AU673989B2 - A bail - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SP EC I F I CATION

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FOR A STANDARD PATENT

ORIGINAL

0 0* *0 Name of Applicant: Actual Inventor: MOUNT ISA MINES LIMITED, A.C.N. 009 661 447 Ian STEWART Address for Service: Invention Title: SHELSTON WATERS 60 Margaret Street SYDNEY NSW 2000 "A BAIL" Details of Original Application No. 20984/92 dated 12th August 1992 The following statement is a full description of this invention, including the best method of performing it known to us:- L I dl ~C- -2- The present invention relates to an expansion shell and in particular to an expansion shell for anchoring a rockbolt in a hole and more particularly to an improved bail for use with the expansion shell. This application is a further application in respect of an invention disclosed in our copending application AU 20984/92 and claimed in original claims 1 to 36 thereof. The entire disclosure in the complete specification and claims of said application AU 20984/92 is by this cross-reference incorporated into the present specification.

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 Suse and is also suitable for use with aboveground excavations, such as cuttings and the like.

An expansion shell is a device for anchoring a first end of a rockbolt in a hole such that a second end of the rockbolt extends from the hole. The expansion shell 15 includes 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 slidably engaged with the body for movement away from the rockbolt during progression of the body toward the second 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 hole.

The present invention relates to an improvement to the bail of such an expansion shell, namely a bullet shaped shroud. Such a shroud enables the expansion shell to be easily lead into the hole.

According to a first aspect, the present invention consists in a bail for use with an expansion shell anchor comprising: c Ym -a a bullet shaped shroud; and at least two substantially parallel arms extending from diametrically opposed sides of the shroud.

According to a second aspect the present invention consists in an expansion shell for anchoring a first end of a rockbolt in a 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 said first end, said bail comprising a bullet shaped shroud for preventing contact of said first end with the oo..

periphery of said hole by maintaining the first end at least a predetermined distance from

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the periphery of the hole and at least two substantially parallel arms extending from diametrically opposed sides of the shroud and respectively engaging said leaves.

The arms are preferably formed integral with the shroud. Preferably the arms each include at least one projection for engaging the periphery of the hole. The *0 projection(s) are preferably located on or adjacent the end of the arms attached to the leaves and are formed in a substantially semi-circular shape.

0: The expansion shell can be used as part of a rockbolting system with the second end of the rockbolt cooperating with a face plate which includes an engagement surface for abutting an excavated surface around the periphery of the hole (such as that described in application AU 20984/92) for allowing tensioning of the rockbolt.

Preferably, the rockbolt is tubular for allowing the pumping of cementitious grout therethrough and is formed from either seamless cold drawn tube or electrically 9 -C -4resistance welded tube. Preferably, the second end of the rockbolt includes a rope thread or the like for providing resistance to blast damage. In a preferred form the first end of the rockbolt is swaged and includes a thread for engaging the complimentarily threaded expansion shell.

When a hollow rock bolt is used, the shroud is preferably spaced apart from the leaves and selectively engageable with the first end for allowing grout to flow substantially unhindered through the hollow rockbolt. The shroud preferably includes a plurality of spaced apart apertures for further facilitating an unhindered flow of grout through the rockbolt. Because the shroud is bullet shaped a gap is formed between the bolt and the shroud which aids in facilitating flow of the grout. The apertures are **preferably disposed such that grout is able to flow through the rockbolt with the first end :abutted against the shroud.

o 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 shows a rockbolting system using a preferred expansion shell of the "ivention; Figure 2 is a hollow groutable rockbolting system for providing temporary and/or permanent support; Figure 3 is a front view of a preferred expansion shell according to the invention; Figure 4 is a side view of the expansion shell of Figure 3; Figure 5 is a top view of the wedge used in Figure 3; and Figure 6 is a sectional view taken along line 35-35 of Figure

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I--I -L With reference to Figure 1, a rockbolt 2 is shown inserted in a suitably placed hole 20 located in an excavated surface 21. Rockbolt 2 includes threaded end 22 which extends outwardly from excavation 21.

The rockbolt is retained in hole 20 by an expansion shell 23 which fixedly engages the sides of the hole. A face plate 1 having a corrugation 10, as described in Figure 1 of AU 20984/92, is retained to rockbolt 2 by a composite nut 27 which includes a concave hemispherical washer 28 having a complementary radius of curvature to a convex surface 25 provided by a raised portion 3. Although shown separate, washer 28 and nut 27 are generally welded together. In further embodiments the weld is designed 10 to shear at a predetermined torque for providing assistance in establishing an optimal engagement between the abutted surfaces.

i To tension rockbolt 2, nut 27 is progressed along threaded end 22 by a suitable tool (not shown) such that washer 28 is presented to surface 25. Due to the complementary nature of surface 25 and washer 28 a maximum area of contact is established therebetween for substantially reducing the risk of face plate 1 being pierced by washer 27.

As also shown in Figure 1, 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 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.

I -r Ir_ -6- Referring to Figure 2 there is illustrated a rockbolting system 200 for providing temporary and/or pernianent support for rock 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 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 mm due to grouting requirements. The bolt illustrated includes 10 nominal internal and external diameters of 18 mm and 25 mm respectively.

Fixed end 207 is swaged and has intenal and external diameters of about 15 mm ee..

and about 22 mm respectively and is threaded with a 24 mm cold rolled left hand thread for receiving a complementarily formed bail type expansion shell 210. The expansion shell includes leaves 211 which are brought into 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.

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 predetermnnined tension in bolt 205.

However, this latter embodiment would not be suited for 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.

I dld 4L4~ I I -7- 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 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-operates with a second concave nut 222 and rockbolt 205. Mesh 220 is 150 mm x 150 mm arc mesh, however, many other meshes are suitable, for example, chainlink type mesh.

To install bolt 205 for temporary support, hole 206 is drilled to an appropriate 10 length. Bolt 205 is then inserted and rotated in order to bring leaves 211 into 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.

C oC 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

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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 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 through expansion shell 210

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-~--~IL~lgll 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 expansion 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 205 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 10 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 progress along bolt 205 and bring fac, 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 both retensioned after the further work and the *0o0 installation of mesh 220 with curn 221 as required.

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

The rockbolting system incorporating the expansion shell according to the invention dispenses with separate temporary and permanent ground support and allows for adjustment of the installed bolts 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.

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L I C-d L -9- In circumstances where mechanical installation of bolts is practiced it is preferred to use an expansion shell such as that illustrated in Figures 3 and 4. Expansion shell 250 includes a cylindrical wedge 251 threadedly engaged with end 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 254 also includes intermediate bullet shaped shroud 257. The shroud includes two spaced apart apertures 258 and a domed end 259.

The free end of arms 255 and 256 are deformed outwardly from leaves 252 and 254 for engaging the surface 212. The degree of deformation is sufficient to allow .10 relatively unhindered progression of shell 250 into hole 206, while movement in the opposing direction is 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 Ssubsequently radially advance leaves 252 and 253 into anchored engagement with opposing surfaces of wall 212. The deformed ends of arms 255 and 256 ensure sufficient frictional contact with wall 212 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 particularly advantageous where later grouting is required. The shroud ensures that grout will not be prevented from exiting end 207 of bolt 205.

I- I~ ist b ~eL~r- Moreover, apertures 258 and the open side of the domed head also facilitate a free flow of 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.

Figures 5 and 6 illustrate a preferred wedge 260 for use in expansion shell 250.

Wedge 260 includes an internal thread 261 and preferably four external equally angularly spaced apart axially extending grooves 262 for facilitating a free flow of grout past the wedge and for preventing the wedge from rotating with respect to the bail and .o shells. 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.

Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

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Claims (8)

1. A bail for use with an expansion shell anchor comprising: a bullet shaped shroud; and at least two substantially parallel arms extending from diametrically opposed sides of the shroud.

2. A bail according to Claim 1 wherein the arms are formed integral with the shroud.

3. A bail according to Claim 1 or 2 wherein the shroud further comprises a plurality of spaced apart apertures.

4. A bail according to any one of claims 1 to 3 where the arms each include at least one projection. An expansion shell for anchoring a first end of a rockbolt in a 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 S" 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 said first end, said bail comprising a bullet shaped shroud for preventing contact of said first end with the periphery of said hole by maintaining the first end at least a predetermined distance from the periphery of the hole and at least two substantially parallel arms extending from diametrically opposed sides of the shroud and respectively engaging said leaves.

6. An expansion shell according to Claim 5 wherein the arms are formed integral with the shroud.

12- 7. An expansion shell according to claim 5 or claim 6 wherein said rockbolt is hollow dnd said shroud is spaced apart from said leaves and selectively engageable with said first end for allowing grout to flow substantially-unhindered through said hollow rockbolt. 8. An expansion shell according to claim 7 wherein said shroud includes a plurality of spaced apart apertures for further facilitating an unhindered flow of grout through said rockbolt. 9. An expansion shell according to claim 8 wherein the apertures are disposed such that grout is able to flow through said rockbolt with said first end abutted against the 10 shroud. 10. An expansion shell according to any one of claims 5 to 9 wkco said arms each include at least one projection for engaging the periphery of said hole. o 11. An expansion shell according to claim 10 wherein said projection(s) are located O or adjacent that end of the arms attached to said leaves and are formed in a o* e substantially semi-circular shape. 12. An expansion shell according to any one of claims 5 to 11 in combination with a face plate which includes an engagement surface for abutting an excavated surface O around the periphery of the hole.

13. A bail as claimed in Claim 1 substantially as herein described with reference to any one of the accompanying drawings.

14. An expansion shell as claimed in Claim 5 substantially as herein described with reference to any one of the accompanying drawings. DATEDthis 19th Day of September, 1995 MOUNT ISA MINES LIMITED Attorney: RUTH M. CLARKSON Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS ~1 I ABSTRACT A bail (254) for use with an expansion shell anchor (250) is disclosed. The bail (254) comprises a bullet shaped shroud (257) and at least two substantially parallel arms (255, 256) extending from diametrically opposed sides of ti 1 shroud. (Fig. 3) a e I- U