility for blasting tasks requiring a very low level of vibration so as to protect critical infrastructure, property and structures in close proximity to the blast.

The invention comprises a cartridged or bulk explosive, each cartridge being able to be connected to the other, and a commercial electric, shock tube or electronic detonator which can be inserted into in each cartridge. The cartridges may be conveniently fashioned from rigid plastic tube or plastic film, and tamped together in a borehole, much the same way as for ordinary commercial packaged high explosives, such as dynamite or cap sensitive emulsion.

The bulk material can be poured directly into a borehole and initiated with a commercial detonator.

First Preferred Embodiment

Turning now to the drawings, with reference to Figure 1, the breaking agent formulation described above may, in a first preferred embodiment, be encapsulated in suitable packing to form cartridges 12. One or more cartridges 12, either interconnected by a joiner 14, or alternatively abutting, are lowered into a pre-drilled bore-hole 16 in strata 10. A detonator 18 is located at the lower end of the lower cartridge with a signal tube or lead wires 20 exiting the bore-hole and connected to some suitable detonation point (not shown). The bore-hole is then provided with stemming material 22 and the low velocity detonation initiated.

Second Preferred Embodiment

In a second preferred embodiment of the invention with reference to Figure 2, the formulation is formed as a chub or cartridge 112. The chub or cartridge is likewise provided with a detonator 118 at its lower end and a signal tube or lead wires 120 led from the bore-hole to a detonation point.

Third Preferred Embodiment

In a third preferred embodiment with reference to Figure 3, a low velocity detonating formulation as described above, may be poured as a loose mixture 212 into a bore hole 216, after first lowering a correctly oriented detonator 218 to the bottom of the bore hole. Again the upper portion of the bore-hole is filled with a suitable stemming 222.

The advantages of the breaking agent of the present invention over any other non detonating or detonating products in use currently, is that the operator can treat the low detonation velocity between 1200 and 2000 metres per second, low detonation pressure cartridged product exactly the same as a cartridged high explosive like dynamite.

Likewise, the bulk product can be treated in much the same way as a bulk, pourable high explosive like Ammonium Nitrate/Fuel Oil (the most commonly used commercial explosive in the world), and users can fully avail themselves of the advantages offered by modern detonating systems, while retaining the advantages of using a low power explosive to drastically reduce vibration and throw when compared to a conventional high explosive.

This means better rock or concrete breakage due to more control over the sequencing of shots and also greatly reduced vibration by virtue of the low order detonation nature of the novel explosive.

The current invention is safer and more powerful than gunpowder and similar deflagrants, has very reduced shattering effect in comparison to conventional high explosives. Furthermore, it burns with difficulty, is extremely insensitive to external stimuli such as friction and impact, only detonates when supplied with stimulus from a commercial detonator. As well, it produces more than adequate amounts of gas for efficient breaking of rock or concrete, and may be contained in easy to use, easy to link together cartridges or as a bulk poured material.

It can also be initiated to low velocity detonation of between 1200 and 2000 meters per second by any commercial detonating system, offering great advantage to the skilled shot-firer who can minimize vibration and maximize breakage by skilled use of modern mining delay products such as shock tube and electronic delay detonators and shot plan computer programmes. This is in contrast to existing deflagrating products that only offer instantaneous, fixed, ignition, with no possibility of efficient delay patterning and extremely cumbersome, time consuming and inefficient wiring up procedures. The Formulation

The general formulation components of the novel explosive and their functions are as follows; • Ammonium Nitrate powder or prill (oxidizer), • Sodium Nitrate powder or prill (oxidizer), • Potassium Nitrate powder or prill (oxidizer), • Potassium Perchlorate powder or prill (oxidizer), • Sodium Perchlorate powder or prill (oxidizer), « Ammonium Perchlorate powder or prill (oxidizer), • Gunpowder (black powder) granular (ignition aid), • Fuel Oil, Paraffin Oil, Polyisobutylene, • Urea powder or prill (fuel, gassifier), • Hexamine powder or prill (fuel, gassifier), ® Graphite or charcoal powder (fuel, antistatic agent), • Aluminium Powder (fuel), • Aluminium fine turnings or swarf (fuel), • Guar Gum (fuel ,waterproofing agent and binder), • Water (working fluid enabling binding and guar gelling)

The specific formulations may vary according to job requirements, as some components can be interchanged for various purposes, such as bulk loading into a borehole, use in wet boreholes, or small diameter cartridging for use in small diameter boreholes. A dry formulated formulation may be cartridged or bulk poured into a borehole.

The use of guar gum confers a degree of water resistance to the formulation mixtures.

The addition of water to a formulation containing guar gum can result in a rubbery gel or granules coated with a waterproof guar/water gel that can be either cartridged or provided as large diameter chubs or pumped directly into a borehole.

In general, the ammonium nitrate content will be kept at or below 60% if the formulation is to be initiated with a detonator. This is to prevent the tendency of Ammonium Nitrate (A.N) fuel mixtures to detonate at a relatively high velocity compared to the detonation velocity of the present invention, even if heavily diluted with other substances when exposed to a severe shock from a commercial detonator or high explosive booster for example. The low A.N formulation will detonate with a low detonation velocity of between 1200 to 2000 metres per second depending on formulation with more than adequate generation of the high pressure gasses to crack and heave rock or concrete.

The A.N will, along with the other oxidizers and fuels generally described above, undergo low velocity detonation as described above, with the attendant production of large quantities of gas, predominantly nitrogen, with carbon dioxide and water vapour, as well as alkali metal oxides and chlorides.

Generally, the ratio of alkali metal and ammonium nitrates, perchlorates will be between 60 and 95 percent of the total formulation mix, depending on application, borehole diameter and method of initiation. The ratio of the "fuel" components will vary from between 40 to 5 percent depending on the conditions elucidated above.

In all cases, the formulation will be blended to promote low velocity detonation in large, medium or small diameter boreholes, The formulations will vary according to the job requirements .

For example, a small diameter cartridged product formulation may have more A.N, Perchlorate and. aluminium in it than a medium or large diameter application, in which the ratio of AN will drop in relation to Sodium or Potassium Nitrate, and the fuel and gassifier content will be increased, because of the tendency of medium to large diameter masses of AN/fuel containing formulations to transit from low velocity detonation to high order detonation and small diameters of AN/fuel formulations having difficulty detonating , especially when the AN is in prill form, and not finely divided.

There is a limit to this tendency to low velocity detonation, probably around less than 30 percent AN, so the formulation will be optimized for the conditions, preventing the A.N/fuel from transiting to high velocity detonation, that is, to above 2000 metres per second, and tailored for the formulation to undergo a low velocity detonation in conditions of borehole confinement.

Manufacture

Manufacture is relatively simple, ingredients may simply be added one by one (or part premixed) to an epoxy coated or stainless steel cement mixer type, rotating open ended mixing drum, rotating the drum. Alternatively a ribbon blender may be employed for mixing the ingredients. Water may be sprayed in if required. After sufficient mixing, the product is then packaged either in cartridges, chubs or loaded by auger into bulk carrier dispenser units, in much the same way as into ANFO (ammonium nitrate/fuel oil) loading trucks.

The present invention comprises a general formulation from which specific formulations can be derived, tailored to detonate with low velocity of between 1200 to 2000 metres per second, rather than detonate with higher velocities above 2000 metres per second with detonator initiation in all desired circumstances, providing a valuable and flexible addition to safe and efficient blasting practice.

The particular formulation will very much depend on application; extensive trialing before commercial production will indicate what the best formulae are for given work conditions, so a body of specialist knowledge built up during the pre commercial stage will indicate what specific formulations are best for specific job conditions.

Fourth Preferred Embodiment

In this further preferred embodiment, the formulation is again directed to providing a very low detonation pressure and velocity in the range of 1600 to 2000 meters per second as described above, while retaining reliability to initiation by a detonator plus a small critical diameter, particularly suited for use in small diameter bore holes. The critical diameter of an explosive is the minimum diameter which will sustain a stable detonation; it is a threshold dimension below which detonation cannot be sustained.

In this embodiment, with reference to Figure 4, cartridges 300 are formed of, preferably, injection moulded modular components, comprising a tubular element 302, a first end cap 304 and a second end cap 306. The components, preferably of PVC, are designed to be assembled into a sealed, completely waterproof cartridge.

First end cap 304 is formed with a tubular projection 308, sealed at its outer end 310, extending from inside an upper portion of the first end cap 304, and adapted to receiving therein a detonator 330 (as shown in Figure 5), as a close sliding fit. An ignition cable 312 extends from the upper end of the detonator to issue from the first end cap 304. Preferably the first end cap 304 is formed with a well 314 which communicates with the tubular element 308 and from which it extends. First end cap 304 is provided with retaining structures 316 acting to clip the ignition cable 312 securely to the first end cap 304.

The second end cap 306 is preferably formed with an internal annular ring 318 extending from the internal surface of the base of the cap to form an annular groove 320 for receiving the lower end 322 of the tubular element 302. The cartridges are prepared for filling with the breaking agent 332 (see Figure 5) of the invention by firstly assembling and securing the first end cap 304 to the upper end 324 of the tubular element 302. In the case of PVC, the first end cap is glued to the tubular element with a PVC solvent to form a waterproof seal. After filling with the breaking agent 332, the second end cap 306 is likewise assembled to the tubular element 302 by means of the PVC solvent to form a waterproof cartridge. Finally, the cartridge 300 is prepared for use by the insertion of a detonator 330. As for the other embodiments described above, in use a number of cartridges 300 may be stacked in abutment in a bore hole 340 as shown in Figure 5. The formula of the breaking agent of this fourth embodiment comprises effective volumes of Ammonium Nitrate, a suitable Fuel and Aluminium in the form of swarf or powder. In addition, the formulation of this embodiment includes ingredients which act to dampen or reduce the explosive pressure without reducing detonator sensitivity, or adversely increasing the critical diameter, and without creating a mixture that would be too sensitive, to typical manufacturing process stimuli, to safely manufacture. These ingredients include for example Potassium Nitrate, Urea Prill, Guar Gum and Potassium Perchlorate.

This latter feature, that is small critical diameter, is of vital importance if the application is for bore holes of relatively small diameter. The formulation of the breaking agent of this embodiment of the present invention has been shown to reliably detonate in bore holes of diameters as small as 32 mm. The formulation of the breaking agent of this embodiment of the present invention has been shown to reliably detonate, using only a detonator for initiation, in bore holes of diameters as small as 32 mm. A preferred formulation of the breaking agent of the invention comprises the following ingredients by preferred percentage of volume and tolerance: - Ammonium Nitrate Prill (Crushed) 56.4 +/- 10.0 - Diesoline (with waxoline dye additive) 3.6 +/- 0.3 (OR Paraffin Oil, Coal Dust, or Charcoal) - Potassium Nitrate (Technical Grade) 23.8 +/- 5.0 (OR Sodium Nitrate or Calcium Nitrate) - Urea Prill 3.0 +/- 0.2 (OR Biuret Prill) - Guar Gum 2.0 +/-0.1 (OR Xanthum Gum or Gum Acaroides) - Potassium Perchlorate 6.2 +/- 1.2 (OR Sodium Perchlorate, Ammonium Perchlorate, Potassium Iodate, Sodium Iodate or Ammonium Iodate) - Aluminium Powder 5.0 +/- 1.0

Manufacture

Preferably, Ammonium Nitrate Prill between 55.4 and 57.4% of the volume by weight of a batch of the formulation, is firstly crushed in a hammermill and then placed in a rotating drum mixer. The fuel, preferably Diesoline between 3.3 and 3.9%, is added to the drum mixer and the drum rotated for some four minutes. A premix consisting preferably of Potassium Nitrate between 23.3 and 24.3%, Potassium Perchlorate between 5 and 7.4%, Aluminium swarf or powder between 4 and 6%, Guar Gum powder between 1.9 and 2.1% and Urea Prill between 2.8 and 3.2%, is prepared, either by hand, in a paddle mixer or in a drum mixer.

At the completion of the drum mixing of the Ammonium Nitrate and Diesoline, the premix is added to the drum mixer and the drum rotated for a further four minutes.

The mixture is then removed and placed in an anti-static bag supported, for example, in an open head drum.

The cartridges are now filled with the breaking agent. Preferably the tubular element 302 of the cartridge is 325 mm in length with an internal diameter of approximately 45 mm, and can accept approximately 1 Kg of the mix. It will be understood that the length and diameter of the cartridge may vary according to field conditions and as noted above the formulation is effective in cartridges with diameters as small as 32mm.

The second end cap is then assembled and secured by PVC solvent to the other end of the tubular element. Cartridges manufactured and assembled in this way are completely waterproof to 1 bar of water pressure.

In Use

It will be understood that the above described product will be offered to users with a linkable, joinable cartridge system for use in small diameter boreholes, enabling one detonator to initiate an entire column of linked cartridges. The aim of this linkable cartridging system is to supply a product as much like a conventional high explosive product as possible, for example resembling any one of a number of joinable or linkable cartridge systems as used by the seismic explosives industry.

This functionality is in marked contrast to the above described existing commercial smokeless powder or other deflagrating composition containing cartridge system, each cartridge with a separate instantaneous electric or shock tube detonator, which obliges the shot-firer to engage in complicated and misfire prone large series circuit hook-ups or instantaneous initiation of a large number of shock tube initiated units, sacrificing the ability to adequately delay between shots, and thus being unable to optimize blasting practice.

Experiments

In experiments conducted by the inventors, cartridges of breaking agent according to the current invention, in diameters ranging from 25 to 52 mm and quantities up to 300 grams, were placed in varying levels of confinement. These included placement in conditions of mild confinement (plastic pipe), medium confinement (aluminium pipe) and severe confinement (steel pipe. All were reliably detonated at 1600 meters per second, plus or minus 100 meters per second, with a commercial No8* detonator as shock stimulus. In contradistinction, crushed ANFO displayed a detonation velocity of 2750 meters per second in a diameter of 30 mm when confined in an aluminium pipe with a No8* detonator shock stimulus.

The exemplary formulation utilised in both the velocity determinations and in quarry trial were the following:

Crushed ammonium nitrate - 58 Fuel Oil - 3.3

Crystalline potassium nitrate - 29 Urea prill - 6.5 Guar - 1.5

Coated aluminium powder - 3.7 Sodium perchlorate - 3.7

The inventors also conducted comparative trials of the current invention in comparison with the above described deflagrating smokeless powder product in a sandstone quarry. Because the current invention enables the use of modern delay detonation systems, vibration was reduced and fragmentation was better. The "half barrels" left in the free face after the shots, indicated that there was no shattering around the cartridge locations, in contradistinction to a conventional high explosive such as ANFO or a cartridged dynamite or emulsion. "Hooking Up", (the attachment, connection and running out of initiation systems) was in all cases much faster and simpler in comparison to the deflagrating smokeless powder product, which relies on instantaneous electric igniters for initiation, necessitating a time consuming and complex "hook up".

Technical Notes • General reaction Equation:- 2784NH4N03 + 62C16H34 + 976KN03 + 196CH4N02 + 20C12H24O12 + 176KC104 + 728A1 □ 6958H20 + 3468N2 + 1236C02 + 592KOH + 36502 + 364A1203 + 192K2C03 + 176KC1 ( slightly oxygen rich to account for the PVC cartridge casing and end cap components) • Density - tubes are loose packed to maintain low density of approx. 0.9 g/cc (cf. densities of 1.02-1.25 g/cc for modern gassed emulsions and slurries) • Low density of the breaking agent mix and low detonation velocity (1600-200,0 metres/sec) leads to low detonation pressure [ detonation pressure proportional to density multiplied by the square of the detonation velocity ] • The breaking agent of the invention is detonator sensitive, unlike most emulsions, slurries and ANFO mixes, which generally require a booster to function adequately. • Low detonation velocity means less vibration transmitted through rock when the breaking agent detonates compared to conventional slurries and emulsions and ANFO mixes (velocities typically from 3500 to 5500 meters /sec) • The breaking agent of the invention is a good gas producer and results in good "heave" of broken rock, and the low detonation velocity and detonation pressure (less than 20 Kbar, as compared to conventional explosives with detonation pressures from 50 - to 140 Kbar*) is also beneficial in winning rock such as marble and granite for use as building and decorative construction functions, fact that the cartridges are completely waterproof enables the formulation of the breaking agent as a dry powder mix to be placed within to be changed within fairly wide parameters regarding variation of the various constituents to raise or lower the density, detonation velocity, detonation pressure, gas production etc. • This enables these types of formulations to be tailored to the rock characteristics so as to maximise blast performance per rock type and drilling pattern characteristics . • The breaking agent of the invention is ideally suited to tight construction sites and rapid hand loading of drill holes . • Low detonation velocity means clean barrels (half drill hole profiles as shot) and little or no shattering of rock around a drill hole. • The breaking agent has also been successfully fired in smaller diameter cartridges (32 mm cartridges) • Trials have validated claims as to low vibration and good heave . *CJ-state pressure calculation gives :- 1600m/s, 0.9g/cc Pd = 9.4kbar - SG 5 lower detonation velocity range 2000m/s, 0.9g/cc Pd = 14.8kbar - SG 5 upper detonation velocity range 3500m/s, l.Og/cc Pd = 49kbar - typical AN Prill /Fuel (ANFO) V.O.D in small diameter holes 3500m/s, l.lg/cc Pd = 53kbar - typical lower density gassed emulsion with Low Density inclusions 5500m/s, 1.2g/cc Pd = 139kbar -Typical denser gassed emulsion velocity

The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims (15)

1. A breaking agent for use in boreholes and other rock or concrete breaking operations; said breaking agent operable with commercial detonator initiation systems without requiring a booster element; said breaking agent comprising a cartridged volume of a powdered explosive formulation, so formulated as to maintain a low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; characterised in that the explosive formulation comprises a dry mix of effective amounts of: Ammonium Nitrate Diesoline (with waxoline dye additive) Potassium Nitrate (Technical Grade) Urea Prill Guar Gum Potassium Perchlorate Aluminium Powder wherein tolerances by percentage volume of the components of the explosive formulation are: - Ammonium Nitrate Prill (Crushed) 56.4 + /- 10.0 - Diesoline (with waxoline dye additive) 3.6 + /- 0.3 - Potassium Nitrate (Technical Grade) 23.8 + /- 5.0 - Urea Prill 3.0 + /- 0.2 - Guar Gum 2.0 +/- 0.1 - Potassium Perchlorate 6.2 +/- 1.2 - Aluminium Powder 5.0 +/- 1.0 and wherein said non-detonating oxidizer and said aluminium act to decrease detonating pressure while maintaining reliable initiation sensitivity to commercial detonator systems .

2. The breaking agent of claim 1 wherein components to decrease explosive pressure and maintain reliable initiation sensitivity to detonators further include amounts of Potassium Nitrate, Urea Prill, Guar Gum and Potassium Perchlorate.

3. The breaking agent of claim 1 or 2 wherein said components comprise by percentage of batch volume: - Ammonium Nitrate Prill (Crushed) 56.4 - Diesoline (with waxoline dye additive) 3.6 - Potassium Nitrate (Technical Grade) 23.8 - Urea Prill 3.0 - Guar Gum 2.0 - Potassium Perchlorate 6.2 - Aluminium Powder 5.0

4. The breaking agent of claim 3 wherein reliable initiation sensitivity to commercial detonators is maintained in said formulation applied to bore holes egual to or less than 50mm diameter.

5. The breaking agent of any one of claims 1 to 4 wherein said breaking agent in use is contained in a waterproof cartridge; said cartridge comprising a tubular element and first and second end caps.

6. The breaking agent of claim 5 wherein the first end cap includes a projecting tubular element closed at an inner end; said tubular element adapted to receive therein a detonator.

7. The breaking agent of claim 5 or 6 wherein said first and second end caps provides closures for respective first and second ends of said tubular element.

8. The breaking agent of any one of claims 5 to 7 wherein said tubular element, said first and second end caps are injection moulded in PVC; said first and second end caps secured to said tubular element by a PVC solvent to form a waterproof cartridge.

9. The breaking agent of any one of claims 1 to 8 wherein initiation of said low velocity detonation of one, or an interconnected series, or a poured column of said breaking agent, may be initiated by any one of, an electric detonator, a shock tube detonator or an electronic detonator.

10. The breaking agent of any one of claims 1 to 9 wherein said formulation includes one or more oxidisers in powder or prill form in combination with an effective amount of gasification or fuel; said formulation when activated adapted to said low velocity detonation.

11. A method of formulating a dry powder breaking agent for low velocity detonation in conditions of borehole confinement; velocity of said detonation being between 1200 and 2000 metres per second; formulation of said dry powder breaking agent including at least Ammonium Nitrate, a Fuel and Aluminium; the method including the steps of: a. crushing Ammonium Nitrate in prill form in a hammermill, b. adding crushed Ammonium Nitrate to a drum mixer, c. combining said Fuel with said crushed Ammonium Nitrate in said drum mixer and rotating the drum of said drum mixer for a predetermined period, d. forming a premix of Potassium Nitrate, Potassium Perchlorate, Aluminium swarf or powder, Guar Gum powder and Urea, e. combining said premix with said Ammonium Nitrate and said Fuel and rotating said drum of said drum mixer for a further predetermined period, wherein said premix acts to decrease detonating pressure while maintaining reliable initiation sensitivity to commercial detonators .

12. The method of claim 11 wherein percentage volumes and tolerances of ingredients of said formulation are: - Ammonium Nitrate Prill (Crushed) 56.4 + /- 10.0 - Diesoline (with waxoline dye additive) 3.6 + /- 0.3 - Potassium Nitrate (Technical Grade) 23.8 +/- 5.0 - Urea Prill 3.0 +/- 0.2 - Guar Gum 2.0 +/- 0.1 - Potassium Perchlorate 6.2 +/- 1.2 - Aluminium Powder 5.0 +/- 1.0

13. The method of claim 11 or 12 wherein a predetermined volume of said dry powder breaking agent is poured into a cartridge; said cartridge comprising an assembly of a tubular element and a first end cap assembled to a first end of said tubular element.

14. The method of claim 13 wherein said cartridge is formed into a waterproof cartridge by closing a second end of said tubular element with a second end cap.

15. The method of claim 13 or 14 wherein outer diameter of said cartridge is equal to or less than 50 mm.