AU758275B2 - A roof support module - Google Patents

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): BHP STEEL (RP) PTY LTD A.C.N. 000 148 289 Invention Title: A ROOF SUPPORT MODULE The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 A ROOF SUPPORT MODULE The invention relates to a roof support module for stabilising roof strata of underground mines.

It is known to stabilise roof strata of underground mines with rock bolt assemblies that comprise rock bolts anchored, typically by means of cement or chemical resin grout, in holes drilled in roof strata and tensioned by nuts threaded onto the rock bolts. Typically, bearing plates are positioned between the nuts and roof strata. The purpose of rock bolt assemblies is to apply a clamping or confining action to a failing section of roof strata to control deformation of the failing section and to enhance the strength of the failing section. More specifically, the purpose of rock bolt assemblies is to allow load to be transferred from a failing section to rock 20 bolts to sustain the load. The spacing of rock bolt assemblies is a function directly of the characteristics of *roof strata.

It is also known to stabilise roof strata by the use of W-straps formed from pressed or roll-formed metal.

The W-straps are positioned against roof strata so that rock bolts extend through spaced apart pre-drilled holes in the W-straps. The tensioning nuts and bearing plates of rock bolt assemblies hold the W-straps in position and, more particularly, clamp the W-straps at a series of spaced positions to roof strata. The purpose of the W-straps is to resist downward sagging of roof strata such sagging places in tension the sections of W-straps that are between rock bolt assemblies. W-straps are prone to failure at relatively low loads by rock bolt assemblies shearing the W-straps when W-straps are tensioned in response to roof sagging. A further disadvantage of W-straps is a H:\Maria\Kee\BHF 36067.97 DIVISIONAL AFTLN.doc. 27/04/00 3 restricted number of drill hole locations which necessarily slows down installation.

Conventional W-straps are relatively narrow and do not cover the whole roof strata. In order to retain loose rock that otherwise could fall into a drive from sections of roof strata not covered by W-straps, it is known to use modified W-straps which comprise mesh tied or welded to W-straps to cover the spaces between adjacent Wstraps. The modified W-straps have a number of disadvantages including bulkiness, weight, and a restricted number of drill hole locations.

It is also known to stabilise roof strata by the use of roof support modules comprising mesh formed from an array of longitudinal wires of the same diameter and transverse wires of the same diameter, with uniform spacings between the longitudinal wires and the transverse wires, and with down-turned longitudinal edge sections.

The mesh avoids the drill hole location limitation of Wstraps, and the down-turned edges provide increased rigidity.

OoO It is also known to stabilise roof strata by the 25 use of roof support modules comprising mesh formed from an array of longitudinal and transverse (ie cross) wires that '-define a reinforced section and a loose rock retention section. The longitudinal wires have the same diameter and the transverse wires have the same diameter. However, the wires in the reinforced section are spaced together more closely than the wires in the loose rock section. The purpose of the reinforced section is to define a location for rock bolt assemblies with the closer spaced wires having greater resistance to being sheared when roof strata sags. This product is shown by way of example in Registered Design 124938 of the applicant.

H,\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 4 An object of the present invention is to provide an improved roof support module.

There are two separate aspects of the present invention.

In accordance with a first aspect of the present invention, which is defined in the claims, there is provided a support module for stabilising roof strata of an underground mine, the module being adapted to be held against a section of a roof strata of an underground mine by a plurality of spaced apart rock bolt assemblies, the module comprising a rectangular array of longitudinal and transverse elongate members, with the array comprising a major planar section and longitudinal and transverse edge sections, and one of the longitudinal or transverse edge sections extending from the major section and being up- :turned relative to the major section and the opposite longitudinal or transverse section extending from the major section and being down-turned relative to the major section.

It is preferred that the major section be planar.

ooo° 25 It is preferred that the module comprise up- °turned and down-turned longitudinal edge sections.

o oo It is preferred that the up-turned and downturned sections be inclined at an angle in the range of 40' to the plane of the major section.

It is preferred particularly that the angle of inclination be 300.

It is preferred that the array of longitudinal and transverse elongate members define a reinforced section Sfor locating rock bolt assemblies and a loose rock 1H:\Bkrot\Keep\speci\HP\30164-OO.doc 10/01/03 snd 5 retention section.

It is preferred that the reinforced section be defined by longitudinal and/or transverse elongate members that have a larger cross-sectional area than the elongate members in the loose rock retention section.

Alternatively, or in addition, it is preferred that the reinforced section be defined by longitudinal and/or transverse elongate members that have a closer spacing than that of the longitudinal and/or transverse elongate members in the loose rock retention section.

In accordance with a second aspect of the present 15 invention, which is the subject of Australian patent oooo 720908, there is provided a support module for stabilising roof strata of an underground mine, the module being :adapted to be held against a section of a roof of an underground mine by a plurality of spaced apart rock bolt assemblies, the module comprising an array of longitudinal and transverse elongate members, the array defining a reinforced section for locating the rock bolt assemblies and a loose rock retention section, and the reinforced section comprising longitudinal and/or transverse elongate 25 members which have a substantially larger cross-sectional eeoc area than the elongate members in the loose rock retention section.

The roof support module of the second aspect of the invention concentrates reinforcement in the reinforced section which is the only section of the support that requires substantial reinforcement. In addition, the roof support module of the second aspect provides a prominent indication of the required position of rock bolts.

It is preferred that the reinforced section comprise only one pair of elongate longitudinal members or H;\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 -6 only one pair of longitudinal transverse members.

It is preferred that the elongate members be wires.

It is preferred that each elongate member in the reinforced section comprise two or more wires welded together.

It is preferred particularly that each elongate member in the reinforced section comprise only two wires welded together.

It is preferred that the spacing of adjacent longitudinal and/or transverse elongate members in the 15 reinforced section be less than that of the longitudinal and/or transverse elongate members in the loose rock retention section.

It is preferred that the spacing be less than It is preferred particularly that the spacing be less than 25 It is preferred more particularly that the spacing be less than It is preferred that the array of elongate members be a rectangular grid.

It is preferred that the module comprise a longitudinal or transverse edge section that is up-turned relative to a major section of the array and an opposite longitudinal or transverse edge section that is down-turned relative to the major section of the array.

T According to the present invention there is also H:\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 7 provided a roof support for an underground mine comprising a plurality of the roof support modules in accordance with the first aspect of the invention positioned against the roof in overlapping relationship and held in position against the roof by rock bolt assemblies that extend through the overlapping sections of the modules.

Preferably the modules extend transversely to the direction of excavation of the mine.

Preferably the overlapping sections include the reinforced sections of the modules.

According to the present invention there is also provided a roof support for an underground mine comprising a plurality of the roof support modules in accordance with ***the second aspect of the invention positioned against the roof in overlapping relationship by rock bolt assemblies.

The present invention is described further by way of example with reference to the accompanying drawings of which: Figure 1 is a perspective view of a preferred 25 embodiment of a roof support module in accordance with the oo.. first aspect of the present invention; e Figure 2 is a vertical section of a drive in an underground mine which illustrates installation of a plurality of the roof support module shown in Figure 1 to a roof of the mine; Figures 3a and 3b are plan and enlarged end views of one preferred embodiment of a roof support module in accordance with the second aspect of the present invention; Sand H.\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 8 Figures 4a and. 4b are plan and end views of another preferred embodiment of the roof support module in accordance with the second aspect of the present invention.

The roof support modules 3 shown in Figures 1 to 4 are adapted to stabilise roof strata of underground mines. As is described in more detail in relation to Figure 2, in use, the modules 3 are held in position against roof strata by rock bolt assemblies and thereby provide support to roof strata between the rock bolt assemblies.

Each module 3 comprises a sheet of mesh in the form of a rectangular array of parallel longitudinal wires 15 5 and parallel transverse wires 7 that are welded together oooo at the intersections of the wires 5, 7.

oooo oo With reference to Figures 1 and 2, in accordance with a preferred embodiment of the first aspect of the present invention, one longitudinal edge section 9 of the module 3 is up-turned and the opposite longitudinal edge section 11 of the module 3 is down-turned relative to the flat central section of the module 3. The angle of inclination may be selected as required, although the 25 preferred range is 20-40', and the preferred angle is ••co The up-turned and down-turned longitudinal edge sections 9,11 improve the rigidity of the module 3 and, as is evident from Figure 2, allow a plurality of the modules 3 to be positioned in overlapping positions.

It is noted that it is within the scope of the present invention to provide the up-turned and down-turned edge sections 9, 11 of the module 3 in the opposed transverse rather than longitudinal elongate edge sections.

%In the embodiment shown in Figures 1 and 2 the S array of longitudinal wires 5 and transverse wires 7 H4\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 9 defines a reinforced section, generally identified by the numeral 13, and a loose rock retention section, generally identified by the numeral 15. The reinforced section 13 is provided as a preferred area of the module 3 for locating rock bolt assemblies and is formed by spacing the longitudinal wires 5 more closely together than in the loose rock retention section Whilst not shown, alternatively or in addition, the reinforced section 13 may be formed by using longitudinal wires 5 that have a larger diameter than the longitudinal wires in the loose rock retention section With reference to Figure 2, in use, a plurality *15 of the module 3 of the first aspect of the present invention are installed on a roof 17 of an underground mine by placing a first module 3a against the roof 17, with the longitudinal wires 5 extending transverse to the direction of excavation, and holding the module in position by means of a predetermined number of rock bolt assemblies located with the rock bolts 19 extending through apertures in the reinforced section 13 and the bearing plates 23 and nuts :acting against the reinforced section 13. A second module 3b is then placed against the roof strata in overlapping 25 relationship with the first module 3a typically 100-200mm -overlap and then bolted through the reinforced section 13. This procedure is continued with successive modules 3c, 3d as the heading is excavated in the direction of the arrow in the figure. In this embodiment, the preferred module widths range from 0.9 to 1.5m and the module length range from 4 to 5.1m.

With reference to Figures 3a and 3b, one preferred embodiment of the module 3 in accordance with the second aspect of the present invention comprises a flat sheet of mesh having longitudinal and transverse wires 5, 7 Sand a reinforced section 13 defined by a pair of adjacent H:\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 10 longitudinal elongate members 21 that are formed by welding together two of the longitudinal wires 5 that form the loose reinforced section 13. The longitudinal elongate members 21 in the reinforced section 13 may be in any suitable form: the requirement for the members is that the cross-sectional area of the members be larger than that of the longitudinal wires 5 that form the loose rock retention section 15 of the module.

In relative terms, the larger cross-sectional area of the longitudinal elongate members 21 concentrates reinforcement in the appropriate section of the module 3 and allows the weight of the module to be reduced in the loose rock retention section In addition, such concentration of the reinforcement enables the spacing between the longitudinal elongate member 21 to be reduced. The minimum spacing of longitudinal wires in conventional mesh roof supports is 50mm. The above described arrangement enables the minimum spacing to be reduced to less than 50mm without loss of performance and this has the advantage of enabling smaller sized bearing plates (or alternative forms of oo bearing members) to be used with the modules without loss 25 of performance.

Furthermore, the longitudinal elongate members 21 are prominent visually and this greatly simplifies and speeds up installation of the module 3. In this context, the preferred method of installation is as outlined in relation to Figure 2.

The preferred embodiment of the module 3 in accordance with the second aspect of the invention shown in Figures 4a and 4b is similar to that shown in Figures 3a and 3b, and the only difference is that the module 3 also Scomprises up-turned and down-turned longitudinal side edges H \Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 11 29, 31.

Many modifications may be made to the preferred embodiments without departing from the spirit and scope of the present invention.

For example, whilst the preferred embodiments are described in the context of supporting roof strata of underground mines, it can readily be appreciated that the present invention is not restricted to this application and extends to supporting the walls of underground mines and tunnels, and in civil engineering applications generally.

*0PP o ooo o o *•go *o H:\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03

Claims (9)

1. A support module for stabilising roof strata of an underground mine, the module being adapted to be held against a section of a roof strata of an underground mine by a plurality of spaced apart rock bolt assemblies, the module comprising a rectangular array of longitudinal and transverse elongate members, with the array comprising a major planar section and longitudinal and transverse edge sections, and one of the longitudinal or transverse edge sections extending from the major section and being up- turned relative to the major section and the opposite longitudinal or transverse section extending from the major section and being down-turned relative to the major **15 section.

2. The module defined in claim 1 comprises up- turned and down-turned longitudinal edge sections.

3. The module defined in claim 1 or claim 2 wherein the up-turned and down-turned sections are inclined at an angle in the range of 20-40' to the plane of the major section. 25

4. The module defined in claim 3 wherein the gag• angle of inclination is 300. oo

5. The module defined in any one of the preceding claims wherein the array of longitudinal and transverse elongate members define a reinforced section for locating rock bolt assemblies and a loose rock retention section.

6. The module defined in claim 5 wherein the reinforced section is defined by longitudinal and/or transverse elongate members that have a larger cross- Ssectional area than the elongate members in the loose rock H:\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03 13 retention section.

7. The module defined in claim 5 or claim 6 wherein the reinforced section is defined by longitudinal and/or transverse elongate members that have a closer spacing than that of the longitudinal and/or transverse elongate members in the loose rock retention section.

8. A roof support for an underground mine including a plurality of the roof support modules defined in any one of the preceding claims positioned against the roof in overlapping relationship and held in position against the roof by rock bolt assemblies that extend through the overlapping sections of the modules.. 1

9. The roof support defined in claim 8 wherein .000. the modules are positioned inside by side overlapping S.00. *relation and extend transversely to the direction of excavation of the mine. The roof support defined in claim 8 or claim 9 when dependent on any one of claims 5 to 7 wherein the overlapping sections include the reinforced sections of the 25 modules. Dated this 10 th day of January 2003 BHP STEEL (RP) PTY LTD By Its Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia. Ht\Bkrot\Keep\speci\BHP\30164-OO.doc 10/01/03