AU2017101914A4 - Improvements in the installation of rockbolts and the like - Google Patents

Abstract

A lining (10,100) for preventing borehole collapse during the insertion of rockbolts, rock dowels or the like into strata, particularly coal strata, the lining comprising an annular sleeve (20, 100), and an annular cutting head (10, 110) fixed to one end of the annular sleeve wherein the interior of the lining defines a first engagement means (40, 136) for engagement with a corresponding second engagement means (36, 150) on a drill steel or the like for use in rotating the sleeve and forming a borehole. 7/15 S oW| CI ~~1 t9 9/15 m1 GW1 C6 -Ie 01 -J C -n C -I CD

Description

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Improvements in the installation of rockbolts and the like

Cross-Reference to Related Applications

[0001] The present application claims priority from Australian Provisional Patent Application No 2016903637 filed on 9 September 2016, the content of which is incorporated herein by reference.

Technical Field

[0002] The present invention relates to improvements in the installation of rockbolts and the like for use in the reinforcement of earth strata, such as in underground mining and in particular in tunnelling in coal mines.

Background

[0003] Rockbolts and rock dowels are installed into the wall (rib) of a coal mine to provide stability. This is done by drilling a borehole to accept a resin capsule and a rockbolt. The resin is inserted into the borehole by hand, and then the rockbolt is pushed and spun through the resin capsule to rupture it and mix the resin. The resin sets and anchors the rockbolt in the borehole.

[0004] In some mines, the rib material can be severely crushed and fractured. In these cases, the crushed material can collapse into the borehole, preventing the insertion of the resin capsule. When this happens, the borehole needs to be re-drilled in order to complete the installation. This has a significant impact on rockbolt installation times, and as a result, slows down roadway development rates.

[0005] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

Summary

[0006] According to a first aspect of the present invention there is provided a lining for preventing borehole collapse during the insertion of rockbolts, rock dowels or the like into strata, particularly coal strata, comprising an annular sleeve, and an annular cutting head fixed to one end of the annular sleeve wherein the interior of the lining defines a first engagement means for engagement with a corresponding second engagement means on a drill steel or the like for use in rotating the sleeve and forming a borehole.

[0007] Generally, when drilling a borehole in coal, the "crush zone", where the coal does tend to collapse and block the borehole is limited in depth from the face of the wall. Placing a sleeve in the crush zone prevents the borehole from blocking with crushed material while the rock bolt extends past the sleeve into the borehole beyond the crush zone. While the sleeve inhibits the binding of the rockbolt and resin in the crush zone, the binding of the rockbolt to the coal strata in the distal end of the borehole is sufficient to retain the rockbolt in the borehole.

[0008] Typically, the engagement means comprises a female engagement means, such as a square cavity defined in the cutting head. The second engagement means comprises a male engagement means, typically a square drive.

[0009] Alternatively, the first engagement means comprises an internally threaded rope drive, defined in the annular cutting head, and the second engagement means comprises an externally threaded rope drive defined on the drill rod. Typically the rope threads are R32.

[0010] Ina preferred embodiment, the annular cutting head defines one or more teeth at a first end and a first projection which projects from the second or opposite end of the cutting head from the first end and wherein the drill rod defines a second projection which, in use, when the cutting head is threadingly engaged on the drill rod, abuts the first projection to inhibit further travel of the cutting head on the externally threaded rope drive.

[0011] The annular sleeve maybe formed from a plastic material.

[0012] The annular sleeve may alternatively be formed from steel.

[0013] The annular sleeve may defines a series of holes or perforations.

[0014] Ina related embodiment, the invention provides a method of inhibiting borehole collapse, the borehole being preferably for rockbolt or rockdowel insertion, comprising the steps of:

forming a borehole in a strata using a drill steel or the like, while simultaneously forming a larger diameter hole surrounding a part of the borehole proximal to the face of the strata, but not the distal end of the borehole, using a lining including an annular sleeve, with an annular cutting head fixed to one end of the annular sleeve, rotating with the drill steel to define a first borehole portion having a narrower diameter which is not enclosed by the sleeve and a contiguous second wider portion which is enclosed by the sleeve.

[0015] Ina preferred embodiment the method further includes the step of disengaging the drill string from the lining after completion of the borehole and withdrawing the drill steel through the lining.

[0016] Subsequent to the withdrawal of the drill steel, the method may also include the steps of inserting a resin capsule into the first borehole portion; inserting a rockbolt or rock dowel in the borehole; spinning the rockbolt or rock dowel to mix the resin; and allowing the resin to set.

[0017] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of Drawings

[0018] Specific embodiments of the present invention will now be described, byway of example only, and with reference to the accompanying drawings, in which:

Figure 1 is an isometric view of afirst embodiment of a reamer;

Figure 2 is an isometric view of afirst embodiment of a drive insert;

Figure 3a is a side view of an assembly of the reamer attached to a plastic tube;

Figure 3b is an isometric view of the assembly;

Figure 3c is an enlarged view of the cutting end of the assembly;

Figure 4a is an exploded view showing the reamer of Figure 1 and a sleeve;

Figure 4b is an exploded view showing a drill steel, the drive insert of Figure 2 and a drill bit;

Figure 5 is a side view showing the drive insert inside the reamer;

Figure 6 is a sectional view of drive insert inside the reamer;

Figure 6a shows a view of a variant of the reamer illustrating flushing ports;

Figure 7 is a schematic side view illustrating a first stage in the formation of a borehole in a wall (rib) of a coal mine using a drill steel;

Figure 8 is a schematic side view illustrating a second stage in the formation of the borehole showing the hole completed;

Figure 9 shows the drill steel partly withdrawn from the borehole;

Figure 10 shows the drill steel removed from the borehole;

Figure 11 shows a resin capsule inserted in the hole and a rockbolt being inserted into the borehole;

Figure 12 shows the rockbolt encapsulated in the borehole;

Figure 13 shows a second embodiment of a reamer;

Figure 14 shows a section through the reamer of Figure 13 illustrating the internal R32 rope thread;

Figure 15 is a side view of an inline drive mechanism showing the external male R32 rope thread;

Figure 16 is an isometric view of the inline drive mechanism of Figure 15;

Figure 17 is a side view showing the reamer of Figure 13

Figure 18 shows a perforated sleeve; and

Figure 19 shows the attachment of the reamer to the perforated sleeve.

Description of Embodiments

[0019] Referring to the drawings, Figures 1 to 6 show components for use when installing a rockbolt or the like in a wall of a coal mine. Figure 1 shows a cutting head in the form of a reamer 10 which when rotated about its axis can be used to enlarge or finish a hole. A circular hole 12 extends through the front face 14 of the reamer along its central longitudinal axis. The front or cutting face 14 defines a plurality of (typically four) teeth 16 for cutting into coal or the like. The rear of the reamer defines a stepped down portion 18 so that the reamer can slot into the end of a rigid sleeve in the form of a length of, typically plastic, tubing 20 (refer to Figure 3 and Figure 7) to form a lining. The external diameter of the step down portion preferably equals the internal diameter of the sleeve to ensure a tight fit of the reamer 10 in the sleeve.

[0020] The reamer 10 is fixed to the sleeve 20 by any suitable means such as using adhesive or by a mechanical fitting such as a bayonet connection, so that as the reamer rotates, the sleeve is also rotated about its longitudinal axis. Figures 3a to 3c show one embodiment of a reamer and plastic sleeve connected by a bayonet fitting 22. It can be seen that in the embodiment of Figures 3a to 3c the majority of the external surface of the reamer is cylindrical and of the same diameter as the sleeve although the four teeth 16 extend radially outwardly beyond that diameter. The sleeve will typically be about 600 mm long.

[0021] Figure 4 shows a drill rod in the form of a drill steel 30. As shown, the drill steel is in three parts and includes a first relatively long steel 32, the proximal end of which engages with a dolly/drill rig (not shown), a further drive component 34 which defines a 25mm square drive means 36 and a further length of steel 38, defining, at its distal end, a drill bit 40. The function of the square drive is to provide a means of engaging with and driving (rotating) the reamer 10 as the drill steel is rotated about its longitudinal axis. Although Figure 4 shows that the drill steel is formed in three parts, it could be manufactured as one integral component.

[0022] With reference to Figure 2, at one end the drive component defines one externally threaded end for insertion into the shorter length of drill steel, and at the opposite end it defines an internally threaded portion for receiving a threaded end of the longer steel 32.

[0023] Figures 5 and 6 illustrate the engagement of the reamer 10 with the drill steel 30 and in particular with the square drive portion 36 of the drill steel. The interior of the reamer defines a female drive engagement means in the form of a cavity 40 having a generally square cross section. When the square drive means 36 is inserted in the reamer as shown in Figure 6, rotation of the drive means rotates the reamer by virtue of the engagement of the drive means 36 in the square cavity 40. The aperture 12 in the front of the reamer is smaller than the square drive 36.

[0024] Figure 6a shows a variant of the reamer illustrating flushing ports 19 in the reamer which allow the flow of water back along the borehole during flushing, as is described in more detail below.

[0025] Figure 7 shows the first stage in the formation of a borehole 70 for a rockbolt in a wall (rib) of a coal mine. In particular a drill steel 30, including a drive portion, not shown, is inserted through the sleeve 20 with the drive portion engaged in the female drive engagement means, so that rotation of the drill string using a drill rig (not shown) rotates both the drill string and the reamer 10 with thrust being applied to push the drill steel 30 and reamer into the coal strata to form the borehole 70.

[0026] As the drill string is rotated under thrust, the drill bit and the reamer both penetrate into the coal wall. The drive steel is rotated until the proximal end of the sleeve 20 is flush with the coal face as shown in Figure 8 or is slightly countersunk. Once the borehole 70 is completed, water is then flushed through the distal end of the drill steel to flush the debris resulting from the drilling out of the borehole. During this process water may pass through the flushing ports 19 in the reamer.

[0027] With reference to Figure 9, the drill steel is then withdrawn from the borehole through the hole 12 in the centre of the reamer 10 with the square drive disengaging from the cavity 40. Figure 10 shows the drill steel fully withdrawn from the borehole, with the sleeve 20 keeping the proximal end of the hole free from debris. It will be seen that the borehole has a first borehole portion 72 having a narrower diameter which is not enclosed by the sleeve which opens out to a contiguous second wider portion 74 which is enclosed by the sleeve, and is in fluid communication with the first portion.

[0028] Next, as shown in Figure 11, a resin capsule 50 is inserted in the narrower first portion of the borehole and a rockbolt 60 is inserted into the hole using a drilling rig (not shown). Once fully inserted, as shown in Figure 12 the rockbolt 60 is spun to mix the resin. After the resin is allowed to set, tension is applied to the bolt by rotation.

[0029] Generally, when drilling a borehole in coal, the "crush zone", where the coal does tend to collapse and block the borehole is limited in depth from the face of the wall. Placing the sleeve in the crush zone protects the integrity of the borehole 70 and prevents the borehole from blocking with crushed material while the rock bolt extends past the sleeve into the borehole beyond the crush zone. While the sleeve inhibits the binding of the rockbolt and resin in the crush zone, the binding of the rockbolt to the coal strata in the distal end of the borehole is sufficient to retain the rockbolt in the borehole.

[0030] The system can hasten roadway development in highly fractured rib conditions. The placement of the square drive and the length of the plastic sleeve can be tailored to match the expected depth of the crush zone in a specific mine.

[0031] The use of a plastic sleeve, if used in conjunction with a plastic rock bolt or dowel, makes the system more suitable for use with coal faces that are to be subsequently cut, as the only metal component, that might damage the coal cutter is the reamer. However the system may equally be used with a steel rock bolt such as an M24 rockbolt.

[0032] Whilst the system is described above with reference to its use in a coal mine, it will be appreciated that it may have other applications in other types of mining and in reinforcing strata generally.

[0033] While the sleeve shown is continuous, it would be possible for the sleeve to be perforated. Figure 18 shows an example of a perforated sleeve 100 which is formed from steel, although it would equally be possible to provide a perforated plastic sleeve, or a sleeve made from other suitable materials. In the case of the steel sleeve, the reamer 110 (which is shown in more detail in Figures 13 and 14) is welded to the perforated steel sleeve 100. The use of a perforated sleeve allows resin to flow from inside the sleeve to the outside of the sleeve during installation and provides an improved resin bond between the bolt and the borehole for the length of the bolt protected by the sleeve.

[0034] Figures 13 to 17 show a reamer 110 and drive mechanism. The reamer is a variant of the first reamer 10 shown in Figure 1. A circular hole 112 extends through the front face 114 of the reamer along its central longitudinal axis. The front or cutting face 114 defines a plurality of (typically four) teeth 116 for cutting into coal or the like. The rear of the reamer defines a stepped down portion 118 which includes an externally threaded portion 119 so that the reamer can be threaded into the end of an internally threaded rigid plastic sleeve 200 (refer to Figure 19). As shown in Figure 19, the external diameter of the stepped down portion preferably equals the internal diameter of the sleeve to ensure a tight fit of the reamer 110 in the sleeve 200.

[0035] The interior of the reamer defines a 'female' R32 rope thread 120. A longitudinally extending projection in the form of a tag 122 is defined at the opposite end of the reamer to the cutting face.

[0036] Figures 15 to 17 illustrate the engagement of the reamer with a drive component 134 of a drill steel 130. The drive component defines an externally threaded R32 rope drive 150 and an key block 162 at one end of the rope thread.

[0037] As shown in Figure 17, the drive component 134 defines the externally threaded R32 rope thread 150 towards one end of the drill steel (noting that only the part of the drill steel having the drive mechanism is shown in Figures 15 to 17). The drill steel may be the same as the drill steel shown in Figure 4b, except for the change in the drive component. Adjacent the rope thread 150 there is a larger diameter portion 160. The key block 162 is defined on the drive mechanism adjacent the larger diameter portion 160. When the reamer is threaded onto the rope thread 150, as shown in Figure 17, the tab 112 abuts the key 162 and prevents the rope thread from binding and over tightening during the drilling operation. The tab-and-key also allows the drill rod drive component and drill steel to freely disengage from the reamer once drilling is complete. The use of the rope thread drive mechanism also allows the reamer to more consistently disengage from the drill steel once drilling is complete.

[0038] The rope thread drive mechanism has the advantage that when drilling downwards, the reamer remains engaged with the drive mechanism. In the case of the drive mechanism of the first embodiment, there is a greater possibility of disengagement in those circumstances.

[0039] The process to install the variant shown in Figures 13 to 17 is essentially the same as that of the first embodiment, the only difference being the slightly different engagement connection between reamer and drive component.

[0040] Figure 19 shows the reamer 110 attached to a plastic sleeve 200. In this case instead of the bayonet fitting of the first embodiment, the reamer is externally threaded and screws into a corresponding internal thread in the sleeve.

[0041] Also while the drawings of the first embodiment show a square drive on the drill steel for driving the reamer, it will be appreciated that the drive may have other configurations such as hexagonal.

[0042] It is envisaged that the square drive connection between the sleeve and the drill steel may in some embodiments be replaced with a threaded connection.

[0043] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (14)

CLAIMS:

1. A lining for preventing borehole collapse during the insertion of rockbolts, rock dowels or the like into strata, particularly coal strata, comprising an annular sleeve, and an annular cutting head fixed to one end of the annular sleeve wherein the interior of the lining defines a first engagement means for engagement with a corresponding second engagement means on a drill rod or the like for use in rotating the sleeve and forming a borehole.

2. A lining as claimed in claim 1 wherein, the first engagement means comprises a female engagement means, typically a square cavity defined in the cutting head.

3. A lining as claimed in claim 2 wherein the second engagement means comprises a male engagement means, typically a square drive.

4. A lining as claimed in claim 1 wherein, the first engagement means comprises an internally threaded rope drive, defined in the annular cutting head.

5. A lining as claimed in claim 4 wherein, the second engagement means comprises an externally threaded rope drive defined on the drill rod.

6. A lining as claimed in claim 5 wherein the rope thread is R32.

7. A lining as claimed in any one of claims 5 to 6 wherein the annular cutting head defines one or more teeth at a first end and a first projection which projects from the second or opposite end of the cutting head from the first end and wherein the drill rod defines a second projection which, in use, when the cutting head is threadingly engaged on the drill rod, abuts the first projection to inhibit further travel of the cutting head on the externally threaded rope drive.

8. A lining as claimed in any preceding claim wherein the annular sleeve is formed from a plastic material.

9. A lining as claimed in any one of claims 1 to 7 wherein the annular sleeve is formed from steel.

10. A lining as claimed in any preceding claim wherein the annular sleeve defines a series of holes or perforations.

11. The combination of a drill steel and a lining as claimed in any preceding claims wherein the drill steel defines a second engagement means for engagement with the first engagement means of the lining.

12. A method of inhibiting borehole collapse, the borehole being preferably for rockbolt or rockdowel insertion, comprising the steps of: forming a borehole in a strata using a drill steel or the like, while simultaneously forming a larger diameter hole surrounding a part of the borehole proximal to the face of the strata, but not the distal end of the borehole, using a lining including an annular sleeve, with an annular cutting head fixed to one end of the annular sleeve, rotating with the drill steel to define a first borehole portion having a narrower diameter which is not enclosed by the sleeve and a contiguous second wider portion which is enclosed by the sleeve.

13. The method of claim 12 including the step of disengaging the drill string from the lining after completion of the borehole and withdrawing the drill steel through the lining.

14. The method of claim 13 including, subsequent to the withdrawal of the drill steel, the steps of: inserting a resin capsule into the first borehole portion; inserting a rockbolt or rock dowel in the borehole; spinning the rockbolt or rock dowel to mix the resin; and allowing the resin to set.

2017101914 24 Aug 2017 1/15