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Publication numberUS3696703 A
Publication typeGrant
Publication dateOct 10, 1972
Filing dateAug 4, 1970
Priority dateAug 22, 1969
Publication numberUS 3696703 A, US 3696703A, US-A-3696703, US3696703 A, US3696703A
InventorsFox Richard
Original AssigneeIci Australia Ltd, New Zealand Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Blasting agent package
US 3696703 A
Abstract
A water-proof package for water-sensitive bulk-loaded blasting agents such as ammonium nitrate slurries and ammonium nitrate fuel oil mixtures comprising an inner and outer plastic tube and mounted between them a liner folded up onto the inner tube in concertina fashion, said tubes optionally being fitted with a constriction to retain the liner within the tubes and with a cap to protect the bottom end of the assembly; the package is attachable to a loading hose for blasting agent and the liner is pushed out through the bottom end of the outer tube by the loading hose or the blasting agent, when charging commences.
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Description  (OCR text may contain errors)

United States Patent Fox [451 Oct. 10,1972

[54] BLASTING AGENT PACKAGE [72] Inventor: Richard Fox, Hawthorn, Victoria,

Australia [73] Assignee: Imperial Chemical Industries of Australia and New Zealand Limited, Melbourne, Victoria, Australia [22] Filed: Aug. 4, 1970 {21] App]. No.: 60,873

[30] Foreign Application Priority Data vr. I... I I. I. I. I. I I. I.

3,188,906 6/1965 Beck ..86/20 C 3,199,399 8/1965 Gardner ..86/20 C FOREIGN PATENTS OR APPLICATIONS 171,305 l/ 1964 U.S.S.R. 102/24 703,542 2/1965 Canada ..102/21.8

Primary Examiner-Verlin R. Pendegrass Attorney-Cushman, Darby & Cushman [57] ABSTRACT A water-proof package for water-sensitive bulk-loaded blasting agents such as ammonium nitrate slurries and ammonium nitrate fuel oil mixtures comprising an inner and outer plastic tube and mounted between them a liner folded up onto the inner tube in concertina fashion, said tubes optionally being fitted with a constriction to retain the liner within the tubes and with a cap to protect the bottom end of the assembly; the package is attachable to a loading hose for blasting agent and the liner is pushed out through the bottom end of the outer tube by the loading hose or the blasting agent, when charging commences.

18 Claims, 18 Drawing Figures BLASTING AGENT PACKAGE This invention relates to an improved method of blasting, and in particular to a blasting method wherein the explosive employed is of the type which is susceptible to desensitization by water which may be present in the borehole.

Boreholes, i.e. blast holes, for example, in quarrying or open pit mining, are normally prepared by drilling or jet piercing to a pre-determined depth in the stratum to be blasted, Frequently such drilling operations intersect stratum or fissures containing water. Alternatively, water may be present in boreholes as a result of wetdrilling procedures or again water may enter the borehole from rainfall or melting snow. While conventional explosives such as dynamite and gelatinized dynamite may be water-resistant at least for short periods and may be employed in wet boreholes, the more popular and economical blasting agents based on water soluble inorganic salts are generally not suitable as the action of the water may desensitize the blasting agent before initiation and result in detonation failure. Both free-flowing ammonium nitrate/fuel oil type (AN/F) explosives and the more recent pumpable slurry type blasting agents normally must be provided with means for protection against attack by water in wet boreholes.

In the past, protection against water attack has been provided by cartridging the water-sensitive blasting agent in metal or other water-proof containers or in plastic bags which may then be lowered into the borehole for detonation. More recently, in blasting operations where the blasting agent is compounded at the blasting site, the practice has developed to place a tubular plastic liner or sleeve of flexible material such as polythene in the borehole; thereafter the blasting agent is poured or pumped into the lined hole. Such plastic borehole liners additionally prevent the loss of blasting agent, particularly slurry type explosives, through migration into fissures which may intersect the borehole. The use of such plastic liners is disclosed, for example, in Canadian U.S. Pat. Nos. 536,595, 578,71 1 and 667,05 I.

There are, however, certain difficulties and problems associated with the use of plastic borehole liners. Generally, the liner employed comprises a thin-wall material so that it may conform to any irregularities within the borehole and so provide a full compaction of the contained explosive to fill the interstices in the wall of the hole. Such liners, whether of a single-wall or double-wall type are subject to tearing or perforation when they are placed in the borehole, as a result of contact with sharp edges of rock in the hole wall.

Furthermore the insertion of the conventional liner involves several operations. First the conventional borehole liner is cut to a length equal to the hole depth, the bottom end of the liner is sealed by tying or similar means and weighted with a rock or small explosive charge and lowered to the bottom of the hole. A primer charge is then lowered inside the liner to the hole bottom, normally by means of an attached detonating fuse down line. Alternatively, the primer may be lowered by means of an electrical conductor and attached blasting cap, that is, an electric blasting cap with insulated leg wires. Finally a loading hose or pipe for introduction of the blasting agent is lowered inside the liner and the required amount of blasting agent is poured, blown by pressurized air or pumped into the liner to fill the liner and borehole to a predetermined level. While generally suitable for use in dry holes, this procedure is less suitable in water-containing holes since a section of liner collapses in wet holes owing to the pressure of thesurrounding water, thus making the lowering of the primer charge difficult. It is normally necessary to retract the liner to a point above the water level and the primer lowered to this point with subsequent raising and lowering of the liner until the primer charge is positioned in the bottom of the liner. Such operations almost invariably cause damage to the liner by attrition against the wall of the borehole as mentioned above. With the liner and primer in position, the loading hose is inserted down the liner to the water level where further insertion is prevented by the collapsed liner. If the blasting agent is of sufficient density, for example a slurry explosive having a density above about 1.3 gms/cm", loading can be started and the slurry may sink inside the liner displacing the water. On the other hand, if a less dense bulk explosive is employed, the loading hose must be inserted to the bottom of the liner using the technique described above.

An alternative method used in charging conventional liners, consists of the steps of inserting a primer charge attached to a primer detonating means, for example, a detonating fuse down line into the liner before the liner is placed in the borehole. The liner assembly is then threaded over the loading hose, and, by means of the loading hose, the liner is pushed to the bottom of the hole. This method is objectionable because of the labor involved in threading the liner over the detonating fuse and primer and the loading hose and because of the hazard of damage to the liner.

We have now found that the several'operations of inserting a liner into the borehole, inserting a primer and charging the borehole can conveniently be combined in a single, simple operation; furthermore we have found a method of protecting the liner against damage by tearing or piercing while it is being inserted and/or charged; in addition we have devised simple apparatus by which the liner is preassembled in a convenient manner and may be attached to the loading hose and inserted into the borehole together with it in one convenient operation. Finally we provide an improved method of blasting with bulk loaded, water sensitive blasting agents, employing an improved borehole linerassembly.

Accordingly we provide a protected preassembled package for blasting agents susceptible to desensitisation by water which comprises in combination:

1. an inner rigid and self-supporting tube, the upper end of which is suited to be connected, or attached, preferably sealingly,to the discharge end of a loading hose for a blasting agent and the lower end of which is open,

2. a flexible tubular liner made of water-resistant film, having a diameter greater than that of the inner tube and, preferably, greater than the diameter of the borehole, and a length at least equal to the desired depth of its insertion into the borehole, said liner being sleeved over the length of said inner tube and compressed in regular or irregular folds, concertina-fashion, towards its upper end so as to fit the length of the liner in a loose fit onto said inner tube, the upper end of said liner being attached to said inner tube and the lower end of said liner being closed eg by sealing, knotting or tying it with string so as to prevent substantial discharge of the explosive mixture therefrom when the latter is pumped into it, and

3. an outer rigid, self-supporting tube of a diameter sufficient to envelop in a loose fit said inner tube together with the liner sleeved thereon and of a length approximately equal to that of the inner tube, thereby protecting said folded-up liner along its length, said outer tube being roughly concentrical with said inner tube, rigidly attached to it near or at its upper end and open at its lower end; and in addition preferably,

4. liner-delivery-restraining means at and between the lower open ends of said outer and inner tubes, causing the maximum frictional resistance against forces pushing or pulling said folded-up liner off the outer mantle of the inner tube outwardly through the bottom opening of the outer tube to occur between said lower ends of both tubes, said maximum frictional resistance, however, being below the tear strength of the material of the liner and below the force of the downward thrust exercised upon the interior of said liner by the blasting agent being pumped into it; and, finally, optionally,

5. across the opening at the bottom end of the tubes a cap attached removably to, and protecting, the assembly against physical damage and ingress of foreign material into the tubes.

The tubes, both inner and outer, may have cross sections of a variety of shapes, as long as they are sufficiently similar for the outer tube to fit over the inner tube and leave a roughly even annulus between them capable of containing the folded-up liner. Thus, the tubes could be of oval, square, hexagonal or octagonal or even somewhat irregular cross-section, but in practice the simplest and most convenient cross-section is, of course, circular. Their material of construction must be rigid enough to be self-supporting and withstand scraping, knocking and general handling when being mounted on the hose or lowered into the borehole. Rigid water resistant paper or metals, such as aluminum, galvanised iron or thin timber would be acceptable; rigid water-resistant plastics, such as low or high density polythene, polypropylene, polyvinylchloride, polyethylene-terephthalate, rigid rubber, e.g. acrylonitrile-butadiene-styrene rubber are preferred; polythene is most preferred; polythene tubing I to I2 or even cm smaller in outer diameter than the borehole and having a wall thickness between 0.5 and 15 mm, preferably 3 to 8 mm, to most suited.

The choice of the diameters of the liner and the inner and outer tubes relative to each other depends also on the desired looseness of the fit of the folded-up liner between the two tubes. In principle, it is necessary that the folded-up liner does not slide off the inner tube under gravity, i.e. not before fairly strong downward thrust is exerted upon it when the blasting agent is pumped in. Thus when the optional, (but preferred) delivery-restraining means is omitted, the liner should fit fairly tightly on the inner tube or be held in fairly tightly by the outer tube; if, on the other hand, the

preferred delivery-restraining means is used and/or the liner is folded backward at an acute angle as shown in FIG. 7 item 33 and discussed below, the liner is held in by this means and the diameters may be chosen to give a fairly loose fit of the liner.

The length of both tubes depends, primarily, on the desired length of the liner i.e. the depth of the borehole, the method of folding up the liner and, to a lesser extent, on the method of attaching the outer tube to the inner tube and the liner-delivery-restraining means. I to 6 feet long tubing, usually, suffices to accommodate the lengths of liners required in practice, from ID to feet.

The upper end of the assembly of both tubes and liner must be capable of being connected or sealingly attached to the discharge end of loading hose for the blasting agent. Most conveniently this connection is made directly to the inner tube, e.g. by an interference fit between the hose and the tube, or a thread, or a bayonet fit as described below in FIGS. 8 and 9. Indirectly the inner tube may be made attachable to the loading hose by joining it sealingly to a fitting such as a threaded bush into which both inner and outer tubing are recessed or even by attaching the outer tube to the hose and then attaching the inner tube sealingly around the internal circumference of the outer tube. The diameter of the tubes need not be exactly the same along the whole length; thus the inner tube may be slightly tapered, say 2-10 mm less in diameter at the lower end, so as to facilitate sliding off of liner.

The flexible liner is made of a water-resistant film of high tear-strength; water'proofed textile or even paper might be used, but plastic film such as polythene (e.g. Visqueen" Reg. Trademark of Imperial Chemical lndustries), polypropylene, polyvinylchloride, polyethyleneterephthalate (known as Melinex, Registered Trademark of Imperial Chemical Industries), nitrocellulose or rubber of wall thickness in the range from 0.001 to 0.10 in. are much preferable. Particularly preferred are plastics combining high flexibility with a low coefficient of friction such as polythene or polypropylene, which are easy to fold and slide smoothly over and off the inner tube. Liners of crosssections similar to those described for the rigid tubes are suitable.

If desired the outer side of the inner tube and/or the plastic film may be treated with fine dust, e.g. talcum powder, to increase the ease of slipping the film off the tubing. The diameter of the liner is wider than that of the inner tubing and, preferably also wider than that of the borehole, so that, after deposition in the hole and after loading with explosive, it fills out the whole of the borehole; since the outer tubing is clearly smaller in diameter than the borehole and yet the liner is preferably of wider diameter than the borehole, the latter may need to be folded neatly between inner and outer tube; to facilitate this, it is preferred to fold the liner into folds pressed upwardly against the walls of the inner tube to accomodate the excess width, each fold forming an acute angle between the center of the fold and tube wall, pointing downwardly in the direction of discharge of the liner from outer tube, as shown schematically at point 33 in Fig. 7. In addition, depending on the amount of liner to be folded in, the annulus between inner and outer tube must be chosen accordingly to accomodate the relatively longer folds; the annulus usually is from 5 to 30 mm wide.

In one particular embodiment of this invention the liner is made of a thin walled corrugated tubular film, such as the known flexible hoses used for gas masks; these concertinas consist of alternating widening and narrowing sections, roughly describing, in lengthwise cross-section, a sinoidal curve as shown in FIG.14; such hoses are moulded or they may be blown by rapidly alternating the pressure in the air bubble of a polythene film while the latter is being blown from an extruder. In another special embodiment the liner is made up from a multiplicity of annuli of thin flat plastic film, having an outer diameter d and an inner diameter d shown in plan in FIG. the outer and inner circumferences of each annulus are alternatingly sealed with the outer and inner circumference of the adjacent upper or, respectively, lower annulus to constitute, in assembly, a concertina as shown in schematic, isometric sketch in FIG.16.

The bottom of the liner is closed to prevent discharge of the explosive mixture from it when it is filled; to this end it may be sealed or simply knotted or tied with a string. In a special embodiment of the invention the seal at the bottom of the liner is selective to substantially prevent the discharge of the fairly viscous blasting agent, particularly of explosive slurry from it, while at the same time, above a certain pressure, permitting water to enter the liner and subsequently be discharged from it. This selective entry and discharge of water may be achieved by providing a multiplicity of small orifices at the bottom of the liner, in the region of the open lower end of the inner tube, which orifices have a very high flow resistance to viscous fluids, but permit a moderate flow of water. The purpose of the selectively permeable seal is to permit the liner to be pushed by the loading hose into a pool of water at the bottom of the borehole, without the back pressure of the water causing the liner to burst or become entangled; by the ingress of water, the pressure is reduced; when the liner subsequently is filled with the fluid blasting agent, most of the water is pushed out again, while the blasting agent is retained even under the pressure of the discharge pump.

In another, preferred embodiment of the invention the loading hose is pushed downward inside the inner tube approximately or nearly as far as the open end of the inner tube and is fitted with a (one way) non-return discharge valve, shown as item 14 in FIG. 3, which prevents flow into the hose, remains closed up to a predetermined line pressure in the hose greater than the force of the static head of the column of blasting agent when the hose is fully loaded but smaller than the total discharge pressure of the loading pump. Consequently, in operation, the non-return valve prevents the ingress of water into the hose; the valve thereby supports the end of the flexible liner which is exposed to the outside water pressure and, but for this support, could be pushed inside the inner tube, thus causing entanglement or damage to the liner. Instead of pushing the hose down and fitting it with a valve it is, of course, also possible to fit the inner tube with a second, innermost tube having a non-return valve at its end as described, to make both innermost tube and valve part of the assembly and fit the innermost tube sealingly to an ordinary loading hose. It is obvious that in this manner the innermost tube merely extends the function of the hose as described.

By liner-delivery-restraining means we mean any means which will cause the resistance to pulling or pushing the liner off the inner tubing downward from the annulus between the tubings to be greatest at the lower end of the tube. The purpose of this means is to ensure that the liner is not paid out before it is filled at its end with explosives; the restraining means thus ensures that that part of the liner which has been paid out from the inner tubing is filled with blasting agent at all times. This purpose is further aided by folding the linerfolds backward towards the tube at an acute angle as shown in FIG. 7 at point 33.

One simple restraining means is a constriction between the inner and outer tube; this may be caused either by allowing the outer tube to project marginally beyond the inner tube and then constricting it in an open conical bottom section, forming a constriction, as shown in item 7 in FIG. 1, 6 and 7. Alternatively the inner tubing may flare outwardly towards the outer tube at its bottom end to form a constriction (item 7); by making the tubes either of exactly equal length or making the inner tube slightly shorter or longer, the constriction 7 may be positioned at the end (FIG. 2), just above the end (FIG. 3) or just below the end (FlG.l0) of the outer tubing. The flared section of the inner (see FIG.10) or the outer (see FIG. 7) tube may be wider than the outer tube itself to guide the liner in operation towards the wall of the borehole, thus causing it to fill the hole in its whole width and by virtue of the larger surface area of the expanded liner (see FIG. 7), exerting an upward thrust against the inner tube and thereby the loading hose, as more blasting agent is pumped into the hole. This, in operation, facilitates the withdrawal of the loading hose and the timing of this operation. Optionally the outwardly flared section may be provided with an annular slip lip, made, e.g. from a split ring of soft foam rubber, as shown in FIGS. 6 and 7, item 18, which facilitates slipping without tear and increases the surface area.

The opening at the bottom of the outer or inner tube, may be closed by a removable cap, made preferably from a rigid plastic the same or similar to that of the outer tubing, thus protecting the liner and the tubes against damage from stone, sharp edges or ingress of water, particularly during the insertion of the assembly into the borehole. The cap may be clipped over the end of the outer or inner tube. The cap is dislodged from the tubing by pressure from the inside, such as the pressure of the blasting mixture or slurry being pumped into the liner and causing the liner to be paid out. A friction fit over the outer or inner tube, optionally fitted with a rim or even a very weak adhesive may be used to secure the cap temporarily to the tube.

Priming of the charge is carried out by one of several known methods. The primer charge may be placed inside, towards the bottom of the liner and the detonating fuse down line is then led outside the assembly through an orifice in the liner; the orifice may be sealed and reinforced against tearing by means of a plasticeyelet, attached by adhesive, as described below in connection with FIG. 2. Alternatively, in the assembly shown in FIG. 1, the fuse down-line is led out through the annulus between inner tube and loading hose, which is wide enough to allow the fuse line to pass through it without interference as the liner is paid out into the hole. Yet another method is to insert a small bag of blasting agent with a primer into the upper portion of the explosive column, when this has been charged into the hole. Other techniques are known in the art.

In operation the assembly, comprising inner and outer tubing with the liner sleeved over and compressed in folds, concertina-fashion, onto the inner tube is connected to the explosives loading hose. It may then be put into the borehole by one of two methods; either, as shown in schematic cross-section in FIG. 1, it is fastened firmly in a vertical position above the borehole, the hose is pushed through the inner tube into the borehole and in the process pushes the liner out and into the hole. The constriction 7 and, optionally, folding the folds upwardly in an acute angle pointing downward, as shown in FIG. 7, item 33, ensure that the liner is paid out commencing from the folds nearest to the constriction, thus preventing uncontrolled slip of whole folded sections into the hole. In this method, conveniently, the fuse line is passed through an orifice between loading hose and inner tube and paid out as the liner slides into the hole.

In an alternative preferred method the assembly, comprising the inner tube with the liner folded into it as described, the outer tube and optionally and preferably a protective cap (such as item 15 in FIGS. 4 and 5), is attached sealingly to a loading hose, passed into the borehole to the desired depth, usually the bottom, and then pumping of the fluid blasting agent is commenced.

Under the pump pressure the blasting charge pushes the closed end of the liner outwardly through the open end of the outer tube, while, at the same time, filling up the liner; as the charged liner is paid out from the tube assembly it expands and fills the whole width of the hole.

Ideally the hose is then withdrawn at the rate of delivery of blasting agent into the liner, so that, theoretically, the end of the inner tube attached to the hose is at or near, preferably just below the head of the column of blasting mixture or slurry filling up the liner. As further blasting agent is charged into the liner, more liner is paid out and filled simultaneously or just before the tube is withdrawn from this section.

By providing an outwardly flared truncated conical section of the inner or outer tube such as item 25 in FIG. or item 17 in FIGS. 6 and 7 respectively, the tube may be made to ride on the discharged blasting agent thus exerting upward thrust and using, indirectly, the pump pressure to withdraw or aid withdrawal or the timing of the withdrawal of the hose. When the liner and hole are filled, the liner may be closed and the charge detonated in the usual manner.

Accordingly we also provide a process which comprises the steps:

I. sleeving a flexible tubular water resistant plastic film liner, closed against discharge of a fluid blasting agent at its lower end, in a loose fit over a first self-supporting tube, preferably a plastic tube, referred to hereinafter as the inner tube and pushing the liner towards the upper end of said inner tube to form a multiplicity of folds, thus accommodating on said inner tube said plastic film liner,

which when fully extended is at least 3, preferably more than 20 times as long as said inner tube,

2. sliding in a loose fit a second wider, rigid self-supporting tube, preferably a plastic tube of a length roughly equal to said inner tube over said inner tube so as to be approximately concentrical and envelop, when fully assembled, the inner tube and the sleeved-on tubular liner,

3. attaching the liner to the upper end of the liner tube 4. fastening the outer and inner tubes together at their respective upper ends 5. optionally and preferably, fitting the assembly, preferably the inner tube, at its upper end with means for removably connecting it to a loading hose for blasting agents, and, optionally and preferably,

6. closing the open, lower end of the outer or, the

inner tube with a removable protective cap.

In addition we provide a process of blasting by means of a water sensitive pumpable bulk loaded blasting agent which comprises preparing an assembly as herein before described, inserting it into a borehole and causing the charge to explode.

Throughout this specification the invention is described by reference to its use in vertical boreholes and the locations of its various parts are referred to accordingly. It is to be understood that in mining practice the invention is, of course, not limited to strictly vertical boreholes only whether they are bored upwardly or downwardly from the boreface; on the contrary, boreholes inclined at various angles to the vertical plane, even horizontal holes, are drilled in practice and may equally be charged by means of the assembly and method described above, particularly by the embodiments described in FIGS. 2 to 18 inclusive; the references to the various positions such as lower or upper end are then, of course, to be understood accordingly, mutatis mutandis.

The invention is useful for all pourable or pumpable explosive mixtures; it is particularly suitable for the ammonium nitrate fuel oil mixtures or aqueous ammonium nitrate slurries and the many variations thereof, including e.g. the pumpable mixtures of our US. Pat. No. 3,457,126 and our South African patent specification 69/3009.

It should be noted that the invention extends to range of useful ammonium nitrate slurries. In the past many formulations had to be rejected because they were highly susceptible to inactivation by water; such formulations, which often permit economies, or are more readily pumpable can now also be used by virtue of the complete elimination in the present invention of the risk of desensitisation by ingress of water. The invention is useful in wet boreholes and may also be of use in extending the use of explosive mixtures in underwater applications such as for example underwater blasting operations for deepening existing harbors, waterways, rivers, lakes and the like, or in off-shore mining and drilling operation used in prospecting and/or recovering of natural resources such as minerals, gas or oil from underwater locations.

While the use of our invention has been exemplified with reference to explosive compositions, it is in no way restricted to such a use. Our invention may be applied generally to situations where it is desired to confine a pourable, pumpable or blowable material in a particular position or to separate it from contact from its immediate environment. Thus, for example in the erection of buildings on wet, marshy or sandy soils it is sometimes difficult to prepare foundations for the buildings since the components of such foundations may be absorbed by the surrounding earth or caused to move from their original position because of the nature of the environment. It is therefore desirable that such foundation material be separated from the surrounding earth and supported in some manner until it becomes self-supporting. Our protected assembled package is eminently suited for this purpose. Thus for example a slurry of a previously mixed concrete composition may be pumped, poured or blow into such a package situated in a foundation site. Our package then confines the concrete composition in the desired position until it is set sufficiently not to move from its desired position.

Accordingly we provide a process of confining a pourable, pumpable or blowable material in a desired position which process comprises preparing an assembly as hereinbefore described, inserting it into the desired position and transferring said material into said assembly.

We also provide a process of preparing foundations for buildings which process comprises preparing an assembly as hereinbefore described, inserting it into a foundation site, transferring suitable foundation forming material into said assembly and allowing said foundation forming material to set.

Our invention is now exemplified by, but not limited to the following examples and the attached drawings, of which FIGS. 1 to 14 inclusive are schematic cross-sections and FIGS. l5, l7 and 18 are plans and FIG. 16 is an isometric sketch.

FIG. 1

In FIG. 1 borehole 1 drilled into fissured rock is shown. Borehole liner 2, consisting of polythene tubing, 0.005 inch thick, having both diameter and length greater than that of borehole l is contained in a plastic packaged assembly in the form of a tightly compressed concertina. Inner tube (casing) 3 of the package (wall thickness 3 mm) has a diameter greater than that of loading hose 4 and is affixed to outer tube 5 (wall thickness 3 mm) by means of clip attachment 6. Both inner tube 3 and outer tube 5 are constructed from polythene but other rigid materials such as PVC or polypropylene would be suitable. Outer tube 5 being of a diameter 1 inch in excess of inner tube 3 serves to contain liner 2 in concertina form and to protect it in practical operation. Clip attachment 6 may be simply a high density polythene cap which is welded sealingly to inner tube 3 and is a friction, fused or welded fit over the top end of outer tube 5; the top of liner 2 is attached to 6 firmly and sealingly, between the tubes. The bottom end of liner 2 is sealed or tied by a string or any other suitable means. Constriction 7 is achieved by making outer tube 5 larger than inner tube 3 and reducing the diameter of outer tube 5 at its lower end in such a way as to constrain liner 2 firmly but not rigidly in the concertina form. Primer charge 8 is placed in the bottom of liner 2 and attached thereto is detonating fuse downline 9 with other priming charges (not shown) at various distances along its entire length, if so desired. The cartridge is supported above borehole 1 on three legs 10 which are attached to outer tube 5 and are firmly positioned on the ground.

In operation at the blasting site, an assembly containing a liner of suitable length and diameter is seated over the borehole. When bottom priming is desired a primer with a detonating fuse downline attached is placed in the bottom of the liner. Whenever multiple boostering is required additional primers may be attached to the detonating downline at suitable intervals. The loading hose is then inserted into and pushed through the tube 3 into the borehole paying off the liner and the detonating downline as it goes. When the hose has reached the base of the borehole the blasting agent is loaded into the liner through the loading hose. The loadinghose is slowly withdrawn as the hole fills leaving the liner filled with blasting agent and expanded to the hole diameter. Water which may be present in the borehole is driven up ahead of the advancing column of blasting agent or displaced into crevices. On delivery of the predetermined quantity of charge the loading hose is removed, the liner disconnected from the assembly and sealed, and the borehole stemmed ready for firing. Whenever excessive abrasion is likely to be encountered in the borehole the end of the liner which would be most exposed may be protected by capping with a suitable material, e.g. a rigid polythene cap.

FIG. 2

FIG. 2 and subsequent FIGS. 3 to 13 inclusive differ from FIG. 1 in so far as the whole assembled package is attached to the end of the loadinghose and lowered with the loading hose to the bottom of the borehole before delivery of the blasting material commences.

With reference to FIG. 2 a borehole liner 2 is shown tightly compressed, as in FIG. 1, in the form of a concertina. The outside diameter of loading hose 4 is equal to the inside diameter of inner tube 3 thus fitting tightly into it. Inner tube 3 and outer tube 5 with the top end of liner 2 attached sealingly between them are held firmly to loading hose 4 by a suitable clamping device 11 (for example, a hose clip). Constriction 7 is formed by expanding the bottom of inner tube 3 to a diameter slightly less than that of outer tube 5. The bottom of borehole liner 2 is suitably sealed and has a series of small holes 12 punched into it. Detonating fuse downline 9 passes through reinforcing eyelet 13 into the bottom of liner 2 to a printing charge 8. The eyelet is sealed against leakage by adhesive or a tight friction fit.

At the blasting site a cartridge containing a compressed liner of the desired length (slightly longer than the depth of the borehole) and diameter(slightly wider than the borehole) is attached to the end of the loading hose. When bottom priming is required in this and in all following examples a detonating fuse downline may be threaded through the reinforcing eyelet and secured to a priming charge. The priming charge is placed inside the liner and the liner is sealed below the perforation. In larger holes where multiple boostering may be desired this is readily obtained by attaching additional priming charges to the detonating downline at the desired intervals. The loading hose with the cartridge attached is lowered to the bottom of the borehole pulling down the detonating fuse downline in the process. When the borehole contains water of such a depth that it could exert sufficient back pressure against the liner to cause it to be pushed inside the inner tube with a risk of tearing or entangling it, water passes through the holes into the bottom of the liner until the pressure is reduced or equalised; thus bursting or entanglement of the liner by excess pressure is prevented. On delivery of the blasting agent most of the water in the liner is forced out through the holes; the holes are, however, sufficiently small to prevent excessive discharge of the viscous blasting agent. The hose with the assembled cartridge attached is withdrawn slightly ahead of the advancing column of blasting agent which fills the liner to the maximum borehole diameter. After charging to the required height the assembly is disconnected from the filled liner and the hole is ready for stemming and then blasting. If top priming only is required this may be achieved in this example and in all other examples by pushing a priming charge with a detonating fuse attached to it inside the liner and into the column of blasting agent, to the desired depth. The liner is then sealed and the borehole is stemmed as before. Bottom priming may also be accomplished by seating an electric detonator in the priming charge contained in the bottom of the assembled package. The electric detonator is then connected to an electric downline of fine, flexible wire which is attached to the liner material before it is formed into a concertina.

FIG. 3

FIG. 3 is similar to FIG. 2; the numerals have the same meanings and functions in both figures. Constriction 7 is formed by reducing the diameter at the end of outer tube and by increasing the diameter at the end of inner tube 3. Valve 14, a conical non-return diaphragm valve, is an integral part of the end of loading hose 4, which extends to the bottom of inner tube 3.

Alternatively, valve 14 could be part of a separate tube sealingly attached to the loading hose and operating as its extension into inner tube 3.

In operation this system does not require holes in the borehole liner to alleviate any back pressure due to water in the borehole. The non-return valve supports the exposed area of the liner which covers the opening of the inner tube and thereby prevents excessive strain on the liner; valve 14 also serves to support a long column of blasting agent which may be present in the loading hose from a previous charging and which could otherwise break, but valve 14 opens at a predetermined pressure in excess of the static head of explosive in the hose, particularly under the full discharge pressure of the loading pump. In all other aspects operation in FIG. 3 is exactly as that detailed for FIG. 2.

FIGS. 4 and 5 FIGS. 4 and 5 show two additional features of the invention which are essentially similar. Push-on cap is fitted over the bottom end of outer tube 5 in FIG. 4 and inner tube 3 in FIG. 5. In FIG. 4 the diameter of outer tube 5 is increased and then decreased to its original size, thus forming ridge 16 which holds cap 15 firmly in place. In FIG. 5 cap 15 forms a friction fit over the end of inner tube 3. Cap 15 is constructed from polythene.

In both figures constriction 7 is formed by expanding the diameter of inner tube 3.

The additional cap 15 serves to protect the liner from abrasion on the way down the borehole and to eliminate any undesirable effects resulting from back pressure. When the loading hose, with the cartridge attached, is in position at the bottom of the borehole the caps are readily dislodged by the pressure exerted by the blasting agent in the bottom of the liner once pum ping commences. Otherwise the operation is identical to that detailed in FIG. 1.

FIGS. 5 and 7 A further modification to the end of the assembled cartridge is shown in FIGS. 6 and 7 showing the package being lowered in FIG. 6 and being withdrawn in FIG. 7. outer tube 5 is slightly longer than inner tube 3 and, at its end, has its diameter reduced to almost that of inner tube 3 thus forming constriction 7. The diameter of outer tube 5 is then increased again beyond its original size but to less than that of borehole l, to obtain rim 17. Ring or split ring 18 of soft, flexible material, for example foam rubber, is affixed by its inner edge to rim 17. In FIG. 6 the outer edge of ring 18 is folded back on itself and wedged firmly between liner 2 and outer tube 5 in constriction 7. FIG. 7 shows a partially released liner 2 fitted to the diameter of borehole l with blasting agent 19. Ring 18 is extended and overlaps rim 17 almost to the side of borehole 1.

In operation the assembled package on the end of the loading hose is lowered to the bottom of the borehole as before. The expanded rim on the outer tube is of a suitable diameter less than that of the borehole to avoid snagging. On delivery of the blasting material the liner falls forward dislodging the trapped outer edge of ring 18. As the delivery proceeds the hose is raised and more liner is paid out completely unfolding the ring until it lies along and overlaps the rim. The effective diameter of the rim is extended almost to the walls of the borehole. Since the ring is of a flexible material there is no danger of the cartridge being impeded on retrieval. The liner fills out to the diameter of the borehole until the blasting agent comes into contact with the rim; the rim and hence the cartridge is then pushed upwards paying out liner as the charging continues. In this manner the borehole is loaded. All other procedures are as previously described.

FIGS. 8 and 9 FIGS. 8 and 9 show some of the possible variations in the methods of assembling the package and of attaching it to loading hose 4.

In FIG. 8 bayonet 20 is fitted to loading hose 4 and socket 21 forms the upper portion of the extended inner tube 3. Retaining clip 22 fixed to outer tube 5 serves as an additional means of holding inner tube 3 liner 2 and outer tube 5 firmly together. FIG. 9 differs from FIG. 8 in so far as socket 21 is formed on the end of loading hose 4, which extends inside inner tube 3 to bayonet 20 attached thereto. An improved clamping arrangement is shown whereby rim 23 is added to outer tube 5 and complementary seat 24 is provided on original clip attachment 6.

With these modifications the package may be safely assembled in locations other than at the blasting site and may be attached to the loading hose more securely and quickly. Otherwise the operation is carried out as described above.

FIG. 10

FIG. 10 shows the bottom of an assembled package. Outer tube is reduced in diameter and then expanded to form rim 17 as in FIGS. 6 and 7. Inner tube 3 is extended and expanded to a diameter greater than that of rim 17. Thus sloping rim 25, having a surface area considerably greater than rim 17, is formed. Otherwise the package may be designed according to any of the earlier examples and Figures.

In operation the embodiment of FIG. 10 behaves in a manner similar to that detailed for FIGS. 6 and 7, but a greater surface area is provided in more immediate contact with the blasting agent. The package is therefore pushed ahead of the rising column of blasting agent more effectively. The possibility of blasting agent forcing its way between the inner tube and outer tube whenever pumping and withdrawal of the hose are not fully synchronized is excluded by this design of rim 25.

FIGS. 11,12 and 13 FIGS. l1, l2 and 13, although similar to the previous drawings, are particularly applicable to operations in which the blasting agent is delivered to the borehole in a stream of compressed gas. The bottom of the assembled package is not illustrated as any combination of the preceding examples may be used.

In FIG. 11 loading hose 4 extends into the package and is of a diameter less than that of inner tube 3. Inner tube 3 extends above outer tube 5 and has its diameter reduced at its end to that of loading hose 4. The extended portion of inner tube 3 has a series of small holes 26 punched in it and is attached to loading hose 4 by a suitable clip arrangement 6. Flap valve 27 is held under clip 6 and serves to seal holes 26.

The package, attached firmly to the loading hose, is lowered to the bottom of the borehole in the above described manner. On delivery of the blasting agent the carrier gas is released up the annulus between the loading hose and inner tube and escapes through the holes at the top of the inner tube by pushing open the flap valve.

FIG. 12 shows inner tube 3 with bayonet fitting and loading hose 4 with socket fitting 21 and between these is adaptor 28. Adaptor 28 has the socket 21 and bayonet fitting 20 complementary to those on loading hose 4 and inner tube 3. Non-return valve 29, for example a ball valve, is fitted in the side of adaptor 28 and has attached to it a narrow gas outlet tube 30 which leads down inside loading hose 4 to the bottom of inner tube 3. The adaptor piece with the inserted tubing and ball valve is constructed from materials sufficiently substantial to withstand prolonged usage. The package containing a liner of the desired length and diameter is connected to the loading hose via the adaptor. In operation the assembly works as described above; the gas stream is released up the outlet tube and through the non-return valve.

An alternative to the embodiment shown in FIG. 11 is shown in FIG. 13. In this case inner cylinder 31 of a diameter close to that of loading hose 4 is held firmly inside inner tube 3 by spacers 32 in such a way as to form air passages. Spacers 32 may be formed from strips or suitably corrugated material and may be understood more fully by reference to the inserted end sections (FIGS. 17 and 18). Inner cylinder 31 extends from the top of outer tube 5 to a point part of the way down the package. All other details are as enumerated above.

This embodiment of the invention operates in the same way as that shown in FIG. 11. On delivery of the blasting agent the carrier gas is released up the air passages in the annulus between the inner cylinder and inner tubes and out via the flap valve.

Example 1 polyethylene tube liner of diameter 4% inches, of wall thickness 0.006 inch and 30 feet in length was attached to the top portion of, and sleeved in loose fit and folded in concertina fashion over, a rigid tube, referred to hereinafter as the inner tube, comprised of a polyvinylchloride composition and having a length of 32 inches and an overall diameter of 1.5 inches. There was then slid over the above assembly approximately concentrically a further, or outer, tube made of a rigid polyvinylchloride composition and of an overall diameter of 3.5 inches and a length of 29 inches. The positions of the inner and outer tubes where so adjusted that the inner tube extended 2 inches beyond the top and 1 inch beyond the bottom of the outer tube. The top of the outer tube was then attached to the upper portion of the inner tube. The bottom end of the inner tube was fitted with a cone of flexible rubber 6 inches high and of base diameter 4.5 inches. An annular priming charge was fitted above the flexible cone. A detonating fuse cord was connected to the priming charge. The polyethylene liner was pulled over the priming charge and the cone and sealed by tying it at the bottom. A series of small holes approximately one thirty-second inch in diameter was punched in the lower region of the polyethylene liner. A cardboard cap was fitted over the liner, cone and priming charge. The top portion of the inner tube was inserted into a loading hose fitted with a one way valve and a sliding metal collar tightened around the loading hose and inner tube. A pull cord was attached to the collar to facilitate ultimate removal of the hose from the borehole. The assembly was then placed in a borehole substantially filled with water and being 4 inches in diameter and 40 feet deep. The assembly was then lowered through the water to the bottom of the borehole, paying out detonating fuse connected to the priming charge at the same time. A non-water proofed blasting composition consisting of ammonium nitrate 68 parts; sodium nitrate 2 parts; aluminum 10 parts; sugar 5 parts; water l4 parts; surfactant 0.5 part and thickening agent 0.5 part all parts being by weight per I00 parts by weight of the composition was pumped through the loading hose. The pump pressure of the blasting composition opened the valve in the loading hose and the blasting composition was pumped into the assembly through the inner tube. As pumping proceeded air was forced out of the assembly through the small holes in the liner, the cone was expanded and the cardboard cap was torn. The

cone was expanded further and caused the liner to be placed against the wall of the borehole. The whole assembly then began to rise up the borehole, displacing water as it rose, and the polyethylene liner was automatically paid out in the form of a tube containing the blasting composition as the assembled package, loading hose and withdrawn detonating fuse advanced in an upward direction in the borehole. When the tubular liner was filled with the blasting composition the assembly was disconnected from the loading hose which was then removed from the borehole. The borehole was stemmed and the blasting composition was detonated successfully.

I claim:

1. A protected preassembled package for blasting agents susceptible to desensitization by water which comprises in combination:

1. an inner rigid and self-supporting tube, the upper end of which is suited to be connected, or attached, to the discharge end ofa loading hose for a blasting agent and the lower end of which is open,

2. a flexible tubular liner made of water-resistant film, having a diameter greater than that of the inner tube and a length at least equal to the desired depth of its insertion into the borehole, said liner being sleeved over the length of said inner tube and compressed in regular or irregular folds, concertina-fashion, towards its upper end so as to fit the length of the liner in a loose fit onto said inner tube, the upper end of said liner being attached to said inner tube and the lower end of said liner being closed e.g. by sealing, knotting or tying it with string so as to prevent substantial discharge of the explosive mixture therefrom when the latter is pumped into it, and

3. an outer rigid, self-supporting tube of a diameter sufficient to envelop in a loose fit said inner tube together with the liner sleeved thereon and of a length approximately equal to that of the inner tube, thereby protecting said folded-up liner along its length, said outer tube being roughly concentrical with said inner tube, rigidly attached to it near or at its upper end and open at its lower end.

2. A protected preassembled package for blasting agents according to claim 1 wherein the upper end of an inner rigid and self-supporting tube is suited to be connected or attached sealingly to the discharge end of a loading hose for a blasting agent and wherein the flexible tubular liner made of water resistant film has a diameter greater than the diameter of the borehole.

3. A protected preassembled package for blasting agents according to claim 1 comprising in addition liner-delivery-restraining means at and between the lower open ends of said outer and inner tubes, causing the maximum frictional resistance against forces pushing or pulling said folded-up liner off the outer mantle of the inner tube outwardly through the bottom opening of the outer tube to occur between said lower ends of both tubes, said maximum frictional resistance, however, being below the tear strength of the material of the liner and below the force of the downward thrust exercised upon the interior of said liner by the blasting agent being pumped into it; and, optionally, across the opening at the bottom end of the tubes a cap attached removably to, and protecting, the assembly against physical damage and ingress of foreign material into the tubes.

4. A protected preassembled package for blasting agents according to claim 1 wherein the material of construction of the inner and outer rigid and self-supporting tubes is selected from the group consisting of metals, timber, rigid water resistant paper or plastics and rigid rubber.

5. A protected preassembled package for blasting agents according to claim 1 wherein the material of construction of the inner and outer rigid and self-supporting tubes is selected from the group consisting of aluminum, galvanized iron, low density polyethylene, high density polyethylene, polypropylene, polyvinylchloride, polyethyleneterephthalate and acrylonitrile-butadiene-styrene rubber.

6. A protected preassembled package for blasting agents according to claim 1 wherein the inner and outer rigid and self-supporting tubes are constructed from polyethylene tubing having an outer diameter which is from 1 to 15 cm less than the diameter of the borehole in which it is to be used, said polyethylene tubing having a wall thickness from 3 to 15 mm.

7. A protected preassembled package for blasting agents according to claim 1 wherein the material of construction of the flexible tubular liner is selected from the group consisting of water-proofed textile, water-proofed paper and plastic film.

8. A protected preassembled package for blasting agents according to claim 1 wherein the material of construction of the flexible tubular liner is selected from the group consisting of polyethylene, polypropylene, polyvinylchloride, polyethyleneterephthalate, nitrocellulose and rubber of wall thickness in the range from 0.00] to 0.10 inch.

9. A protected preassembled package for blasting agents according to claim 1 wherein the flexible tubular liner is a thin walled corrugated tubular film in concertina form consisting of alternating widening and narrowing sections roughly describing in lengthwise crosssection a sinoidal curve.

10. A protected preassembled package for blasting agents according to claim 1 wherein the flexible tubular liner is a multiplicity of annuli of thin fiat plastic film the outer and inner circumference of each annulus being alternatively sealed with the outer and inner circumference of the adjacent upper, or, respectively, lower annulus to constitute, in assembly a concertina as hereinbefore described.

ll. A protected preassembled package for blasting agents according to claim 1 wherein the flexible tubular liner is provided in the region of its lower end with a multiplicity of small orifices.

12. A protected preassembled package for blasting agents according to claim 1 which comprises in the region of its lower end a one way non-return discharge valve.

13. A process which comprises the steps:

1. sleeving a flexible tubular water resistant plastic film liner, closed against discharge of a fluid blasting agent at its lower end, in a loose fit over a first self-supporting tube, referred to hereinafter as the inner tube and pushing the liner towards the upper end of said inner tube to form a multiplicity of folds, thus accommodating on said inner tube said plastic film liner, which when fully extended is at least 3 times as long as said inner tube,

2. sliding in a loose fit a second wider, rigid self-supporting tube of a length roughly equal to said inner tube over said inner tube so as to be approximately concentrical and envelop, when fully assembled, the inner tube and the sleeved-on tubular liner,

3. attaching the liner to the upper end of the inner tube 4. fastening the outer and inner tubes together at their respective upper ends.

14. A process according to claim 13 which comprises the additional step of fitting the assembly at its upper end with means for removably connecting it to a loading hose for blasting agents.

15. A process according to claim 13 which comprises the additional step of fitting the inner tube at its upper end with means for removably connecting it to a loading hose for blasting agents.

16. A process according to claim 13 which comprises the additional step of closing the open, lower end of the outer or inner tube with a removable protective cap.

17. In a process of blasting wherein a water sensitive pumpable blasting agent is bulk loaded into a borehole and detonated therein, the improvement which comprises preparing an assembly according to claim 1, locating said assembly in a borehole, transferring a charge of a water sensitive pumpable blasting agent into said located assembly to form in situ a package charge and detonating said package charge.

18. In a process of confining a pourable, pumpable or blowable material in a desired confined location the improvement which comprises preparing an assembly according to claim 1, placing said assembly into said location and transferring said pourable, pumpable or blowable material into said assembly to form in situ a packaged material in said confined location.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2745346 *May 11, 1953May 15, 1956Union Carbide & Carbon CorpMethod of charging holes with explosives
US2903969 *May 28, 1953Sep 15, 1959Maumee Collieries CoMethod of blasting
US3188906 *May 16, 1963Jun 15, 1965Phillips Petroleum CoExpansible means for loading a shot hole
US3199399 *May 17, 1963Aug 10, 1965Phillips Petroleum CoShot hole loading device
CA703542A *Feb 9, 1965Express Dynamit AbMeans for inserting a plastic foil tubing into bore holes
SU171305A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3867867 *May 15, 1973Feb 25, 1975Ici LtdCavities with fluent material
US4040330 *Dec 23, 1975Aug 9, 1977Nils Denny MatzenMethod of charging drill holes and means for carrying out the method
US4369711 *Nov 24, 1980Jan 25, 1983Harold LeaderBag for explosives with lower reinforcing sleeves
US4537133 *Mar 31, 1983Aug 27, 1985The United States Of America As Represented By The Secretary Of The InteriorNon-incendive rock-breaking explosive charge
US5259316 *Nov 9, 1992Nov 9, 1993Nelson James EMethod and apparatus for wet/dry, small bore hole explosive device
US6209458Nov 3, 1997Apr 3, 2001Orica Australia Pty Ltd.Inflatable plugs for charging blastholes
US6520089 *Jun 19, 2000Feb 18, 2003Dynaenergetics Gmbh & Co. KgMethod for setting and igniting a charge of explosives for geological investigations and explosive device associated therewith
US6886466Jun 11, 2002May 3, 2005Jeffrey S. SenulesWater-permeable woven borehole sleeve having apertures and receiving explosive chare; rigid casing adapted to guide; leakage prevention; sealing
US7294138 *Jun 28, 2004Nov 13, 2007Shippert Ronald DNose pack method and apparatus
US7950328Dec 10, 2007May 31, 2011Dave HowertonBlast hole liner
US8276517 *Jul 16, 2007Oct 2, 2012E.M.I. (1997) Ltd.Method, device and system of deploying a payload
US8820242 *Mar 20, 2012Sep 2, 2014Brent Dee AlexanderHot hole charge system
US20100107917 *Sep 27, 2007May 6, 2010Montanuniversitat LeobenExplosive Cartridge And A Method Of Arranging An Explosive Cartridge In A Blast Hole
US20130247789 *Mar 20, 2012Sep 26, 2013Brent Dee AlexanderHot hole charge system
EP2000764A1 *Jun 4, 2007Dec 10, 2008Montanuniversitšt LeobenA device, charging unit and method of filing a borehole with a explosive material
WO1998020295A1 *Nov 3, 1997May 14, 1998Ici Australia OperationsInflatable plugs for charging blastholes
WO2000079212A1 *Jun 19, 2000Dec 28, 2000Aurellius Juessen AvanciMethod for setting and igniting a charge of explosives for geological investigations and explosive device associated therewith
WO2008037483A1Sep 27, 2007Apr 3, 2008Montanuniversitaet LeobenAn explosive cartridge and a method of arranging an explosive cartridge in a blast hole
WO2008148544A1 *Jun 4, 2008Dec 11, 2008Montanuniversitaet LeobenA device, charging unit and method of filling a borehole with an explosive material
WO2011117394A1 *Mar 25, 2011Sep 29, 2011Montanuniversitaet LeobenExplosive cartridge
WO2011127491A2 *Apr 6, 2011Oct 13, 2011Sandvik Mining And Construction Rsa (Pty) LtdA rock breaking product
WO2012131525A1 *Mar 19, 2012Oct 4, 2012Ael Mining Services LimitedCharging of blasting boreholes
Classifications
U.S. Classification86/20.15, 102/324
International ClassificationF42D1/10
Cooperative ClassificationF42D1/10
European ClassificationF42D1/10