AU664787B2

AU664787B2 - Wooden rib support dowel

Info

Publication number: AU664787B2
Application number: AU53132/94A
Authority: AU
Inventors: Geoffrey William Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-01-13
Filing date: 1994-01-12
Publication date: 1995-11-30
Anticipated expiration: 2014-01-12
Also published as: AU5313294A

Description

664787 p00011 Regulation 3.2

AUSTRALIA

Patents Act, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Original TO BE COMPLETED BY THE APPLICANT o r r NAME OF APPLICANT: ACTUAL INVENTOR: ADDRESS FOR SERVICE: GEOFFREY WILLIAM JONES GEOFFREY WILLIAM JONES Peter Maxwell Associates Blaxland House, Suite 10, 5 Ross Street, NORTH PARRAMATTA NSW 2151 WOODEN RIB SUPPORT DOWEL AU PL 6786 13/01/93 INVENTION TITLE: DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO: The following statement is a full description of this invention, including the best method of performing it know to me:- CO 0 894 0 1 2 JAN94 f I y -2- The present invention relates to a support assembly for a mine wall and, in particular, to the use of a wooden dowel in combination with other dowel co-operating elements for temporary reinforcement of coal mine walls. The assembly has particular application in either split and lift pillar extraction or long wall extraction processes for removal of coal from mines.

It is well known to drill holes into the coal face or other strata of underground mines and then to insert tensioned or fully bonded steel rockbolts through the holes for strata reinforcement. More recently, use has been made of wood or fibreglass reinforcing dowels which are rotatably inserted through drilled holes so t at they may reinforce the strata. The reinforcing dowels are partly resin bonded to the wall of the drill hole so that the dowel may strengthen the composite structure and also act as a filler within the bonding resin, thereby strengthening the strata and forming a strong composite beam of the mine. Such resin bonded dowel structures are particularly important where reinforcement is :.20 only of a temporary nature and the reinfoiud strata is subsequently mined.

The wood or fibreglass reinforcing dowel may be cut more easily and safely by modern mining machinery than a S" steel rockbolt which cannot be cut and would seriously obstruct the rock cutting and extraction procedures.

Consequently the use of non-metallic reinforcing elements has enabled reinforcement to be placed in the most effective position, which is frequently wholly or partially within the cutting path of the mining equipment.

However, the use of fibreglass reinforcing dowels also poses certain problems. When fibreglass dowels are cut by mining equipment, the fibreglass may occasionally be caught up in the equipment or in conveyor belts and transfer points owing to its stringy nature and lead to equipment breakdown or maintenance delay. The washery downstream of the conveyor may also be fouled by the long stringy pieces of fibreglass.

Therefore, wooden dowels are the most advantageous as they can readily be cut by the reinforced strata cutting machines and will not impair the operation of the conveyor belts and washery, unlike steel rockbolts and fibreglass dowels. Furthermore, cut pieces of wooden dowel may be 15 easily floated off in washery baths of very low specific gravity.

Wooden dowels that have been used to date have not been fully encapsulated by the chemical anchor material or adhesive resin that bonds the dowel to the wall of the drill 20 hole. There has only been partial encapsulation and this has occurred at the furthermost end of the hole so as to form an anchor to the strata remote from the hole opening. It has been discovered that there is a susceptibility to snapping of wooden dowels anchored in this way under the pressure of slight vertical movements of the strata. This weakness may be worsened by incomplete or uneven hardening of the chemical anchor material.

The present inventor has found that the use of a wooden -4dowel with a high viscosity adhesive to fully encapsulate the dowel when inserted into the drilled hole in the mine wall provides advantages over prior art systems. The inventor has also found that the wooden dowel may be advantageously used in combination with a spinning ferrule, a lockirg block and a locking wedge to obtain a higher than normal loading on the strata wall or rib of the mine.

According to the present invention there is provided a support assembly for a mine wall, said assembly including a wooden dowel adapted to be rotatably inserted into a borehole penetrating the mine wall with an end of the dowel emerging from the hole, an adhesive that fully encapsulates and bonds the inserted portion of the dowel to the wall of the hole, a spinning ferrule connected to the dowel and adapted to engage a means for rotatably inserting the dowel into the hole, a locking block adapted to be fitted around a portion of the emerging end of the dowel and to be locked in a pressure bearing position so as to exert pressure in a direction towards the mine wall, and a locking wedge adapted to engage a wedge receiving means in the emerging end of the dowel so as to lock the locking block in the pressure bearing position, thereby causing pressure to be exerted in a direction towards the mine wall.

Preferably, the assembly includes a rib plate which is 0**0*0 also adapted to be fitted around a portion of the emerging end of the dowel, and which is secured flushly against the mine wall by pressure exerted thereagainst by the locking block when locked in a pressure bearing position.

In a preferred form of the invention, the spinning ferrule is a metal sleeve bonded to the dowel adjacent the emerging end of the dowel.

It is preferred that the dowel is substantially cylindrical and the wedge receiving means is a slot formed diametrically across the emerging end of the dowel and the slot extends longitudinally along the dowel for a predetermined length.

Preferably, the longitudinal length of the slot in the dowel is determined by the location of the spinning ferrule on the dowel.

It is also preferred that the spinning ferrule is partly longitudinally slotted and that the position of the slot in the spinning ferrule is in linear alignment with the 15 slot in the dowel so as to form a continuous slot extending between the spinning ferrule and dowel.

The end of the dowel which is inserted into the hole is preferably chamfered to an angle of about 550.

The wooden dowel may be made of a hardwood such as mountain ash or similarly grained timber.

Preferably, the adhesive is a high viscosity adhesive.

In accordance with another aspect of the invention, there is provided a method for securing the aforementioned support assembly to a mine wall, which comprises the steps of:drilling a borehole into the mine wall, the borehole having a diameter greater than the -6diameter of the dowel and a length shorter than the length of the dowel, locating an adhesive preparation in the borehole such that, when the dowel is inserted therein, the adhesive will fully encapsulate the inserted portion of the dowel, inserting rotatably the dowel into the borehole such that the leading inserted end of the dowel is substantially adjacent the end of the borehole, the rotating action of the dowel causing a mixing of the adhesive in the remaining annular space of the borehole and the bonding of the inserted portion of the dowel to the wall of the borehole, applying a locking block around a portion of the emerging end of the dowel, and forcing a locking wedge into the wedge receiving means of the dowel so as to lock the locking block in a pressure bearing position where it causes pressure to be exerted in a direction towards the mine wall.

Optionally, the method may include the additional step following step of fitting a rib plate around a portion of the emerging end of the dowel so that when the locking block 025 is locked in a pressure bearing position, the locking block will exert pressure against the rib plate so that the rib plate will be secured flushly against the mine wall.

-7- It is preferred that the dowel is rotatably inserted into the borehole by means of the spinning ferrule receiving a spinning dolly fitted to a pneumatic air drill.

In order that the invention may be more readily understood and put into practical effect, reference will be made to the accompanying drawings, in which:- Fig. 1 is a side elevational view of a wooden dowel used in a support assembly according to a preferred embodiment of the invention, Fig. 2 is a top view of the dowel shown in Fig. 1, Fig. 3 is an exploded perspective view of various components of a support assembly according to a preferred embodiment of the invention, and Fig. 4 is a sectional side elevational view of the 15 support assembly of Fig. 3 in use to support a mine wall.

The cylindrical wooden dowel 11 shown in Figs. 1 to 4 comprises a 22 mm diameter hardwood (mountain ash or similarly grained timber) dowel with a 550 chamfered cut at 20 the front end 11. The angled end 11 helps mix the adhesive chemical 28 when the dowel 10 is spun into the rib wall The dowel 10 is preferably about 1000 to 1500 mm in length.

The tail end 12 of the dowel 10 has a central slot 13 to a depth of about 80 mm.

A tubular steel ferrule 14 (50 mm long x 25.4 mm O.D. x 1.6 mm thick), with a similarly located slot 16 of about 16 -8to 17 mm depth, is fitted past the slot 13 in the dowel such that the closed ends of the two slots 13 and 16 are in alignment. The ferrule 14 is set in place with epoxy resin.

As shown in Fig. 3, a wooden locking plate 17 is also used in the support assembly. It is 80 x 80 x 19 mm in size, centrally drilled with a 22 mm diameter hole 22, and made of ply.

Also employed is a smooth wooden wedge 18 made of clear hardwood. It is rectangular in cross section, 20 x 10 mm in its widest cross-section and tapers to zero over 75 mm.

Some special ancillary equipment may be needed, such as a spinning dolly (not shown) which is a tubular steel section designed to fit around the tail end 12 of the dowel 10, and which locks into the slotted steel ferrule 14 by way of a 15 cross bar (not shown).

A pneumatic drill (not shown) is used to power the dolly and spin the dowel 10 into the mine wall As shown in Figs. 3 and 4, a rib plate 19 may be used as a mine rib wall bracing member. This is preferably a 20 timber slab with an appropriately drilled hole 21 to receive the tail or slotted end 12 of the dowel 10 therethrough and has a preferred thickness of about 20 to 25 mm.

The locking block 17 and locking wedge 18 are used to secure the rib plate 19 in place. The locking wedge 18 is inserted through the hole 22 of the locking block 17 and through the hole 21 of the rib plate 19 and then into the continuous slot 13 and 16 at the tail or slotted end 12 of -9the dowel 10 after the dowel 10 has been rotatably inserted or installed in the mine wall The method of assembling the support assembly to support a coal mine wall, as shown in Fig. 4, may be described in greater detail as follows:- A 27-28 mm diameter hole 23 is drilled in the mine wall, and cleared of drillings. The smaller diameter is used for harder coals.

The length of the hole should be such that the forward tip of the dowel 10 is touching the end of the hole 23 when the dolly presses against the mine wall 20 during installation.

An appropriate adhesive preparation, in this case in the form of a resinous cartridge (not :15 shown), is inserted into the hole 23. The amount of adhesive present in the cartridge is sufficient so as to completely encapsulate the dowel when the dowel is fully installed in the hole 23.

A special dolly (not shown) is then fitted to the spinning ferrule 14 adjacent the tail end 12 of the dowel S• The dowel 10 is spun with a pneumatic drill (not shown) at high torque through the adhesive resinous cartridge inside the hole 23 at least until the edge of the dolly touches the mine wall 20. The operator must ensure that spinning times appropriate for the cartridge are adhered to. The present dowel can withstand high torque loads whilst spinning. The adhesive in the cartridge is thus caused to be mixed and spread through the hole so as to form an adhesive bond 28 between the dowel 10 and the wall of the hole 23.

The dolly is removed from the dowel The rib wall bracing member or rib plate 19 is placed over the tail end 12 of the dowel The locking block 17 is then placed over the exposed slotted end 12 of the dowel 10. This is held firmly against the rib plate 19.

The locking wedge 18 is then passed through the holes 22 and 21 and placed in the slots 13 and 16. he locking wedge 18 is subsequently tapped firmly into the slots 13 and 16 so as to push apart the opposed tails of the dowel 10 on either side of the slot 13. This action will cause the opposed tails of the dowel to lock against the sides of the centre hole 22 in the locking block 17.

A major advantage of using a wooden dowel in the support assembly of the invention is that the wooden dowel easily breaks up into small pieces of bout 200-250 mm in length when a fully installed unit and the surrounding coal is cut away from the coal seam by continuous mining machinery such as longwall shearers.

-11- Tb're are several spin off benefits from this feature.

In the main, they consist of greatly reducing repairs and maintenance costs, and improving conveyor availability, by avoiding current problems caused by use of existing steel and fibreglass rib supports.

The most common and most expensive delay in coal production is a stopped conveyor belt, whether it be due to a blockage, or serious damage caused to the belting itself.

These blockages and damage are often caused by foreiqn matter on the conveyor, such as long pieces of solid steel. The assembly of the present invention dramatically reduces the frequency of both of these events, because there are no long pieces of steel or rigid material in it.

Similarly, the present assembly avoids the possibility of long pieces of rib support material, such as steel or fibreglass being caught up in mining equipment or in conveyor belts and transfer points, thus improving valuable conveyor *o belt and face mining equipment availability.

Unlike many current steel rib supports, the section of wooden dowel with the steel ferrule attached to it is usually only small; around 200-250 tmm long. Hence, a magnet will eas ly pull it out from under coal on a conveyor, well prior to most downstream mine conveyors and the coal washing plant.

Another major advantage of the present assembly is its strength. This is an important factor in choosing a rib support, as many underground mines have high lateral stresses which can push the solid rib coal into the open roadway.

This activity can injure workers, damage equipment, and -12threaten the integrity of the roadway. Rib ports can often be more significant to the sustainability of mine operations than the roof supports over the workers' heads.

The 22 mm wooden dowel in this assembly will produce the same or higher rib loadings as a 16 mm steel "wriggle" bolt, or a 21 mm fibreglass bolt. Both of these bolts are in common use as rib supports in coal mines in Australia.

The higher rib loadings are due partly to the spinning ferrule which is designed to increase the load-carrying capacity of the wooden dowel. This is achieved by two means: a) the dowel is set in place whilst still being torqued, and b) the volume of adhesive chemical used is mixed I at a high velocity, caused by the spinning motion of the dowel.

A further advantage of the support assembly of the present invention is that the mine ribs stay intact until they are physically cut away by face machinery, whereas current supports often fail to do this well in advance of the retreating textraction face. The present support assembly therefore ensures that competent roadways will remain useful for longer periods. Rib spillage into walkways and wheeling roads is minimised.

Furthermore, smaller stooks (or remnant pieces of solid coal) can be left standing in pillar extraction operations whilst equipment is moved to another extraction site nearby.

This is possible because the present support assembly virtually clamps adjacent coal tightly together, providing -13clear advantages for pillar extraction techniques, such as improved recovery rates or safer operations for workers.

Various modifications may be made in details of design and construction and the details of the method steps without departing from the scope of the invention.

i S*

Claims

1. A support assembly for a mine wall, said assembly including a wooden dowel adapted to be rotatably inserted into a borehole penetrating the mine wall with an end of the dowel emerging from the hole, an adhesive that fully encapsulates and bonds the inserted portion of the dowel to the wall of the hole, a spinning ferrule connected to the dowel and adapted to engage a means for rotatably inserting the dowel into the hole, a locking block adapted to be fitted around a portion of the emerging end of the dowel and to be locked in a pressure bearing position so as to exert pressure in a direction towards the mine wall, and a locking wedge adapted to engage a wedge receiving means in the emerging end of the dowel so as to lock the locking block in the pressure bearing position, thereby causing pressure to be exerted in a direction towards the mine wall.

2. The support assembly of claim 1 further including a rib plate which is adapted to be fitted around a portion of the emerging end of the dowel, and which is secured flushly against the mine wall by pressure exerted thereagainst by the locking block when locked in a pressure bearing position.

3. The support assembly of claim 1 or claim 2 wherein the spinning ferrule is a metal sleeve bonded to the dowel adjacent the emerging end of the dowel.

4. The support assembly of any one of claims 1 to 3 wherein the dowel is substantially cylindrical and the wedge receiving means is a slot formed diametrically across the emerging end of the dowel and the slot extends longitudinally along the dowel for a predetermined length.

The support assembly of claim 4 wherein the longitudinal length of the slot in the dowel is determined by the location of the spinning ferrule on the dowel.

6. The support assembly of claim 4 or claim 5 wherein the spinning ferrule is partly longitudinally slotted and the position of the slot in the spinning ferrule is in linear alignment with the slot in the dowel so as to form a continuous slot extending between the spinning ferrule and dowel.

7. The support assembly of any one of claims 1 to 6 wherein the end of the dowel which is inserted into the hole is chamfered to an angle of about 550, S"

8. The support assembly of any one of claims 1 to 7 wherein the wooden dowel is made of a hardwood selected from mountain ash or a similarly grained timber.

9. The support assembly of any one of claims 1 to 8 wherein the adhesive is a high viscosity adhesive. e*e

10. A method for securing the support assembly of claim 1 to a mine wall, which comprises the steps of:- drilling a borehole into the mine wall, the borehole having a diameter greater than the diameter of the dowel and a length shorter than the length of the dowel, locating an adhesive preparation in the borehole such that, when the dowel is inserted -16- therein, the adhesive will fully encapsulate the inserted portion of the dowel, inserting rotatably the dowel into the borehole such that the leading inserted end of the dowel is substantially adjacent the end of the borehole, the rotating action of the dowel causing a mixing of the adhesive in the remaining annular space of the borehole and the bonding of the inserted portion of the dowel to the wall of the borehole, applying a locking block around a portion of the emerging end of the dowel, and forcing a locking wedge into the wedge receiving means of the dowel so as to lock the locking block in a pressure bearing position where it causes pressure to be exerted in a direction towards the mine wall.

11. The method of claim 10 further including the step following step of fitting a rib plate around a portion of the emerging end of the dowel so that when the locking block V is locked in a pressure bearing position, the locking block will exert pressure against the rib plate so that the rib plate will be secured flushly against the mine wall.

12. The method of claim 10 or claim 11 wherein the dowel is rotatably inserted into the borehole by means of the spinning -17- ferrule receiving a spi.nning dolly fitted to a pneumatic air drill. Dated this 11th day of January 1

1994. GEOFFREY WILLIAM JONES Patent Attorneys for the Applicant PETER MAXWELL ASSOCIATES 0O S S. S* S S S *S 55 5 S. S S 5*55 *SeS S S 55 S 5.5*5. *55. S S. S S 0 ABSTRACT A support assembly for a mine wall includes a wooden dowel (10) which, in use, is rotatably inserted into a borehole (23) drilled into the mine wall An end (12) of the dowel (10) emerges from the hole (23) and has a partly slotted spinning ferrule (14) bonded concentrically thereto and there is a slot (13) formed diametrically across the end (12) of the dowel. The slot (13) is aligned with the slot (16) formed in the spinning ferrule Adhesive (28) is used to fully encapsulate and bond the inserted portion of the dowel (10) to the wall of the hole The spinning ferrule (14) is engaged to a spinning dolly of a pneumatic drill or like spinning device for rotatably inserting the O dowel (10) into the hole A rib plate (19) has a hole 9 (21) which is used for inserting the end (12) therethrough and locating the rib plate (19) adjacent the mine wall se. A locking block (17) which has a hole (22) is similarly fitted against the rib plate (19) and a locking wedge (18) is then urged into the slots (13 and 16). The locking block o (17) and rib plate (19) are thereby locked in a pressure bearing position so as to exert pressure against the mine wall CV) 71 01 I6-3 o-J j LI $1 LJ.j 11"' I jAit~ I ~~l1 WL. :1 11~ .0 K I~ V +KJ 4~)