AU8990198A

AU8990198A - Pillar bag support

Info

Publication number: AU8990198A
Application number: AU89901/98A
Authority: AU
Inventors: Roderick Macdonald Smart
Original assignee: Fosroc International Ltd
Current assignee: Fosroc International Ltd
Priority date: 1997-08-18
Filing date: 1998-08-14
Publication date: 1999-03-08
Anticipated expiration: 2018-08-14
Also published as: WO1999009299A1; ZA987379B; AU739209B2; GB9717387D0

Description

WO 99/09299 PCT/GB98/02363 PILLAR BAG SUPPORT FIELD OF THE INVENTION This invention relates to a pillar bag support for yieldably supporting a hanging wall in a mine working. 5 SUMMARY OF THE INVENTION A pillar bag support according to the invention includes a closed ended tubular bag of flexible material, a plurality of hoops of a reinforcing material which are attached to and located circumferentially around the bag in a vertically spaced relationship with at least selected hoops on the bag each including at lease one tie 10 which is attached to the hoop for restraining movement of that portion of the hoop in radially outward direction while the pillar bag is under a compressive load. The flexible material from which the bag is made is a woven plastic which is woven in a tube shape by circular weaving. In one form of the invention one or each hoop tie extends diametrically across 15 and is fixed at both ends to the hoop. In another form of the invention a plurality of hoop ties are each fixed at one end to the hoop and in the centre of the hoop to each other. The hoops and ties may be made from metal, flexible strapping or the like which has adequate tensile strength for the purpose of the hoops and ties. 20 Further according to the invention the hoops and ties are made from a single length of strapping with loops of the strapping, at intervals about the hoop, being inwardly directed towards the centre of the hoop at which they are attached to each other to provide the hoop ties. The pillar bag support preferably includes WO 99/09299 -2- PCT/GB98/02363 slotted bracing plates with the inwardly directed strapping loops each passing through a slot in a bracing plate which in use bears on an outer component of the pillar bag. Still further according to the invention the pillar bag support includes mesh 5 reinforcing, which surrounds the pillar on either the inside or outside of the bag. Conveniently the mesh is a wire mesh. BRIEF DESCRIPTION OF THE DRAWINGS The invention is now described by way of example only with reference to the drawings in which: 10 FIGURE 1 is a side elevation of one embodiment of the pillar bag of the invention in use with the bag material being shown stripped in stages on the right hand side of the drawing, FIGURE 2 is a plan view of the bag of Figure 1 shown sectioned on the line 2-2 in Figure 1, 15 FIGURES 3 to 9 are test graphs of nine of the pillar bags of the invention which were subjected to compressive loads in a press, FIGURE 10 is a side elevation of a second embodiment of a pillar bag according to the invention, and FIGURE 11 is a fragmentary view of the reinforcing arrangement of the bag of 20 Figure 10.

WO 99/09299 -3- PCT/GB98/02363 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiment of the pillar bag 10 of the invention as shown in Figures 1 and 2 of the drawings includes a bag composed of a flexible outer tube 12 which is made from a woven material and which is closed top and bottom and an inner 5 open ended cylindrical tube of wire mesh reinforcing 14 and, in this embodiment of the invention, four vertically spaced metal hoops 16, with one also at the top and bottom. The material of the bag tube 12 could be any suitable material such as woven polypropylene which is water pervious to the extent that when the bag is filled with 10 grout water in the grout will bleed or weep through the material. If drainage of water from the grout is not required, a water impermeable material may also be used. The wire mesh is preferably a conventional domestic fencing diamond mesh wire in which the zig-zagged horizontal strands of the mesh are not tied to each other 15 so that the mesh is collapsible in the axial direction of the pillar bag for ease of transport and erection of the bag. As is more clearly seen from Figure 2 the hoops 16 are circular and include diametric ties 18 which are fixed at their ends to the hoop and to one another at right angles in the hoop. The ties are fixed to the hoop and one another to be non 20 slip for the purpose which will be explained below. The hoops 16 are preferably tied by wire or like ties to the mesh in whatever vertically spaced relationship is selected for a particular roof support application. In Figure 1, the vertically spaced outer hoops are shown against the foot and hanging walls 20 and 22 but in practice would be spaced a little way from the 25 walls.

WO 99/09299 -4- PCT/GB98/02363 The pillar bag of the invention is erected between the hanging and foot walls 20 and 22 in any conventional manner such as by external propping or roof bolting. Although not mentioned above or shown in the drawings the bag obviously includes any conventional and well known filling apertures or tubes which need no 5 further explanation in this specification. With the pillar bag erected at its site of use the bag is filled with whatever type of grout is required in a particular application and allowed to cure, if drainage of the grout is required, excess water can be drained through the material of the bag component 12. In this application the pillar bags are filled with a fast setting 10 foamed or solid grout. As the hanging and foot walls 20 and 22 close on the support 10 the cured grout rapidly accepts the increasing load imposed on it until the transverse tensile load imposed on the hoops causes them or their ties to fail with the result illustrated in the pillar bag load test in the nine test graphs. 15 All of the nine pillar bags which were tested had a height of 1,2m and a diameter of 750mm. For the tests the hoops and ties illustrated in Figure 1 and 2 were made from mild steel strip having a thickness of 4mm and a width of 25mm. Both the hoops and ties were welded. 20 Prior to the compression tests the fast setting grout in each of the pillar bags was allowed to cure for two hours. The sudden load sheds A shown in graphs 1, 2, 3, 4, 7, 8 and 9 were caused by failure of either the hoops or in some cases their ties.

WO 99/09299 -5- PCT/GB98/02363 TABLE 1 LOAD vs. UNTIED AND TIED HOOPS Convention Tied Foamed Load at Load at Graph al Circular Circular Grout yield 50% No. Hoops Hoops Density (tons) Compressio n (tons) 1 5 0 1.25 137 80 2 0 5 1.25 151 227 3 6 0 1.25 254 145 4 0 6 1.25 386 445 TABLE 2 LOAD vs. FOAM DENSITY Conventiona Tied Foamed Load at Load at 50% Graph No. I Circular Circular Grout yield Compressio Hoops Hoops Density (tons) n (tons) 5 0 5 1.0 97 212 2 0 5 1.25 151 227 6 0 5 1.5 265 362 5 TABLE 3 LOAD vs. SOLID GROUT Conventional Tied Grout Load at 50% Graph No. Circular Circular Type Compression Hoops Hoops (tons) 7 5 0 Solid 59 8 5 0 Solid 58 9 0 5 Solid 187 The bags of graphs 1 to 4, Figures 3, 4 and 5, were filled with the fast setting foamed grout having a common density of 1.25. The results of the compression tests on these bags are summarised in Table 1. 10 Table 2 illustrates the effect of variable grout density of pillar bag load bearing capacity.

WO99/09299 -6- PCT/GB98/02363 In Table 3, results are given for pillar bags filled with a solid grout as shown. The data in the Tables will now be discussed with reference to the individual graphs. Table 1 5 Graphs 1 and 2 in Figure 3 illustrate the different behaviour of pillar bags with 5 untied and tied circular hoops respectively. Without ties, graph 1, three of the hoops failed at points A, resulting in load shedding, yielding only 80 tons load at 50% compression. With the tied hoops, 2 noticeable hoop failures occurred with recovery of load capacity thereafter to yield 227 tons of support. 10 Graphs 3 and 4 of Figures 4 and 5 must be similarly compared, these representing pillar bags with 6 untied and tied hoops respectively, tied hoops giving much improved load capacity, from 145 to 445 tons respectively. Table 1 illustrates the effect of tied hoops on pillar bag performance. Table 2 15 Graphs 5, 2 and 6 of Table 2 illustrate the performance effect of various foamed grout densities on identically reinforced pillar bags according to the invention, each with 5 tied hoops, and illustrating increasing load capacity with increasing grout foam density. Table 3 20 The Table 3 bags of graphs 7 and 8, which were filled with solid unfoamed grout, performed poorly due to their untied hoops, as was the case with the bag tests of graphs 1 and 3. The Figure 9 graph 9 bag with its 5 tied hoops, however, performed will in providing support to a load of 187 tons.

WO 99/09299 -7.- PCT/GB98/02363 A post mortem on the pillar bags after the tests indicated that the snapped hoops of the tests of graphs 1, 3, 7 and 8 which were unconstrained by cross ties lost all of their hoop strength on breaking. On the other hand, however, it was found that, in the pillar bags having tied hops, graphs 2, 4, 5, 6 and 9, the hoop failure 5 occurred between the attachment point of two cross ties leaving the remaining three quadrants of the hoop firmly held by the ends of the ties against slip to maintain their hoop tensile strength. Similarly, in one or more of the tests the cross ties parted at their central joint to result in small load sheds on the graphs of the tests. 10 From these graphs, 2, 4, 5, 6 and 9 it is immediately apparent that the hoop cross ties played a significant part in the significantly improved pillar support performance compared to those pillar bags using the conventional circular hoops with no cross ties. Results confirm that with the cross-tie reinforcing and within specific ranges of 15 foamed grout densities, it is possible to design pillar bag supports having predictable load bearing characteristics for very specific load support applications. A second embodiment 24 of the pillar bag of the invention is shown in Figures 10 and 11 to include a circular weave tubular bag 26 which is woven from a suitably strong plastics material such as polypropylene and which, like the bag of the 20 Figure 1 embodiment, is closed top and bottom and includes, not shown, the conventional grout filling spouts and so on. The bag 24 additionally includes a plurality of circumferential straps 28 which are made from woven polypropylene to a heavy industrial grade and which are made to be slightly elastic with about a twenty percent stretch capability. 25 The straps 28 are each composed of a single length of strapping which is looped inwardly at four quadrant positions on the bag with the four inward loops being WO 99/09299 -8- PCT/GB98/02363 passed through slots in a metal bracing plates 30, as more clearly seen in Figure 11, with the inner strap loops 32 being passed through and folded over a heavy duty metal ring 34 which, in use, is situated on the vertical axis of the pillar bag. The ends of the loop straps 32 are sewn back on themselves as illustrated in the 5 drawing with the two ends of the single strap 28 then being sewn together to lie on the outside of the pillar bag. The entire outer portion of each strap 28 is sewn on to the material of the bag 26. The looped straps 32 on the inside of the bag provide ties similar to the ties 18 of the Figure 1 embodiment. The purpose of the bracing plates 30 is to hold the two strap portions of the 10 looped portion 32 of the straps together on the outer surface of the bag 26 to prevent them from separating and so tearing the bag 26 when the bag is deformed under load. The ring 34 is merely one method of attaching the ties defined by the looped straps 32 to each other and any other suitable method of tying the straps could 15 be employed to achieve the same result. For example the looped ends of the straps could merely be sewn together in some suitable manner. Almost all pillar bags, when placed under extreme compressive load, tend to deform in a manner indicated by the chain lines in Figure 10 with the greatest extension being in the central portion of the bag. To cater for the greater 20 transverse movement of the pillar bag wall in this central portion of the bag the central straps 28 are preferably arranged to be closer to each other than the outer straps so that greater hoop reinforcement is provided in the central zone of the bag. The elasticity of the straps 28 further enables the straps and their ties 32 to retain their integrity without failure far more so than is the case with the less elastic 25 metal bars or straps 16 of Figure 1. The invention is not limited to the precise details as herein described. For example, the hoops, particularly in the case where they are made from a sewable material such as belting, could sewn directly onto either the inner or outer surface WO 99/09299 -9- PCT/GB98/02363 of the material 12 of the bag and the reinforcing mesh 14, if used, could be wrapped and tied around the outer surface of the bag material 12. Alternatively, the ties may be of wire incorporated into the pack from the structure of the mesh. The invention is not limited to passive support only but may also be used where 5 pillar bag pre-stressing is required.

Claims

1. A pillar bag support including a closed ended tubular bag of flexible material, a plurality of hoops of a reinforcing material which are attached to and located circumferentially around the bag in a vertically spaced relationship with at 5 least selected hoops on the bag each including at lease one tie which is attached to the hoop for restraining movement of that portion of the hoop in radially outward direction while the pillar bag is under a compressive load.

2. A pillar bag support as claimed in claim 1 wherein the or each hoop tie extends diametrically across and is fixed at both ends to the hoop. 10

3. A pillar bag support as claimed in claim 1 wherein a plurality of hoop ties are each fixed at one end to the hoop and in the centre of the hoop to each other.

4. A pillar bag as claimed in any one of the above claims wherein the hoops and ties are made from metal.

5. A pillar bag as claimed in any one of claims 1 to 3 wherein the hoops and 15 ties are made from flexible strapping.

6. A pillar bag as claimed in claim 5 wherein the strapping is stretchable.

7. A pillar bag as claimed in either one of claims or 6 wherein the hoops and ties are each made from a single length of strapping with loops of the strapping, at intervals about the hoop, being inwardly directed towards the centre of the hoop at 20 which they are attached to each other to provide the hoop ties.

8. A pillar bag support as claimed in claim 7 including slotted bracing plates with the inwardly directed strapping loops each passing through a slot in a bracing plate which in use bears on an outer component of the pillar bag. WO 99/09299 1 1 PCT/GB98/02363

9. A pillar bag support as claimed in any one of the above claims including mesh reinforcing, which surrounds the pillar.

10. A pillar bag support as claimed in claim 9 wherein the mesh is a wire mesh. 5

11. A pillar bag support as claimed in any one of the above claims wherein the reinforcing hoops are spaced closer to each other in the horizontally central portion of the pillar in use than those towards the ends of the pillar.

12. A pillar bag support substantially as herein described with reference to and as illustrated in Figures 1 and 2 or Figures 10 and 11 of the drawings.