AU663323B2

AU663323B2 - Face plate

Info

Publication number: AU663323B2
Application number: AU20984/92A
Authority: AU
Inventors: Ian Stewart
Original assignee: Mount Isa Mines Ltd
Current assignee: Mount Isa Mines Ltd
Priority date: 1991-08-12
Filing date: 1992-08-12
Publication date: 1995-10-05
Anticipated expiration: 2012-08-12
Also published as: AU2098492A

Description

-t i ;I S663323

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPEC I F I CATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventor: MOUNT ISA MINES LIMITED, A.C.N. 009 661 447 IAN STEWART *4*4 4".o 4,, 4* Address for Service: 4 i4 Ca SHELSTON WATERS Clarence Street SYDNEY NSW 2000 "FACE PLATE" Invention Title: Details of Associated Provisional Application No: PK7717 dated 12/8/91 and PL1712 dated 3/4/92 The following statement is a full description of this invention, including the best method of performing it known to me/us:a

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2 -2- The present invention relates to a rockbolt and in particular to a face plate for use with a rockbolt or the like.

The invention has been developed primarily for ground support in underground excavations and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to this particular field of use and is also suitable for use with aboveground excavations, such as cuttings and the like.

When an underground excavation is formed, the load that was supported by the excavated material is transferred to the surrounding area. Subsequently, the likelihood of rock movement in the area adjacent an o 0 o 15 excavation is increased. This movement may be sudden, 00 but is more generally spaced over time as the gradual redistribution of forces throughout a body of rock occurs.

To ameliorate the abovementioned problems, a plurality of generally parallel rockbolts are inserted 000" 20 into the rock material adjacent an excavation through a o00,0 number of strata layers and tensioned t form a laminated beam. If st.-ata layers are not present and the rock is oJ ,broken into numerous slabs or irregular interlocking fragments, a plurality of tensioned rockbolts are arranged in an arch formation and create a circular zone of c, ipression to create a solid mass. A number of the slabs or fragments at the centre of the "arch" form the "key stones".

3 If, as a result of the excavation a reasonably smooth surface is provided and the rockbolts are intended to be inserted substantially perpendicular to this surface then a flat face plate is appropriate. In practice, however, both of these conditions are rarely met, making a flat face plate unsuitable. Furthermore, any subsequent movement of material about the bolt may cause unfavourable stresses on both the bolt and the face plate which in turn results in spalling and unravelling.

A more versatile face plate includes a generally hemispherical plate having a centrally located aperture being spaced from the wall of the excavation for receiving the rockbolt. The rockbolt is provided with a convex hemispherical washer or convex domed nlit which S° 15 cooperates with the aperture to allow the rockbolt to 0 extend at an oblique angle from the face plate.

However, the bolts are tensioned to approximately o 50% of their yield strength resulting in the convex hemispherical washer or domed nut tending to pierce the o 20 face plate and allow it to move from the rockbolt. To 0 00 0. ameliorate this problem the plates are of substantial thickness to provide adequate strength and resistance to :piercing. Present domed face plates are at least 8 mm thick low carbon steel resulting in a high mass and cost I for the surface area being supported. 4 It is an object of the present invention, at least in its preferred embodiment, to overcome or substantially ameliorate at least some of these deficiencies of the

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I v i 4 prior art.

According to a first aspect of the invention there is provided a face plate for use with a rockbolt or the like including an engagement surface for abutting an excavated surface into which the rockbolt is to be installed, a raised portion extending from the engagement surface and an aperture in the raised portion for receiving the rockbolt, the engagement surface including means for allowing progressive deformation of said face 10 plate comprising a plurality of radially diverging

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corrugations extending from said raised portion to the .Z periphery of said engagement surface along which Scorrugation deformation can occur.

According to a second aspect of the invention, there is provided a face plate for use with a rockbolt or the like including an engagement surface for abutting an excavated surface into which the rockbolt is to be installed, a raised portion extending from the engagement surface and an aperture in the raised portion for receiving the rockbolt, the engagement surface including means for allowing progressive deformation of said plate so that under load, said raised portion remains spaced apart from uaid excavated surface; said means comprising a circumferential corrugation about which deformation can take place, said corrugation being spaced apart from and surrounding said raised portion.

Preferably, the raised portion is substantially sALU hemispherical and the aperture is centrally located.

i 0! It is preferable that the engagement surface is curved such that when it is not under load it will peripherally abut the excavated surface. However, it is also preferred that as the rockbolt is tensioned the engagement surface progressively deforms for providing an increased area of contact between the engagement and excavated surfaces.

Preferably also, the face plate includes a circumferential corrugation adjacent to and surrounding the raised portion. In a further preferred form, the face plate includes four corrugations equally angularly spaced about the raised portion and radially extending to 4all t the periphery o the face plate. In a more preferred form the face plate is generally square and includes both circumferential and radially extending corrugations.

In another preferred form the face plate is generally rectangular and includes both circumferential and radially extending corrugations. Preferably, four radial corrugations extend fzom ,e-pective corners of the face plate.

Preferably either at least one corrugation forms a concave impression in the engagement surface or at least one corrugation forms a convex impression in the engagement surface. More preferably the face plate includes a combination of corrugations forming both concave and convex impressions in the engagement surface.

In other preferred forms, the raised portion is at i% Ci least partially turned back upon itself to form a lip pi I i r -i I Ill-* It t B t Illt It It t.

5a which defines the aperture. The lip in use strengthening the aperture and facilitating mechanical installation.

Preferably the face plate is in combination with retention means, the retention means including a complementary surface presentableto the raised portion and adapted to co-operate with the free end of the rockbolt for tensioning the rockbolt. The complementary surface preferably remains in substantially maximal engagement with said raised portion for a predetermined range of angular displacements of said rockbolt with respect to the face plate. The range of angular displacements with respect to the face plate is preferably ±200, most preferably ±12.50 from a perpendicular configuration.

Preferably, the raised portion is substantially hemispherical and the retention means includes a concave washer having a radius of curvature substantially equal to that of the raised portion of the face plate.

Preferably also, the washer is integrally formed with a nut which engages a complimentarily threaded portion on said free end.

According to a third aspect of the invention there is provided a rockbolting system for providing support to a body of rock, the system including a rockbolt having a first end for anchoring in a hole in said body of rock and a second end for extending from the hole and co-operating with any one of the face plates as described above for allowing tensioning of the rockbolt.

RI Y 1 h i.j 6 Preferably, the rockbolt is tubular for allowing the pumping of ce ititious grout therethrough and is formed from either seamless cold drawn tube or electrically resistance welded tube.

Preferably also, the second end includes a rope thread or the like for providing resistance to blast damage.

In a preferred form the first end is swaged and includes a thread for engaging a complimentarily threaded expansion shell.

According to a fourth aspect of the invention there is provided an expansion shell for anchoring a first end of a rockbolt in a drilled hole such that a second end of °a the rockbolt extends from the hole, the expansion shell including a wedged shaped body for rotatably engaging the first end of the rockbolt, a plurality of leaves extending along a portion of the rockbolt and being slidably engaged with the body for movement away from the rockbolt during progression of the body toward the second o 20 end, and a bail extending both between at least two of the leaves and around the first end for preventing contact of the first end with the periphery of the oo.. drilled hole.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a plan view of a square face plate according to the invention for use with a 16 mm threaded or a 15.2 mm cable rockbolt; 1 i. 7 Figure 2 is a side view of Figure 1; Figure 3 is a sectional view taken on line 3-3 of Figure 1; Figure 4 is a sectional view taken on line 4-4 of Figure 1; Figure 5 is the face plate of Figure 1 shown retained to a rockbolt by a composite nut and washer; Figure 6 is a cross-sectional view of an integral nut and washer for use with the face plate of Figure 1; Figure 7 is a sectional view of a barrel for use with the face plate of Figure 1 in conjunction with a cable bolt; 0 Figure 8 is -A face plate according to the invention o 0 for use with a W-strap; Of "ooo 15 Figure 9 is a section through line 9-9 of Figure 8; Figure 10 is a section through line 10-10 of Figure 8; °o -Figure 11 is a plan view of a rectangular face plate according to the invention for use with a 24 mm 20 rebar; Figure 12 is a side view of the face plate of .0 :Figure 11; 0 Figure 13 is a section taken along line 13-13 of Figure 11; J Figure 14 is a section taken on line 14-14 of Figure 11; Figure 15 is a section taken along line 15-15 of Figure 11; 8 Figure 16 is a plan view of a square face plate according to the present invention for uc with a 46 mm friction rock stabiliser; Figure 17 is a partial section taken on line 17-17 of Figure 16; Figure 18 is an enlarged view of Figure 17; Figure 19 is a rectangular face plate for use with a 33 mm friction rock stabiliser; Figure 20 is a side view of Figure 19; Figure 21 is a section taken on line 21-21 of Figure 19; Figure 22 is a plan view of an alternative to the face plate of Figure 16; 04 Figure 23 is a sectional view taken on line 23-23 15 of Figure 22; t a Figure 24 is a sectional view taken on line 24-24 of Figure 22; Figure 25 is a hollow groutable rockbolt for providing temporary and/or permanent support; o 20 Figure 26 is a plan view of an alternative W-strap washer according to the invention; Figure 27 is a section taken on line 27-27 of -y Figure 26; Figure 28 is a section taken on line 28-28 of Figure 26; Figure 29 is a section taken on line 29-29 of Figure 26; FiAu;e 30 is a washer for use with the W-strap i 9 washer of Figure 26; Figure 31 is a section taken on line 31-31 of Figure Figure 32 is a front view of an expansion shell according to the invention; Figure 33 is a side view of the expansion shell of Figure 32; Figure 34 is a top view of the wedge used in Figure 32; and Figure 35 is a sectional view taken along line 35-35 of Figure 34.

Referring to Figures 1 to 5, a generally square face plate 1 for use with a 16 mm threaded rockbcIt 2 o° includes a centrally !ocated generally hemispherical o*o 0 oo e 15 raised portion 3, a top surface 4 and a curved engagement surface 5 for abutting an excavated surface into which a.

rockbolt is to be installed. An aperture 6 is centrally o disposed in portion 3 for receiving the threaded end of rockbolt 2 for allowing tensioning of the rockbolt.

20 A circumferential corrugation 10 is adjacent to and surrounds portion 3. Four radial corrugations 11, 12, 13 and 14 extend from portions 3, through corrugation 10, to respective corners 15, 16, 17 and 18 of plate 1. The corrugations cooperate to allow plate 1 to be effective when used on uneven surfaces, as the plate will progressively deform to accommodate the surface contour and increase the area eo contact between plate 1 and the excavated surface. During any subsequent movement of 1 10 rock restrained by rockbolt 2, face plate 1 will continue to compensate for changes in rockbolt tension.

The face plate of Figure 1 preferably includes sides having a length of substantially 165 mm and is stamped from a 3.5 mm steel plate. However, other suitable lengths and thickness are appropriate where different deformation characteristics are required or loads experienced. Similarly, the material specifications are variable according to specific requirements.

Face plate 1 includes two service loops 19 which allow connection of other articles to the plate. The Snumber of loops and their location are variable. Some embodiments are intended not to include loops.

15 Although face plate 1 has been described in conjunction with a 16 nun threaded rockbolt, scaling of aperture 6 allows other diameter bolts to be used.

Moreover, the plate described above is suitable for use with 15.2 mm cable bolts and is similarly adaptable to 20 accommodate other sizes of cable bolts.

With particular reference to Figure 5, where :corresponding features are denoted with corresponding reference numerals, a rockbolt 2 is inserted in a suitably placed hole 20 located in an excavated surface 21. Rockbolt 2 includes threaded end 22 which extends outwardly from excavatic- 21.

The rockbolt is retained in hole 20 by an expansion shell 23 which fixedly engages the sides of the hole.

Face plate 1 is disposed such that threaded end 22 extends through aperture 6 whereby engagement surface is presented to excavated surface 21. In this configuration raised portion 3 provides a convex surface past which threaded end 22 extends.

Face plate 1, as shown in Figure 5, is retained to rockbolt 2 by a composite nut 27 which includes a concave hemispherical washer 28 having a complementary radius of curvature to surface 25. Although shown separate, washer 28 and nut 27 are generally welded together. In further Fa embodiments the weld is designed to sheer at a S predetermined torque for providing assistance in establishing a optimal engagement between the abutted surfaces. i 1 0To tension rockbolt 2, nut 27 is progressed along threaded end 22 by a suitable tool (not shown) such that S. 20 washer 28 is presented to surface 25. Due to the S vcomplementary nature of surface 25 and washer 28 a maximum area Of contact is established therebetween for a.

S substantially reducing the risk of face plate 1 being pierced by washer 27.

As also shown in Figure 5, rockbolt 2 extends perpendicularly into wall 21. In circumstances where rockbolt 2 extends obliquely into wall 21, nut 27 and washer 28 are displaced from the centrally illustrated I 12 position. However; as raised portion 3 and washer 28 are generally hemispherical the maximum contact area therebetween will be substantially maintained while also face plate 1 will be maintained in a position of maximum surface contact with wall 21. Angular displacement of rockbolt 2 of at least 100 from the normal of surface 21 is possible, with this figure increasing as face plate 1 is deformed under load.

Nut 27 can also be included in an integral unit, as shown in Figue 6. Forged nut 31 includes hexagonal walls 32 and a threaded section 33 which is either cut or cold formed. A flange 34 extends obliquely from an edge of walls 33 to define a concave surface 35 which is B° complementary to convex surface 25. Nut 31 is t o" 15 advantageous in that time need not be spent finding and arranging two separate components in an area that may not be well lit. Moreover, inventory and logistical problems 'are reduced.

Similarly, when face plate 1 is used with cable i 4t'. 20 bolts a barrel and wedge device is able co be configured o. c such that an additional concave washer is not required.

As illustrated in Figure 7, a barrel 40 includes outer S and inner walls 41 and 42, which extend between ends 43 and 44. Innr wall 42 defines a cavity 45 which progressively narrows from end 43 to end 41 for accepting a complimentarily shaped wedge, as is well known. At end 44 walls 41 and 42 are separated by a hemispherical surface 46 having a radius which corresponds to that of I- V 1 1 1 i. /13 13 surface 25. A maximum engagable surface area between the barrel and face plate is able to be achieved, while also allowing a similar degree of angular displacement as provided by nut 27.

Face plate 1 is able to be manufactured to a thickness dependant upon the application due to the interaction between raised portion 3 and corrugations 11, 12, 13 and 14. The result is a reduced mass and cost compared to prior face plates.

The corrugations and raised portion further facilitate tensioning of the rockboit, as a bias away from wall 21 is provided by plate 1. This results in an S increased tension being applied for the same torque input.

In a less preferred embodiment, face plate 1 would accommodate a prior art convex hemispherical washer or nut.

Where mechanical installation is practiced face plate 1 can include an inwardly protruding lip (not shown) around aperture 6 to prevent jamming of the face plate on the threaded portion of a rockbolt. The time and subsequent cost savings associated with mechanical installation are considerable, notwithstanding the Sadditional expense involved in the forming of the lip and a small reduction in the available angular displacement between the face plate and rockbolt. However, mechanical installation is possible without such a lip.

Face plate 1 is one preferred embodiment for use with threaded or cable bolts. Other preferred MiJmmI *i! ,s -14 embodiments of the invention include other corrugation configurations. For example, Figures 8 to 10 illustrate a face plate 50 for use as a W-strap washer. That is, in applications where spalling is prevalent a larger portion of the excavated surface requires support by the face plate. Additional surface support is generally provided by a W-strap used in conjunction with a washer. Plate functions as such a washer and includes a curved engagement surface 51 for abutting a W-strap and a central raised hemispherical portion 52 having an aperture 53 for receiving the free end of a 24 mm rockbolt. Four equally angularly spaced corrugations 0° 56, 57 and 58 radially extend from raised portion 51 to respective corners 59, 60, 61 and 62.

Once disposed on a tensioned rockbolt, engagement surface 51 progressively deforms against the W-strap as the tension increases. Although it is preferable to use a composite nut and hemispherical washer or a forged nut, as described above, face plate 50 will accommodate prior art nuts and washers.

Face plate 50 further includes a service loop If required, a number of such loops are provided, however, generally such locps are not necessary.

An alternative to the abovementioned W-strap and washer is a single rectangular face plate as illustrated in Figures 11 to 15. Generally rectangular face plate 71 is designed for use with a 24 mm threaded rockbolt and includes an engagement surface 72 for abutting an excavated surface into which the rockbolt is to be installed. Scaling of the plate is possible to allow use with split sets or cable bolts.

A raised hemispherical portion 73 extends from surface 72 and a centrally located aperture 74 in raised portion 73 receives the free end of the rockbolt.

Plate 71 includes longitudinally and transversely extending axes of symmetry indicated by broken lines and 81 respectively which intersect at a point 82 and extend parallel to the broad and narrow sides 83, 84 and 86 respectively. Point 82 coincides with the centre *of aperture 74 and the broad and narrow sides have respective lengths of about 340 mm and about 165 mm.

:A circular corrugation 87 surrounds raised portion 73 and is centred at point 82. Corrugation 87 and raised portion 73 are separated by a trough 88.

:.aRadial corrugations 89, 90 and 91, 92 extend along axes 80 and 81 respectively between raised portion 73 and corrugation 87. These corrugations allow the progressive deformation of face plate 71 under load about the axes of symmetry and more particularly they allow deformation of trough 88 without causing any tearing or undue stressing of the plate.

Alternately angularly disposed between corrugations 89 to 92 are radial corrugations 93 to 96 which extend outwardly at 450 to both axes 80 and 81. Corrugations 93, 94 and 95, 96 extend from raised portion 73 to respective broad sides 83 and 84.

16 A third set of radial corrugations 97, 98 and 99, 100 extend from corrugation 87 to respective narrow sides and 86. These corrugations extend at substantially 22.50 from axis 80 and provide further strength to surface 72 while allowing progressive deformation of surface 72 without tearing of face plates 71.

All the radially extending corrugations shown radiate from point 82. However, if required for special purposes or alternate manufacturing techniques this common point is not essential. In less preferred embodiments, for example, corrugations 97 and 98, and 99 *and 100 intersect at corrugation 67.

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Raised portion 73 is similar to that described with .o :reference to the square face plate of Figure 1, and is designed for use with similar nuts, washers or barrel and wedge devices. Both the number of corrugations and the lengths of sides 83 to 86 are varied depending upon the required application. I °Face plate 71 is used where a greater degree of surface contact is required to prevent spalling or unravelling as surface 72 is much larger than that of the corresponding square face plate. Consequently, this face plate is used to replace the conventional W-strap and washer and thereby reducing the problems associated with i having two separate components. Furthermore, the resilient deformation of plate 73 commences much earlier due to the curved nature of surface 72, as is best shown in Figure 12.

17 When initially installed only narrow sides 85 and 86 will be in contact with the excavated surface. As the rockbolt is tensioned, the outer surfaces 105 and 106 of surface 72 will be progressively presented to the excavated surface as plate 71 deforms. After further tensioning and the broad sides 83 and 84 will be presented to the excavated surface and thereafter the inner surfaces 107 of surface 72 will be progressively deformed.

Once installed, rock movement can result in increased stresses being placed on the face plate.

However, even if trough 88 is in contact with the excavated surface a degree of resiliency is still osrr *00 provided by raised portion 73 and the associated corrugations.

Face plates according to the invention are also applicable for use with friction rock stabilisers.

Referring in particular to Figures 16 tc 18 there is o* .illustrated a generally square face plate 110 for use with a 46 mm friction rock stabiliser and produced from a stamped or otherwise formed steel sheet. Plate 110 includes a curved engagement surface 111 extending inwardly and upwardly from four edges 112 to 115 and terminating about a central raised portion 116. The edges are about 145 nn in length and the raised portion includes an aper:ure 117 defined by a folded lip 118.

Four equally angularly spaced apart radial corrugations 120 to 123 extend from raised portion 116 to respective

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18 corners 124 to 127 of surface 111.

The curved nature of surface 111, allows progressive deformation of plate 110 as a load is applied. The corrugations further this effect while also strengthening plate 111 such that a reduced thickness of steel is required to produce plate 110. Face plate 110 also includes a service loop 128, however, more or less of such loops are included as required.

Referring in particular to Figure 18, a friction rock stabiliser 130 includes at free end 131 a retaining ring 132 which is fixed by weld 133. On installation of ~stabiliser 130, weld 133 engages lip 118 and transfers any axial load to engagement surface 111. Lip 118 provides a strengthened aperture which prevents piercing of face plate 110 by stabiliser 130. This face plate is also suitable for use with stabilisers of other diameters, for example, suitable scaling results in a 125 x 125 mm face plate for use with 33 mm stabilisers.

Where spalling is an important consideration a rectangular face plate, such as that illustrated in Figures 19 to 21, is substituted for the square face 4 plate 110 of Figure 16. This rectangular face plate 140 includes broad sides 141, 142 and narrow sides 143, 144 having respective lengths of about 250 mm and about 125 mm. These sides define a curved engagement surface 145 which includes a centrally located raised portion 146 and eight radially e:tending corrugations 147 to 154 extending from the raised portion. An aperture 155 is wood

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19 defined by a lip 156 and is designed to receive a 33 mm friction rock stabiliser. In other embodiments different sized stabilisers are accommnodated, for example, a plate having dimensions of about 145 mm x 290 mm is used with a 46 mm stabiliser.

Corrugations 147 to 154 extend similarly to corrugations 89 to 92 and 97 to 100 of Figure 11 to provide the necessary strength to face plate 140 while allowing progressive deformation without tearing of the plate. A service loop 157 is also included, however, its positioning and inclusion are optional.

An alternative embodiment: of the face plate of Figure 16 is illustrated in Figures 22 to 24 and includes a square face plate 160 for use with a 33 mm friction rock stabiliser. Face plate 160 includes a curved earth engaging surface 161 which is peripherally defined by edges 162, 163, 164 and 165. A central hemispherical raised portion 169 includes a downwardly projecting lip 170 which defines an aperture 171 for receiving the stabiliser and is surrounded by an adjacent concentric corrugation 172. Four equally angularly spaced radially extending corrugations 175, 176, 177 and 178 extend from raised portion 169 to respective corners 180, 181, 182 and 183 and a further four radial corrugations 184, 185, 186 and 187 respectively interspaced between corrugations 175 to 178 extend between raised portion 169 and corrugation 172.

This combination of corrugations allows face plate I r- 160 to progressively deform to provide a favourable distribution of forces across the plate under load conditions on uneven surfaces. The plate is able to provide the necessary performance at a reduced mass in comparison to prior art plates having the same surface area. For example, this 165 x 165 mm plate made from mm stamped sheet steel is about 17% lighter than the standard prior art 150 x 180 x 5 mm plate.

The face plate of Figure 22 is alternately configured with a suitably dimensional aperture for use with threaded and cable bolts, such bolts being tensioned *with a composite or integral hemispherical nut and washer as described above. Raised portion 116 is complementary to the concave surface of the nut or washer to allow a maximum area of contact therebetween and movement thereto. In this configuration face plate 110 is I i particularly advantageous for mechanical installation as lip 118 prevents the face plate jamming with the thread "t of the rockbolt. However, for manual installation face plate 110 is also manufactured without lip 118.

Face plates produced in accordance with the invention include a reduced mass to strength ratio. Many S. corrugation configurations are available to achieve the objects of the present invention, the abovementioned description being illustrative only. For example, neither the width nor depth of the corrugations need be uniform as illustrated. Particular applications or manufacturing processes are able to influence these -21features.

Referring to Figure 25 there is illustrated a rockbolting system 200 for providing temporary and/or permanent support for rocX, 201 adjacent an excavated surface 202. System 200 includes a 2200 mm long hollow groutable rockbolt 205 extending from a fixed end 207 to a free end 208 along a drill hole 206 having a diameter of 45 mm.

Bolt 205 is formed from either seamless cold drawn tube or electrically resistance welded tube, as is well known to those skilled in the art. The material 9,,.',specification and the internal and external diameters of bolt 205 are variable depending upon application.

However, if grout is to be pumped through bolt 205 the minimum internal diameter is approximately 11 mun due to grouting requirements. The bolt illustrated includes onominal internal and external diameters of 18 mm and mm respectively.

~Fixed end 207 is swaged and has internal and external diameters of about 15 mm and about 22 mm respectively and is 'chreaded with a 24 mm cold rolled left hand thread for )receiving a complementarily formed Ibail type expansion shell 210. The expansion shell includes leaves 211 which are brought int secured engagement with the walls 212 of hole 206 upon threaded progression of wedge 213 along bolt 205. In this way end 207 is anchored to allow subsequent tensioning of bolt 205.

t 22 *44W 4 4* *4*4 4* 4 4.

4* 4 4 **4444 Free end 208 is threaded with about 750 mm of left hand rope thread which is resistant to blast damage.

Other less preferred embodiments include a thread having a finer pitch such that less torque is required to induce a predetermined tension in bolt 205. However, this latter embodiment would not be suited fo- use in areas where further blasting is intended to be carried out.

Free end 208 extends beyond surface 202 and co-operates with a face plate 215 which is similar to the face plate shown in Figure 1. However, any of the face plates described for use with threaded bolts are adaptable for use with bolt 205.

Face plate 215 is secured into deformed engagement with surface 202 by a forged nut 216 having complementary cut or cold formed thread to free end 208. Nut 216 is similar to nut 31 as illustrated in Figure 6 in that it includes a complementary concave hemispherical surface for ensuring maximum overlap of face plate 215 and nut 216.

In certain applications mesh 220 is required. This mesh is held in proximity to surface 202 by a holding cup 221 which co-operatk-.s with a second concave nut 222 and rockbolt 205. Mesh 220 is 150 mm, x 150 min arc mesh, however, many other meshes are suitable, for example, chainlink type mesh.

To install bolt 205 for temnporary support, hole 206 is drilled to an appropriate length. Bolt 205 is then inserted and rotated in order to bring leaves 211 into 23 anchoring engagement with walls 212. Thereafter, face plate 215 is placed on the bolt and presented to surface 202. Nut 216 is then advanced to tension bolt 205.

If mesh 220 is required it is positioned and held by cup 221. Although cup 221 is shown having an elongate central raised portion to allow clearance of nut 216, other cups having shallower raised portions are suitable. In some embodiments a second face plate is used as a substitute for cup 221. It will be appreciated that this second face plate will allow retention of mesh 220 adjacent surface 202 although not in contact therewith.

The blast resistant threaded end 208 allows readjustment of bolt tension following ground movement caused by blasting or otherwise.

If more permanent support is required it is not necessary to drill further holes for the installation of grouted bolts as grout is able to be pumped through bolt 4'4 205. That is, the rockbolting system 200 allows a one pass system which provides both temporary, or following the encapsulation of bolt 205 with grout, permanent support. The grout is injected through the central bore of bolt 205 and flows out thi-ugh expansion shell 210 and back along the annular cavity defined by walls 212 and bolt 205. Consequently, bolt 205 becomes encapsulated in grout to provide a corrosion resistant permanent support.

Bolt 205 is also ideally suited to mechanical installation. That is, bolt 205 including at end 207 an

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-24expansion shell 210 and along its length a face plate 215, is mounted on the installation apparatus (not shown). A forged nut 216 is bonded to bolt .05 with anaerobic resin at approximately 70 mm to 90 mm from end 208. Other resins, such as hot melt resins are also suitable. Preferably face plate 215 includes a lip defining the aperture to prevent jamming of the plate as it moves along threaded end 208.

After the drilling of hole 206, end 207 is inserted therein and bolt 205 rotated via nut 216 by the installation apparatus to present leaves 211 into anchored engagement with wall 212. Once sufficiently anchored the resin bond between nut 216 and bolt 205 will shear and nut 216 will piogre-s alog bolt 205 and bring face plate 215 into deformable engagement with surface 202. Thus installed immediate support is provided and "further work, for example excavation or blasting are possible. The damage resistant rope thread allows rockbolt 205 to be bo'-h retensioned after the further work and the installation of mesh 220 with cups 221 as required.

Grouting of the mechanically installed bolts is K possible either immediately after installation or when required. Moreover, the placement of mesh 220 does not hinder the grouting operation.

The rockbolting system according to the invention dispenses with separate temporary and permanent ground support and allows for adjustment of the installed bolts !i I where spalling/unravelling result in a loss of tension.

The versatility of the system is further enhanced by the compatibility with either manual or mechanical installation.

In circumstances where mechanical installation of bolts is practiced it is preferred to use an expansion shell such as that illustrated in Figures 32 and 33.

Expansion shell 250 includes a cylindrical wedge 251 threadedly engaged with ead 207 of bolt 205. Leaves 252 and 253 slidably engage the wedge and are connected by way of a bail 254 having two parallel arms 255 and 256 for respectively engaging leaves 252 and 253. Bail -54 4 also includes intermediate bullet shaped shroud 257. The B shroud includes two spaced apart apertures 258 and a domed end 259.

The free end of arms 255 and 256 are deformed a. outwardly from leaves 252 and 254 for engaging the surface 212. The degree of deformation is sufficient to allow relatively unhindered progression of shell 250 into a hole 206, while movement in the opposing direction is *11 resisted. The semi-circular configuration of the deformations prevent any catching or snagging of objects or persons during transportation of the expansion shell.

In use, shell 250, suitably threaded onto end 207, is inserted into hole 206 to the desired depth. Rotation of bolt 205 will progress wedge 251 away from end 207 and subsequently radially advance leaves 252 and 253 into anchored engagement with opposing surfaces of wall 212.

01 i' i 1 26 The deformed ends of arms 255 and 256 ensure sufficient frictional contact with wall 2!.2 such that the leaves are not rotated with bolt 205.

Shroud 257 prevents the abutment of end 207 against the base of hole 206 during both insertion of bolt 205 into the hole and rotation of the bolt to activate expansion shell 250. This feature is particularladvantageous where later grouting is required. The shroud ensures that grout will not be prevented from exiting end 207 of bolt 205. Moreover, apertures 258 and the open side of the domed head also facilitate a free flow oi grout.

The expansion shell 250, although particularly advantageously used in conjunction with mechanical installation of bolts, is also suitable for use with manually installed rock bolts.

4 t" Figure 34 illustrates a preferred wedge 260 for use in expansion shell 250. Wedge 260 includes an internal o thread 261 and four external equally angularly spaced apart axially extending grooves 262 for facilitating a a n free flow of grout past the wedge. This feature, in combination with the open sided shroud ensure that grout is able to freely progress along the length of the hole to fully encapsulate bolt 205.

All the face plates which have been described above have included radially extending corrugations which form a concave impression on the engagenent surface.

Alternative configurations are available where the lc-; 27 corrugations form a convex impression. In particular, referring to Figures 26 to 29 a W-strap washer 230 includes a curved engagement surface 231 peripherally defined by sides 232, 233, 234 and 235 each being 95 mm in length. A centrally disposed hemispherical raised portion 236 extends upwardly and away from the concave engagement surface 231 and includes an aperture 237 for accepting the threaded end of a 24 mm rockbolt. The aperture is able to be appropriately proportioned to accept bolts of different size, and in some embodiments portion 235 includes a lip for defining the aperture such that mechanised installation is facilitated.

so oFour rndially diverging corrugations 239, 240, 241 and 242 extend from an intermediate portion of raised portion 235 to respective corners of washer 230. These corrugations are convex and project into curved o engagement surface 231 and raised portion 236 for allowing washer 230 to deform under load. During an o increase in the load to which washer 230 is subjected, a progressive increase in the contact area occurs between engagement surface 231 and thn W-strap against which washer 230 is abutted. Furthermore, under normal load the corrugations prevent tearing of the plate by providing a more even distribution of forces across the washer.

The width of corrugations 239 to 242 vary along their lengths, however, in other embodiments this width is substantially constant.

28 Referring to Figures 30 and 31 a hemispherical washer 245 for use with the W-strap washer 230 of Figure 26 is illustrated. Washer 245 includes two annular surfaces 246 and 247 being respectively concave and convex which define a central aperture 248. Washer 245 is produced from 3.5 mm steel plate and is complementarily formed for engagement with raised portion 236 of washer 230. The use of this washer 248 allows a range of angular displacement of a rockbolt with respect to washer 230 without reducing the effectiveness of the engagement between washer 248 and hemispherical raised So, portion 236 and between engagement surface 231 and the W-strap.

Face plates (or W-strap washers) made in accordance with the invention are preferably produced by stamping suitable metal sheet. If the raised portion is required to include a lip an additional forming operation will be required. Although the invention has been described with reference to a specific example, it will be appreciated a by those skilled in the art that the invention may be embodied in many other forms.

I

I 28 Referring to Figures 30 and 31 a hemispherical washer 245 for use with the W-strap washer 230 of Figure 26 is illustrated. Washer 245 includes two annular surfaces 246 and 247 being respectively concave and convex which define a central aperture 248. Washer 245 is produced from 3.5 mm steel plate and is complementarily formed for engagement with raised portion 236 of washer 230. The use of this washer 248 allows a range of angular displacement of a rockbolt with respect to washer 230 without reducing the effectiveness of the engagement between washer 248 and hemispherical raised I o portion 236 and between engagement surface 231 and the W-strap.

Face plates (or W-strap washers) made in accordance with the invention are preferably produced by stamping suitable metal sheet. If the raised portion is required to include a lip an additional forming operation will be required. j Although the invention has been described with reference to a specific example, it will be appreciated by those ski'led in the art that the invention may be embodied in many other forms.

'4 j.1

Claims

4. 4 a f 4 0 a 0 29 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- i. A face plate for use with a rockbolt or the like including an engagement surface for abutting an excavated surface into which the rockbolt is to be installed, a raised portion extending from theengagement surface and an aperture in the raised portion for receiving the rockbolt, the engagement surface including means for allowing progressive deformation of said face plate comprising a plurality of radially diverging corrugations 10 extending from said raised portion to the periphery of said engagement surface along which corrugation deformation can occur. 2. A face plate according to claim 1 wherein said engagement surface includes a circumferential corrugation surrounding said raised portion and intersecting said radial corrugations for facilitating said deformation. 3. A face plate according to claim 2 wherein said engagement surface includes a plurality of radially diverging corrugations extending between said raised portion and said circumferential corrugation for further facilitating said deformation. 4. A face plate accor:ing to claim i, 2 or 3 wherein said raised portion is substantially hemispherical and said aperture is centrally located in said raised portion.
5. A face plate according to any one of claims 1 to 4 wherein said engagement surface is curved such that when the plate is not under load it will peripherally abut the excavated surface. 30
6. A face plate according to claim 5 wherein said engagement surface progressively deforms for providing an increased area of contact between the engagement surface and the excavated surface as load is applied to the face plate.
7. A face plate according to any one of the preceding claims having a generally square or rectangular shape and wherein said radially diverging corrugations are equally angularly spaced about said raised portion and extend to respective corners of said face plate.
8. A face plate according to any one of the preceding claims wherein said raised portion is at least partially turned back upon itself to form a lip which defines said aperture.
9. A face plate according to any one of the preceding claims wherein at least one corrugation forms a concave impression in said engagement surface. A face plate according to any one of claims 1 to 8 wherein at least one of the corrugations forms a convex impression in said engagement surface. V 9 0
11. A face plate according to claim 10 including a combination of corrugations forming both concave and convex impressions in said engagement surface.
12. A face plate according to any one of the preceding cla.-; used in combination with a W-strap.
13. A face plate as defined in any one of the precedinig claims in combination with retention means, said 01LI retention means including a complementary surface 63 <q zsti~ dT i IUa ::I F e: it C 4 4t II I C 31 presentable to the raised portion and adapted to co-operate with the free end of the rockbolt for tensioning the rockbolt.
14. A face plate according to claim 13 wherein said complementary surface remains in substantially maximal engagement with said raised portion for a predetermined range of angular displacements of said rockbolt with respect to said face plate. A face plate according to claim 14 wherein said 10 range is about 200 from a perpendicular configuration.
16. A face plate according to claim 15 wherein said range is about 12.50,
17. A face plate according to any one of claims 13 to 16 wherein said raised portion is substantially 15 hemispherical and said retention means includes a concave washer having a radius of curvature substantially equal to that of the raised portion.
18. A face plate according to claim 17 wherein said washer is integrally formed with a nut which engages a complementarily threaded portion on said free end.
19. A face plate for use with a rockbolt or the like including an engagement surface for abutting an excavated surface into which the rockbolt is to be installed, a raised portion extending from the engagement surface and an aperture in the raised portion for receiving the rockbolt, the engagement surface including means for allowing progressive deformation of said plate so that S under load, said raised portion remains spaced apart from U 32 said excavated surface, said means comprising a circumferential corrugation about which deformation can take place, said corrugation being spaced apart from and surrounding said raised portion.
20. A face plate according to claim 19 wherein said engagement surface is bowed outwardly such that, in use and unloaded, only the periphery of said engagement surface abuts said excavated surface and during tensioning of said rockbolt the excavated surface is sequentially abutted by: the engagement surface between said periphery and said corrugation, t I. (ii) the engagement surface between said corrugation and said raised portion, 15 while said raised portion remains spaced apart from said excavated surface.
21. A face plate according to claim 19 or 20 wherein said engagement surface includes a plurality of radially diverging corrugations extending from said raised portion to the periphery of said engagement surface, each said radial corrugation intersecting said circumferential corrugation for facilitating said deformation.
22. A face plate according to claim 19, 20 or 21 wherein said engagement surface includes a plurality of radially diverging spaced apart corrugations extending between said raised portion and said circumferential corrugation.
23. A rockbolting system for providing support to a
33- body of rock, the system including a rockbolt having a first end for anchoring in a hole in said body of rock, and a second end for extending from the hole and co-operating with any one of the face plates as defined in any one of claims 1 to 22. 24. A system according to claim 23 wherein said rockbolt is tubular for allowing the pumping of grout therethrough. A system according to claim 24 wherein said rockbolt is formed from either seamless cold drawn tube or electrically resistance welded tube. 26. A system according to any one of claims 23 to wherein said second end includes a rope thread or the like for providing resistance to blast damage. 15 27. A system according to any one of claims 23 to 26 wherein said first end is swaged to a reduced diameter and includes a thread for engaging a complementarily threaded expansion shell. 28. A system according to claim 27 wherein the expansion shell anchors a first end of the rockbolt in the hole such that a second end of said rockbolt extends from said hole, said shell including a wedged shaped body for rotatably engaging said first end of said rockbolt, a plurality of leaves for extending along a portion of said bolt and being slidably engaged with said body for movement away from said rockbolt during progression of said body toward said second end, and a bail extending both between at least two of said leaves and around f:aid i C, f~1 34 first end for preventing contact of said first end with the periphery of said drilled hole. 29. A system according to claim 28 wherein said bail includes at least two substantially parallel arms extending from respective leaves. A system according to claim 28 or 29 wherein said rockbolt is hollow and said bail includes a shroud supported by said arms and being spaced apart from said leaves and selectively engageable with said first end for allowing grout to flow substantially unhindered through said hollow rockbolt. 31. A system according to claim 30 wherein said shroud includes a plurality of spaced apart apertures for further facilitating an unhindered flow of grout through said rockbolt. 32. A system according to claim 30 or claim 31 wherein said shroud is curved for maintaining said first end at S;least a predetermined distance from the periphery of said bore. 33. A system according to claim 32 wherein said shroud is dome shaped and selectively centrally engages the first end of said hollow rockbolt and said apertures are disposed such that grout is able to flow through said rockbolt with said first end abutted against said shroud.
34. A system according to claim 29 wherein said arms each include at least one projection for engaging the periphery of said bore. A system according to claim 34 wherein said t p.- -4 u 35 t« t: projections are located on or adjacent that end of the arms attached to said leaves and are formed in a substantially semi-circular shape.
36. A face plate substantially as herein described with reference to the accompanying drawings.
37. A rockbolting system substantially as herein described with reference to the accompanying drawings. DATED this 9th day of August 1995 MOUNT ISA MINES LIMITED Attorney: RUTH CLARKSON Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS 1/V ;i. W t tr s ^r L i NI .A ABSTRACT A generally square face plate for use with a 16 mm threaded rockbolt includes a centrally located generally hemispherical raised portion a top surface and a curved engagement surface for abutting an excavated surface into which a rockbolt is to be installed. An aperture is centrally disposed in portion for receiving the threaded end of rockbolt for allowing tensioning of the rookbolt. A circumferential corrugation (10) is adjacent to and surrounds portion Four radially corrugations (11,12,13,14) extend from portions through sit- corrugation two respective corners (15,16,17,18) of plate The corrugations co-operate to allow plate to be effective when used on uneven surfaces, as the plate will progressively deform to accommodate the surface contour and increase the area of contact between 2 plate and the excavated surface, During any subsequent movemen'-- of rock restrained by rockbolt face plate will continuri to compensate for changes in 23 rockbolt tension.