WO2025210487A1

WO2025210487A1 - A structural spacer member, a washer assembly, and a rock bolt assembly

Info

Publication number: WO2025210487A1
Application number: PCT/IB2025/053380
Authority: WO
Inventors: Werner Cornelius BELLINGHAM; Peter Muller
Original assignee: Rocbolt Technologies Pty Ltd
Current assignee: Rocbolt Technologies Pty Ltd
Priority date: 2024-04-02
Filing date: 2025-04-01
Publication date: 2025-10-09
Anticipated expiration: 2026-10-02

Abstract

A structural spacer member (100) is for use in a rock bolt assembly (200) and has a body defining a longitudinal axis (110). The body has a longitudinally outer end (104) configured to bear against a tensioning element and a longitudinally inner end (108) configured to bear against a washer (or rock plate) (202). The body has a main channel (112) extending longitudinally between the outer and inner ends, the main channel configured to receive a shaft therethrough, an auxiliary opening (120) at a side of the body, and an auxiliary channel (122) extending laterally between the auxiliary opening and the inner end, the auxiliary channel configured to receive at least one tube (210, 212) therethrough.

Description

A Structural Spacer Member, a Washer Assembly, and a Rock Bolt Assembly

FIELD OF INVENTION

This invention relates generally to rock bolts for use in mining and more specifically to a structural spacer member, a washer assembly, and a rock bolt assembly.

BACKGROUND OF INVENTION

In mining and construction, it is well known to install rock bolts in walls to provide support and stability to the walls — this is an important aspect of health and safety. This is common in roofs of mines to support rock and prevent rock or other debris from falling down. These rock bolts may also be known as wall anchors or rock anchors, and when installed in roofs (or hanging walls) of mines, they may be called roof bolts.

To install rock bolts, a hole is drilled into a rock wall. A rock bolt including a shaft, usually a little shorter than the depth of the hole, is inserted into the hole. The shaft may be a solid rod or a flexible cable. The wall bolt includes an anchoring mechanism at its inner end (or dead end). A washer (or rock plate) is provided at the outer end (or live end) to engage the rock wall. The shaft extends through a hole in the washer and is tensioned to the washer by means of a nut or barrel.

One example of an anchoring mechanism is use of a cementitious material, like cement or grout. This is pumped into the hole. One practice is to use a feeder tube (or grout tube) which extends through the washer, into the hole, alongside the shaft, and to the end of the hole. A breather tube may also be provided adjacent to the feeder tube to permit air to escape so that it does not become trapped and cause air pockets. The washer may include additional holes to accommodate the tubes adjacent the main hole which accommodates the shaft.

A drawback that the Applicant has experienced is that the tubes can be interfered with, or damaged, by the barrel/nut and/or the washer. Washers which provide dedicated holes for the tubes tend to be thick or expensive or have limitations in their angular correction and spacing for the pipes. This generally causes the feeder or breather tubes to get bent during pretensioning of the rock bolt. When either of the two tubes are occluded, the grouting of the installation becomes difficult and could lead to poor grouting. If the hole is not properly supported with grout, the wall bolt cannot perform optimally, which causes a safety hazard. (The Applicant is aware of a solution with a hollow centre in the cable strand, but this is costly and not suitable for the Applicant’s purposes.)

Accordingly, the Applicant desires a solution to accommodate the tubes during installation and grouting.

SUMMARY OF INVENTION

Accordingly, the invention provides a structural spacer member for use in a rock bolt assembly, the spacer member having a body defining a longitudinal axis, wherein the body defines: a longitudinally outer end configured to bear against a tensioning element; a longitudinally inner end configured to bear against a washer (or rock plate); a main channel extending longitudinally between the outer and inner ends, the main channel configured to receive a shaft therethrough; an auxiliary opening at a side of the body; and an auxiliary channel extending laterally between the auxiliary opening and the inner end, the auxiliary channel configured to receive at least one tube therethrough.

For brevity, the structural spacer member is referred to merely as a spacer member.

The spacer member may be made of metal. The spacer member may be of unitary or monolithic construction. The spacer member may be forged.

The body may be hollow. The body may be cuboid. The body may comprise three sidewalls. The body may lack a fourth sidewall thereby defining the auxiliary opening.

The auxiliary channel may extend transversely or obliquely relative to the longitudinal axis. The auxiliary channel and the main channel may merge at the inner end.

The body may have an outer wall at the outer end which defines an outer aperture configured to receive the shaft.

The body may lack an inner wall. Inner ends of the sidewalls may be configured to bear against the washer.

The body may include one or more reinforcing members, e.g., ribs, crosspieces, webs, etc.

The invention extends to a washer assembly including: the spacer member as defined above; and a washer configured for engaging a rock wall, the washer defining a central aperture, wherein the longitudinally inner end of the spacer member is connected to the washer and the main channel of the spacer member is aligned with the central aperture.

The washer and the spacer member may be fixed together. The washer and spacer member may be welded together.

The central aperture may be larger than an intended drilled hole size. Conventional drilled hole sizes may be 34-38 mm. The aperture may be 35-50 mm.

The washer may be flat or planar. The washer may be convex or domed shaped. The washer may be concave or inverted. The concave or inverted washer may be suitable for bad surfaces, as typical in South African hard rock mines, as it may allow for better seating of the washer and/or for better angular adjustment.

The invention extends to a rock bolt assembly including: the washer assembly defined above; and at least one shaft configured to extend through the main channel of the spacer member and the central aperture of the washer.

The rock bolt assembly may further include one or more tubes (e.g., feeder tube and/or breather tube) configured to extend through the auxiliary channel of the spacer member and the central aperture of the washer. The tubes may be used for grouting.

The shaft may be a rigid rod or a flexible cable.

The rock bolt assembly may include a tensioning element, e.g., nut or barrel, attached to the shaft and configured to bear against the longitudinally outer end of the spacer member. BRIEF DESCRIPTION OF DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings. ln the drawings:

FIG. 1 shows a three-dimensional view from an outer end of a spacer member, in accordance with the invention;

FIG. 2 shows a three-dimensional view from another side of the spacer member of FIG. 1 ;

FIG. 3 shows a three-dimensional view from an inner end of the spacer member of FIG. 1 ;

FIGS 4-6 show a series of side views of a first embodiment of a rock bolt assembly incorporating the spacer member of FIG. 1 ;

FIGS 7-9 show a series of side views of a second embodiment of a rock bolt assembly incorporating the spacer member of FIG. 1 ; and

FIGS 10-12 show a series of side views of a third embodiment of a rock bolt assembly incorporating the spacer member of FIG. 1 .

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

The following description of an example embodiment of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that changes can be made to the example embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the example embodiment without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the example embodiment are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description of the example embodiment is provided as illustrative of the principles of the present invention and not a limitation thereof.

FIGS 1-3 illustrate a spacer member 100, in accordance with the invention. The spacer member 100 has a hollow body 102 which is generally cuboid. The body 102 is forged of metal, e.g., steel.

The body 102 defines a longitudinally outer end 104 (which, when installed at a mine roof, will be an operatively lower end). This outer end 104 is configured to bear against a tensioning nut or barrel in use (See FIGS 4-12). The outer end 104 includes a partial outer wall and defines an outer aperture 106 configured to accommodate a shaft of a rock bolt assembly.

A longitudinally inner end 108 (which, when installed at the mine roof, will be an operatively upper end) of the body 102 is configured to bear against a washer in use. The inner end 108 has no inner wall and is therefore open. The body 102 defines a longitudinal axis 110.

Notably, the body 102 defines a main channel 112 extending longitudinally along the longitudinal axis 110 between the outer and inner ends 104, 108, specifically through the outer aperture 106 of the outer end 104. The main channel 112 is configured to receive and accommodate a shaft therethrough.

The body 102 defines an auxiliary opening 120 at one of its sides. The auxiliary opening 120 may simply be in the form of a missing sidewall. The body 102 defines an auxiliary channel 122 extending laterally or obliquely between the auxiliary opening 120 and the inner end 108. The auxiliary channel 122 is configured to receive at least one tube therethrough, in a path that is partially separate from the main channel 112. The body 102 may include various structural or reinforcing elements. For example, the outer aperture 106 includes a peripheral rim around it. A reinforcing crosspiece 124 is provided inside the body 102, effectively between the main channel 112 and the auxiliary channel 122. An intended load may influence wall thickness of the body 102 and configuration of the reinforcing elements. The present spacer member 100 is configured for use with pretensioning in the order of 10-20 T.

The spacer member 100 is intended to be integrated with a washer or rock plate (see FIGS 4-12). The spacer member 100 may be welded to the washer, or otherwise fastened (e.g., interlocked), to constitute a washer assembly. This washer assembly is used with a rock bolt to form a rock bolt assembly.

FIGS 4-6 illustrate a first embodiment of a rock bolt assembly 200, in accordance with the invention. In this embodiment, an inverted washer 202 is provided. The inverted washer 202 has a concave configuration which may allow for better seating of the washer 202 as well as angular adjustment thereof. The washer 202 defines a central aperture (not illustrated). The spacer member 100 is welded to the washer 202 such that the main channel 112 is aligned with the central aperture.

The rock bolt assembly 200 has various other (largely conventional) components, namely a shaft in the form of a wire cable 204. This rock bolt assembly 200 is a cabletype assembly but rigid rod-type assemblies may be practicable too. A barrel 206 is fixed to the cable 204.

In use, two breather tubes 210, 212 form part of the rock bolt assembly 200. The first tube 210 may be a feeder tube (specifically a grout tube 210) to feed grout into the hole, while the second tube 212 may be a breather tube 212. The tubes 210, 212 are fed into the auxiliary opening 120, through the auxiliary channel 122, and through the central aperture, such that they extend along the cable 204. The tubes 210, 212 may be bound or fastened to the cable 204, but their free end stick outwardly from the spacer member 100. In installation, the rock bolt assembly 200 is installed in a hole 12 in a rock wall 10 (which may be a roof or hanging wall in a mine). The combination of the cable 204 and tubes 210, 212 is fed upwards into the hole 12, until the washer 202 abuts the wall 10. The rock bolt assembly 200 is then pretensioned to a desired load (e.g., 10-20 T). During pretensioning, the barrel 206 (or a device used to drive the barrel) does not interfere with the tubes 210, 212 as they are provided in a different channel 122 from that of the cable 204. This prevents the barrel 206 from bending or occluding the tubes 210, 212. This is important because bend or occluded tubes can limit or even prevent proper dispensing of grout, leading to a sub-standard installation.

FIGS 7-9 illustrate a second embodiment of a rock bolt assembly 220 with a domed or convex washer 222, the assembly 220 otherwise being the same as the assembly 200.

FIGS 10 -12 illustrate a third embodiment of a rock bolt assembly 220 with a flat washer 242, the assembly 240 otherwise being the same as the assembly 200.

The Applicant believes that the rock bolt assembly 200, 220, 240 is advantageous in that the spacer member 100 allows better alignment of the grout and breather tubes 210, 212 relative to the hole 10, and is more accessible for the user for grouting. The barrel 206 is placed above the point where the tubes 210, 212 enter the washer 202, 222, 242 which makes it easier for the user to pretension. The location of the tubes 210, 212 also makes it easier to install into the hole 10 which under normal circumstance is quite tight. For very bad surfaces, as is typical in South African hard rock mines, an inverted dome washer 202 can be incorporated which allows for better seating of the washer 202, and the washer 202 also allows for angular adjustment - like spherical seats would for bolts.

Where the hanging wall surface is of better quality, a flat bearing plate 242, or more traditional dome plate 222, can also be utilised using the same spacer member 100. The central aperture where the spacer member 100 interfaces with the washer 202, 222, 242 may be slightly larger than the typical holes drilled in hard rock mines (drilled holes normally range between 34-38 mm). This allows for the grout and breather tubes 210, 212 to be aligned for grouting purposes, and prevents the tubes 210, 212 from catastrophically bending during pretensioning, which impedes the grouting process.

Claims

1. A structural spacer member for use in a rock bolt assembly, the spacer member having a body defining a longitudinal axis, wherein the body defines: a longitudinally outer end configured to bear against a tensioning element; a longitudinally inner end configured to bear against a washer or rock plate; a main channel extending longitudinally between the outer and inner ends, the main channel configured to receive a shaft therethrough; an auxiliary opening at a side of the body; and an auxiliary channel extending laterally between the auxiliary opening and the inner end, the auxiliary channel configured to receive at least one tube therethrough.

2. The spacer member as claimed in claim 1 , which is metal, forged, and of unitary construction.

3. The spacer member as claimed in any one of claims 1-2, in which the body is hollow, cuboid, has three sidewalls, and lacks a fourth sidewall thereby defining the auxiliary opening.

4. The spacer member as claimed in any of claims 1-3, in which the auxiliary channel extends transversely or obliquely relative to the longitudinal axis.

5. The spacer member as claimed in any one of claims 1-4, which includes an outer wall which defines an outer aperture configured to receive the shaft.

6. The spacer member as claimed in any one of claims 1-5, in which the body lacks an inner wall, inner ends of the sidewalls being configured to bear against the washer.

7. The spacer member as claimed in any one of claims 1-6, in which the body includes one or more reinforcing members including at least one internal crosspiece.

8. A washer assembly including: the spacer member as claimed in any one of claims 1-7; and a washer configured for engaging a rock wall, the washer defining a central aperture, wherein the longitudinally inner end of the spacer member is connected to the washer and the main channel of the spacer member is aligned with the central aperture.

9. The washer assembly as claimed in claim 8, in which the washer and the spacer member are fixed together by welding.

10. The washer assembly as claimed in any one of claims 8-9, in which the washer is one of: flat or planar; convex or domed shaped; or concave or inverted.

11. A rock bolt assembly including: the washer assembly as claimed in any one of claims 8-10; and at least one shaft configured to extend through the main channel of the spacer member and the central aperture of the washer.

12. The rock bolt assembly as claimed in claim 11 , further including one or more tubes configured to extend through the auxiliary channel of the spacer member and the central aperture of the washer.

13. The rock bolt assembly as claimed in any one of claims 11-12, in which the shaft is flexible cable, and which includes barrel attached to the cable and configured to bear against the longitudinally outer end of the spacer member.