GB2200965A - Rock bolt - Google Patents

Abstract

A rock bolt has several sections (12, 13, 14) of loop form interconnected in chain fashion, so that the sections are relatively hinged. A leading section (14) can be inserted into a drilled hole with the adjacent section (12) at an oblique angle. The adjacent section can then be aligned with the leading section and also inserted in the hole. This arrangement allows a long rock bolt to be used in a confined space. The rock bolt is adhered in the hole and then tensioned. Tensioning is effected by insertion of a wedge between the face which has been drilled and the trailing end of the bolt. <IMAGE>

Description

ROCK BOLT This invention relates to a rock bolt for securing strata, for example in mines, quarries and tunnels.

The use of rock bolts consolidates the strata, for example in a mine roof, and reduces the risk of collapse.

Where thin coal seams are being mined, the height of the roof from the floor is often less than the required length of bolt to be inserted into a drill hole. In these cases, several bolt sections are usually connected together end-to-end using internally threaded connecting sleeves. Each bolt section is a solid rod having screwthreaded end portions. After insertion of a first section, a second section is secured to it by a threaded connecting sleeve and the combined sections are then advanced into the drilled hole, the process being repeated as required. Rupturable containers of settable resin and accelerator or catalyst are first inserted in the hole and the bolt is spun to rupture the containers and mix the materials. The resin runs down the belt and sets hard adhering the bolt to the rock.After setting, a nut is screw-tightened on the bolt against a washer bearing on the mine roof, so that the rock strata are consolidated.

It is inconvenient and time consuming to have to connect sections of the bolt together with sleeve connectors and the bolt does not form a good key for the set resin.

The present invention provides a rock bolt which can be used in confined spaces without the necessity for attaching sections together in situ and which may provide a better key for the resin and may be more cheaply manufactured.

The present invention provides a rock bolt comprising first and second elongate sections hinged together near their adjacent ends whereby the sections can be angularly moved into and out of alignment, the interengagement of the sections being such that a leading section can be advanced in a drill hole by force exerted on the trailing section.

Preferably, each section comprises a looped elongate link interlinked with the other section and a shoulder on the leading link against which the trailing link bears during insertion of the rock bolt.

From a different aspect, the invention resides in a rock bolt assembly comprising a shank of elongate loop form having a leading end and a trailing end, a washer engageable over the trailing end, and a wedge for engagement between the trailing end and the washer for tensioning the bolt.

Reference is now made to the accompanying drawings, wherein Figure 1 is a side elevation of a first embodiment of a rock bplt according to the invention; Figure 2 is an elevation of a modification of the rock bolt of Figure 1; Figure 3 is a side elevation of a chuck for use with the rock bolt; Figure 4 is an end elevation of the chuck of Figure 3; Figure 5 is a perspective view of a washer and a wedge for use with the rock bolt; Figure 6 illustrates use of the washer and wedge; Figure 7 illustrates use of rock bolts according to the invention in a low roof mine excavation; and Figures 8 to 12 show alternative embpdiments of rock bolts according to the invention.

Referring to Figure 1, the rock bolt shown comprises three links 11, 12, 13 of loop form interlinked in a chain. More links may be used, or the central link 12 may be omitted. Each link is formed by looping a length of metal rod, with elongate major portions 14, 15 of the link in side-by-side contact and with an eye formed at each end. The ends of the looped material are welded together as at 10.

One end 16 of the leading link 11 pivotally engages with an eye 17 of the central link 12 and, similarly, one eye 18 of the trailing link 13 pivotally engages with the other eye 19 of the central link. The other eye of the trailing link 13 is larger and defines an engagement portion 20. The other eye of the leading link 11 defines a leading portion 21.

In the modification of Figure 2, the leading portion 121 is shaped to facilitate insertion in a drill hole and the eyes are all symmetrically formed, whereas some of the eyes of the embodiment of Figure 1 are asymmetrically formed. In this modification, the ends of the looped material in each link lie adjacent each other, but are not welded together.

The rock bolts shown can be folded by relative hinging of the links, so that the bolt can be inserted in a drill-hole in a confined space.

Referring to Figure 7, in use, capsules 30, 31 of settable resin and accelerator are inserted in a drill hole 32. A hinged bolt 9 is then inserted in the hole with its trailing end portion remaining protruding from the hole. This portion is attached to a rotatably driven device which spins the bolt to break the capsules and mix the resin and accelerator, which sets around the bolt.

The bolt is then tensioned as described hereafter.

Figure 7+ illustrates a different embodiment of a rock bolt 9 having only two links. The bolt is shown being inse-rted in the drill hole 32 in a roof 34 with a restricted head space.

Referring to Figures 3 and 4, a chuck adaptor is illustrated comprising a screw-threaded portion 40 for securance to the rotatably driven device and an attachment portion 41. The attachment portion is of cylindrical form with a deep slot 42 complementary to the engagement portion 20 of the rock bolt. By engagement of the chuck adaptor with the portion 20 of the rock bolt, the latter can be spun, as described above.

Referring to Figure 5, there is shown a washer 50 having an elongate aperture 51, and a wedge 52 having a head 53 and a tapered shank 54.

As shown in Figures 6 and 7, the rock bolt is tensioned by engaging the washer 50 over the engagement portion 20 of the rock bplt in contact with the rock face 34 around the drill hole 32, engaging the shank of the wedge in the eye of the engagement portion 20, between its trailing end and the washer, and driving the wedge therebetween.

The rock bolt is of exceptionally simple construction and is easily usable in confined spaces, without the need to join sections together. The looped form of each link provides a good key for retention of the rock bplt in a drill hole by the set resin. The use of the wedge for tensioning the bolt is a simple operation and avoids the necessity for welding a screwthreaded trailing end portion onto the bolt.

Figure 8 illustrates a rock bolt which is provided with an adaptor 60 for tensioning of the bolt by means of a nut, in the conventional manner, instead of with the wedge. The adaptor has a body provided with a cross-pin 61 which engages in the eye of the engagement portion 20 so as pivotally to connect the adaptor to the rock bolt.

A screw-threaded shank 62 projects from the body for engagement with the nut.

Figure 9 illustrates a different form of link 70 for a rock bolt, in which two or more straight members 71, 72 are welded together at their ends with connecting pieces 73 to define the loop.

Figure 10 shows another form of rock bolt in which the links 80, 81 are formed from a loop of wire and a bridging member 82 is welded across one 80 of the links to form an eye 83 and to define a bearing face for the other link 81 during insertion of the rock bolt.

Figure 11 shows a modified rock bolt in which each link 90, 91 is twisted for strength.

Figure 12 shows a modified link 95 having a tube secured thereto to permit injection of resin into a drill hole through the tube. This arrangement avoids the use of resin and accelerator capsules and the need for a special adaptor for spinning the bolt.

It is envisaged that a rock bolt having a single loop may be utilised with the wedge, where there is not a problem of confined head room. The advantages of cheap manufacture and simple tensioning technique are thereby achieved.

Claims (7)

1. A rock bolt comprising first and second elongate sections hinged together near their adjacent ends whereby the sections can be angularly moved into and out of alignment, the interengagement of the sections being such that a leading section can be advanced in a drill hole by force exerted on the trailing section.

2. A rock bolt according to Claim 1, wherein each section comprises a looped link interlinked with the other section and a shoulder on the leading link against which the trailing link bears during insertion of the rock bolt.

3. A rock bolt according to Claim 2 wherein the shoulder is defined by a bridging member.

4. A rock bolt according to Claim 2 wherein the shoulder is defined by formation of an eye which receives the trailing link.

5. A rock bolt according to Claim 1, 2, 3 or 4, comprising more than two sections hinged together in a chain.

6. A rock bplt according to any preceding claim having an apertured engagement portion at the trailing end of the bolt, in combination with a washer complementary to the engagement portion and a wedge for insertion in the apertured engagement portion in contact with the washer, for tensioning the rock bolt.

7. A rock bolt constructed substantially as herein described with reference to the accompanying drawings.

7. A rock bolt assembly comprising a bolt of elongate loop form having a leading end and a trailing end, a washer engageable over the trailing end, and a wedge for engagement between the trailing end and the washer for tensioning the bolt.

8. A rock bplt constructed substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A rock bolt comprising first and second elongate sections hinged together near their adjacent ends whereby the sections can be angularly moved into alignment, with said - second section forming an extension of the first section, and out of alignment, the interengagement of the sections being such that a leading section can be advanced in a drill hole by force exerted on the trailing section.

2. A rock bolt according to Claim 1, wherein each section comprises a looped link interlinked with the other section and a shoulder on the leading link against which the trailing link bears during insertion of the rock bolt.

3. A rock bolt according to Claim 2 wherein the shoulder is defined by a bridging member.

4. A rock bolt according to Claim 2 wherein the shoulder is defined by formation of an eye which receives the trailing link.

5. A rock bolt according to Claim 1, 2, 3 or 4, comprising more than two sections hinged together in a chain.

6. A rock bolt according to any preceding claim having an apertured engagement portion at the trailing end of the bolt, in combination with a washer complementary to the engagement portion and a wedge for insertion in the apertured engagement portion in contact with the washer, for tensioning the rock bolt.