AU2004200570A1 - Rock Bolt Assembly - Google Patents
Rock Bolt Assembly Download PDFInfo
- Publication number
- AU2004200570A1 AU2004200570A1 AU2004200570A AU2004200570A AU2004200570A1 AU 2004200570 A1 AU2004200570 A1 AU 2004200570A1 AU 2004200570 A AU2004200570 A AU 2004200570A AU 2004200570 A AU2004200570 A AU 2004200570A AU 2004200570 A1 AU2004200570 A1 AU 2004200570A1
- Authority
- AU
- Australia
- Prior art keywords
- rock bolt
- nut
- drive
- projections
- rock
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000011435 rock Substances 0.000 claims description 114
- 239000000126 substance Substances 0.000 claims description 21
- 238000006073 displacement reaction Methods 0.000 claims description 5
- 238000000034 method Methods 0.000 claims description 5
- 238000003780 insertion Methods 0.000 claims description 4
- 230000037431 insertion Effects 0.000 claims description 4
- 230000000717 retained effect Effects 0.000 claims description 2
- 230000003019 stabilising effect Effects 0.000 claims description 2
- 230000003213 activating effect Effects 0.000 claims 1
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 229920000642 polymer Polymers 0.000 description 4
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000005065 mining Methods 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
Landscapes
- Dowels (AREA)
Description
AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT ROCK BOLT ASSEMBLY Field of the Invention The present invention relates to rock bolt assemblies of the kind used in tunnelling and underground mining to support the roof or sides of the cavity.
Background of the Invention A conventional rock bolt assembly includes a threaded rod (referred hereafter as 'rock bolt'), a nut and a bearing plate. The rock bolt is inserted into a hole drilled into coalface, and is anchored within the hole by means of a chemical anchor. The bolt is then tensioned against the coalface by the nut screwed onto the threaded portion of the bolt and bearing against the plate which in turn bears the coalface.
A conventional procedure for installing a rock bolt assembly includes the following steps: drill a hole into coalface to a required depth, insert a cartridge with a chemical anchor into the drilled hole, insert a bolt and start driving the bolt to rupture the cartridge and start the chemical setting of the anchor, when the chemical sets, rotate the nut on the rock bolt until a required tension is established in the rock bolt.
A conventional chemical anchor comprises a two-component chemical. The two components are commonly provided in a single frangible polymer tube wherein they are initially separated in individual compartments by a polymer divider. Upon the insertion of the cartridge into the hole, the head portion of the rock bolt is used to rupture the cartridge and mix the components so that setting may take place. Although
I
the head portion of the rock bolt is commonly modified to facilitate the piercing and tearing of the cartridge, the tearing action often results in 'gloving', that the polymer tube simply slides over the rock bolt like a glove or sleeve. As a result, the rock bolt and the coal are separated by a polyethylene barrier, which substantially reduces the effectiveness of the chemical anchor.
Another problem arising in conventional rock bolt systems relates to means for driving the rock bolt. There are a number of prior art devices for causing rotation of the bolt in step In some rock bolt systems, the step is effected by applying a torque to the nut. To this end, the nut is modified to enable rotation of the nut and the rock bolt as a unitary member until a pre-determined torque ('the break-away torque') is applied to the nut. In particular, the known modifications of the nut include a crimped section of thread on the end of the nut, a resin or plastic plug inserted into the end of the nut, an increased diameter of the rock bolt immediately above the nut, a shear pin designed to shear or deform at a pre-determined load, double locking nuts, etc. The main disadvantage of such devices is that the break-out characteristics of the nut are difficult to control. Such arrangements can have a premature break-outs or may not break out at all. The plugs can create debris that can clog the thread on the rock bolt. Moreover, some modifications (eg, shear pins) cause considerable costs in manufacturing the nuts.
An object of the present invention is to provide a new rock bolt assembly and a split nut arrangement.
Summary of the Invention In a first aspect the present invention resides in a split nut assembly, including: nut means including two or more nut portions; said nut portions forming a split nut when assembled, said split nut having a threaded opening for engagement with a bolt; said split nut having an outer surface shaped to permit engagement thereof, a drive body including a sleeve portion, said sleeve portion being shaped to fit over and engage the outer surface of said split nut thereby imposing radial constraint on said split nut and preventing rotation of the split nut relative to the drive body, said sleeve portion being adapted to prevent axial displacement of said nut portions in a direction of tensioning the bolt; a drive nut including a first portion and a second portion, said first portion being sized and shaped such that insertion of said first portion into said sleeve prevents axial displacement of said nut portions relative to the drive body; said second portion being shaped to permit gripping of said drive nut by a tool to be rotated thereby; said drive nut including a drive body engaging portion, said drive body engaging portion being adapted to resist disengagement of the drive body from the drive nut only while torque applied to the drive nut is below a particular threshold.
In a second aspect the present invention resides in a rock bolt assembly including said split nut assembly, a rock bolt, and a bearing plate.
Preferably said drive body includes a partly spherical seat portion.
Preferably said bearing plate includes a spherical recess adapted to receive said spherical seat portion.
Preferably at least one said nut portion includes a projection on its external surface, and said drive body includes at least one internal recess, said recess being adapted to slidably receive said projection to prevent rotation of the split nut relative to the drive body.
Preferably said drive nut includes a plurality of axially extending elastic projections formed on the outer periphery thereof, and said drive body includes a plurality of axially extending recesses formed on the inner periphery thereof and matched with said projections of said drive nut, said projections being sized and shaped such as to prevent disengagement of said drive body from said drive nut only while torque applied to the drive nut is below a particular threshold.
In a third aspect the present invention resides in a method of stabilising a rock mass by means of a rock bolt assembly located in a drilled hole in the rock mass and retained in the hole by an anchor, the rock bolt assembly comprising a rock bolt having a threaded portion, the method including the steps of: assembling a split nut assembly, said split nut assembly including a drive nut, a drive body, and a split nut, said split nut assembly preventing disengagement of said drive body from said drive nut only while torque applied to the drive nut is below a particular threshold, rotating the drive nut of the split nut assembly thereby causing rotation of the rock bolt with the nut, after the anchor has set, continuing to rotate the drive nut to tighten the split nut directly or indirectly against the rock mass and thereby tensioning the rock bolt.
In a fourth aspect the present invention provides a rock bolt including a threaded portion, a generally cylindrical body portion, a neck portion, and a head portion.
Preferably said body portion has includes a plurality of wedge-like projections.
Preferably each said projection includes a planar section contacting the body portion of the rock bolt, and a side surface extending between said planar section and the body portion.
Preferably said planar sections are oriented parallel to the longitudinal axis of the rock bolt.
Preferably said side surface includes a plurality of substantially flat sections.
In a preferred embodiment each said projection is inclined at an angle to the transverse axis of the rock bolt and the projections are arranged into pairs such that the planar sections of the projections lie in the same plane facing each other.
Preferably said pairs are equispaced along the length of the cylindrical body portion of the rock bolt.
Preferably, said neck portion of the rock bolt has a generally cylindrical cross-section of a progressively changing circumferential dimension.
In a preferred embodiment the neck portion is provided with a plurality of projections which are configured to extend outwardly from the neck portion substantially equidistantly around a perimeter of the neck portion.
Preferably said projections extend in a direction generally perpendicular to the longitudinal axis of the bolt.
In a preferred embodiment, said projections are arranged into parallel rows extending longitudinally along the neck portion.
Preferably, the number of rows is four.
Preferably, the length of the projections is a function of the change in diameter of the neck porion of the rock bolt.
In a preferred embodiment, no portion of the projections extends beyond the radius of the generally cylindrical body portion of the rock bolt.
Preferably said head portion of the rock bolt is formed as a pair of diverging prongs which extend in a gradually diverging manner from one another to define a V-shaped groove at a distal end of the rock bolt.
Preferably, at least one of said prongs is provided with means for piercing a chemical anchor.
Embodiments of the invention will be described below, by way of example only, with reference to accompanying drawings in which: Fig. 1 is a side elevation of a rock bolt assembly according to a preferred embodiment of the present invention, Fig. 2 is an exploded view of a split nut assembly, Fig. 3 is a perspective view of a threaded segment, Fig. 4 is a perspective view of a drive body, Fig. 5 is a perspective view of a drive nut, Fig. 6 is a partially sectional side elevation of the rock bolt assembly of Fig. 1, Fig. 7 is a cross-sectional view of the drive body of Fig. 4, Fig. 8 is a perspective view of a rock bolt according to a preferred embodiment of the present invention, and Fig. 9 is a perspective view of a section of a length of the rock bolt of Fig.8.
The drawings 1-6 depict a rock bolt assembly suitable for use in tunnelling and underground mining. The rock bolt assembly 10 comprises a rock bolt 12 having a threaded portion 14 and a cylindrical core 16, a bearing plate 18, and a split nut assembly Referring now to Fig. 2, there is shown the split nut assembly 20 for use in the rock bolt assembly 10. The split nut assembly 20 includes a split nut 21 made of two nut segments 22a and 22b, a drive body 24, and a drive nut 26.
Each nut segment 22a (22b) includes a threaded portion 27a (27b) formed on its internal surface and an axially extending projection 28a (28b) formed on its external surface. When held together, segments 22a and 22b form a conventional nut with a threaded opening for engagement with the rock bolt 12.
As it can be seen in Fig. 4, the drive body 24 includes a sleeve portion 30 having a generally cylindrical opening 32 and a pair of grooves 34a and 34 b disposed opposite each other. The dimensions of the grooves 34a and 34b are such that they slidably receive projections 28a and 28b of the nut segments 22a and 22b thereby preventing rotation of the split nut 21 relative to the drive body 24.
As it can be seen in Fig. 7, the sleeve portion 30 includes an abutting surface 36 for contacting a face of the split nut 21 and against which the split nut 21 will be tightened. The abutting surface 36 prevents axial displacement of the nut portions 22a and 22b in a direction of tensioning the rock bolt 12 thereby allowing tightening of the split nut 21.
The drive body 24 includes a seat portion 38 having a generally cylindrical opening for accommodating the rock bolt 12. The opening 40 is not threaded and is large enough to provide clearance for the rock bolt 12.
The seat portion 38 is of generally spherical form to allow the bearing plate 18 to operate at an angle to the long axis of the rock bolt 12. To this end, the bearing plate 18 is provided with a spherical recess 41 sized such as to receive the seat portion 38 of the drive body 24.
As can be seen from Figs. 4 and 5, the sleeve portion 30 of the drive body 24 includes a plurality of axially extending recesses 42 formed on the inner periphery of the sleeve 30 and matched with a plurality of axially extending elastic projections 44a, 44b, 44c, etc formed on the outer periphery of the drive body engaging portion 45 of the drive nut 26. The projections 44 are sized and shaped such as to prevent disengagement of said drive body 24 from the drive nut 26 while torque applied to the drive nut 26 is below a particular threshold.
As shown in Fig. 5, the head 46 of the drive nut 26 is shaped to permit gripping of the drive nut 26 by a tool. It is understood that while the drive nut 26 is shown to have a hex configuration, other shapes may be employed. The drive nut 26 includes a nonthreaded friction-fit opening 48 for the rock bolt 12.
The drive nut 26 includes an abutting surface 50 and is sized and shaped such that insertion of the drive body engaging portion 45 into the drive body 24 causes the abutting surface 50 to contact a face of the split nut 21 thereby permitting tensioning of the rock bolt 12.
In the use of split nut assembly 20, the two segments 22a and 22b of the split nut 21 are put together over the rock bolt 12 adjacent the place where it will be tightened, and while being held together, the sleeve 30 of the drive body 24 is put over the split nut 21 with the projections 28a and 28 fitting into the recesses 34a and 34b, as illustrated in Fig.6. The seat portion 38 of the drive body 24 must face the bearing plate 18. The drive body engaging portion 45 of the drive nut 26 is then inserted into the sleeve of the drive body 24 with the projections 44 of the drive nut 26 fitting into the recesses 42 of the drive body 24. As a result, the split nut 21 will be accommodated between the abutting surface 36 of the drive body 24 and the abutting surface 50 of the drive nut 26.
With reference to the Figs. 8 and 9, the rock bolt 12 shown in the drawings includes a threaded portion 14, a generally cylindrical core 16, a neck section 60, and an end portion 62.
Formed on the cylindrical core 16 is a profile comprising a plurality of wedge-like projections 70. As can be seen from Fig. 9, each projection 70 includes a planar section 72 and a side surface 74 which extends between the planar section 72 and the cylindrical core 16. The planar sections 72 are oriented parallel to the longitudinal axis of the rock bolt 12. The side surface 74 includes a plurality of substantially flat sections 80, 82, 83, and 84 (not shown).
Each projection 70 is inclined at an angle to the transverse axis of the rock bolt 12.
The projections 70 are arranged into pairs 74a, 74b, etc. such that the planar sections 72a, 72b lie in the same plane facing each other. The pairs 74a, 74b etc are equispaced along the length of the cylindrical body portion of the rock bolt 12.
The dimensions of the planar and the side sections 72, 74, and the distance L between adjacent pairs of projections 70 may be selected as required, provided that the dimensions ensure a secure mechanical attachment between the rock bolt 12 and the set chemical thereby providing maximum anchoring of the rock bolt.
The neck portion 60 of the rock bolt 12 has a generally cylindrical cross-section of a progressively changing circumferential dimension. The neck portion 60 is provided with a plurality of projections 90 which are configured to extend outwardly from the neck portion 60 substantially equidistantly around a perimeter of the neck. In a preferred embodiment the projections 90 extend in a direction generally perpendicular to the longitudinal axis of the bolt 12. The projections 90 are arranged into parallel rows 92a, 92b, 92c and 92d (not shown) extending longitudinally along the neck portion 60. In a preferred embodiment the number of rows is four.
The length of the projections 90 is a function of the change in diameter of the neck porion 60 of the rock bolt 12. In a preferred embodiment, no portion of the projection 90 extends beyond the radius of the core portion 16. The shape of projections and distance between adjacent projections may be selected as required, provided that the projections ensure substantial distributive mixing and some shear mixing of the chemical as the chemical is forced to flow through and past these projections as the bolt is thrust and rotated into the prepared hole.
The head portion 62 of the rock bolt 12 formed as a pair of diverging prongs 1 00a and 100b which extend in a gradually diverging manner from one another to define a Vshaped groove at a distal end of the rock bolt 12. Such arrangement facilitates the penetration and tearing of the polymer cartridge containing the chemical anchor.
In a preferred embodiment at least one of said prongs is shaped such as to facilitate the piercing of the chemical anchor.
The rock bolt assembly may be formed by any suitable means and of any suitable material. It is preferred that the rock bolt assembly be formed from plastic.
In use of the rock bolt assembly 10, a hole is drilled in coalface of a mine, a split nut assembly 20 and a bearing plate 18 are pre-assembled on a rock bolt 12, and a chemical anchor is inserted into the hole. Thereafter, the rock bolt 12 is driven into the hole until the head 62 of the rock bolt ruptures the chemical anchor thereby starting the chemical setting. As the bolt 12 is thrust and rotated into the hole, the chemical flows past and through the projections 90 located on the neck portion 60 of the rock bolt. The projections 90 provide rapid and vigorous distributive mixing and some shear mixing of the chemical.
When the chemical sets, the wedge-shaped projections 70 formed on the external surface of the body portion of the rock bolt 12 will ensure a secure mechanical attachment between the bolt and the chemical.
As a result, the bolt 12 will stop turning, but the drive nut 26 will continue to turn. The drive nut 26, through the connection with the drive body 26, which contains the split nut 21, will screw along the threaded portion 14 of the rock bolt 12 until the bearing plate 18 is secure against the coalface. By continuing to drive the drive nut 26 the bolt 12 will be tensioned until the projections 44 on the drive nut 26 begin to slip thereby limiting the tension generated in the rock bolt 12.
While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein. It will further be understood that any reference herein to known prior art does not, unless the contrary indication 11 appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates.
Claims (23)
1. A split nut assembly, including: nut means including two or more nut portions; said nut portions forming a split nut when assembled, said split nut having a threaded opening for engagement with a bolt; said split nut having an outer surface shaped to permit engagement thereof, a drive body including a sleeve portion, said sleeve portion being shaped to fit over and engage the outer surface of said split nut thereby imposing radial constraint on said split nut and preventing rotation of the split nut relative to the drive body, said sleeve portion being adapted to prevent axial displacement of said nut portions in a direction of tensioning the bolt; a drive nut including a first portion and a second portion, said first portion being sized and shaped such that insertion of said first portion into said sleeve prevents axial displacement of said nut portions relative to the drive body; said second portion being shaped to permit gripping of said drive nut by a tool to be rotated thereby; said drive nut including a drive body engaging portion, said drive body engaging portion being adapted to resist disengagement of the drive body from the drive nut only while torque applied to the drive nut is below a particular threshold.
2. A split nut assembly according to claim 1 wherein at least one said nut portion includes a projection on its external surface, and said drive body includes at least one internal recess, said recess being adapted to slidably receive said projection to prevent rotation of the split nut relative to the drive body.
3. A split nut assembly according to claim 1 wherein said drive nut includes a plurality of axially extending elastic projections formed on the outer periphery thereof, and said drive body includes a plurality of axially extending recesses formed on the inner periphery thereof and matched with said projections of said drive nut, said projections being sized and shaped such as to prevent disengagement of said drive body from said drive nut only while torque applied to the drive nut is below a particular threshold.
4. A rock bolt assembly including a split nut assembly according to claim 1, a rock bolt, and a bearing plate.
A rock bolt assembly according to claim 4 wherein said drive body includes a partly spherical seat portion.
6. A rock bolt assembly according to claim 4 wherein said bearing plate includes a spherical recess adapted to receive said spherical seat portion.
7. A method of stabilising a rock mass by means of a rock bolt assembly located in a drilled hole in the rock mass and retained in the hole by a settable anchor, the rock bolt assembly comprising a rock bolt having a threaded portion, the method including the steps of: assembling a split nut assembly, said split nut assembly including a drive nut, a drive body, and a split nut, said split nut assembly preventing disengagement of said drive body from said drive nut only while torque applied to the drive nut is below a particular threshold, rotating the drive nut of the split nut assembly thereby causing rotation of the rock bolt with the nut, after the anchor has set, continuing to rotate the drive nut to tighten the split nut directly or indirectly against the rock mass and thereby tensioning the rock bolt.
8. A rock bolt adapted to be anchored in a hole in a rock formation by means of a settable anchor, said rock bolt including: a generally cylindrical body provided with a threaded portion, a head portion for activating said settable anchor, and I a neck portion for facilitating mixing of said settable anchor, said neck portion being interposed between said body and said head portion.
9. A rock bolt according to claim 8 wherein said body portion has includes a plurality of wedge-like projections.
A rock bolt according to claim 9 wherein each said projection includes a planar section contacting the body portion of the rock bolt, and a side surface extending between said planar section and the body portion.
11. A rock bolt according to claim 10 wherein said planar sections are oriented parallel to the longitudinal axis of the rock bolt.
12. A rock bolt according to claim 10 wherein said side surface includes a plurality of substantially flat sections.
13. A rock bolt according to claim 10 wherein each said projection is inclined at an angle to the transverse axis of the rock bolt and the projections are arranged into pairs such that the planar sections of the projections lie in the same plane facing each other.
14. A rock bolt according to claim 13 wherein said pairs are equispaced along the length of the cylindrical body portion of the rock bolt.
A rock bolt according to claim 8 wherein said neck portion of the rock bolt has a generally cylindrical cross-section of a progressively changing circumferential dimension.
16. A rock bolt according to claim 8 wherein said neck portion is provided with a plurality of projections which are configured to extend outwardly from the neck portion substantially equidistantly around a perimeter of the neck portion.
17. A rock bolt according to claim 16 wherein said projections extend in a direction generally perpendicular to the longitudinal axis of the bolt.
18. A rock bolt according to claim 16 wherein said projections are arranged into parallel rows extending longitudinally along the neck portion.
19. A rock bolt according to claim 18 wherein the number of said rows is four.
A rock bolt according to claim 16 wherein the length of the projections is a function of the change in diameter of the neck porion of the rock bolt.
21. A rock bolt according to claim 16 wherein no portion of the projections extends beyond the radius of the generally cylindrical body portion of the rock bolt.
22. A rock bolt according to claim 8 wherein said head portion of the rock bolt is formed as a pair of diverging prongs which extend in a gradually diverging manner from one another to define a V-shaped groove at a distal end of the rock bolt.
23. A rock bolt according to claim 22 wherein at least one of said prongs is provided with means for piercing a chemical anchor. DATED this 13 th day of February 2004 AIRLAW PTY LTD Patent Attorneys for the Applicant: HALFORD CO
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2004200570A AU2004200570A1 (en) | 2003-02-13 | 2004-02-13 | Rock Bolt Assembly |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2003901054A AU2003901054A0 (en) | 2003-02-13 | 2003-02-13 | Rock bolt assembly |
| AU2003901054 | 2003-02-13 | ||
| AU2004200570A AU2004200570A1 (en) | 2003-02-13 | 2004-02-13 | Rock Bolt Assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| AU2004200570A1 true AU2004200570A1 (en) | 2004-09-02 |
Family
ID=34378434
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU2004200570A Abandoned AU2004200570A1 (en) | 2003-02-13 | 2004-02-13 | Rock Bolt Assembly |
Country Status (1)
| Country | Link |
|---|---|
| AU (1) | AU2004200570A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110939475A (en) * | 2019-12-24 | 2020-03-31 | 鄂尔多斯市昊华红庆梁矿业有限公司 | Temporary support system and method for roof bolt of coal mine tunnel |
| CN112360505A (en) * | 2020-09-28 | 2021-02-12 | 中煤科工开采研究院有限公司 | Drilling, grouting, anchoring and pre-tightening integrated anchor rod supporting device and construction method |
| CN113187532A (en) * | 2021-04-30 | 2021-07-30 | 中煤科工开采研究院有限公司 | Self-drilling anchor rod |
| CN117684558A (en) * | 2024-02-02 | 2024-03-12 | 国网山东省电力公司东平县供电公司 | A kind of fixed anchor rod for electric power construction |
-
2004
- 2004-02-13 AU AU2004200570A patent/AU2004200570A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110939475A (en) * | 2019-12-24 | 2020-03-31 | 鄂尔多斯市昊华红庆梁矿业有限公司 | Temporary support system and method for roof bolt of coal mine tunnel |
| CN110939475B (en) * | 2019-12-24 | 2024-05-24 | 鄂尔多斯市昊华红庆梁矿业有限公司 | Temporary support system and support method for roof anchor rod of coal mine tunnel |
| CN112360505A (en) * | 2020-09-28 | 2021-02-12 | 中煤科工开采研究院有限公司 | Drilling, grouting, anchoring and pre-tightening integrated anchor rod supporting device and construction method |
| CN113187532A (en) * | 2021-04-30 | 2021-07-30 | 中煤科工开采研究院有限公司 | Self-drilling anchor rod |
| CN117684558A (en) * | 2024-02-02 | 2024-03-12 | 国网山东省电力公司东平县供电公司 | A kind of fixed anchor rod for electric power construction |
| CN117684558B (en) * | 2024-02-02 | 2024-05-10 | 国网山东省电力公司东平县供电公司 | A fixed anchor rod for power construction |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MK1 | Application lapsed section 142(2)(a) - no request for examination in relevant period |