WO2003046471A2

WO2003046471A2 - A method of loading a blast hole and a plug therefore

Info

Publication number: WO2003046471A2
Application number: PCT/IB2002/002260
Authority: WO
Inventors: Dewald Opperman; Jacobus Opperman
Original assignee: VILJOEN ABRAHAM CAREL
Current assignee: VILJOEN ABRAHAM CAREL
Priority date: 2001-11-30
Filing date: 2002-06-17
Publication date: 2003-06-05
Anticipated expiration: 2004-05-30
Also published as: AU2002258117A1; WO2003046471A3; AU2002258117A8

Abstract

This invention relates to a method of loading a blast hole (80, 200) which includes introducing into the blast hole (80, 200) a charge (84) of gas generating material, and sealing the blast hole (80, 200) using a plug (10, 100, 110, 120, 130, 180), at least part of which is formed of a resiliently deformable material. The invention extends to a blast hole plug (10, 100, 110, 120, 130, 180) which includes an expansile element (12, 132, 182) which is displaceable between a rest position, in which is receivable in a blast hole (80, 200), and an expanded position. The blast hole plug (10, 110, 120, 130, 180) includes sealing means displaceable on expansion of the expansile element (12, 132, 182) between a rest position, in which, in use, the sealing means is clear of a surface (90) of a material (82) defining the blast hole (80, 200), and a sealing position, in which, in use, the sealing means sealingly engages the surface (90) of the material (82) to seal the blast hole (80, 200).

Description

A METHOD OF LOADING A BLAST HOLE AND A PLUG THEREFORE

THIS INVENTION relates to blasting. More particularly, it relates to a method of loading a blast hole and to a blast hole plug.

In the breaking of rock during mining and quarry or civil excavations, one method of rock-breaking includes inserting explosive material into a pre-drilled blast hole in the material to be blasted. The ensuing blast tends to cause resultant shock waves which may result in an unstable environment in the region of the blast. Furthermore, because of the danger inherent in the use of explosive materials, special storage and transport techniques are required.

The difficulties associated with the use of explosives in rock blasting have led to the development of so-called "non-explosive" blasting methods. The non-explosive materials used in such methods include those which produce a gas on activation/ignition, the generation and expansion of which, within a confined space, results in gas pressure build-up which serves to break the rock.

With the introduction of high-pressure gas systems for use in rock breaking, containment of the high-pressure gas has become a requirement. This is true too where "black powder" is used to generate the high-pressure gas required. Containment/confinement of the high- pressure gas facilitates utilisation of a maximum energy of gas buildup/expansion for breaking of the rock. It is thus desirable to seal the pre-drilled hole into which the gas-generating material is inserted as near possible air tight.

It will be appreciated that this technique has application in fields other than rock breaking, for example, demolition and other areas where high explosives cannot be employed.

Accordingly the invention provides a method of loading a blast hole, which method includes introducing into the blast hole a charge of gas-generating material; and sealing the blast hole using a plug, at least part of which is formed of a resiliently deformable material.

Said at least part of the plug may be elongate and snugly receivable in the blast hole, and sealing the blast hole may include inserting the plug into the blast hole and, once the plug has been inserted into the blast hole, expanding said at least part of the plug laterally, sealingly to engage the surface of a material defining the blast hole. Expanding said at least part of the plug laterally may include compressing said at least part of the plug longitudinally.

Said at least part of the plug may be hollow and expanding said at least part of the plug may include laterally expanding an expansile element positioned within said at least part of the plug. In another embodiment of the invention, sealing the blast hole may include urging said at least part of the plug into sealing contact with material surrounding a mouth of the blast hole.

The method may then include securing an anchor member in the blast hole and displacing said at least part of the plug relative to the anchor member into contact with the material around the mouth of the blast hole.

According to another aspect of the invention, there is provided a blast hole plug which includes an expansile element which is displaceable between a rest position, in which it is receivable in a blast hole, and an expanded position; and sealing means displaceable on expansion of the expansile element between a rest position, in which, in use, the sealing means is clear of a surface of a material defining the blast hole, and a sealing position, in which, in use, the sealing means sealingly engages the surface of the material to seal the blast hole.

In one embodiment of the invention, the expansile element includes an elongate body of resiliently deformable material which is capable of expanding laterally outwardly on longitudinal compression thereof.

The sealing means may then be defined by an outer surface of the body of resiliently deformable material which, in use, sealingly engages the surface of the material defining the sides of the blast hole. The expansile element may include complementary inter- engaging screw-threaded elements which act on ends of the body, the body being longitudinally compressible under action of the screw- threaded elements. The screw-threaded elements may include a central element having a shank with at least one screw-threaded end, the body defining a sleeve which is generally circular in cross-section and is received over at least part of the central element. It will be appreciated that the shank may be threaded along the entire length thereof.

The at least one screw-threaded end of the central element may protrude from at least one end of the sleeve, the screw-threaded elements including at least one complementary internally threaded fastener screw-threadedly received or receivable on the at least one screw-threaded end of the central element. In one embodiment of the invention, the central element protrudes from each end of the sleeve and an internally threaded fastener is screw-threadedly received or receivable on each protruding portion of the central element. It will be appreciated that the central element may instead have a fixed head defined at one protruding end/portion thereof, an internally threaded fastener being screw-threadedly received or receivable on the other protruding portion.

The sleeve is typically of an elastomeric (i.e. natural or synthetic rubber) or a synthetic plastics material. In a preferred embodiment of the invention, the sleeve is formed from ethylene- propylene diene monomer (or EPDM) .

The expansile element may include load distributing means for distributing a load applied to the at least one fastener over an end of the sleeve. The load distributing means may be provided by a lock washer fixed to an/each end of the sleeve so as to, in use, be disposed between the at least one threaded fastener and/or the head of the central element and the sleeve.

Instead of bearing a head or having an internally threaded fastener received thereon, one end of the central element may be welded to the lock washer disposed at that end of the sleeve.

The blast hole plug may include a support element positioned within the sleeve, the support element being laterally expandible to displace the sleeve laterally outwardly.

The support element may be in the form of an expansion sleeve positioned between the inner surface of the body and the central element. Instead, the support element may be in the form of a coil spring.

In another embodiment of the invention, the expansile element includes an anchor member. Typically the anchor member includes co-axial inner and outer expansion elements, the inner expansion element being snugly received within the outer expansion element and the inner and outer elements being configured to co-act by means of a wedging action so that relative longitudinal displacement between the outer and inner elements results in lateral displacement of the outer element. The expansile element may further include a central element, having a shank which is threaded at least partly along the length thereof, and for, in use, expanding the anchor member. To this end, the inner element of the anchor member may be screw-threadedly received on the central element so as to be axially displaceable relative to the outer element.

The sealing means may be provided by a body of resiliently deformable material which, in use, extends laterally outwardly relative to the central element at an end of the central element remote from the anchor member. The body may be mounted to an operatively inwardly disposed side of a sealing plate which, in use, extends laterally outwardly relative to the central element. The sealing plate may be axially displaceably received on the end of the central element and may be retained thereon by an internally threaded fastener, screw-threadedly received on the end of the central element or against a fixed head of the central element.

The expansile element may further include a sleeve of a resiliently deformable material received at least partly over the anchor member to be laterally outwardly expandible on expansion of the anchor member.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings,

Figure 1 shows a side view of a blast hole plug in accordance with the invention;

Figure 2 shows a part sectional view of the blast hole plug of Figure 1 inserted into a blast hole; Figure 3 shows a side view of another blast hole plug in accordance with the invention;

Figure 4 shows a side view of still another blast hole plug in accordance with the invention; Figure 5 shows a side view of yet another blast hole plug in accordance with the invention;

Figure 6 shows a side view of a further blast hole plug in accordance with the invention;

Figure 7 shows a side view of a still further blast hole plug in accordance with the invention; and

Figure 8 shows a part sectional view of the blast hole plug of Figure 6 inserted into a blast hole.

In Figure 1 of the drawings, reference numeral 10 refers generally to a blast hole plug in accordance with the invention. The blast hole plug 10 includes an expansile element, generally indicated by reference numeral 1 2. The expansile element 1 2 includes an elongate body 1 4 of resiliently deformable material which is capable of expanding laterally outwardly, in the direction of the arrows 1 6, on longitudinal compression of the body 14 (i.e. in the direction of the arrows 1 7) .

The body 14 defines a sleeve 18, which is generally circular in cross-section and is received over a central threaded shank 20. In the embodiment shown in Figure 1 of the drawings, the shank 20 has a hexagonal head 30 defined at an end 32 thereof which protrudes from an end 24 the sleeve 18. A threaded free end 26 of the shank 20 protrudes from the other end 22 of the sleeve 18. The sleeve 18 is typically formed from ethylene-propylene diene monomer (or EPDM) . Naturally, however, the sleeve may be of any resiliently deformable material, and, more particularly of any elastomeric (i.e. natural or synthetic rubber) or synthetic plastics material.

The sleeve 1 8 is longitudinally compressible under action of complementary screw-threaded elements, provided by the threaded shank 20 and a nut 34 screw-threadedly received on the free end 26 of the shank. It will be appreciated that the nut 34 is longitudinally displaceable on the shank 20, relative to the head 30, such that the screw-threaded elements, comprised by the threaded shank 20 with its head 30 and the nut 34, act on the ends 22, 24 of the sleeve 18.

A radially outer surface 39 of the sleeve 18 defines sealing means for, in use, when the sleeve 18 is expanded laterally within a blast hole into which the plug 10 is inserted, sealingly engaging the surface of the material defining sides of the blast hole, as described in more detail below.

Lock washers 50, 52 are fixed respectively to the ends 22,24 of the sleeve 1 8 so as to be disposed between the nut 34 and end 22 of the sleeve 18 and the head 30 and end 24 of the sleeve 18, respectively. Two angularly spaced teeth (one of which 54 is shown in Figure 1 ) project inwardly from an inwardly disposed face 56 of each lock washer 50, 52 and bite into the deformable material of the sleeve 1 8 thereby to lock the washer 50, 52 to the relevant end 22, 24 of the sleeve 18. Instead, the lock washers 50, 52 may be fixed to the ends 22, 24 by use of a suitable adhesive.

A lubricated flat washer 65 is fitted between the lock washer 50 and the nut 34 thereby to permit relative rotation between the nut 34 and the lock washer 50.

It will be appreciated that, instead of bearing a head 30, an end 32 of the shaft 20 may be threaded and may protrude from the end

24 of the sleeve 18 and have a complementary nut received thereon.

In still another embodiment of the invention, the end 32 of the shaft 20 may be welded to the lock washer 52 (see Figures 3 to 5).

A longitudinally extending channel recess 60 is defined in an outer surface of the sleeve 18 and provides, in use, a passage from an interior of a blast hole into which the plug 10 is inserted, for accommodating, for example, electrical wiring from a charge received in the blast hole which is plugged.

Typically, the sleeve 1 8 has an outer diameter which is selected so that it is a snug fit in the borehole in which it is intended to be used. The outer diameter will typically be between about 27 mm and about 40 mm. Similarly, each lock washer 50, 52 has an outer diameter of between about 27 mm and about 40 mm, the outer diameter of a lock washer 50, 52 fitted to a sleeve 1 8 being approximately equal to the diameter of that sleeve 1 8. Typically, teeth of a washer 50, 52 are spaced by an angle of about 90 degrees. The shaft 20, nut 34 and lock washers 50, 52 are typically of mild steel.

Typically, the shaft 20 has a diameter of about 10mm and a length of about 170 mm. The sleeve 18 has an internal diameter and a length dimensioned such that the sleevel 8 is receivable over the shaft 20 so that at least one end 26, 32 of the shaft 20 protrudes from an end 22, 24 of the sleeve 18. Typically the sleeve 18 is about 150 mm in length.

Reference is now made to Figure 2 of the drawings in which, unless otherwise indicated, the same reference numerals used above are used to designate similar parts. In use, the plug 10 is inserted into a pre-drilled blast hole 80 defined in a material 82 to be blasted. Prior to introduction of the plug 10 into the hole 80, a charge 84 of gas generating material is placed in the hole 80 proximate an end 86 of the hole 80 remote from a mouth 88 of the hole 80. Typically, the hole 80 and/or the plug 10 selected for insertion into the hole 80 will be dimensioned such that the plug is snugly received in the hole 80.

Once the plug 10 has been inserted into the blast hole 80, the nut 34 is screw-threadedly displaced longitudinally inwardly along the shank 32 by use of conventional tools, such as, for example, a spanner. A load applied to the nut 34 is distributed over the end 22 of the sleeve 18 by the lock washer 50. Similarly, a load is applied across the end 24 of the sleeve 1 8 by the lock washer 54 disposed between the head 30 of the shaft 20 and the end 24 of the sleeve 1 8. The sleeve 18 is thereby compressed longitudinally and the resiliently deformable material of the sleeve 18 is simultaneously expanded laterally outwardly sealingly to engage the surface 90 of the material 82 defining sides of the blast hole 80. That is, the sleeve 1 8 is longitudinally compressed between the head 30 and the nut 34, as a result of which longitudinal compression the sleeve 1 8 expands radially to engage the hole surface 90.

Electrical wires 92, or other components, from the charge 84 are received in the recess 60 to be passed from an interior of the blast hole 80 to the outside via the mouth 88 of the hole 80.

On ignition of the charge, gas is generated and gas build-up occurs within the blast hole 80 and is contained therein by the plug 10 leading to eventual fracture of the material 82 in which the hole 80 is defined.

In Figure 3 of the drawings, reference numeral 100 refers generally to another blast hole plug in accordance with the invention.

The blast hole plug 100 is similar to the blast hole plug 10 and, unless otherwise indicated, the same reference numerals used above in relation to Figure 1 of the drawings indicate similar parts. An end 32 of the shaft 20 is welded to the lock washer 52. A longitudinally compressible laterally expandible support element 102 in the form of plastic expansion sleeve 104 of circular cross-section is received between the shaft 20 and the sleeve 1 8 of resiliently deformable material. An outer diameter of the expansion sleeve 104 is just less than an internal diameter of the sleeve 18. In use, when the nut 34 is displaced longitudinally inwardly along the shaft 20 and the sleeve 1 8 is expanded radially sealingly to engage sides of the blast hole and to take on the shape of the hole, the expansion sleeve 1 04 is compressed longitudinally to fold concertina- fashion. The concertinaed expansion sleeve 1 04 applies a load to the sleeve 1 8 at spaced points thereby to provide internal support to the sleeve 1 8 and limit collapse thereof.

Reference is now made to Figure 4 of the drawings, in which reference numeral 1 1 0 refers generally to another blast hole plug in accordance with the invention and, unless otherwise indicated, the same reference numerals used above with respect to Figures 1 and 3 of the drawings designate similar parts. A longitudinally compressible laterally expandible support element 1 1 2 is received between the shaft 20 and the sleeve 1 8 of resiliently deformable material. In this embodiment of the invention, the support element 1 1 2 is provided by a coil spring 1 1 4. The coil spring 1 14 is fitted between the lock washers 50, 52 and, in use, is compressed so as to expand radially when the nut 34 is displaced longitudinally inwardly along the shaft 20, thereby to provide lateral support to the sleeve 1 8.

In Figure 5 of the drawings, reference numeral 1 20 refers generally to still another blast hole plug in accordance with the invention, similar to the blast hole plugs 1 0, 1 00, 1 10 and, unless otherwise indicated, the same reference numerals used above indicate similar parts. A support element 1 22, which is longitudinally compressible to be laterally expandible, is here provided, between the shaft 20 and the sleeve 1 8, by a so-called "rawl bolt" arrangement 1 24, or wedge-bolt anchoring arrangement, including an inner expansion element 1 26 and an outer expansion element 1 28, within which the inner expansion element 1 26 is snugly received . The inner and outer elements 1 26, 1 28 are so configured as to co-act by means of a wedging action and are operable between a contracted position, and an expanded position, in which the inner element 1 26 is displaced longitudinally relative to the outer element 1 28 and the outer element 1 28 is in turn expanded laterally outwardly.

The inner element 1 26 is screw-threadedly received on the shank 20. The outer diameter of the "rawl bolt" arrangement 1 24 is approximately equal to the inner diameter of the sleeve 18. In use, when the nut 34 is displaced inwardly along the shaft 20 and the sleeve 1 8 is expanded laterally sealingly to engage sides of the blast hole into which the plug 1 20 has been inserted, the "rawl bolt" arrangement 1 24 is expanded laterally to provide support to the sleeve 18 and to permit improved sealing contact of the sleeve 18 with sides of the blast hole.

In Figure 6 of the drawings, reference numeral 130 refers generally to a further blast hole plug in accordance of the invention. The blast hole plug 130 includes an expansile element, generally indicated by reference numeral 132. The expansile element 132 includes an anchor member 134 including co-axial inner and outer expansion elements 1 36, 1 38, respectively. The inner expansion element 1 36 is snugly received within the outer expansion element 138. The outer expansion element 1 38 is generally U-shaped in cross-section, transversely spaced legs or blades 140 of the outer element 138 having an inclined inner surface 142. The inner element 1 36 is comprised by a complementary tapering body 144. The inclined surfaces 142 and the tapering body 144 facilitate wedging co-action of the inner element 1 36 and the outer element 138. The expansile element 132 further includes a central element 146 in the form of a bolt shank 148 which is threaded along its length. The inner element 1 36 is screw-threadedly received on the bolt shank 148 so as to be axially displaceable relative to the outer element 1 38 with the shank 148, thereby to co-act in a wedging fashion with the outer element 138 to splay the legs 140 of the outer element 138 into contact with side walls of a blast hole into which the plug 1 30 has been inserted. Thus on rotating a fixed head 1 50 of the bolt, the plug 1 30 is anchored in the blast hole.

The blast hole plug 130 further includes sealing means, generally indicated by reference numeral 160. The sealing means 160 is displaceable, on expansion of the expansile element 132/anchor member 1 34, between a rest position, in which, in use, the sealing means 160 is clear of material surrounding a mouth of a blast hole into which the plug 130 has been inserted, and a sealing position, in which, in use, the sealing means 1 60 sealingly engages the material around the mouth of the blast hole. The sealing means 1 60 is provided by a disc 1 62 of resiliently deformable material, the disc 1 62 being received on the end 1 64 of the bolt shaft 148 remote from the anchor member 134. The disc 1 62 is mounted to an operatively inner side of a disc-like sealing plate 1 66 of mild steel. The sealing plate 1 66, with its resiliently deformable layer 1 62, is received on the end 1 64 of the shaft 148 and is retained thereon against the bolt head 1 50.

In use, when it is desired to seal a blast hole, the plug 130 is inserted into the blast hole 200, anchor member 1 34 first (see Figure

8). The bolt head 1 50 is then drivingly engaged and rotated by use of, for example, a spanner. The sealing plate 1 66 with its resiliently deformable layer 1 62 is thereby brought into sealing contact with the material 202 around the mouth 204 of the blast hole 200. Continued rotation of the bolt head 1 50 displaces the inner expansion element 1 36 relative to the outer expansion element 1 38 such that the legs 140 are splayed into contact with the material 82 defining side walls 206 of the blast hole 200 to anchor the plug 1 30 in the blast hole 200.

The disc of resiliently deformable material 1 62 is typically vulcanised onto one side of the sealing plate 1 66. A lubricated washer 1 68 may be provided between the bolt head 1 50 and the sealing plate

1 66 to reduce the effects of metal lock between the bolt head 1 50 and the plate 1 66.

Reference is now made to Figure 7 of the drawings, in which reference numeral 180 refers generally to still a further blast hole plug in accordance with the invention and, unless otherwise indicated, the same reference numerals used above in relation to Figure 6 of the drawings, indicate similar parts. The plug 180 includes an expansile element 1 82, similar to the expansile element 132 and further including a shoe-like body of resiliently deformable material 1 84 received over the anchor member 1 34 to be laterally outwardly expandible on expansion of the anchor member 1 34. It will be appreciated that, in use, on expansion of the blades 140, as described above, the resiliently deformable material of the shoe 1 84 will be sealingly engaged with a surface of the material defining side walls of the blast hole into which the plug 1 80 is inserted. The inner diameter of the shoe 1 84 is approximately equal to the outer diameter of the outer element 1 38 of the anchor member 1 34.

The Applicants believe that the blast hole plug 1 0, 1 00, 1 1 0, 1 20, 1 30, 1 80 in accordance with the invention will provide an effective means of sealing a blast hole into which a gas-generating material has been inserted as near possible airtight thereby to contain the gas within the blast hole and facilitate a maximum breaking of the material in which the blast hole is defined in response to the pressure build-up. The Applicants believe that the plug 1 0, 1 00, 1 1 0, 1 20, 1 30, 1 80 will also be of use in fastening equipment into pre-drilled holes provided in structural elements such as, for example, walls and floors. It is believed that the plug 1 0, 1 00, 1 1 0, 1 20, 1 30 and 1 80 in accordance with the invention may further find application in the mining industry for use as a so-called "roof bolt" .

Claims

1 . A method of loading a blast hole, which method includes introducing into the blast hole a charge of gas-generating material; and sealing the blast hole using a plug, at least part of which is formed of a resiliently deformable material.

2. A method as claimed in Claim 1 , in which said at least part of the plug is elongate and snugly receivable in the blast hole, sealing the blast hole including, inserting the plug into the blast hole and, once the plug has been inserted into the blast hole, expanding said at least part of the plug laterally, sealingly to engage the surface of a material defining the blast hole.

3. A method as claimed in Claim 2, in which expanding said at least part of the plug laterally includes compressing said at least part of the plug longitudinally.

4. A method as claimed in Claim 2 or Claim 3, in which said at least part of the plug is hollow and expanding said at least part includes laterally expanding an expansile element positioned within said at least part of the plug.

5. A method as claimed in Claim 1 , in which sealing the blast hole includes urging said at least part of the plug into sealing contact with material surrounding a mouth of the blast hole.

6. A method as claimed in Claim 5, which method includes securing an anchor member in the blast hole and displacing said at least part of the plug relative to the anchor member into contact with the material around the mouth of the blast hole.

7. A blast hole plug which includes an expansile element which is displaceable between a rest position, in which it is receivable in a blast hole, and an expanded position; and sealing means displaceable on expansion of the expansile element between a rest position, in which, in use, the sealing means is clear of a surface of a material defining the blast hole, and a sealing position, in which, in use, the sealing means sealingly engages the surface of the material to seal the blast hole.

8. A blast hole plug as claimed in Claim 7, in which the expansile element includes an elongate body of resiliently deformable material which is capable of expanding laterally outwardly on longitudinal compression thereof.

9. A blast hole plug as claimed in Claim 8, in which the sealing means is defined by an outer surface of the body of resiliently deformable material which, in use, sealingly engages the surface of the material defining sides of the blast hole.

10. A blast hole plug as claimed in Claim 8 or Claim 9, in which the expansile element includes complementary inter-engaging screw- threaded elements which act on ends of the body , the body being longitudinally compressible under action of the screw-threaded elements.

1 1 . A blast hole plug as claimed in Claim 10, in which the screw-threaded elements include a central element having a shank with at least one screw-threaded end, the body defining a sleeve which is generally circular in cross-section and is received over at least part of the central element.

1 2. A blast hole plug as claimed in Claim 1 1 , in which the at least one screw-threaded end of the central element protrudes from at least one end of the sleeve, the screw-threaded elements including at least one complementary internally threaded fastener screw-threadedly received or receivable on the at least one screw-threaded end of the central element.

1 3. A blast hole plug as claimed in Claim 1 2, in which the expansile element includes load distributing means for distributing a load applied to the at least one fastener over an end of the sleeve.

14. A blast hole plug as claimed in Claim 1 3, in which the load distributing means is provided by a lock washer fixed to an end of the sleeve so as to, in use, be disposed between the at least one fastener and the sleeve.

1 5. A blast hole plug as claimed in any one of Claims 1 1 to 14, inclusive, which includes a support element positioned within the sleeve, the support element being laterally expandable to displace the sleeve laterally outwardly.

1 6. A blast hole plug as claimed in Claim 1 5, in which the support element is in the form of an expansion sleeve positioned between the inner surface of the body and the central element.

17. A blast hole plug as claimed in Claim 1 5, in which the support element is in the form of a coil spring.

1 8. A blast hole plug as claimed in any one of Claims 7 to 1 7, inclusive, in which the sleeve is of an elastomeric or a synthetic plastics material.

1 9. A blast hole plug as claimed in Claim 7, in which the expansile element includes an anchor member.

20. A blast hole plug as claimed in Claim 19, in which the anchor member includes co-axial inner and outer expansion elements, the inner expansion element being snugly received within the outer expansion element and the inner and outer elements being configured to co-act by means of a wedging action so that relative longitudinal displacement between the outer and inner elements results in lateral displacement of the outer element.

21 . A blast hole plug as claimed in Claim 1 9 or Claim 20, in which the expansile element includes a central element, having a shank which is threaded at least partly along the length thereof, and for, in use, expanding the anchor member.

22. A blast hole plug as claimed in Claim 21 , in which the sealing means is provided by a body of resiliently deformable material which, in use, extends laterally outwardly relative to the central element at an end of the central element remote from the anchor member.

23. A blast hole plug as claimed in Claim 22, in which the body is mounted to an operatively inwardly disposed side of a sealing plate which, in use, extends laterally outwardly relative to the central element.

24. A blast hole plug as claimed in any one of Claims 20 to 23, inclusive, in which the expansile element further includes a sleeve of a resiliently deformable material received at least partly over the anchor member to be laterally outwardly expandible on expansion of the anchor member.

25. A blast hole plug as claimed in any one of Claims 1 9 to 24, inclusive, in which the sleeve is of an elastomeric or synthetic plastics material.

26. A method as claimed in Claim 1 , substantially as herein described and illustrated.

27. A blast hole plug as claimed in Claim 7, substantially as herein described and illustrated.

28. A new method or a new blast hole plug, substantially as herein described.