AU712831B2 - Sleeving blast holes - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE

SPECIFICATION

FOR A STANDARD

PATENT

Name of Applicant: COST EFFECTIVE BLASTING PTY. LTD.

010 708 031) S q

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Actual Inventor: William Lee GANE Address for Service:

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*CC.

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C C. CULLEN

CO.,

Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

Invention Title: SLEEVING BLAST HOLES Details of Associated Provisional Application: No. PP2380 filed on 17 March 1998 The following statement is a full description of this invention, including the best method of performing it known to us: SLEEVING BLAST HOLES FIELD OF THE INVENTION This invention relates to a method and an assembly for sleeving a blast hole and finds particular use in water filled blast holes.

BACKGROUND

ART

This invention relates to a method and an apparatus for sleeving a blast hole in an improved manner.

Blast holes are widely used in open cut mining to blast large sections of rock for subsequent moving or excavation. The blast holes are drilled using conventional techniques and can be anywhere between 10 100m or more in length.

~A popular blasting agent is ANFO which is an ammonium .nitrate-based blasting composition.

~Blast holes can be formed a considerable time before blasting 15 takes place and occasionally the blast holes can partially or fully fill with water. In other circumstances, blast holes need to be formed in wet areas where water seeps into the blast hole.

The ANFO and other explosives used are sensitive to excessive water or prolonged contact with water.

S: 20 Sleeving of blast holes is well-known and has been done for ol.over 30 years. Sleeving is used in a dry hole with cavities where broken or cracked ground is lined with a plastic lay flat liner. This ensures that a good uniform explosion occurs. Another type of blast hole that requires sleeving is a hot hole where the hole is lined to prevent the explosive from premature combustion in the hot hole. For water logged or seeping blast holes, the water is initially pumped out and a liner is inserted and filled with explosive before too much water seeps back in.

Occasionally, blast holes cannot be dewatered and the invention is particularly directed to this type of blast hole, although the invention can also be suitable for other blast holes that require sleeving.

The sleeve is usually formed from plastic hose which needs to be sufficiently flexible to allow it to pass down the bore hole. Plastic lay flat liner is widely used in the industry. One problem with sleeving blast holes is in ensuring that the sleeve passes down the hole without tearing. Mostly, the sleeve is manually fed down the hole to the desired distance and explosive is then poured or pumped into the sleeve.

Conventional sleeves are made from thin walled fairly stretchable polythenes which have the advantage in allowing a rather large length of the sleeve to be stored as a fairly small roll. However, these sleeves do have a number of disadvantages. Tearing or rupturing of the lo sleeve is always a possibility. If the sleeve is used in a water filled hole (that is a blast hole that cannot be dewatered), water can seep in through the tear and dilute or even wash out the blasting agent.

Another disadvantage with existing sleeve materials is that the *":sleeve is fairly stretchable. This is done deliberately to allow the sleeve to 15 stretch up against the wall of the bore hole as the sleeve is filled. However, sometimes the bore extends through an underground cavity and as the sleeve is filled, the sleeve will bulge in the cavity region. The bulging sleeve can bulge to bursting point in which a large rupture occurs with the resultant risk of removal of the blasting agent. Even if the sleeve does not rupture, the 20 bulge in the sleeve results in a non-uniform charge, and also results in excessive blasting agent being loaded into the bore hole which increases cost.

Another disadvantage with extruded plastic sleeves is that the sleeves are water impermeable. If the sleeve is pushed down a water filled hole, there is a possibility that at the bottom of the bore hole, the back pressure of the water is sufficient to cause the liner to burst or to become entangled. It is known to have a waterproof liner formed with a number of small holes at the bottom of the liner, but these holes are not always sufficient to reduce the back pressure and to not provide any relief to pressure along the length of the sleeve where there are no holes. These holes are formed in the plastic sleeve and can rupture or join to form a larger I t 4 hole which can result in loss of blasting agent.

Because of the difficulties associated with conventional sleeves, for water filled bore holes, there is a tendency to use a highly water resistant blasting agent. The blasting agent can be made more water resistant but this increases the cost of the blasting agent. One way of making the blasting agent more water resistant is to increase its density thereby making it better at displacing water. A high density waterproof emulsion can be placed in a bore hole for weeks or even months prior to detonation, but these emulsions are quite expensive. However, with conventional sleeves, there is little lo choice but to use the more expensive emulsions as opposed to the lesser expensive lower density but less water resistant emulsions to reduce the risk :.of loss of blasting agent over time.

After much research and experimentation, one form of the ~invention resides in the use of a particular type of sleeving which may at least 15 partially reduce the abovementioned disadvantages or provide the public with 5S55 0 S 0. a useful or commercial choice.

Other difficulties with sleeving bore holes is in the insertion of the sleeve into the bore hole in a correct manner. It is important to ensure that the sleeve goes down the bore hole, and either to the bottom of the bore 20 hole, or to a desired position within the bore hole. It can be appreciated that 000the bore hole wall may not always be uniformly smooth, and the hole may contain cavities, fissures, and there are particular difficulties when the bore hole is filled or partially filled with water as this will interfere with the smooth passage of the sleeve down the bore hole. U.S. patent 3,696,703 shows a sleeving apparatus which has a support framework positioned above the bore hole, a sleeve positioned within a housing with the lower end of the sleeve being attached to a rigid inner tube which facilitates passage of the sleeve down the bore hole. A loading hose can be connected to the inner tube and pushed down the bore hole which pushes the inner tube and thus the attached sleeve down the hole. This arrangement is rather slow to use and quite expensive and has not found general acceptance in the marketplace.

Also, the support framework needs to be disassembled and removed from the top of each blast hole which can be a time consuming process. Once the sleeve has been inserted, the remainder of the apparatus cannot be readily re-used and a new sleeve arrangement cannot be readily placed in the remainder of the apparatus which means that an entirely new apparatus is required for each blast hole which is to be sleeved.

One form of the present invention is directed to a sleeve assembly which does not require a rigid inner tube member to facilitate passage of the sleeve down the bore hole.

Another difficulty and potential disadvantage with existing methods in sleeving bore holes is that subsequent to blasting, it is important that the sleeve is totally destroyed. The blasted rock is removed using excavating equipment, and it is found that any residual patches of plastic oa...

sleeve material gets caught on the excavating buckets and shovels and will S* 15 melt on the warmer or hot areas of the shovels or buckets which are usually the friction bearings which causes seizure of the bearings.

One form of the present invention is directed to an assembly and a method which can facilitate complete destruction of the sleeve.

OBJECT OF THE INVENTION a.00: 20 It is an object of the invention to provide a method and assembly which may at least partially overcome some of the abovementioned disadvantages or provide the public with a useful or commercial choice.

In one form, the invention resides in a sleeve for a blast hole S° and for holding a blasting emulsion, the sleeve being made of a woven flexible non elastic material which is water permeable but which prevents the blasting emulsion from passing through the weave.

Conventional sleeves are formed from extruded plastic sheets or films and these sleeves, while being flexible, are also quite stretchable and are prone to rupturing or bulging should the bore pass through a cavity. By having the sleeve formed from a woven non-elastic material, these problems can be overcome or at least minimised. The sleeve can be water permeable 6 as it is not essential for the sleeve to be impermeable to water, but the weave must be such that the blasting emulsion (which can have the property of a grease) is unable to pass through the weave or at least that a significant portion of the emulsion is unable to pass through the weave during a typical resident time of the emulsion in the bore hole (which can be several days or weeks).

A woven flexible non-elastic material which suits the purpose is a weave of flat polypropylene strips. Other materials are also envisaged including a cloth weave, a metal weave, composite weaves and the like providing that the resultant sleeve is flexible but substantially inextensible such that when filled with the blasting emulsion, it forms a column of substantially uniform diameter, or a diameter dictated by the configuration of .the sleeve as opposed to any bulging or stretching of the sleeve as is the case with conventional sleeves.

15 In another form, the invention resides in a sleeve assembly for a blast hole, the assembly having a length of sleeve which is axially compressed to form a concertina shape, the lower end of the sleeve being :.closed, releasable retention means to hold the sleeve in its compressed shape, the retention means able to be released upon passage of a loading 20 hose through the sleeve, a lower end area of the sleeve not being retained by the retention means and thus able to be placed into the bore hole before insertion of the loading hose.

aIn this assembly, there is no longer a requirement for a Sa complicated arrangement as found in U.S. patent 3,696,703, and the need for an inner rigid tube is eliminated by having a lower part of the sleeve able to be dropped into the bore hole with the wall of the bore hole forming a guide for the loading hose. This ensures that the loading hose travels through the sleeve and down the bore hole correctly.

The assembly is extremely simple yet reliable, inexpensive and can be used quickly and easily by an operator.

The releasable retention means, in a simple form, can be one or more strips of sticking tape or sticking plaster which can be placed along the outside of the compressed sleeve. The tape or plaster will hold the sleeve in the compressed state with the lower part of the sleeve being free from the tape and able to be dropped into the bore hole. The tape should have sufficient adhesion to prevent the remainder of the sleeve from falling into the bore hole until it is pushed by the loading hose.

The length of the lower end which is not retained by the retention means can vary but is typically between 50cm to 3m.

The entire sleeve assembly containing the attached sticky tape or plaster can be held together by an elastic band when being transported and when the elastic band is cut, the lower end of the sleeve becomes loose and can be dropped or pushed into the bore hole.

In another form of the invention, the sleeve assembly includes a container in which the axially compressed sleeve can be placed. The 15 container can be a simple bowl having an open top and an open bottom with the dimensions of the open bottom being such that the compressed sleeve cannot pass through the open bottom but as the sleeve is unraveled it can °pass through the open bottom. The container can be simply placed over the top of the bore hole, and when finished, can be removed and a new sleeve 20 assembly can be placed into the container which means that the container sees s Sitself can be re-used several times. The container can be made from a lightweight yet robust plastic material.

In another form of the invention, the sleeve has a length less

S

than the depth of the bore hole ensuring that the upper end of the sleeve is below the open mouth of the bore hole by a distance which forms the stemming zone.

When a bore hole is filled with blasting agent, the blasting agent usually terminates about 1 to 3m below the top of the bore hole. This area is called the "stemming zone" and is filled with gravel or cuttings to plug the top of the bore hole. In the past, sleeves have been of a length to pass through the stemming zone and even out of the bore hole itself. When the 8 charge is detonated, it is found that the sleeve in the stemming zone does not blow to pieces but instead can form quite large strips which can damage the excavator, buckets and shovels.

In one form of the invention, the sleeve extends to the bottom of the stemming zone such that when detonated, there is little likelihood of any large pieces of sleeve remaining. A line member is provided which is attached to an upper area of the sleeve such that the upper end of the sleeve is supported at the lower end of the stemming zone.

Therefore, in another form the invention resides in a sleeve assembly for a blast hole, the assembly having a length of sleeve which is axially compressed to form a concertina shape, the lower end of the sleeve being closed, releasable retention means to hold the sleeve in its compressed shape, the retention means able to be released upon passage of 0 a loading hose through the sleeve, a lower end area of the sleeve not being retained by the retention means and thus able to be placed into the bore hole 5before insertion of the loading hose, and a line member attached to the sleeve to hold the upper end of the sleeve below the mouth of the bore hole.

S. *S In yet another form, the invention resides in a sleeve assembly .0 0for a blast hole, the assembly having a length of sleeve which is axially compressed to form a concertina shape, the lower end of the sleeve being ~closed, releasable retention means to hold the sleeve in its compressed S" shape, the retention means able to be released upon passage of a loading hose through the sleeve, the lower end area of the sleeve not being retained by the retention means and thus able to be placed into the bore hole before insertion of the loading hose, a container in which the sleeve is placed the container having an open bottom through which the sleeve can pass into the bore hole.

The container may be formed with a slot or cut in the side wall through which the line member can pass such that the container can be lifted away from the bore hole while still holding the line member.

In another form, the invention resides in a method for charging 9 a water filled blast hole of known length the method comprising: positioning a sleeve assembly above of adjacent the blast hole mouth, the assembly comprising a length of sleeve which is axially compressed to form a concertina shape, the lower end of the sleeve being closed, releasable retention means to hold the sleeve in its compressed shape, the retention means able to be released upon passage of a loading hose through the sleeve, a lower end area of the sleeve not being retained by the retention means and thus able to be placed into the bore hole before insertion of the loading hose, a container in which the sleeve is placed the container having an open bottom through which the sleeve can pass into the bore hole, a line member attached to an upper pert of the sleeve, the length of the sleeve being less than the depth of the bore hole the line member being sufficiently long enough to extend out of the bore hole to hold the sleeve in the bore hole, dropping the lower end area of the sleeve into the bore hole, placing a primer into the lower end area of the sleeve, pushing a loading hose into the sleeve and down to the bottom of the bore, the loading hose pulling the sleeve down the hole and releasing the retention means, the upper end of the sleeve terminating below the mouth of the bore hole to define a stemming zone between the sleeve and the mouth of the bore hole, holding the sleeve by the line member to prevent it from falling down the hole, passing emulsified blasting agent through the loading hose to fill the sleeve from the lower end thereof, and progressively raising the hose until the sleeve is filled, removing the loading hose from the bore hole, and placing stemming material in the stemming zone.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be described with reference to the following drawings in which Figure 1 shows a sleeve assembly according to an embodiment of the invention.

Figure 2 shows a container in which the sleeve assembly can be placed.

Figure 3 shows the sleeve assembly and container and a line member positioned above a blast hole.

Figure 4 shows the lower area of the sleeve dropped into the blast hole and a loading hose about to be inserted into the sleeve.

Figure 5 shows the sleeve fully extended into the blast hole and 10 terminating at the bottom of the stemming zone. 9 9*° Figure 6 shows a filled bore hole ready for detonation.

~Figure 7 illustrates an alternative embodiment of the invention.

Figure 8 illustrates one way in which the sleeve can be ":concertinad.

Referring to the drawings and initially to Figures 1 to 4, there is 9. 9illustrated a sleeve assembly 30 which is formed from a sleeve which is 9*• axially compressed to form a concertina shape with Figure 8 illustrating one embodiment on how to achieve this. The sleeve can have any particular desired length depending on the length of the bore hole. In the embodiment, the length of the sleeve is less than the length of the bore hole such that the :o sleeve, when fully extended, terminates at the base of the stemming zone 31 *o*illustrated in Figures 5 and 6. Thus, for a 20m bore hole, the sleeve has a length of approximately 17m to 18m such that it terminates 2 to 3m below the open mouth of the bore hole.

Sleeve 32 is formed from flat strips of polypropylene plastic woven together into a tight mesh arrangement. The woven sleeve is not watertight in the sense that if the sleeve is filled with water, water will leak from it, but that weave is tight enough to prevent the grease like blasting emulsion from leaking out of the sleeve.

Convention wisdom has always been to provide water impermeable sleeves and it is considered a radical departure to provide a woven somewhat water permeable sleeve which provides excellent strength but is also substantially inextensible which means that the weight of the blasting agent will not bulge the sleeve should the sleeve pass through a cavity along the bore length.

Once the suitable length of the sleeve has been axially compressed, strips of adhesive tape 33 are stuck onto the outside of the compressed sleeve and at diametrically opposed positions. The lower end of tape 33 does not extend entirely to the bottom of the sleeve which means that a lower end area 34 is not retained by the tape. An elastic band 35 is 10 temporarily stretched about the sleeve primarily to hold area 34 from falling open. A rope 36 is attached to the upper part of sleeve 32 the reason for io- which will be described in greater detail below.

The bundled sleeve arrangement illustrated in Figure 7 can be dropped into a container 37 illustrated in Figure 8. Container 37 can be made from plastic and is cut or slotted at 38 down one side to form an open *slot. Container 37 has a lower opening 39 which is sized such that the compressed sleeve arrangement cannot pass through opening 39, but as the sleeve is pulled down it can pass through opening 39.

The entire arrangement of the sleeve assembly and the container is lightweight and is typically less than 10 to 20kg which means that *0 it can be readily lifted and walked over to the top of a bore hole.

Slot 36 functions to allow container 37 to be pulled away from the bore hole and allowing rope 36 to pass through slot 38 such that the container can be pulled totally free.

Figures 3 and 4 show the arrangement above a bore hole Bore hole 40 is pre-formed and as the invention is particularly suited to water filled bore holes, in the embodiment bore hole 40 is filled with water.

The container 37 containing the bundled sleeve arrangement is simply placed over the open mouth of the bore hole and the elastic band is cut away. This now releases the lower end area 34 of the sleeve. A primer charge weighing approximately 300g to 500g is placed into the bottom of the 12 sleeve area which assists in causing the lower area of the sleeve 34 to drop into the bore hole until further downward movement of the sleeve is prevented by adhesive tapes 33. This arrangement is illustrated in Figure 4.

A loading hose 41 is then passed through sleeve 32 such that the lower end of hose 41 passes along area 34 and into the bottom of the sleeve. The loading hose is long enough to go to the bottom of bore hole and is pushed into the bore hole which causes the sleeve to now travel down the bore hole. The force and weight of the loading hose is sufficient to allow the axially compressed sleeve to become released from the adhesive tapes S 10 33 and pulled down the bore hole with the loading hose. Water is displaced from the bore hole as the hose travels down.

:Once the loading hose is in the bottom of the bore hole S emulsified blasting agent is pumped through the hose and therefore into the bottom of the sleeve 42. The weave arrangement of the sleeve means that water at the bottom of the bore can pass into the sleeve rather than rupture the sleeve by virtue of back pressure.

As emulsified blasting agent is pumped into the sleeve, the i* loading hose is slowly pulled out of the bore until the sleeve has been filled.

When fully extended, the top 43 of the sleeve is below the open mouth of the bore hole 40 and is at the lower area of the stemming zone 31.

The reason for rope 36 now becomes clear as rope 36 needs to be held while the top 43 of the sleeve passes down the bore hole and to prevent the sleeve from collapsing further down the bore hole. Once the sleeve has been filled with emulsified blasting agent, rope 36 can be thrown down the bore hole and stemming material 44 can be shoveled into the hole to plug it.

The assembly is inexpensive to manufacture and very easy to use and does not require complicated guiding equipment or support structures above the bore hole. By ensuring that the top of the sleeve is in the bottom of the stemming zone, detonation of the blasting agent will result in the sleeve being totally destroyed and therefore posing little or no risk to resultant excavating apparatus such as shovels and buckets.

The invention is designed particularly for bore holes that have dynamic ground water that is water that cannot be removed by pumping as the end flow volume rate exceeds pumping capacity. The sleeve is inserted by the loading hose passing down the blast hole below the water level.

When the submersible sleeve and hose have reached the bottom of the hole, the sleeve is filled with a waterproof or water resistant explosive agent.

When the required volume of explosive has been discharged into the sleeve, the hose is withdrawn and the filling unit moves on to the next hole.

The sleeve protects the explosive from being washed away by dynamic water flow. The explosive is contained within the sleeve through cavities which maintains column rise. A lower density less water resistant S and therefore cheaper explosive emulsion can be used which reduces operating costs. The invention allows an increase in holes charged per tonne of explosive used due to the ability to use lower density water resistant product.

S. S Referring to Figures 7 and 8, there is disclosed a form of the Sinvention which resides in a method to insert a sleeve into a blast hole comprising the steps of providing an elongate sleeve of sufficient length to allow it to pass to a desired distance into the blast hole, axially compressing the sleeve to form a concertina shape, placing the compressed sleeve above or adjacent the blast hole mouth, and forcing the sleeve into the bore hole.

In this form, the invention resides in an apparatus for sleeving a blast hole, the apparatus having an elongate sleeve axially compressed into a concertina shape, the sleeve having a lower end and an open upper end, a first support to support the sleeve above or adjacent the blast hole, a second support to releasably hold the lower end of the sleeve.

By concertining the sleeve, the sleeve can sit above the blast hole and can be more easily pushed down the blast hole with a reduced risk that the sleeve can abrade, tear or rip as it passes down the blast hole.

The flexible sleeve can be made from synthetic material, cloth 14 weave, a plastic lay flat material, and can be manufactured to the required length and diameter as will be dictated by the length and diameter of the blast hole.

The sleeve can be compressed axially by placing one end over an elongate insert and then crushing or compressing the sleeve on to the insert. Once the required length has been axially compressed, it can be taped or tied to hold it in position.

In another form, the apparatus is a portable compact unit which can be readily moved to site and above or adjacent a blast hole. For instance, the apparatus has a first support to support the sleeve, and this can be in the form of a frame arrangement which can be positioned above the blast hole. The frame arrangement can have spaced apart legs the legs S sitting on each side of the blast hole such that the central portion of the frame :sits immediately above the blast hole.

e15 The frame suitably supports the axially compressed sleeve in a substantially vertical arrangement such that the sleeve can readily drop down into the bore hole in a convenient and efficient manner.

"-•The sleeve can be pushed into the bore hole by a weighted Sobject, although it is preferred that the sleeve is pushed down by inserting a blast charging hose into the sleeve and down through the lower end. As the *blast charging hose gets pushed down the bore hole, it will also pull down the sleeve. It is preferred that the bottom end of the sleeve is closed off or otherwise arranged such that the blast charging hose grips the lower end of the sleeve and pulls it down as the hose is pushed down the bore hole.

It should be appreciated that other arrangements could be used to push the sleeve down the bore hole such as various types and shapes of weights, push rods and the like. However, it appears to be most efficient if the blast charging hose is the means to force the sleeve into the bore hole.

The apparatus has a second support to releasably hold the lower end of the sleeve. For instance, the second support can hold the sleeve while the apparatus is being transported but can release the sleeve upon forcing the sleeve into the bore hole.

A preferred way of carrying this out is to form the second support in the form of a bucket-like container having a lower open end which is restricted in size such that the axially compressed sleeve cannot fall through the bucket but where the lower hole is sufficient to allow the blast charging hose to pass through the container and to take the sleeve with it.

Referring to Figure 7, there is shown an apparatus 10 which is formed from lightweight portable yet sufficiently strong frame members which can be welded or otherwise attached to each other. The apparatus consists of a number of spaced apart feet 11 (the apparatus illustrated in Figure 7 being a tripod construction with the third foot not illustrated). The feet 11 straddle each side of a blast hole in use. The apparatus has an upper mouth portion 12 which can secure the upper end 13 of a flexible sleeve 14. That is, mouth portion 12 is usually of a smaller diameter than the diameter of sleeve 14 such that sleeve 14 can be simply turned over the edges of mouth portion 12 and clamped or otherwise secured in place. This arrangement provides a oo good sized upper opening 15 without any obstructions.

~Apparatus 10 has a second support in the form of a bucket-like container 15A. Container 15A has a tapered shape and has an upper open end 16 and a lower open end 17. Lower open end 17 has an opening size which is less than the diameter of sleeve 14 which means that the sleeve can be held in container 15A in a releasable manner. For transportation, the sleeve can be pre-loaded into container 15A and tied off against mouth portion 12 and the entire apparatus can be transported into position without the sleeve falling through container Sleeve 14 is formed from flexible materials which are used in sleeving blast holes. The sleeve is sized and formed to the desired length and is then axially compressed into a concertina shape. The compressed sleeve is then placed within container 15A with the upper end of sleeve being tied off against mouth portion 12 and the lower end 18 of sleeve 14 either extending slightly below container 15A or being located entirely within 16 container 15A (it being appreciated that the size of open end 17 is smaller than the compressed diameter of sleeve 14 and therefore sleeve 14 will not naturally fall from container 15A. The size of container 15A can vary depending on the amount of sleeve material which is to be located within the container.

Figure 8 shows how sleeve 14 can be conveniently concertinerd. In Figure 8, there is illustrated an insert 20 about which sleeve 14 can pass and be axially compressed.

Once apparatus 10 is placed above a blast hole, a blast lo charging hose (such hoses being known in the art) can be fed through top opening 15 and into sleeve 14 until the bottom of the blast charging hose contracts lower end 18 of the sleeve. The charging hose is pushed into the bore hole which in turn drags the sleeve into the hole.

Explosive material can then be forced through the blast charging hose to fill the sleeve to a desired amount and the explosive can then be detonated in due course.

One advantage of the sleeve arrangement is that it can be used 0 0in blast holes which are full of water. In this arrangement, lower end 18 is ".°sealed shut and as the blast charging hose passes through sleeve 14 and drags the sleeve with it, the sleeve displaces water from the hole. In this arrangement, it is no longer necessary to pump the hole as dry as possible before adding explosive (it being appreciated that the explosive material often has to sit in the blast hole for a period of time until a number of blast holes are ready to be detonated together or sequentially).

It should be appreciated that various other changes and modifications can be made to the embodiment described without departing from the spirit and scope of the invention.

Claims (12)

1. A sleeve assembly for a blast hole, the assembly having a length of sleeve which is axially compressed to form a concertina shape, the lower end of the sleeve being closed, releasable retention means to hold the sleeve in its compressed shape, the retention means able to be released upon passage of a loading hose through the sleeve, the lower end area of the sleeve not being retained by the retention means and thus able to be placed into the bore hole before insertion of the loading hose.

2. The assembly of claim 1, wherein the lower end area has a length of between 0.5m to

3. Assembly of claim 1 or claim 2, wherein the sleeve is made of a flexible substantially inextensible material.

4. The assembly of claim 3, wherein the sleeve is made of a woven material.

5. The assembly of claim 4, wherein the material is a weave of flat polypropylene strips.

6. The assembly of any one of the preceding claims, wherein the releasable retention means is one or more adhesive strips attached to the "outside wall of the compressed sleeve.

7. The assembly of any one of the preceding claims, including a container into which the compressed sleeve is positioned, the container a having an opening in a lower portion, preferably the bottom wall, which is dimensioned to prevent the compressed sleeve from falling through the opening, but which allows the extended sleeve to pass through.

8. The assembly of any one of the preceding claims, wherein a line member is attached to an upper end of the sleeve.

9. The assembly of claim 8, wherein the container is slitted from the base to the upper end of the container to allow the line member to pass through the slit.

10. The assembly of any one of the preceding claims, wherein the length of the sleeve is less than the length of the blast hole such that in use, I I 18 the top of the sleeve is adjacent the bottom of the stemming zone.

11. A method for charging a water filled blast hole of known length the method comprising: positioning a sleeve assembly above or adjacent the blast hole mouth, the assembly comprising a length of sleeve which is axially compressed to form a concertina shape, the lower end of the sleeve being closed, releasable retention means to hold the sleeve in its compressed shape, the retention means able to be released upon passage of a loading hose through the sleeve, a lower end area of the sleeve not being retained by 10 the retention means and thus able to be placed into the bore hole before insertion of the loading hose, a container in which the sleeve is placed the 9container having an open bottom through which the sleeve can pass into the .9 bore hole, a line member attached to an upper pert of the sleeve, the length t' "of the sleeve being less than the depth of the bore hole the line member 15 being sufficiently long enough to extend out of the bore hole to hold the sleeve in the bore hole, dropping the lower end area of the sleeve into the bore hole, placing a primer into the lower end area of the sleeve, .oo. pushing a loading hose into the sleeve and down to the bottom o. 20 of the bore, the loading hose pulling the sleeve down the hole and releasing the retention means, the upper end of the sleeve terminating below the mouth of the bore hole to define a stemming zone between the sleeve and the mouth of the bore hole, holding the sleeve by the line member to prevent it from falling down the hole, passing emulsified blasting agent through the loading hose to fill the sleeve from the lower end thereof, and progressively raising the hose until the sleeve is filled, removing the loading hose from the bore hole, and placing stemming material in the stemming zone.

12. An assembly substantially as hereinbefore described with 19 reference to the drawings. DATED this 15tlh day of March 1999 COST EFFECTIVE BLASTING PlY. LTD. 010 708 031) By their Patent Attorneys CULLEN CO. *000 to 0 to 0# :9000 too* a 0