WO2010054436A1

WO2010054436A1 - Plug member, method of manufacture and plugging method

Info

Publication number: WO2010054436A1
Application number: PCT/AU2009/001479
Authority: WO
Inventors: Sean Peter Buxton
Original assignee: Buxton Ip Pty Ltd
Priority date: 2008-11-17
Filing date: 2009-11-13
Publication date: 2010-05-20
Also published as: CL2011001134A1

Abstract

A plug member for retaining grout in a substantially cylindrical bore in underground excavations comprises: at least one transverse wall portion, adapted to act as a barrier to grout and having at least one port disposed therein, the port being arranged to allow a member to pass through the wall portion; and at least one axially extending wall portion; and the plug member comprises first and second axially spaced apart sealing portions each adapted to create a seal between the plug body and a wall of a substantially cylindrical bore in which a plug member is retained in use.

Description

PLUG MEMBER, METHOD OF MANUFACTURE AND PLUGGING METHOD

Field of the Invention

The present invention relates to a plug member, to a method of manufacture thereof and a method of plugging a bolt hole.

Background of the Invention

A plug member for retaining grout in a bolt hole is described in international patent application publication no. WO2005/045194, the entire disclosure of which is incorporated herein by reference. The plug member allows a number of other members , such as rockbolt members and members in the form of a grout pipe and/or a breather pipe, to extend therethrough, whilst still acting to retain grout in the bolt hole . The present inventor has discerned that an improved or at least alternative plug member may be desirable. Furthermore, the inventor has developed a manufacturing method for production of bolt hole plug members. Still further, the inventor has developed a method for plugging bolt holes which can enhance the sealing properties of plug members described herein .

Summary of the Invention

According to a first aspect of the present invention, there is provided a plug member for retaining grout in a substantially cylindrical bore in underground excavations, the plug member having an axis which in use is aligned substantially parallel to the axis of a cylindrical bore in which the plug member is, in use, retained, the plug member comprising: a plug body comprising: at least one wall portion extending in the transverse direction relative to the axis and adapted to act as a barrier to grout, the at least one transverse wall portion having at least one port disposed therein, the port being arranged to allow a member to pass through the wall portion; and at least one axially extending wall portion; and wherein the plug member comprises first and second axially spaced apart sealing portions each adapted to create a seal between the plug body and a wall of a substantially cylindrical bore in which a plug member is retained in use .

Preferably the transverse wall portion is provided with a plurality of ports therein, for allowing a plurality of members to pass therethrough .

In use, the at least one member may be one or more of : one or more rockbolt members ; a grout pipe ; and a breather pipe . Preferably the transverse wall portion is provided with at least one grout pipe port adapted to allow a member in the form of a grout pipe to pass through the lateral wall portion .

Preferably the transverse wall portion is provided with at least one breather pipe port adapted to allow a member in the form of a breather pipe to pass through the lateral wall portion .

Preferably the transverse wall portion is provided with at least one rockbolt port adapted to allow member in the form of a rockbolt member to pass through the transverse wall portion .

In one embodiment the transverse wall portion is provided with first and second rockbolt ports adapted to allow respective first and second rockbolt members to pass therethrough.

The transverse wall portion may be provided with third and/or subsequent rockbolt ports adapted to allow third and/or subsequent rockbolt members to pass therethrough . Preferably the one or more rockbolt ports are adapted to allow rockbolt members which are parts of cable bolts to pass therethrough. Preferably the axially extending wall portion comprises a generally tubular wall portion.

It should be appreciated that in this context "tubular" is not intended to imply that the axial length of the axially extending wall portion is necessarily greater than the transverse dimension of the tubular wall portion .

Preferably the axially extending wall portion is generally cylindrical . Preferably the axially extending wall portion depends generally perpendicular from the transverse wall portion.

Preferably the transverse cross sectional area defined by the axially extending wall portion is substantially equal in size to the area of the transverse wall portion.

Preferably at least one sealing portion is provided on the exterior of the axially extending wall portion .

Preferably at least one sealing portion comprises a flange or skirt projecting outwardly from the axially extending wall portion.

Preferably the first and second sealing portions are both provided on the axially extending wall portion .

Preferably the first and second sealing portions comprise axially spaced apart skirts or flanges . Preferably the first and second sealing portions are formed from a resilient material .

Preferably the plug member further comprises a third sealing portion for providing a seal between the plug body and a wall of a generally cylindrical bore . It will be appreciated that the generally cylindrical bore will typically be a cylindrical bore in rock, in an underground excavation, such as a rockbolt hole, but that the plug member could be utilized or adapted for use in other types of cylindrical bore, such as the cylindrical bore, or passage, which exists in some types of rockbolt.

Preferably the third sealing portion is axially spaced apart from each of the first and second sealing portions .

The plug member may comprise fourth and/or subsequent sealing portions , which may be external , peripheral sealing portions , and may be in the form of external skirts or flanges. The third, fourth and/or subsequent sealing portions may be formed from a resilient material . Preferably the sealing portions are adapted to support the plug body relative to the wall of said cylindrical bore . The sealing portions may act as strengtheners to enhance the stiffness of the plug body and provide resistance to distortion in use.

It will be appreciated that provision of axially spaced apart sealing portions for supporting and axially extending plug body relative to the wall of a cylindrical bore in which the plug member is retained effectively assists in maintaining the plug member stably in an orientation in which the axis of the plug member is parallel to the axis of the cylindrical bore . Furthermore, since the wall of the cylindrical bore may be unpredictably irregular provision of a plurality of sealing portions more reliably retains grout on one axial side of the plug member than would a single sealing portion . Preferably, the first and second sealing portions are integrally formed with the plug body.

Preferably, the transverse wall, axially extending wall portion and first and second sealing portions are formed integrally. Preferably, the plug member is formed by injection moulding .

Preferably, at least one of the ports comprises an aperture provided with at least one support sealing portion to provide a seal around a tube or bolt member passing through said port.

According to a second aspect of the present invention there is provided a method of manufacturing a plug member for retaining grout in a substantially cylindrical bore in underground excavations , the method comprising providing a mould apparatus for injection moulding said plug member, the mould apparatus comprising: a first mould wall portion for at least partially defining a transverse wall portion of the plug member which is adapted to act as a barrier to grout; at least two void formers for forming corresponding voids in said lateral wall portion of the plug member, said voids corresponding to ports provided in the lateral wall of the plug member to allow passage of members such as pipes and or bolts therethrough; wherein, at least one void former comprises a moveable void former , moveable between : an operating position, in which said void former is positioned to form a void in the transverse wall of a plug member so that the plug member is formed with a port corresponding to said void former; and a non-operating position, in which said void former is positioned so that it cannot form a void in the transverse wall portion of a plug member ; selecting whether said moveable void former is in the operating or non-operating position; and injection moulding a plug member using the mould apparatus, said plug member being manufactured with, or without, a port corresponding to the moveable void former depending on whether the moveable void former is selected to be in the operating or non-operating position, respectively . Preferably the operating position is a position in which the void former is present in the mould apparatus during manufacture of a plug member .

Preferably the non-operating position is a position in which the void former is removed from the mould apparatus during manufacture of a plug member.

Preferably the mould apparatus is provided with at least three void formers for providing voids in the — fi —

transverse wall portion of a plug being manufactured.

Preferably the mould apparatus is provided with at least four void formers for providing voids in the transverse wall portion of a plug being manufactured. Preferably, the at least one moveable void former comprises an insert member which can be secured in the mould or removed from the mould.

The mould may comprise at least a first mould part and a second mould part. The first and second mould parts may be adapted to be assembled to at least partially define a cavity corresponding to a shape of a plug member to be produced. The first and second mould parts may be adapted to be separated to allow removal of a moulded plug member produced therein. The first mould wall portion may be part of the first mould part. One or more moveable void formers may be securable to the first mould part. One or more moveable void formers may be securable to the first wall portion. One or more moveable void formers may be securable to the second mould part . Preferably the step of manufacturing a plug member comprises introducing a polymer material into the mould.

Preferably the step of moulding the plug member comprises injection moulding the plug member.

In one mode of use of the method for manufacturing a plug member, when the moveable void former is in the non- operating position the plug member is manufactured with no port in the position where a port corresponding to the moveable void former would have been provided if the moveable void former had been in its operating position. In this mode of use, a blanking insert may be provided in the mould apparatus when the moveable void former is in the non-operating position . The blanking insert may provide a desired shape to the region of the transverse wall where a port corresponding to the moveable void former would have been provided if the moveable void former had been in its operating position.

It will be appreciated that in one mode the manufacturing method allows a single mould to be provided which can manufacture either plug members with four ports in the transverse wall portion (i.e. two ports for bolt members, a grout port and a breather pipe port) or three ports in the transverse wall portions , providing a transverse wall portion in which only one port for a bolt member is provided. The option of providing either of these types of plug members is extremely commercially useful as some types of bolting system require two bolt members and some types require only one bolt member to extend through the plug. The manufacturing method in accordance with this mode allows dedicated plug members for each of these two types of bolting system to be provided with minimal increase in expense. It should be noted that it may be undesirable to have a plug member with unused ports since this may allow undesirable passage of grout through the transverse wall portion of the plug member. Further, it will be appreciated that the number of ports need not be limited to three or four, and that use of more than one moveable void former could allow the number of ports to be varied by more than one .

In one mode of use of the method for manufacturing a plug member, when a first moveable void former is in the non-operating position an alternative moveable void former of different dimensions , for forming a corresponding port Of different size and/or shape to a port corresponding to the first void former, is provided in an operating position .

In this mode of use, the step of selecting whether the moveable void former is in the operating or non- operating position may comprise selecting which of several void formers is provided in an operating position. This can effectively allow selection of the size and/or shape of a port formed in the transverse wall of the plug member.

It will be appreciated that in such a mode the manufacturing method allows a single mould to be provided which can manufacture plug members differently shaped and/or sized ports in the transverse wall portion. The option of providing different plug members with differently sized and/or shaped ports can be extremely commercially useful as different bolting and/or grouting/breather arrangements require differently sized ports . The manufacturing method in accordance with this mode allows dedicated plug members to be provided for different bolting and/or grouting/breather arrangements which can facilitate use of the plug members and improve fitting and sealing to the bolting and/or grouting/breather members .

Preferably the method comprises selecting one of a plurality of peripheral-seal defining members for use in the mould when moulding a plug member.

Preferably each peripheral-seal defining member is adapted to at least partially define a peripheral-seal portion which extends around the external perimeter of a plug member . Preferably different peripheral-seal defining members of the plurality of peripheral-seal defining members allow seals of different shapes, lateral sizes and/or stiffness to be provided on the manufactured plug member .

According to a third aspect of the present invention there is provided a method of manufacturing a plug for retaining grout in a substantially cylindrical bore in underground excavations , the method comprising providing a mould apparatus for injection moulding said plug member, the mould apparatus comprising: a first mould wall portion for at least partially defining a transverse wall portion of the plug member which is adapted to act as a barrier to grout, the first mould wall portion being provided with at least two void forming portions for forming voids in said lateral wall portion of the plug member, said voids corresponding to ports provided in the lateral wall of the plug member to allow passage of pipes and/or bolts therethrough; — Q —

at least one first peripheral-seal defining member adapted to at least partially define a first configuration of external peripheral seal of a plug member in order to determine the lateral size and/or shape of the peripheral seal; and at least one second peripheral-seal defining member adapted to at least partially define a second configuration of external peripheral seal of a plug member, said second configuration comprising a different lateral size and/or shape to the first configuration; and wherein either the first or the second seal defining member (s) can be utilized in order to provide a plug member with a corresponding configuration of external peripheral seal ; selecting whether said first or second seal defining member (s) is utilized for a plug member to be moulded; and injection moulding a plug member utilizing the selected seal defining member (s) said plug member being manufactured with an external peripheral seal with a lateral side and/or thickness corresponding to the selection made .

Preferably each of the first or second seal defining member (s) comprises a substantially annular seal defining member . It will be appreciated that the manufacturing method of the first aspect allows a single mould to be provided which can manufacture plug members with differently shaped and or sized peripheral seals . The option of providing different plug members with differently sized and/or shaped peripheral seals can be commercially useful as differently sized bores may require different lateral sizes of seal.

According to a fourth aspect of the present invention there is provided plug member made by a method in accordance with at least one of the second and third aspects .

According to a fourth aspect of the present invention there is provided a method of plugging a substantially cylindrical bore in underground excavations so that grout can be retained in the plugged bore, the method comprising: providing a plug member which has at least three ports therein; passing a bolt member through a first one of the ports of the plug member; passing a grout pipe through a second one of the ports in the plug member; passing a breather pipe through a third one of the ports in the plug member; applying a high viscosity grout to the plug member prior to insertion of the plug member into the cylindrical bore; and inserting the plug member, with viscous grout applied thereto, at least partially into the cylindrical bore so that the plug member is retained in the bore and so that the viscous grout previously applied to the plug member provides a seal or enhances a seal between the plug member and the wall of the cylindrical bore .

The bore can then be filled with grout via the grout pipe, noting that such grout will have a considerably lower viscosity than the high viscosity grout. It will be appreciated that features described in relation to one or more of the above aspects may be applicable to, or beneficially incorporated into, other aspects .

Brief Description of the Drawings

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which :

Fig. 1 is a diagrammatic lower perspective view of a plug member described in WO2005/045194 ;

Fig. 2 is a diagrammatic side view of the plug member shown in Fig . 1 ; Fig. 3 is a diagrammatic top plan view of the plug member shown in Figures 1 and 2 ;

Fig. 4 is a side elevation of an embodiment of a plug member in accordance with the present invention; Fig . 5 is a top plan view of an embodiment of Fig . 4 ;

Fig. 6 is a top view of the variation of the plug member of Figs . 4 and 5 in which apertures or ports which are different in size to those shown in Fig. 5 are provided; Fig. 7 is a top plan view of a further variation in which three rather than four ports are provided;

Fig. 8 is an axial cross-section on VII-VII of Fig. 5;

Fig. 8a is an axial cross-section, analogous to the cross section of Fig. 8, of an alternative embodiment;

Fig. 9 is a schematic part sectional view of part of an injection moulding apparatus for use in a method in accordance with the present invention;

Fig. 10 is a schematic view corresponding generally to Fig. 9 but with the moulding apparatus set up for manufacture of a different variant of plug member;

Fig. 11A is a cross-sectional view of a moveable insert element of Fig . 9 ;

Fig. 11B is a vertical cross-sectional view of a part of the injection moulding apparatus adapted to receive the insert of Fig. HA;

Fig. HC is a schematic cross-sectional representation of the insert of Fig. HA positioned for use in the injection moulding apparatus; Fig. 12A is a cross-section of an alternative insert for use in the injection moulding apparatus of Figs. 9 and 10, for use in creating a port of a different size to that created by the insert of Fig. HA;

Fig. 12B is a cross-sectional view of the insert of Fig. 12A positioned of use;

Fig. 13A is a cross-sectional view of a further insert for injection moulding apparatus for use when a port at a corresponding position is not required;

Fig. 13B is a cross-sectional illustration of the insert of Fig. 13A positioned for use;

Fig. 14A is a diagrammatic cross-sectional view of an embodiment of injection moulding apparatus, similar to that partially illustrated in Figs. 9 and 10, showing use of inserts for forming two ports ;

Fig. 14B is a perspective view of part of the injection moulding apparatus of Fig. 14A; Fig. 15A is a diagrammatic cross-sectional view of injection moulding apparatus of Fig.s 14A and 14B, but showing a different insert arrangement including one insert for forming a port and one blanking insert; Fig. 15B is a perspective view of part of the injection moulding apparatus of Fig. 15A;

Fig. 16A is a diagrammatic cross-sectional view of injection moulding apparatus for forming plug members of the type shown in Fig . s 1 to 3 , showing two removable and replaceable inserts ; Fig.s 16B and 16C are perspective views of parts of the injection moulding apparatus of Fig. 16A; and

Figs. 17 to 20 are schematic cross-sectional views of a bore illustrating a plugging method in accordance with an embodiment of the present invention . . . .

Description of Embodiments

Referring to Figs. 1 to 3, the plug member 10 described in WO2005/045194 is presented by way of background and in order to facilitate description of the following embodiments of the present invention.

The plug member 10 includes a cap portion 20 comprising a short cylindrical portion 22 provided with a substantially flat wall 24 laterally extending across a circumferential rim 21 of a leading end 9 of the short cylindrical portion 22 and a means to wedge the cap portion 20 within a cylindrical bore. It is envisaged that the cylindrical bore will be a rockbolt hole, a cable bolt hole, or a cylindrical bore of a rockbolt commonly known as a split set bolt.

Preferably, the short cylindrical portion 22 has a diameter marginally smaller than a diameter of a cylindrical bore, typically ranging from 30-90 mm, such that an outer circumferential surface 29 of the short cylindrical portion is substantially contiguous with or adjacent to a circumferential surface of the bore when the plug member 10 is placed inside the bore. The means to wedge the cap portion within the bore preferably comprises a plurality of downwardly inclined flaps 26 depending from a circumferential rim 23 of an opposing end 7 of the cylindrical portion 22. The downwardly inclined flaps 26 are substantially rectangularly shaped and are equidistantly and equiangularly spaced around the circumferential rim 23 of the short cylindrical portion 22 such that a gap 28 between adjacent flaps 26 is substantially triangularly shaped. The gaps 28 may be replaced by a thin triangularly shaped membrane extending between adjacent flaps 26. Each flap 26 is provided with an upwardly tilted flange 25 depending from its lowermost edge 27.

The plug member 10 also includes a pair of spaced cylindrical walls 30 depending substantially perpendicularly from the flat wall 24 of the cap portion

20. Preferably, the cylindrical walls 30 are disposed such that the cylindrical walls 30 are disposed adjacent to the circumferential rim 21 of the cylindrical portion 22. The spaced cylindrical walls 30 are interconnected by a web member 31, and are further stabilised with respect to the cap portion 20 by provision of respective ribs 33 interconnecting the cylindrical walls 30 to the cap portion 20. In use, the pair of spaced cylindrical walls are arranged to receive a pair of cable bolts . A first portion 32a of the flat wall 24 enclosed by the cylindrical walls 30 is provided with a plurality of linear radial grooves 34 extending from a central axis of the first portion 32a and defining a plurality of triangular portions 36. In use, the first portion 32a is torn, by insertion of part of a rockbolt, along at least some of the linear grooves 34 such that the triangular portions 36 form and behave as flexible flaps.

A second portion 32b of the flat wall 24 enclosed by the cylindrical wall 30 is a circular aperture provided with a plurality of inwardly disposed serrations 35. The diameter of the aperture is selected such that the inwardly disposed serrations abut an outer circumferential surface of the cable bolt received therein.

The plug member 10 also includes a first circular indentation 40 in the flat wall 24. A third portion 42 of the flat wall 24 enclosed by. the first circular indentation 40 is provided with a plurality of linear radial grooves 44 extending, from a central axis of the . first circular indentation 40. The grooves 44 are equidistantly and equiangularly spaced around the first circular indentation 40 such that the first circular indentation 40 is segmented- into substantially equal sized triangular portions 46. In use,. the third portion 42 is perforated along the grooves 44 such that the triangular portions 46 form and behave as flexible flaps.

The plug member 10 further includes a second circular indentation 50 in the flat wall 24. A fourth portion 52 of the flat wall 24 enclosed by the second circular indentation 50 is provided with a plurality of linear radial grooves 54 extending from a central axis of the second circular indentation 50. The grooves 54 are equidistantly and equiangularly spaced around the second circular indentation 50 such that the second circular indentation 50 is segmented into substantially equal sized triangular portions 56. The second circular indentation 50 is also provided with a plurality of arc-shaped grooves disposed around the second circular indentation 50 such that the arc-shaped grooves are bisected by the linear radial grooves 54. In use, the fourth portion 52 is perforated along the grooves 54 and the arc shaped grooves such that the triangular portions 56 form and behave as flexible flaps. Typically, the triangular portions 56 are more flexible than the triangular portions 36, 46. In use, the triangular portions 36, 46, 56 are movable between an open position and a closed position. The inherent tendency of the triangular portions 36, 46, 56 is towards the closed position. When a hose or cable bolt is received in the first portion 32a or the first or second circular indentations 40,50 in the cap portion 22, the triangular portions 36,46, 56 are urged to move to the open position wherein the triangular portions 36, 46, 56 engage with an outer surface of the hose or cable bolt received therein. In this way, the first portion 32a, and the first and second circular, indentations 40, 50 are adapted for use as self-closing ports in the cap portion 22.

Preferably, the plug member 10 is formed from a resilient plastics material, a semi rigid plastics material, or a natural or synthetic rubber material.

In use, the short cylindrical portion 22 of the cap portion 20 is placed inside the entrance of a cable bolt hole or rockbolt hole or inside a rockbolt of about 30-90 mm in diameter, such that the flat wall 24 is disposed as a leading face in the hole and a portion of the cylindrical walls 30 extends from the entrance. In this arrangement, the outer circumferential surface 29 of the short cylindrical portion 22 is substantially contiguous with or adjacent to the circumferential surface of the hole. Upon insertion of the short cylindrical portion 22, the flaps 26 depending from the circumferential rim 23 of the short cylindrical portion 22 will be caused to flex towards the short cylindrical portion 22 to a greater or lesser degree, depending on the diameter of the hole, thereby minimising the gaps 28 between adjacent flaps 26 from which grout may leak. The inherent tendency of the flaps 26 is to resist any inward inclination towards the cylindrical portion 22, and thus the flaps 26 exert a circumferential force on the inner surface of the hole which enables the plug member 10 to remain firmly wedged within the hole despite back pressure exerted by the grout on the flat wall 24 of the cylindrical portion 22.

One or more cable tails with one or more grout tubes optionally attached thereto can be readily inserted through the cylindrical walls 30 of the plug member 10 by piercing the grooves 34 found in the first portion 32a of the flat wall 24 and/or engaging the serrations 35 of the second portion 32b in a friction fit. The triangular flaps 36 tightly enclose around the cables and tubes, minimizing any gaps arising therebetween. The triangular flaps 36 also provide a frictional force between the cables , and the plug member 10 to assist in maintaining the plug member 10 in the hole during the grouting process.

The cylindrical walls 30 that depend around the periphery of the first and second portions 32a, and 32b assist in the orientation of the cable/grout tube combination away from the circumferential surface of the hole, thereby enabling the grout to completely fill the void between the cable bolt and the circumferential surface of the hole .

The cylindrical walls 30 are also advantageously arranged to provide stability, stiffness, and minimise torsion of the plug member 10, so providing a gripping point for the plug member 10 as it is inserted into the hole or as the cables and tubes are inserted into the plug member 10. The cylindrical walls 30 may also be gripped as the plug member 10 is slid along one or more cable bolts .

A polyethylene hose or similar (known as a grout hose) is then inserted through the fourth portion 52 of the flat wall 24 by piercing the linear radial grooves 54, and grout is delivered into the hole . The resulting triangular flaps 56 closely grip the outer circumferential surface of the grout hose, however the flexibility of the flaps 56 allow the grout hose to be slid in and out of the hole. The flexibility of the triangular flaps 56 is such that the flaps 56 are arranged to close_.behind the grout hose to prevent excess grout from leaking from the plug member 10. The plug member 10 may remain in the entrance of the hole while the grout cures .

A breather tube or hose may also be inserted through the third portion 42 of the flat wall_.24 by being forced through the linear radial grooves 44. The resulting triangular flaps 46 closely grip, the outer circumferential surface of the breather tube. When the breather tube remains inside the hole alongside, the cable bolt, the flexibility of the triangular, flaps 46 is such that the flaps 46 are arranged to close tightly around the breather tube to prevent grout leaking from, the hole .. An improved plug member in accordance with an embodiment of the present invention is generally designated 110 and will be described with reference to the Figs. 4, 5 and 8. The plug member 110 has some similarities to plug member 10 as will be appreciated by the addressee.

The plug member 110 comprises a top portion 120 which has a lateral wall 124 extending laterally across a circumferential rim 121 of a leading end 109 of the plug member 110. The lateral wall 124 serves a similar function to the wall 24 of the plug member 10. Depending generally perpendicular from the lateral wall 24 is a generally cylindrical axial wall 131. The cylindrical axial wall 131 is considerably longer than the cylindrical portion 22 of plug member 10, and is provided with a plurality of axially spaced apart externally projecting circumferential skirts, in this embodiment first, second and third circumferential skirts 125, 126, 127, respectively. These provide sealing portions each adapted to create a seal between the plug member 110 and a wall of a substantially cylindrical bore in which the plug member 110 is to be retained in use. Provision of a plurality of axially spaced apart sealing portions can assist in maintaining the longitudinal axis of the plug member 110 parallel to the longitudinal axis of the cylindrical bore, that is, it can assist in stably locating the plug member 110. Furthermore, provision of a series of sealing portions can assist in reducing passage of grout between the plug member 110 and the wall of the cylindrical bore, since it provides a number of sequential barriers to passage of grout.

Furthermore, the nature of the cylindrical bores in underground excavations for which the plug member 110 is intended for use is such that the wall of the cylindrical bore may include irregularities . The provision of a number of sealing portions helps to mitigate the potential problem of a plug member with a single sealing portion having the sealing portion located at a part of the cylindrical bore where the wall is irregular which could render a single sealing member ineffective .

It will be appreciated that, at least in the illustrated embodiment, each of the circumferential skirts is radially smaller towards the leading end 109 of the plug member and increases in radial size as distance from the leading end 109 increases. This configuration can provide at least a first (leading) circumferential skirt 125 which can assist in guiding the plug member into a generally cylindrical bore.

In this embodiment the axial length of the generally cylindrical axial wall 131 is of the same order of magnitude as diameter of the plug member 110, and is preferably greater than the diameter of the plug member 110. More specifically, in this particular embodiment the axial length of the generally cylindrical axial wall 131 is between about one and about two times the diameter of the plug member .

The lateral wall 124 is provided with a plurality of ports therein.

A circular closed portion 132 of the lateral wall 124 is a reduced thickness portion of the lateral wall and is provided with a plurality of diametric grooves 134 intersecting at the centre of the circular closed portion 132 and dividing it into a plurality of generally triangular portions 133. The circular closed portion 132 may be regarded as corresponding generally to the first portion 32a of the plug member 10.

A first open portion 135 of the lateral wall 124 provides a first circular aperture 136 which is defined by a first annular sealing portion 137 of the lateral wall 124. The first annular sealing portion 137 is a reduced thickness portion of the lateral wall (and is lesser in thickness than the triangular portions 133) .

The closed portion 132 and first open portion 135 may thus be regarded as providing respective ports and are for allowing respective first and second cable bolt portions of a pair of cable bolts to extend through the lateral wall 124.

Respective second and third open portions 140, 150 of the lateral wall 124 provide respective second and third circular apertures 146, 156 defined respectively by second and third annular sealing portions 147, 157 of the lateral wall 124.

The second and third open portions 140, 150 may be regarded as providing respective ports for allowing a grout hose and a breather hose to extend through the lateral wall 124.

In this embodiment the annular sealing portions 137, 147, 157 have a thickness of approximately lmm. This allows them adequate flexibility to form a good seal against a suitably sized circular-cross section object which extends through the corresponding aperture 136, 146, 156.

With reference to Figs . 5 and 8 the ports which are in the form of second and third open portions 140, 150 will be described in more detail . The description is with particular reference to the third open portion 150, and it will be appreciated that the second open portion has similar structure .

The third open portion comprises a diametrically greater first annular region 152 which is a slightly reduced thickness portion of the lateral wall 124, and which may be regarded as defining a slightly recessed circular portion. The first annular region 152 terminates at its radially inner edge at an annular tapering region 154 which reduces in thickness- ±owards its .radially inner extreme, where it terminates at the annular sealing portion 157. The radial sizes of the first annular region 152, annular tapering region 154 and sealing portion 157 can be preselected to be appropriate for the size of aperture (eg aperture 156) as will be discussed hereafter. This structure, which provides a progressively thicker (and therefore also stiffer) lateral wall with increasing distance from the aperture 157 assists provision of an effective seal .

(It will be appreciated that although in this embodiment some of the ports are provided by apertures 136, 146, 156 referred to as being provided in 'open' portions, in alternative embodiments they can, if desired, be provided in other forms , eg in the same form as the form of circular closed portion 132 of the lateral wall 124.) The interior of the plug member 110 also includes a pair of spaced cylindrical walls 130. One of the spaced cylindrical walls 130 is shown in the sectional view of Fig. 8. The spaced cylindrical walls 130 depend substantially perpendicularly from the lateral wall 124, and are associated with the circular closed portion 132 and first open portion 135. The spaced cylindrical walls 130 correspond to the spaced cylindrical walls 30 of the plug member 10, and are adapted to receive respective first and second cable bolt portions of a pair of cable bolts which extend through the closed portion 132 and first open portion 135 of the lateral wall 124. The spaced cylindrical walls 130 are interconnected by a web member 130a to enhance overall stiffness and may be connected to an adjacent part of the generally cylindrical axial wall 131 if desired. Further, if desired, additional cylindrical walls may be provided and associated with one or more of the other ports (ie, in this embodiment, with the second and third open portions 140, 150) in order to receive the grout hose and breather hose and perhaps assist insertion by guiding these to the other ports (second and third open portions 140, 150) . In a variation the web member may be omitted and cylindrical walls of similar structure and function to the spaced cylindrical walls 130 may- be stiffened by direct connection to each other and/or to the axial cylindrical wall 131. It will also be appreciated that the spaced cylindrical walls (or their analogues) may be of any desired length. Although not shown in the drawings the internal (bottom, as illustrated) surface of the lateral wall may be provided with countersunk regions or other guides to assist insertion of the grout hose and breather tube into one or both of the apertures 146, 156.

The circumferential skirts 125, 126, 127 are preferably formed integrally with the rest of the plug member 110, for example by injection cavity moulding, but if desired one or more (eg the second and third) circumferential skirts could be attached after forming of the rest of the plug member 110.

The generally cylindrical axial wall 131 has a slightly flared wall portion 131a at the end distal from the leading end 109 (although it does not extend radially further from the axis of the plug member than do the circumferential skirts) . The internal diameter of the flared wall portion 131a is slightly greater than the external diameter of the rim 121 > enabling two or more plug members 110 to be stably stacked in use in order to provide what is in effect a longer plug, with more sealing portions, if desired and/or required by the circumstances. Using two or more plug members in this way can further enhance sealing (and thus grout retention) and also further enhance the resistance to axial movement provided by engagement of the circumferential skirts with the wall of the cylindrical bore, since the amount of contact is increased.

Fig. 6 is a top view of a variation, generally designated 210 of the plug member of Figs. 5 and 8 (although the side elevation would be identical to that in Fig. 4) . In the plug member 210, apertures 246, 256 of second and third open portions 240, 250 are larger in diameter than corresponding apertures 146, 156 shown in Fig. 5. Consequently, second open portion 240 is provided with a first annular region 242 which is radially smaller than first annular region 142 of second open portion 142, and third open portion 252 is provided with an annular tapering region 254 which is radially smaller than tapering region 154. (Of course, it would also or alternatively be possible to differ the sizes of annular tapering region 244 of second open portion 240 and first annular region 252 of third open portion 252.) The radial sizes of sealing portions 247, 257 are maintained at a radial size which has been found to provide effective sealing, which in prototypes has been found to be about 1- 1.5mm (although this may vary depending on the flexibility of material used) .

Apertures 246, 256 are different in size to each other to provide sealed receipt of a grout hose with a different diameter to the breather hose .

Fig. 7 is a top plan view of a further variation 310 in which three rather than four ports are provided, so that a planar region 336 of the lateral wall is provided in a position corresponding to where the plug member 110 has the first open portion. This is a variation which may be desirable for use with rockbolts which have a single elongate bolt element.

It will be appreciated that many variations are possible. It is, for example, useful to be able to provide a range of plug members having different radial dimension of the circumferential skirts, in order to allow effective use in cylindrical bores of different diameters, by selection of a plug member with a suitably dimensioned circumferential skirt. A further variation is to provide the lateral wall at the trailing, rather than the leading, end of the plug member . An example of such a plug member 110a is illustrated in Fig. 8a which is a schematic axial cross section illustrating. an example of such an alternative form of plug member. In Fig. 8a, lateral wall 124a is illustrated as being at the bottom of the plug member HOa. A plug member . in accordance with, such a variation could, for example, be structured similarly to the plug member 110, but have the skirts, eg skirt 126a, oriented in the opposite axial direction (relative to the lateral wall) to facilitate insertion of the plug into a bore, with the end at which the lateral wall is located being the trailing end. However, if a flared wall portion is provided in order to facilitate ^λstacking' of plug members, it is considered convenient that it be at the trailing end of the plug member (not least, to assist in avoiding undesirable interference between the flared wall portion and the wall of the cylindrical bore during insertion of the plug member) . Such a flared wall portion 131b, is illustrated in Fig. 8a, and is close to the lateral wall 150a. It will also be appreciated that this embodiment, as illustrated, provides interior spaced cylindrical wall portions 130b, and web member 130c, which extend substantially the entire length of the plug member HOa.

It should also be appreciated that the lateral wall may be provided at any desired axial position, and that if desired more than one lateral wall may be provided. Further, it will be appreciated that the wall portion extending in the transverse direction (exemplified by, eg, the lateral wall 124) need not necessarily be provided in the form of a substantially planar wall provided in a transverse plane of the plug member (although this is convenient, since it is convenient to have the members which extend through the port arranged substantially parallel to the axis of the bore, and to pass substantially perpendicularly through the wall portion) .

Pigs . 9 to 13B illustrate schematically an injection moulding apparatus 400 which facilitates variations of port size, number of ports and skirt size without incurring the expense of requiring separate moulds for each variant.

As illustrated in Fig. 9 the moulding apparatus 400 comprises a cavity end part 410 with a generally planar surface against which lateral wall (eg 124) of a plug member is formed. Provided on the cavity end part 410 are four inserts which provide voids in the moulded plug member corresponding to the ports . A first insert 432 corresponds to a closed portion (eg 132) and second, third and fourth inserts 435, 440, 450 correspond to first, second and third open portions (eg 135, 140, 150, respectively) . It will be appreciated that the inserts have surfaces which correspond in shape to the inverse of the port being formed.

The inserts 432, 435, 440, 450 are removably attached to the cavity end part 410, and may be replaced by differently shaped and/or dimensioned inserts in order to result in correspondingly differently shaped and/or dimensioned ports. Furthermore, one or more of the inserts may be replaced by a blanking insert (437 in Fig. 10) which has a surface which does not project far from the surface of the cavity end part 410 resulting in no port being formed at the corresponding location on the plug member (corresponding to, for example, the planar region 336 of plug member 310 of Fig. 7) . As illustrated in Fig. 10, the blanking insert 437 is, in use, generally coplanar with the surface of the cavity end part 410.

The moulding apparatus further comprises an annular insert 425 which extends around the cavity end part 410 and against which a first circumferential skirt (eg 125) is formed. The annular insert 425 has an inclined circular surface 426 against which the upper (as illustrated in Fig. 4) surface of the upper circumferential skirt (eg 125) is formed. The angle and position of the inclined circular surface 426 and the corresponding size and shape of the cavity formed between the inclined circular surface 426 and one or more other parts (not shown) of the moulding apparatus determine the size and shape of the upper circumferential skirt (eg

125) . The annular insert 425 is removably located in the moulding apparatus and may be replaced by an alternative annular insert 428 (see Fig. 10) with a differently sized and shaped inclined circular surface 429. An annular cavity portion 421 corresponds to the upstanding rim (eg 121) of a plug member.

Fig. 10 is a schematic view corresponding generally to Fig. 9 but with the moulding apparatus set up for manufacture of a different variant of plug member. The second insert 435 has been replaced by blanking insert 437 to provide a planar surface where the insert 435 in the configuration of Fig . 9 would produce a port . The annular insert 425 has been removed and replaced by alternative annular insert 428 which has an inclined circular surface 429 which is less steep than the inclined circular surface 426 and which extends further from the cavity end part, in order to provide a radially larger peripheral skirt . It will be appreciated that the apparatus parts illustrated in Fig. 9 will, in use, interact with one or more other mould parts in order to provide a cavity of desired dimensions, shape and configuration into which a material (such as a suitable plastic) can be introduced in order to form a plug member with desired dimensions , shape and configuration. In one embodiment the apparatus parts illustrated in Fig. 9 are, in use, enclosed within a mould outer 411, illustrated schematically in Fig. 10. It will also be appreciated that one or more inserts may be removably provided on the one or more other mould parts , rather than the cavity end part, if desired.

Fig. HA is a cross-sectional view of a removable insert 440 of Fig. 9. The insert 440 has a surface which comprises a circular distal portion 441 which defines an aperture (eg 146) of a port in a plug member, an annular inclined surface 442 against which an upper surface of an annular tapering region (eg 144) of a port is formed, and an annular planar surface 443, against which an upper surface of a first annular region (eg 142) is formed. The insert 440 also has a stem 444 (which may be threaded or secureable in an alternative manner) for removable attachment to the cavity end part 410.

Fig. HB is a vertical cross-sectional view of a part of the cavity end part 410 which receives the insert 440. The cavity end part includes a receiving hole for removably receiving and securing the stem 444 therein, and a circular recess 412 for seating the main body part of the insert 440 Fig. HC is a schematic cross-sectional representation of the insert 440 of Fig. HA positioned for use, releasably secured to the cavity end part 410. It will be appreciated that the shape of the part of insert 440 which is proud of the cavity end part corresponds to the shape of the second open portions 140, as illustrated in Fig. 8. .

Fig. 12A is a cross-section of an alternative insert 445, for use in creating a port of a different size and shape to that created by insert 440. It will be appreciated that insert 445 will provide a port with a smaller aperture and a radially larger first annular region than will insert 440.

Fig. 12B is a cross-sectional view of the insert 445 of Fig. 12A positioned for use, releasably secured to the cavity end part 410.

Fig. 13A is a cross-sectional view of the blanking insert 437. Fig. 13B illustrates the blanking insert 437 positioned for use, releasably secured to the cavity end part 410. It will be appreciated that in this embodiment that blanking insert 437 is seated in the recess so that no part of the blanking insert 437 stands proud of the cavity end part 410 (although in alternative embodiments the blanking insert could stand somewhat proud of the cavity end part, provided that it interacts with other mould parts such that no port results from the resulting cavity shape . In use, an operator can select and' position suitable inserts, eg 440, 445, 437 in order to obtain a desired port configuration, and select and position a suitable annular insert, eg 425, 428 to obtain a desired skirt size, shape and thickness (and hence a desired stiffness) , in plug members moulded by the apparatus 400. When a desired number of that variant of plug member has been moulded, the operator can change one or more inserts and/or the annular insert to easily and economically manufacture a different variant . Fig. 14A is a diagrammatic cross-sectional view of injection moulding apparatus, suitable for forming plug members similar to those illustrated in 4 to 8A and variants thereof. The moulding apparatus comprises a first mould part 460 and a second mould part 480 which is moveable relative to the first mould part 460 in a manner which will be understood by those familiar with conventional two-part injection moulding apparatus. Similarities of the injection moulding apparatus with conventional two-part injection moulding apparatus will not be described in detail. The first mould part 460 is generally analogous to the injection moulding apparatus 400 illustrated in Fig.s 9 and 10 (although it does not include a cylindrical casing as shown in Fig. 10), and similarities thereto will not, in general, be described, except in relation to the inserts provided. Fig. 14B is a perspective view of the first mould part 460. In the configuration of Fig.s 14A and 14B the first mould part 460 is provided with a cavity end part 461 to which are mounted first and second inserts 462, 463 (analogous to inserts 432, 435 of Fig. 9) for providing ports (in a plug member made using the moulding apparatus) which can accommodate cable bolt portions extending therethrough. It will be appreciated that at least one of the inserts 462, 463 can be removed and replaced with a different insert to provide a variant plug member. The first mould part 460 is also provided with an annular insert (analogous to annular inserts 428, 429 of Fig.s 9 and 10) shaped and dimensioned to assist in forming a desired circumferential skirt of a plug member .

The second mould part 480 comprises a casing 480a defining an internal cavity (into which plastic can be injected) and two internal cylindrical rods 481, 482.

Other parts of the second mould part 480 will be evident to those familiar with conventional two-part injection moulding apparatus and will not be described in detail . As illustrated, the internal cylindrical rods 481, 482 abut the first and second inserts 462, 463 to provide ports which are contiguous with the bores of cylindrical tubes (corresponding to spaced cylindrical walls 130, 130a) . It will be appreciated that the internal cylindrical rods 481, 482 will form voids in the injected plastic which correspond to the bores, and that the plastic immediately surrounding the internal cylindrical rods 481, 482 will form the spaced cylindrical walls.

When the first and second mould parts are assembled together, as illustrated in Fig. 14A, the cavity provided by the mould part will correspond to the shape of the plug member to be formed. The first and second mould parts 460, 480 thus together provide a cavity which has a number of regions corresponding to parts of a plug member to be formed. In this embodiment the moulding apparatus provides: a generally rectangular cavity region 483 which corresponds to an internal web member (eg 130a) of a plug member; a generally cylindrical cavity region 484 which corresponds to a generally cylindrical axial wall (eg 131) of a plug member; an annular tapered cavity region 485 which corresponds to a circumferential skirt (eg 125) of a plug member; and a generally disc shaped cavity region 486, which corresponds to a lateral wall (eg 124) of a plug member. The inserts 462, 463 protrude into the generally disc shaped cavity region 486 to provide ports in a lateral wall of a plug member being moulded.

It will be appreciated that replacing the inserts 462, 463, 468 with alternative inserts will allow variants of plug members to be moulded.

Pig. s 15A and 15B correspond to Fig.s 14A and 14B, except that one of the port forming inserts 462 is replaced by a blanking insert 464. The blanking insert 464 does not contact the second mould part 480, and consequently the configuration of Fig.s 15A and 15B provides one less port in a corresponding plug member than does the configuration of Fig.s 14A and 14B. That is, an additional cavity region 487 is provided in the configuration of Fig.s 15A and 15B which is not provided in the configuration of Fig.s 14A and 14B (although this additional cavity region 487 may be considered part of the generally disc shaped cavity region 486. Of course, alternative or additional inserts may be changed (including the annular insert, eg 468) to provide desired variants of plug member . This allows many variants to be manufactured without the expense of providing a large number of different moulds , one corresponding to each variant . It will be appreciated that embodiments of the moulding apparatus and method disclosed herein are applicable to plug members of the type illustrated in, and described with reference to, Figs. 1 to 3 , to plug members of the type illustrated in, and described with reference to, Figs. 4 to 8, and to many variations and alternative types of plug member .

Fig. 16A is a diagrammatic cross-sectional view of injection moulding apparatus 490 for forming plug members of the type shown in Fig.s 1 to 3. The apparatus 490 of Fig. 16A has many similarities to the moulding apparatus of Fig.s 14A to 15B, and only the differences will be described in detail. The apparatus 490 comprises a first mould part 491 and a second mould part 492. Fig.s 16B and 16C are, respectively, perspective views of the first mould part 491 and second mould part 492.

A first insert 493, suitable for providing a breather tube port in a plug member, is attached to the first mould part 491 and a second insert 494, suitable for providing a grout tube port, is attached to the second mould part 492. One or both of the inserts 493, 494 may be replaced by alternative inserts (not shown) to change the corresponding port configuration. The apparatus 490 is also provided with an annular insert 495 shaped and dimensioned to assist in forming a desired circumferential skirt of a plug member (and, like the annular insert 468 of Fig.s 14A to 15B) can be replaced by an alternative annular insert in order to mould a plug member with a correspondingly different skirt. It will be appreciated that (in various embodiments) inserts other than annular inserts can be used to define the shape of circumferential skirts/seals: for example, a number of insert sections which together form a generally annular shape could be used. It will be appreciated that since the plug member to be moulded does not include the external generally cylindrical axial wall 131, no cavity portion corresponding to such a wall (such as generally cylindrical cavity region 484) is provided. Cavity regions corresponding to spaced cylindrical walls 30 of plug member 10 may be provided, but are not visible in Fig. 16A due to the diametric cross section used: such cavity regions would be visible in a perpendicular diametric cross section and are visible, and designated by reference numeral 496 in Fig. 16C.

The disclosure herein also relates to a method for plugging a bore. Although the plug members disclosed herein are useful, it has been found that under some conditions, such as when the inner surface of the bore hole is unduly irregular, the seal between the plug member and the bore surface is not adequate to prevent an undesirable amount of grout leakage past the plug member.

A method for plugging a bore which addresses this problem will be disclosed with reference to Figs. 17 to 20 which are schematic cross-sectional views of a bore hole illustrating a plugging method in accordance with an embodiment of the present invention .

Fig. 17 illustrates schematically- a generally cylindrical bore hole 500 in a body of rock 501, with a rockbolt 520 attached at a distal end thereof. It is desired to fill the bore hole 500 with grout, and thus there is a need to plug the bore hole 500 in a manner that allows grout to be inserted and retains the grout in the bore hole. For simplicity a single rockbolt 520 is illustrated, but it will be appreciated that this should be taken to represent any type of rockbolt, including a cable bolt or cable bolt pair.

As illustrated in Fig. 18 a plug member 510, which may be of the type illustrated in Figs. 4 to 8 (and which could be of the type illustrated in Figs. 1 to 3) is introduced onto the rock bolt 520 by having the rockbolt pass therethrough. A breather hose 530 and a grout hose 540 are also passed through the plug member.

It is determined that adequate sealed retention of grout introduced into the borehole 500 might not be obtained by using the plug member alone (owing to irregularities in the bore hole surface, or other factors) .

As illustrated in Fig. 19 a viscous sealing material 550 is introduced onto the top, and preferably at least some laterally extending seal portions , of the plug member 510. The viscous sealing material is preferably a viscous cementitious grout, although other materials could be used. At lease some of the viscous sealing material is preferably applied as a wad to the top of the plug member 510.

As illustrated in Fig. 20 the plug member 510 is then pushed into the bore hole 500 by being slid up the rockbolt. At least some of the exterior of the plug member 510 engages the inner surface of the bore hole 500, and some of the viscous sealing material i550 is preferably located on the lateral sides of the plug member 510. The viscous sealing material helps to seal the plug member in the proximal end of the bore hole .

The bore hole can then be filled with, grout by pumping it through the grout hose. It will be appreciated that the viscous sealing material is considerably more viscous than the pumped grout.

Modifications and improvements may be incorporated without departing from the scope of the invention . It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A plug member for retaining grout in a substantially cylindrical bore in underground excavations, the plug member having an axis which in use is aligned substantially parallel to the axis of a cylindrical bore in which the plug member is, in use, retained, the plug member comprising: a plug body comprising: at least one wall portion extending in the transverse direction relative to the axis and adapted to act as a barrier to grout, the at least one transverse wall portion having at least one port disposed therein, the port being arranged to allow a member to pass through the wall portion; and at least one axially extending wall portion; and wherein the plug member comprises first and second axially spaced apart sealing portions each adapted to create a seal between the plug body and a wall of a substantially cylindrical bore in which a plug member is retained in use .

2. A plug member as claimed in claim 1 wherein the transverse wall portion is provided with a plurality of ports therein, for allowing a plurality of members to pass therethrough.

3. A plug member as claimed in claim 2 wherein the ports comprise one or more of: at least one grout pipe port adapted to allow a member in the form of a grout pipe to pass through the lateral wall portion; at least one breather pipe port adapted to allow a member in the form of a breather pipe to pass through the lateral wall portion; and at least one rockbolt port adapted to allow member in the form of a rockbolt member to pass through the transverse wall portion .

4. A plug member as claimed in any preceding claim wherein the axially extending wall portion comprises a generally tubular generally cylindrical wall portion .

5. A plug member as claimed in any preceding claim wherein the axially extending wall portion depends generally perpendicular from the transverse wall portion .

6. A plug member as claimed in any preceding claim wherein a transverse cross sectional area defined by the axially extending wall portion is substantially equal in size to the area of the transverse wall portion.

7. A plug member as claimed in any preceding claim wherein at least one sealing portion is provided on the exterior of the axially extending wall portion.

8. A plug member as claimed in claim 7 wherein at least one sealing portion comprises a flange or skirt projecting outwardly from the axially extending wall portion .

9. A plug member as claimed in claim 7 or claim 8 wherein the first and second sealing portions are both provided on the axially extending wall portion .

10. A plug member as claimed in any preceding claim wherein the first and second sealing portions comprise axially spaced apart skirts or flanges .

11. A plug member as claimed in any preceding claim wherein the plug member further comprises a third sealing portion for providing a seal between the plug body and a wall of a generally cylindrical bore , and the third sealing portion is axially spaced apart from each of the first and second sealing portions .

12. A plug member as claimed in any preceding claim wherein the transverse wall, axially extending wall portion and first and second sealing portions are formed integrally .

13. A plug member as claimed in any preceding claim at least one of the ports comprises an aperture provided with at least one support sealing portion to provide a seal around a tube or bolt member passing through said port.

14. A method of manufacturing a plug member for retaining grout in a substantially cylindrical bore in underground excavations , the method comprising : providing a mould apparatus for injection moulding said plug member, the mould apparatus comprising: a first mould wall portion for at least partially defining a transverse wall portion of the plug member which is adapted to act as a barrier to grout; at least two void formers for forming corresponding voids in said lateral wall portion of the plug member, said voids corresponding to ports provided in the lateral wall of the plug member to allow passage of members such as pipes and or bolts therethrough ; wherein, at least one void former comprises a moveable void former, moveable between: an operating position, in which said void former is positioned to form a void in the transverse wall of a plug member so that the plug member is formed with a port corresponding to said void former; and a non-operating position, in which said void former is positioned so that it cannot form a void in the transverse wall portion of a plug member; selecting whether said moveable void former is in the operating or non-operating position; and injection moulding a plug member using the mould apparatus, said plug member being manufactured with, or without, a port corresponding to the moveable void former depending on whether the moveable void former is selected to be in the operating or non-operating position, respectively .

15. A method of manufacturing a plug member as claimed in claim 14 wherein the operating position is a position in which the void former is present in the mould apparatus during manufacture of a plug member and the non-operating position is a position in which the void former is removed from the mould apparatus during manufacture of a plug member .

16. A method of manufacturing a plug member as claimed in either of claims 14 or 15 wherein the mould apparatus is provided with at least three void formers for providing voids in the transverse wall portion of a plug being manufactured.

17. A method of manufacturing a plug member as claimed in claim 16 wherein the mould apparatus is provided with at least four void formers for providing voids in the transverse wall portion of a plug being manufactured.

18. A method of manufacturing a plug member as claimed in any of claims 14 to 17 wherein the at least one moveable void former comprises an insert member which can be secured in the mould or removed from the mould.

19. A method of manufacturing a plug member as claimed in any of claims 14 to 18 wherein, during injection moulding of a plug member using the mould apparatus , the moveable void former is in the non-operating position and a blanking insert is provided in the mould apparatus to replace the moveable void former.

20. A method of manufacturing a plug member as claimed in any of claims 14 to 19 wherein the step of selecting whether said moveable void former is in the operating or non-operating position comprises selecting whether to manufacture a plug member with four ports in the transverse wall portion or a plug member with three ports in the transverse wall portion .

21. A method of manufacturing a plug member as claimed in any of claims 14 to 19 wherein selecting whether said moveable void former is in the operating or non-operating position results in the selection that the moveable void former is in the non-operating position and further comprising providing, in an operating position, an alternative moveable void former of different dimensions, for forming a port of different size and/or shape to a port corresponding to the moveable void former .

22. A method of manufacturing a plug member as claimed in claim 21, further comprising the step of selecting which of a plurality of alternative void formers is provided in an operating position.

23. A method of manufacturing a plug member as claimed in any of claims 14 to 22 wherein the method further comprises selecting one of a plurality of peripheral-seal defining members for use in the mould when moulding a plug member .

24. A method of manufacturing a plug member as claimed in claim 23, wherein each peripheral-seal defining member is adapted to at least partially define a peripheral-seal portion which extends around the external perimeter of a plug member .

25. A method of manufacturing a plug member as claimed in either of claims 23 or 24, wherein respective different peripheral-seal defining members of the plurality of peripheral-seal defining members provide seals of respective different shapes , lateral sizes and/or stiffness on the manufactured plug member.

26. A method of manufacturing a plug for retaining grout in a substantially cylindrical bore in underground excavations , the method comprising providing a mould apparatus for injection moulding said plug member, the mould apparatus comprising: a first mould wall portion for at least partially defining a transverse wall portion of the plug member which is adapted to act as a barrier to grout, the first mould wall portion being provided with at least two void forming portions for forming voids in said lateral wall portion of the plug member, said voids corresponding to ports provided in the lateral wall of the plug member to allow passage of pipes and/or bolts therethrough; at least one first peripheral-seal defining member adapted to at least partially define a first configuration of external peripheral seal of a plug member in order to determine the lateral size and/or shape of the peripheral seal ; and at least one second peripheral-seal defining member adapted to at least partially define a second configuration of external peripheral seal of a plug member, said second configuration comprising a different lateral size and/or shape to the first configuration; and wherein either the first or the second seal defining member (s) can be utilized in order to provide a plug member with a corresponding configuration of external peripheral seal; selecting whether said first or second seal defining member (s) is utilized for a plug member to be moulded; and injection moulding a plug member utilizing the selected seal defining member (s) said plug member being manufactured with an external peripheral seal with a lateral side and/or thickness corresponding to the selection made .

27. A method as claimed in claim 26 wherein each of the first or second seal defining member (s) comprises a substantially annular seal defining member.

28. A plug member for retaining grout in a substantially cylindrical bore in underground excavations , wherein the plug member is injection moulded by a method as claimed in any one of claims 14 to 27.

29. A method of plugging a substantially cylindrical bore in underground excavations so that grout can be retained in the plugged bore, the method comprising: providing a plug member which has at least three ports therein; passing a bolt member through a first one of the ports of the plug member; passing a grout pipe through a second one of the ports in the plug member; passing a breather pipe through a third one of the ports in the plug member; applying a high viscosity grout to the plug member prior to insertion of the plug member into the cylindrical bore ; and inserting the plug member with viscous grout applied thereto, at least partially into the cylindrical bore so that the plug member is retained in the bore and so that the viscous grout previously applied to the plug member provides or enhances a seal between the plug member and the wall of the cylindrical bore .