Patent Description:
Minerals such as iron ore and coal can be recovered in a variety of methods including above ground open cut mining methods. Such methods can involve the use of blasting with bulk explosives to dislodge bulk quantities of ore for excavation and recovery through subsequent handling via excavators and the like. The blasting process results in the comminution of rock containing the ore into particles of varying sizes. It is desirable for the blasting process to produce material with an average particle size that is as small as possible to minimise the need for further comminution by crushing, grinding, vibrating and other processes.

Bench blasting is a process that involves drilling holes into rock at depths, in diameters, and at spacing and filing the holes with explosive material to form a column charge that fractures the rock in a controlled manner. The blasting holes can have diameters as large as <NUM> to <NUM> or even up to <NUM> millimetres and larger and have depths of as much as <NUM> metres or more. These blast holes are filled with bulk explosive materials that are, at least in part, ammonium nitrate based low velocity explosives. The explosive material will be contacted with a primer and covered or "stemmed" with material such as aggregate. The primer is activated electrically or non-electrically to cause the explosive to detonate.

Most of the rock that is fractured after a blasting operation is removed from the site by excavators for further processing or waste removal. However, significant quantities of loose rock fragments, or "preconditioned" material, can remain on the bench from the sub-drilled region after achieving the Reduced Level (RL). It can be desirable to employ substantially increased sub-drill lengths to deliberately and significantly increase the depth of the preconditioned layer. A preconditioned layer depth of up to <NUM> metres or more can improve the efficiency of the comminution process by maximising the volume of fine fragmentation that results from the subsequent blasting operation.

In the location where blast holes for a subsequent blasting operation are to be drilled these fragments or 'preconditioned' material remain. After blast holes have been drilled loose rock fragments or preconditioned material can collapse into the openings of completed blast holes to partially fill or even block the drill hole prior to depositing explosive material. Where up to the first four or more metres of the depth of the blast hole can be through the preconditioned layer the risk of material collapsing into blast holes can be acute. Wet environments may also lubricate the loose rock fragments, exacerbating the collapsing of loose rock fragments into the blast holes.

<CIT> teaches a blasthole hole protection of the known art.

<CIT> discloses a drilling system in which sheet metal is drawn from a continuous roll and is continuously preformed into a tube. A welding device welds the edges of the sheet to form a welded seam. A drill head is coupled to the end of the tube to bore a hole into rock. The system disclosed in this reference does not require a drill string to be formed by fixing successive drill tubes together but rather forms a single, continuous drill rod.

<CIT> discloses a method for continuously forming and installing a casing into a borehole while simultaneously drilling the bore hole. The method includes attaching a drill bit to the lower end of a rod assembly that produces a borehole. A casing pipe is produced from a plastic film which is unwound from a supply roll in the flat state and is formed into a tubular structure by means by guide rollers. A longitudinal seam of the film is sealed by welding to form the final pipe. As the bore hole is drilled the casing pipe is formed and is carried down into the bore hole by the drill bit at the end of the rod assembly.

Any discussion of background art throughout the specification should in no way be considered as an admission that any of the documents or other material referred to was published, known or forms part of the common general knowledge.

Accordingly, in one aspect, the invention provides an apparatus for preventing surrounding loose rock fragments from falling or collapsing into a blast hole, the apparatus including: a resiliently flexible sheet including a pair of spaced apart longitudinally extending side edges and a pair of spaced apart laterally extending end edges, the sheet having a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends, one end of the curved sheet being insertable into the open end of a blast hole, wherein in the curved form the side edges of the sheet are free and the sheet biases towards a flat form whereby an external surface of the curved sheet is biased against an internal surface of the blast hole and forms a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole.

Preferably, the sheet is adapted to be forced into a substantially cylindrical or a conical form wherein upon insertion through the open end of a blast hole the sheet assumes a substantially cylindrical form coaxially within the blast hole. Preferably, the sheet is adapted to be manipulated manually into the cylindrical or the conical form.

In accordance with the invention, the sheet is formed of resiliently flexible material biased towards a substantially flat form whereby in use within the blast hole the sheet biases against the internal surface of the blast hole. Advantageously, the resilient properties of the material from which the sheet is formed cause the external surface of the sheet to be biased against the internal surface of the blast hole thereby forming a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole.

In embodiments, the longitudinally extending side edges taper at an end thereof. When the sheet is bent over on itself, manually or otherwise, and the transversely opposite parallel edges are brought towards each other the tapering of the ends of the side edges to promote a more uniform cylindrical form of the sheet.

In embodiments, the width of the sheet between the longitudinally extending side edges is less than the circumference of the blast hole. Preferably, the sheet is adapted to assume a substantially cylindrical form within the blast hole wherein the side edges of the sheet are spaced apart. Preferably, the sheet is adapted to be forced, such as by being manually manipulated, into the cylindrical form. Alternatively, the sheet may be mechanically manipulated into the cylindrical form. In embodiments, the width of the sheet between the longitudinally extending side edges is equal to the circumference of the blast hole or is greater than the circumference of the blast hole. It is to be appreciated that a width less than the circumference of the blast hole is preferred as this allows for distortion and non-uniformity of the blast hole and also requires fewer openings in the sheet for use as hand holds thus minimising any weakening of the sheet. However, the embodiments of the sheet where the width of the sheet is equal to or greater than the circumference of the blast hole also fulfils the broad objectives of the invention which is to form a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole.

In embodiments, the longitudinally extending side edges taper at an end thereof. When the sheet is bent over on itself and the transversely opposite parallel edges are brought towards each other the tapering of the ends of the side edges promotes a more uniform cylindrical form for the sheet.

Preferably, the longitudinally extending side edges each include elongated flanges adapted for abutment with each other when the sheet is in the curved form.

In embodiments, the flexible sheet is comprised of a substantially flat sheet of flexible material. The flexible sheet has a normally flat form and is adapted to be rolled into the curved form. That is, in the resting state, the sheet will tend towards a substantially flat form.

In embodiments, the sheet includes at least one opening through the sheet adjacent to each longitudinally extending side edge operable as a hand hold for a user to manually roll the sheet into the curved form. In embodiments embodiment, the sheet includes at least one opening through the sheet adjacent to one of the end edges operable as a hand hold for a user to manually insert and remove the sheet relative to the open end of a blast hole.

In embodiments, the sheet includes a pair of openings through the sheet that are adapted to receive therethrough an elongated member for engaging a surface surrounding the blast hole to prevent further insertion of the panel through the opening of the blast hole. Preferably, the pair of openings are located adjacent to each longitudinally extending side edge and are aligned with each other along the length of the sheet for receiving the longitudinal member therethrough perpendicularly to the length of the sheet.

In another aspect, the invention provides a method for preventing surrounding loose rock fragments from falling or collapsing into a blast hole, the method including: providing a resiliently flexible sheet including a pair of spaced apart longitudinally extending side edges and a pair of spaced apart laterally extending end edges, forming the sheet into a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends, inserting one end of the curved sheet into the open end of a blast hole wherein in the curved form the side edges of the sheet are free and the sheet biases towards a flat form whereby an external surface of the curved sheet biases against an internal surface of the blast hole and substantially coaxially therewith forming a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole.

Preferably, the method includes locating the sheet within the blast hole within a layer of preconditioned loose rock fragments to form a barrier preventing the internal surface of the blast hole within the preconditioned layer from falling or collapsing into the blast hole. Preferably, the method can include inserting an elongated member through apertures in the sheet whereby the elongated member engages a surface surrounding the blast hole to prevent further insertion of the sheet through the open end of the blast hole.

In an embodiment, the method includes: forcing the flexible sheet into a conical form tapering in an axial direction from a larger diameter opening at one of the ends to a smaller diameter opening at the other end, inserting the smaller diameter end through the open end of a blast hole, and releasing the sheet to assume a substantially cylindrical form within the blast hole thereby forming a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole.

In another embodiment, the method includes: forcing the flexible sheet into a cylindrical form and inserting the sheet through the open end of a blast hole and releasing the sheet whereby the sheet biases against the internal surface of the blast hole forming a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole.

Preferably, the method includes forcing the sheet manually into the conical or the cylindrical form. Alternatively, the method may include mechanically forcing the sheet into the conical or the cylindrical form.

Embodiments of the apparatus and method are advantageous in that they provide convenient installation of a barrier in the open end of a blast hole that prevents surrounding loose rock fragments from falling or collapsing into the blast hole.

Embodiments of the apparatus and method are advantageous in that they operate to maintain an open collar for the blast hole to enable ease in depositing typical explosives and other consumables into the blast hole.

In another aspect, the invention provides a bench blasting method including: drilling blast holes through a layer of preconditioned loose rock fragments and into the stable rock below; forming a substantially flat resiliently flexible sheet into a curved form defining a longitudinal passage and openings at longitudinally opposite ends, inserting one end of the curved sheet into an open end of the blast hole wherein in the curved form the side edges of the sheet are free and the resilient sheet biases towards a flat form whereby an external surface of the curved sheet biases against an internal surface of the blast hole within the layer of preconditioned loose rock fragments and forms a barrier preventing the internal surface of the blast hole within the preconditioned layer from falling or collapsing into the blast hole.

Preferably, the method includes forcing the flexible sheet into a conical form tapering in an axial direction from a larger diameter opening at one of the ends to a smaller diameter opening at the other end, inserting the smaller diameter end through the open end of a blast hole, and releasing the sheet to assume a substantially cylindrical form within the blast hole. In another embodiment, the method includes forcing the flexible sheet into a cylindrical form and inserting the sheet through the open end of a blast hole and releasing the sheet whereby the sheet biases against the internal surface of the blast hole.

Preferably, the sheet has a longitudinal length dimension that is <NUM> metre, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres or more or any length therebetween as determined by geological requirements. Preferably, the method includes inserting the curved sheet into the open end of the blast hole whereby the curved sheet closely faces an internal surface of the blast hole down to a depth of about <NUM> metre, about <NUM> metres, about <NUM> metres, about <NUM> metres, about <NUM> metres, about <NUM> metres, about <NUM> metres or more or any depth therebetween within the layer of preconditioned loose rock fragments as determined by geological requirements.

The present invention will now be described in more detail with reference to preferred embodiments illustrated in the accompanying figures, wherein:.

The invention will now be described in further detail with reference to the embodiments illustrated in the Figures.

Referring to <FIG>, there is shown an embodiment of the invention comprising an apparatus <NUM> that, in use, is adapted for preventing surrounding loose rock fragments <NUM> from falling or collapsing into a blast hole <NUM>. In <FIG> a frontal section of an open end of a single blast hole <NUM> is illustrated although it is to be appreciated that a multitude of such blast holes <NUM> would be drilled for a single blasting operation. The blast hole <NUM> can be drilled with a diameter as large as <NUM> to <NUM> millimetres or as much as <NUM> millimetres or more and to depths of as much as <NUM> metres or more. After drilling, the blast hole <NUM> is filled with explosive material appropriate for the ground conditions, such as a mixture of ammonium nitrate and fuel oil (ANFO) or an emulsion or a mixture thereof and is primed for detonation.

Most of the rock that is fragmented after a blasting operation is removed from a mine site by excavators for further processing or waste removal. However, significant quantities of loose rock fragments or "preconditioned" rock fragments can remain on the mine bench from the sub-drilled region after achieving the Reduced Level (RL). It can be desirable to employ substantially increased sub-drill lengths to deliberately and significantly increase the depth of the preconditioned layer. A preconditioned layer depth of up to <NUM> metres or more can improve the efficiency of the comminution process by maximising the volume of fine fragmentation that results from the subsequent blasting operation. In the location where blast holes for a subsequent blasting operation are to be drilled these preconditioned rock fragments remain. As shown in <FIG>, the blast hole <NUM> comprises an open upper end <NUM> which is surrounded by a layer of preconditioning comprised of loose rock fragments <NUM>. The layer of preconditioned rock fragments <NUM> can have a depth of up to <NUM> or more metres. As such, up to the first <NUM> or more metres of the depth of the blast hole <NUM> below the upper open end <NUM> can be through the preconditioned layer of loose rock fragments <NUM>. A quantity of the loose rock fragments <NUM> can collapse into the blast hole <NUM> at or towards the open upper end <NUM> of the blast hole <NUM>.

<FIG> illustrates an embodiment of the apparatus <NUM> of the present invention. The apparatus <NUM> includes a flexible sheet <NUM>, preferably comprised of a resilient material, such as a resiliently flexible polymeric material which may be reinforced with nylon or some other flexible reinforcement. The material from which the flexible sheet <NUM> is formed is a high-density polyethylene (HDPE) composite, which may or may not be reinforced, with anti-static properties. The sheet <NUM> includes a pair of opposite surfaces <NUM>, <NUM> and is preferably formed in a rectangular shape such that it includes a first pair of spaced apart and longitudinally extending parallel side edges <NUM>, <NUM> and a second pair of spaced apart and laterally extending parallel end edges <NUM>, <NUM>. In the embodiment of <FIG> the first pair of parallel side edges <NUM>, <NUM> comprise elongated flanges <NUM>, <NUM> extending along substantially the entire lengths thereof. It is to be appreciated that the second pair of parallel and spaced apart end edges <NUM>, <NUM> need not necessarily be parallel. The sheet <NUM> includes a series of apertures <NUM>, <NUM>, <NUM>, <NUM> that are arranged in laterally spaced apart and longitudinally aligned pairs <NUM>, <NUM> and <NUM>, <NUM>. The sheet <NUM> includes a further aperture <NUM> located adjacent to one of the end edges <NUM> that functions as a handle.

<FIG> illustrate the sheet <NUM> in use. As shown in <FIG>, the sheet <NUM> is adapted to be forced from its resting flat form into a curved form, such as a cylindrical or conical form. The sheet <NUM> may be forced into the cylindrical or conical form by manually or mechanically bending the sheet <NUM>. When the sheet <NUM> is in the cylindrical form or, as illustrated in <FIG>, the conical form the sheet <NUM> defines a longitudinal passage tapering in an axial direction from a larger diameter end <NUM> defining a larger diameter opening to a smaller diameter end <NUM> defining a smaller diameter opening. The larger diameter end <NUM> is comprised of one of the end edges <NUM> closest to the series of apertures <NUM>, <NUM>, <NUM>, <NUM>. The smaller diameter end <NUM> is comprised of the other one of the end edges <NUM> furthest from the series of apertures <NUM>, <NUM>, <NUM>, <NUM>. The smaller diameter end <NUM> has an overall diameter that is smaller than the diameter of the open end <NUM> of the blast hole <NUM>. The smaller diameter end <NUM> of the sheet <NUM>, when it is in the conical form, is inserted first into the open end <NUM> of the blast hole <NUM>.

After the smaller diameter end <NUM> of the sheet <NUM> is inserted into the open end <NUM> of the blast hole <NUM>. The sheet <NUM> is then released so that the resilient properties of the material from which the sheet <NUM> is formed allow the sheet <NUM> to expand and, perhaps in conjunction with some manual manipulation, assume a substantially cylindrical form substantially coaxial with the blast hole <NUM>. As illustrated in <FIG> and <FIG>, one of the opposite surfaces <NUM> of the sheet forms a cylindrical external, outwardly facing surface that faces an inwardly facing substantially cylindrical surface <NUM> of the blast hole <NUM>.

Although the figures illustrate the sheet <NUM> being formed into a conical shape for insertion into the blast hole <NUM> it is to be appreciated that the sheet <NUM> may be formed into a substantially cylindrical shape defining a longitudinal passage extending between the longitudinally opposite ends <NUM>, <NUM> thereof. The diameters of the ends <NUM>, <NUM> may be substantially the same prior to insertion of one of the ends <NUM>, <NUM> into the open end <NUM> of the blast hole <NUM>. When the sheet <NUM> is released it may already be substantially cylindrical and coaxial with the substantially cylindrical surface <NUM> of the blast hole <NUM>. The resilient properties of the material from which the sheet <NUM> is formed cause the external surface <NUM> to be biased against the internal surface <NUM> of the blast hole <NUM>.

As illustrated in <FIG>, the sheet <NUM> locates within the open end <NUM> of the blast hole <NUM> and forms a barrier preventing surrounding loose rock fragments <NUM> from falling or collapsing into the blast hole <NUM> at or near the open end <NUM> of the blast hole <NUM>. As the layer of preconditioned rock fragments <NUM> can have a depth of up to four or more metres the sheet <NUM> helps to support the upper portion of the internal surface <NUM> of the blast hole <NUM> from collapsing. The longitudinal dimension of the sheet <NUM> between the longitudinally opposite end edges <NUM>, <NUM> may be <NUM> metre, <NUM> metres, <NUM>, metres, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres or more in length or any length in between. The length of the sheet <NUM> is selected based on geological requirements. When positioned within the blast hole <NUM> the sheet <NUM> provides support for the internal surface <NUM> through a substantial portion of the preconditioned layer of rock fragments <NUM>. The sheet <NUM> thereby forms a barrier preventing surrounding loose rock fragments <NUM>, such as within the preconditioned layer, from falling or collapsing into the blast hole <NUM>.

The width of the sheet <NUM> between the pair of parallel side edges <NUM>, <NUM> is slightly less than the circumference of the inwardly facing substantially cylindrical surface <NUM> of the blast hole <NUM>. When the sheet <NUM> assumes the substantially cylindrical form within the blast hole <NUM> the side edges <NUM>, <NUM> of the sheet are spaced apart and do not overlap. In the embodiment of <FIG>, the elongated flanges <NUM>, <NUM> are spaced apart a small distance and are adapted for abutment with each other to prevent the edges <NUM>, <NUM> from sliding over one another. The elongated flanges <NUM>, <NUM> prevent the circumference of the sheet <NUM>, in its cylindrical form within the blast hole <NUM>, from decreasing below a threshold. Put another way, the elongated flanges <NUM>, <NUM> along the edges of the panel <NUM> are adapted to come into abutment to support the cylindrical structure of the sheet <NUM> and, hence support the external cylindrical surface <NUM> of the sheet <NUM> against the inwardly facing substantially cylindrical surface <NUM> of the blast hole <NUM> and loose rock fragments <NUM> at or near the open end <NUM> of the blast hole <NUM>.

Each one of the apertures <NUM>, <NUM>, <NUM>, <NUM> extends through the sheet <NUM> from the external surface <NUM> to the internal surface <NUM>. An elongated rod member <NUM> can be inserted horizontally through a pair of the horizontally aligned apertures <NUM>, <NUM> or <NUM>, <NUM>. Each pair of horizontally aligned apertures <NUM>, <NUM>, <NUM>, <NUM> are located at different positions along the length of the sheet <NUM> so that a user can select a height of the sheet <NUM> within the blast hole <NUM>. Opposite ends of the rod member <NUM> engage a surface <NUM> surrounding the open end <NUM> of the blast hole <NUM>. The rod member <NUM> engages the pair of horizontally aligned apertures <NUM>, <NUM> or <NUM>, <NUM> and the surrounding surface <NUM> to prevent the sheet <NUM> from passing further into the open end <NUM> of the blast hole <NUM>. As shown in <FIG>, a small portion of the sheet protrudes from the open end <NUM> of the blast hole <NUM>. The elongated rod member <NUM> functions to anchor the sheet <NUM> at or towards the open end <NUM> of the blast hole <NUM>.

<FIG> illustrates another embodiment of the apparatus <NUM> which is like the embodiments of <FIG> and functions in a similar fashion. Features of the apparatus of <FIG> that are structurally or functionally like, or are the same as, features of the embodiment of <FIG> are represented by like reference numerals. The apparatus <NUM> includes a flexible sheet <NUM>, preferably comprised of a sheet of resilient material such as a resiliently flexible polymeric material That may also be reinforced. The sheet <NUM> includes a pair of opposite surfaces <NUM>, <NUM> and is preferably formed in a rectangular shape such that it includes a first pair of spaced apart and transversely opposite and longitudinally extending parallel side edges <NUM>, <NUM> and a second pair of spaced apart and longitudinally opposite and transversely extending parallel end edges <NUM>, <NUM>. Unlike the embodiment of <FIG>, the embodiment of <FIG> has no elongated flanges along the first pair of parallel side edges <NUM>, <NUM>. It is to be appreciated that the pairs of edges <NUM>, <NUM>, <NUM>, <NUM> need not necessarily be parallel. The sheet <NUM> includes a series of apertures <NUM>, <NUM>, <NUM>, <NUM> that are arranged in laterally spaced apart and longitudinally aligned pairs <NUM>, <NUM> and <NUM>, <NUM>. The sheet <NUM> includes several apertures <NUM> that act as handles or handholds allowing a user to manipulate the sheet <NUM> from a flat condition, as illustrated in <FIG>, into a conical or cylindrical condition as illustrated in <FIG> and <FIG>. The apertures <NUM> acts as a handle allow a user to manoeuvre the sheet <NUM> into and out of or relative to the open end <NUM> of the blast hole <NUM>.

Although in the embodiment of the apparatus <NUM> of <FIG> the width of the sheet <NUM> between the longitudinally extending side edges <NUM>, <NUM> less than the circumference of the blast hole30 it is to be appreciated that in other embodiments the width may be equal to or greater than the circumference of the blast hole <NUM>.

<FIG> illustrate another embodiment of the apparatus <NUM> which is like the embodiments of <FIG> and functions in a similar fashion. Features of the apparatus of <FIG> that are similar or the same as features of the embodiment of <FIG> are represented by like reference numerals. The apparatus <NUM> includes a flexible sheet <NUM>, comprised of a sheet of resilient material such as a resiliently flexible polymeric material that is reinforced. The sheet <NUM> includes a pair of opposite surfaces <NUM>, <NUM> and is formed in a rectangular shape such that it includes a first pair of spaced apart and transversely opposite parallel side edges <NUM>, <NUM> and a second pair of spaced apart and longitudinally opposite parallel end edges <NUM>, <NUM>. Unlike the embodiment of <FIG>, in the embodiment of <FIG> the transversely opposite parallel side edges <NUM>, <NUM> are tapered at ends 21a, 23a thereof. The tapering of the ends 21a, 23a of the transversely opposite parallel side edges <NUM>, <NUM> reduces outward flaring of the corners of the sheet <NUM> when the sheet <NUM> is forced, whether manually or otherwise, into a curved form, such as a cylindrical form as illustrated in <FIG>. Accordingly, when the sheet <NUM> is bent over on itself and the transversely opposite parallel edges <NUM>, <NUM> are brought towards each other the tapering of the ends 21a, 23a of the transversely opposite parallel edges <NUM>, <NUM> promote a more uniform cylindrical form for the sheet <NUM>. The distal end of the sheet <NUM> comprising the tapered ends 21a, 23a is adapted to be inserted first into the blast hole <NUM>. Minimising outward flaring of the corners of the sheet <NUM> at the distal end thereof where the transversely opposite parallel edges <NUM>, <NUM> and the longitudinally opposite parallel edges <NUM>, <NUM> meet aids in ease of insertion of the sheet <NUM> into the blast hole <NUM>.

In another aspect, the invention provides a method for preventing surrounding loose rock fragments <NUM> from falling or collapsing into the blast hole <NUM>. The method includes a step of bending, such as by manually or otherwise forcing a resiliently flexible sheet <NUM>, such as the sheet <NUM> of <FIG> or of <FIG>, into a substantially cylindrical form or a conical form tapering in an axial direction from a larger diameter end to a smaller diameter end, such as is illustrated in <FIG>. The method includes inserting one end of the sheet <NUM>, which may be the smaller diameter end, through the open end of a blast hole <NUM>, such as is shown in <FIG>. The sheet <NUM> is then released, or may be manipulated, to assume a substantially cylindrical form coaxial with the blast hole <NUM> as illustrated in <FIG>. The sheet <NUM> thereby forms a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole <NUM> at or near the open end of the blast hole <NUM>.

In another aspect, the invention provides a bench blasting method. The method includes drilling blast holes through a layer of preconditioned loose rock fragments <NUM> and into the stable rock below. The preconditioned layer <NUM> may be up to or more than <NUM> metres in depth. The method includes forming a substantially flat flexible sheet <NUM>, such as the sheet <NUM> of <FIG> or of <FIG>, into a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends. The method further includes inserting one end of the curved sheet <NUM> into an open end of the blast hole <NUM> whereby the curved sheet <NUM> closely faces an internal surface <NUM> of the blast hole <NUM> within the layer of preconditioned loose rock fragments <NUM> and forms a barrier preventing the internal surface <NUM> of the blast hole <NUM> within the preconditioned layer of loose rock fragments <NUM> from falling or collapsing into the blast hole <NUM>.

The methods can include forcing the flexible sheet <NUM> into a conical form tapering in an axial direction from a larger diameter opening at one of the ends to a smaller diameter opening at the other end, inserting the smaller diameter end through the open end of a blast hole <NUM>, and releasing the sheet <NUM> to assume a substantially cylindrical form within the blast hole <NUM>. Alternatively, the method can involve forcing the flexible sheet <NUM> into a substantially cylindrical form and inserting one end through the open end of the blast hole <NUM> down to a desired depth. An elongated rod <NUM> can then be inserted through apertures <NUM>, <NUM>, <NUM>, <NUM> within the sheet <NUM>. The elongated rod <NUM> engages the surface surrounding the blast hole <NUM>, as illustrated in <FIG>, to maintain the sheet <NUM> at the opening into the blast hole.

Preferably, the sheet <NUM> has a longitudinal length dimension that is <NUM> metre, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres, <NUM> metres or more or any length therebetween. The length of the sheet <NUM> is selected based on geological requirements. Preferably, the methods include inserting the curved sheet <NUM> into the open end of the blast hole <NUM> whereby the curved sheet <NUM> closely faces an internal surface <NUM> of the blast hole <NUM> down to a depth of about <NUM> metre, about <NUM> metres, about <NUM> metres, about <NUM> metres, about <NUM> metres, about <NUM> metres, about <NUM> metres or more or any depth therebetween within the layer of preconditioned loose rock fragments <NUM>.

The sheet <NUM> may remain in position within the blast hole <NUM> during a subsequent step of depositing explosives and other consumables into the blast hole <NUM>. In embodiments of the methods, the sheet <NUM> may remain in the cylindrical form or may be manipulated into a conical form, such as by bending the sheet <NUM> into the conical form, as illustrated in <FIG>, such that the sheet <NUM> may operate as a funnel through which explosives and other consumables may be deposited into the blast hole <NUM>.

In embodiments of the methods, the user selects a desired height for the sheet <NUM> that is located within the blast hole <NUM> by locating the elongated rod member <NUM> through a desired pair of apertures <NUM>, <NUM>, <NUM>, <NUM>. After the sheet <NUM> is inserted into the blast hole <NUM> the elongated rod member <NUM> rests on the surface <NUM> surrounding the blast hole <NUM>. The apertures <NUM>, <NUM>, <NUM>, <NUM> are positioned such that upon insertion of the elongated rod <NUM> therethrough, the elongated rod <NUM> is offset from the central axis of the longitudinal passage extending through the curved sheet <NUM> to facilitate insertion into the blast hole <NUM> of lining material, loading with explosive, priming and providing any other consumables into the blast hole <NUM>. The sheet <NUM> can then be partially withdrawn and formed into a funnel shape prior to depositing of stemming material into the blast hole <NUM>. The sheet <NUM> may be removed from the blast hole <NUM> to assume a flat form for storage.

<FIG> illustrates a deployment device <NUM> for deploying the sheet <NUM> into the blast hole <NUM>. The device <NUM> includes a forming apparatus <NUM> adapted to form the flat flexible sheet <NUM> into a curved form for insertion into the open end of the blast hole <NUM> whereby the curved sheet closely faces the internal surface of the blast hole <NUM> and forms a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole <NUM>.

The deployment device <NUM> includes a plurality of the sheets <NUM> of <FIG> arranged in a stack <NUM>. The device <NUM> includes a sheet picker <NUM> and feeder <NUM> that is operable to pick an individual sheet <NUM> from the stack <NUM> and feed the sheet <NUM> to a vertical forming apparatus <NUM>. In the embodiment illustrated in <FIG>, the picker <NUM> and the feeder <NUM> are comprised of an arrangement of driven belts operable to pick one of the sheets <NUM> at a time from the stack <NUM>. However, any mechanical arrangement that is adapted to pick one sheet <NUM> from the stack <NUM> and feed the sheet <NUM> to the vertical forming apparatus <NUM> may constitute another embodiment of the invention. The forming apparatus <NUM> is operable to form the sheet <NUM> into a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends. The forming apparatus <NUM> includes a vertically oriented shaped passage <NUM> with a wide opening at the top <NUM> and side walls tapering towards a narrower bottom outlet <NUM>. However, any mechanical arrangement that is adapted to form the sheet <NUM> into a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends may constitute another embodiment of the invention.

The outlet <NUM> of the forming apparatus <NUM> is adapted to be manually or automatically located over or to some extent into the open end of a blast hole <NUM>. The sheet picker <NUM> and feeder <NUM> are operable to drive the individually picked sheet <NUM> through the passage <NUM> and through the outlet to thereby feed the curved sheet <NUM> into the open end of a blast hole <NUM>. The forming apparatus <NUM> is operable to continue feeding the sheet <NUM> to a desired depth within the blast hole <NUM> and releases the sheet <NUM> when it has reached a predetermined depth. The released sheet <NUM>, which has a substantially cylindrical form coaxial with the blast hole <NUM> as in <FIG>, thereby forms a barrier preventing surrounding loose rock fragments from falling or collapsing into the blast hole <NUM>.

The deployment device <NUM> may be mounted to a vehicle (not shown) or a trailer (not shown) coupled to a vehicle or any other mobile apparatus adapted to be manoeuvred around a site comprising a plurality of blasting holes <NUM> that have previously been drilled. The vehicle or other mobile apparatus may be a truck that is operable manually by a driver or in an embodiment is configured to operate autonomously or semi-autonomously. The vehicle or other mobile apparatus may comprise a control module that includes a GPS location device and is adapted for controlling a drive means and steering means of the vehicle. The control module is adapted to receive or be programmed with the coordinates of the location of one or more of a plurality of blast holes and to autonomously manoeuvre the deployment device <NUM> to a location adjacent a first one of the blast holes.

When located adjacent the first blast hole <NUM>, the control module may autonomously operate the deployment device <NUM> to deploy one of the sheets <NUM> into the blast hole <NUM>. The control module may cause the outlet of the deployment device <NUM> to locate over the blast hole using the coordinates of the blast hole or using imagery from a camera mounted to the device <NUM> or the vehicle <NUM> or a combination of both. The control module may autonomously or semi-autonomously activate the sheet picker <NUM> and feeder <NUM> to drive the sheet <NUM> through the forming apparatus <NUM> and through the outlet <NUM> to thereby feed the curved sheet <NUM> into the open end of a blast hole <NUM>.

Claim 1:
An apparatus (<NUM>) for preventing surrounding loose rock fragments from falling or collapsing into a blast hole (<NUM>), wherein the apparatus comprises: a resiliently flexible sheet (<NUM>) including a pair of spaced apart longitudinally extending side edges (<NUM>, <NUM>) and a pair of spaced apart laterally extending end edges (<NUM>, <NUM>), the sheet having a curved form defining a longitudinal passage extending between openings at longitudinally opposite ends (<NUM>, <NUM>), one end of the curved sheet being insertable into the open end of a blast hole (<NUM>), wherein in the curved form the side edges of the sheet are free and the sheet biases towards a flat form whereby an external surface (<NUM>) of the curved sheet is biased against an internal surface (<NUM>) of the blast hole and forms a barrier preventing surrounding loose rock fragments from falling or collapsing into the open end of the blast hole.