BACKGROUND TO THE INVENTION [0002] Rock bolts having elongated metal tubes which in use are radially expanded by water at high pressure into gripping contact with the walls of predrilled holes in which they are located are known from the disclosures in the specifications of South African patent No's. 80/1380, 81/6176,82/7161 and 87/8649. In all of the bolts disclosed in the specifications of these patents water pressure is relieved from the bolt tubes after they have been expanded into gripping engagement with the walls of the holes in which they are located. The relief of the water pressure from the tubes results in the resilience of the tube metal causing the tube to spring back in cross-sectional dimension to reduce the tube wall contact pressure from what it was at the initially inflated pressure.

SUMMARY OF THE INVENTION [0003] A method according to the invention of anchoring a rock bolt which comprises an elongated tube which is made from a ductile metal, is closed at one end and includes a one-way liquid inlet valve which opens under liquid pressure into the tube includes the steps of locating the tube in a hole, connecting a liquid hose to the one-way valve, filling the tube with liquid at a pressure high enough to radially expand the wall of the tube into gripping engagement with the wall of the hole and removing the hose from the valve to leave the liquid trapped at pressure in the tube by the valve.

[0004] A portion of the tube wall over at least a substantial portion of the length of the tube is deformed into the tube to reduce its outer circumferential dimension to less than that of the hole in which it is to be anchored with the method conveniently including the step of outwardly deforming the wall deformation by means of the high pressure water to bring the wall into engagement with the wall of the hole during installation of the bolt.

[0005] A rock bolt according to the invention comprises a radially expansible tube which is made from a suitable ductile metal which is closed at one end and carries a one-way fluid inlet which opens under pressure into the tube from its other end.

[0006] A portion of the wall of the tube may be deformed into the tube over at least a substantial portion of the length of the tube so that the outer circumferential dimension of the tube is less than that of a hole in which the tube is to be anchored.

[0007] The bolt may include hoop strengthening ferrule which is fixed over at least the end portion of the tube into which the one-way valve opens. Preferably the ferrule carries, a radially projecting formation on which a face washer may be supported against the material surrounding the mouth of the hole in which the rock bolt is anchored, in use.

[0008] The radially projecting formation may be a washer which is welded to the ferrule at or adjacent the mouth of the tube. The outer end of the ferrule may, however, be outwardly flared to provide the radially projecting formation. In yet a further variation the radially projecting formation may be an annular rib which is formed by rolling the ferrule material from the outer end ferrule back on itself on the outside of the tube.

[0009] The one-way valve of the rock bolt may include a valve body which is sealingly fixed in the open end of the bolt tube with its liquid inlet end projecting from the tube with the body including a liquid bore which passes through it, a hose coupling formation on the projecting end of the body and a diaphragm which is made from an elastomeric material which is peripherally

engaged with the body over its end in the tube to close the body bore outlet into the tube and includes a liquid outlet through it into the tube which is remote from the body bore outlet.

[0010] The liquid inlet to the one-way valve may be surrounded. by a hose coupling formation and the valve may be welded directly into the open mouth of the tube with the hose coupling projecting from the tube.

[0011] In another form of the invention the rock bolt may include an elongated tube bolt which is smaller in cross-sectional dimension than that of the expansible tube and is welded at one end sealingly into the expansible tube with the one-way inlet valve welded into or to the end of the tube bolt in the expansible bolt tube.

BRIEF DESCRIPTION OF THE DRAWINGS [0012] The invention is now described by way of example only with reference to the drawings in which : Figure 1 is a side elevation of the rock bolt of the invention, Figure 2 is a sectioned side elevation of the Figure 1 bolt, Figures 3 to 5 are cross-sectional end elevations of three embodiments of the expansible tube of the bolt of Figures 1 and 2, Figure 6 is a cross-sectional end elevation of the end of the expansible tube of the bolt which carries a filler valve, Figure 7 is an end elevation of the closed end of the expansible tube of the rock bolt which is opposite that which carries the filler valve,

Figure 8 is a sectioned side elevation of a fragmentary end of the rock bolt of the invention in which the filler valve of Figures 9 to 11 is shown located, Figure 9 is a side elevation of the valve body of the filler valve used with this embodiment of the invention, Figure 10 is a sectioned side elevation of a diaphragm for use with the valve body of Figure 9, Figure 11 is an under plan of the Figure 10 diaphragm, Figure 12 is a perspective view from below of the rock bolt in use together with the face washer of the invention, Figure 13 is a side elevation of the rock bolt of the invention located in a hole which is drilled into a skewed face, Figure 14 is a side elevation of a variation of the rock bolt of the invention located in a predrilled hole, Figure 15 is a side elevation of a further variation of the rock bolt of the invention, Figure 16 is the Figure 15 bolt including a hanger loop, Figure 17 is the Figure 15 bolt including a loosely located face washer, and Figure 18 is a fragmentary side elevation of yet a further variation of the bolt.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS [0013] The rock bolt of the invention is shown in Figures 1 to 3 to include a metal tube 10 which carries in one end a one-way water inlet valve 12 and a hoop strengthening ferrule 14 at its valved end. The upper end of the tube may, if required, be sleeved by a second ferrule 16.

[0014] The tube 10 is made from a ductile metal such as mild steel. The tube 10 which is originally circular in cross-section, is deformed, as shown in Figure 3, by pressing a portion of its wall into the tube to provide a deep outwardly widening recess 18 in the tube which extends from just behind the ferrule 14 over the remaining length of the bolt to its rear end. The tube 10 is closed at its upper end in Figures 1 and 2 by welding the C-shaped cavity of the bolt in the ferrule 16 closed as shown in Figure 7. The ferrule 16, if used, is welded to the tube. The forward end of the bolt tube is pressed into the shape illustrated in Figure 6 with the valve 12 being welded into the roughly circular aperture provided by the Figure 6 deformation at the front end of the bolt. The overlapping portions of the wall of tube are welded together and the spaces around the valve 12 are closed by welding.

[0015] Figures 4 and 5 illustrate two further cross-sectional shapes of the tube 10. The Figure 5 cross-sectional profile of the tube could of course include two or more of the wall recesses 20.

[0016] The valve 12, in this embodiment of the invention, is shown in Figures 9 to 11 to include a valve body 22 having on its end which is outermost, in use, a hose coupling formation 24 and on its other end which, in use, is located in the tube 10 a valve

member boss 26. The diaphragm type valve member 28 of Figures 10 and 11 is made from an elastomeric material such as rubber and is cap-shaped in cross-section as shown in Figure 10. The valve member 28 includes a skirt 30 which carries on its underside an inwardly directly rib 32 which, in use, is engaged in an undercut groove 34 in the valve body boss 26, and on its upper end a central boss 36 which is thickened in the axial direction of the valve to enable it to withstand the high water pressure in the tube when it is forced by the water pressure down over the outlet from the bore 37 through the valve body 22. The boss 36 is surrounded by a plurality of water inlet holes 38 which are closed onto the outer surface of the valve body boss 26, as shown in Figure 8, by the water under pressure in the tube 10 in use.

[0017] The ferrules 14 and 16, as illustrated in Figure 8, are of a heavier gauge material than that of the tube 10 to ensure that the end portions of the tube are not deformed by water pressure in use to stress the welding at the tube ends. As is shown in Figure 8, the end of the ferrule 14 which faces the ferrule 16 is, in this embodiment, outwardly flared to provide a seat for a face washer 42 as illustrated in Figures 12 and 13. To ensure that the flared seat of the ferrule 14 is not deformed in use and to provide a larger seat for the face washer, the flared portion of the ferrule could be rolled over to form a bead with its rolled over edge being at least tack-welded to the outer surface of the ferrule.

[0018] The face washer 42 is shown in Figure 12 to be square in plan and includes a central dome 44, and in this embodiment, four buttress ribs 46 which extend radially from the dome 44 to the washer periphery. The washer additionally includes an outwardly bent lug 48 from which cables and the like may be suspended.

10019l Figure 13 illustrates the rock bolt of the invention and the washer 42 in use with a hole 50 which is skewed relatively to a face 52 and against which the washer bears in use. To enable the washer 42 to be skewed on the rock bolt tube the bolt hole through it is in the form of a round ended elongated slot with the width of the slot being no greater than the flared seat on the ferrule 14. Obviously the washer needs to be located on the bolt tube prior to the welding of both ferrules to the tube 10.

[0020] In use, the bolt which has a diameter smaller than that of the hole in which it is intended to be used is slid into the hole with the ferrule 16 towards the distal end of the hole until the washer 42 bears firmly up against the face material surrounding the mouth of the hole. A high pressure water hose is connect to the hose coupler 24 on the exposed end of the valve 12 and water at a supply pressure of between 100 and 300 bar is fed into the tube through the valve 12 with the upper portion of the valve member being lifted from its seat on the valve member boss 26 to permit water to flow from under the central boss 36 of the valve member out through the holes 38 into the tube 10. The high pressure water causes the tube 10 to unfold from its deformed shape as shown in Figures 3,5 or 6 to cause the tube 10 to increase in radial dimension and bring its outer surface into high pressure contact with the wall of the larger diameter hole to lock the rock anchor solidly in position in the hole. The rounded corners of the deformed cross-sectional shape of the tube 10 enable this expansion to occur smoothly by merely unrolling a portion of the tube in the recess 18 outwardly until further movement of the tube wall is prevented by the wall of the hole in which the rock bolt is located.

[0021] When fully pressurised the water hose is removed from the valve 12 and the high pressure water in the tube locks the thickened boss 36 of the valve member over the valve body outlet hole to trap the water at high pressure in the tube 10. Importantly, the high pressurised water which remains trapped in the tube 10 holds the radially expanded tube against resilient cross-sectional spring back and so loss of its initial contact pressure with the wall of the hole as is the case with similar rock anchors of the prior art.

[0022] It is to be noted that for purposes of illustration the rock bolt of the invention is shown in the drawings to be relatively short but could of course be of any practical length which is suitable for a particular rock anchoring application.

[0023] A second embodiment of the bolt of the invention is illustrated in Figure 14 and is shown in the drawing to include the ferruled expansion tube 10 as previously described and a tube bolt 54 which is welded into the end of the tube 10 of the expansible bolt. The expansion tube 10, in this embodiment could be shorter in length than would otherwise be the case as in many applications it would merely serve as an end anchor for the tensioned tube bolt 54. The valve body 22 of the valve 12 could be formed on or welded to the end of the tube bolt 54 to be located in the tube cavity. The free end of the tube bolt could carry over a portion of its length from its free end rolled threads over which a domed washer 56 is slidable and with which a tensioning nut is engaged. In this embodiment of the invention the dome on the face washer 58 would be inwardly concave to form a seat for the domed washer 56.

[0024] If the tube bolt has sufficient diameter its free end could include the hose coupling formation 24 of the previous embodiment or the water hose could include an

outlet nipple which is threadedly engaged with the threads on the end portion of the tube bolt to enable the expandable portion of the bolt to be water filled at high pressure through the tube bolt. Additionally, of course, a threaded sleeve carrying the hose coupling 24 could be screwed onto the free end of the bolt for water filling and then be removed when the valve has closed the water outlet from the tube 10.

[0025] A further variation of the rock bolt of the invention is illustrated in Figures 15 to 17. In this embodiment of the bolt the outer end of the ferrule 14 is outwardly flared, as shown in Figure 15, with the flared mouth of the ferrule being weld filled onto the one- way valve 12.

[0026] In Figure 16 the Figure 15 bolt is shown to include a hanger 60 which in use projects outwardly from the hole in which the bolt is located to enable goods, equipment, service lines and so on to be attached to or suspended from the bolt.

[0027] The Figure 17 bolt is shown supporting the face washer 62 which is slidably located on the ferrule 14.

[0028] Figure 18 shows the bolt of the invention located in a hole 64 to include an outwardly projecting rib 66 which is produced by rolling the outer edge of the ferrule back on itself, as shown on the left in the drawing.