AU2013100231A4 - Tension indicator - Google Patents

Abstract

Abstract A tension indicator for use with a rock bolt assembly having a rock support element configured to be at least partially located in a bore formed in a rock substrate and a bearer configured to engage with the rock support element and bear against the surface of the rock substrate when tension is applied to the rock support element, the indicator comprising a body having a cavity adapted to allow the support element to extend therethrough; and, a base, the base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing section.

Description

1 TENSION INDICATOR Technical Field The present disclosure relates to rock strata applications employing tensioned rock bolt 5 assemblies to provide roof, wall and floor support. Background Roof, wall and ground support is vital in mining and tunnelling operations. Mine and tunnel walls and roofs and floors consist of rock strata, which must be reinforced to 10 reduce the possibility of collapse. Rock bolts are widely used for consolidating the rock strata. In strata support systems, a bore is drilled into the rock by a drill rod, which is removed and a rock bolt is then installed in the drilled hole and secured in place, either 15 mechanically or by using a resin or cement based grout. Ordinarily a bearing plate is engaged with the rock bolt and bears against the surface of the rock substrate to tension the rock bolt. The bearing plate applies compressive tensioning force to the rock substrate through tightening of a nut which bears against the bearing place. The tension allows consolidation of the adjacent strata by placing that strata in 20 compression. The tension levels applied to the rock bolt are prescribed for a rock strata and location and the level of tension placed on the rock bolt is set by the level of torque output onto the nut. The tension is assessed by regular audits to ensure the tension is being 25 maintained at the correct level. Indicators provide visual cues as to the level of tension on rock bolts. Summary of the Disclosure 30 Disclosed in some forms is a tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a rock substrate and a bearer configured to engage with the rock bolt shaft and bear against the surface of the rock substrate when tension is applied to the rock bolt shaft, the indicator comprising a body having a cavity adapted to allow the shaft to extend 35 therethrough; and, a base, the base comprising a bearing portion and at least one 4119355_1 (GHMatters) P89016.AU.1 28/02/13 2 locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing section. 5 Disclosed in some forms is a tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a rock, the indicator comprising a domed washer having a cavity adapted to allow the shaft to extend therethrough, the washer being configured to adopt an inverted state upon application of a predetermined load on the washer, wherein in the inverted state 10 clearance is maintained between the rock bolt shaft and the washer. Disclosed in some forms is a tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a rock substrate and a bearer configured to engage with the rock bolt shaft and bear against 15 the surface of the rock substrate when tension is applied to the rock bolt shaft, the indicator comprising a body having a cavity adapted to allow the shaft to extend therethrough; and, a base, the base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a 20 predetermined load on the bearing section. The tension indicator provides a consistent visual indication of the level of tension on the rock bolt. 25 Further, disclosed is a method of tensioning an array of rock bolt assemblies configured to be at least partially located in bores formed in a rock substrate to one or more predetermined levels of tension, the method comprising positioning a tension indicator on each rock bolt shaft of the array of rock bolt assemblies, the indicator being positioned between a bearer configured to engage with the rock bolt shaft and 30 bear against the surface of the rock substrate and a tensioning nut, the indicator comprising a body having a cavity adapted to allow the shaft to extend therethrough; and, a base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing 4119355_1 (GHMatters) P89016.AU.1 28/02/13 3 portion; placing tension on each rock bolt until the indicator has adopted the inverted state. The foregoing summary is illustrative only and is not intended to be in any way limiting. 5 In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments and features will become apparent by reference to the drawings and the following detailed description. Brief Description of the Drawings 10 Preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a side cross-sectional view of a tension indicator in use on a rock bolt 15 assembly; Fig. 2 is a top view of the tension indicator of Fig. 1; Fig. 3 is a bottom view of the tension indicator of Fig. 1; Fig. 4 is a side view of the tension indicator of Fig. 1; Fig. 5 is a front view of the tension indicator of Fig. 1; 20 Fig. 6 is a cross-sectional view of the tension indicator of Fig. 1; Fig. 7 is a perspective view of a tension indicator in use of a rock bolt assembly; Fig. 8 is a perspective view of the tension indicator of Fig. 7 in an inverted state. Detailed Description of Preferred Embodiments 25 In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised and other changes may be 30 made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure. 35 4119355_1 (GHMatters) P89016.AU.1 28/02/13 4 This disclosure is directed generally to arrangement for rock strata support. The disclosure is described generally in the context of rock bolt assemblies tensioned to provide compressive support to the rock strata. 5 Disclosed in some forms is a tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a rock substrate and a bearer configured to engage with the rock bolt shaft and bear against the surface of the rock substrate when tension is applied to the rock bolt shaft, the indicator comprising a body having a cavity adapted to allow the shaft to extend 10 therethrough; and, a base, the base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing section. 15 In some forms the body is substantially frusto-conical. In some forms the cavity extends through the body and the bearing portion. In some forms the at least one locator comprises a plurality of locators spaced apart 20 around the cavity. In some forms the bearing portion comprises a skirt extending outwardly from the body. 25 In some forms the locators comprise turned in projections extending from the bearing portion. In some forms the bearing section is configured to bear against the bearer. 30 In some forms the bearing section is configured to bear against a nut positioned intermediate the bearer and the indicator. Further disclosed in some forms is a tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a 4119355_1 (GHMatters) P89016.AU.1 28/02/13 5 rock, the indicator comprising a frusto-conical body having a cavity adapted to allow the shaft to extend therethrough and a bearing portion, the indicator being configured to adopt an inverted state upon application of a predetermined load on the body, wherein in the inverted state clearance is maintained between the rock bolt shaft and 5 the body. In some forms the cavity is sized to allow clearance of between 4mm and 8mm between the shaft and the body. 10 In some forms the indicator is adapted to be positioned between a bearer and a tensioning nut, the indicator further comprising a plurality of locators adapted to locate the indicator with respect to the bearer. Disclosed in further forms is a method of tensioning an array of rock bolt assemblies 15 configured to be at least partially located in bores formed in a rock substrate to one or more predetermined levels of tension, the method comprising positioning a tension indicator on each rock bolt shaft of the array of rock bolt assemblies, the indicator being positioned between a bearer configured to engage with the rock bolt shaft and bear against the surface of the rock substrate and a tensioning nut, the indicator 20 comprising a body having a cavity adapted to allow the shaft to extend therethrough; and, a base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing portion; placing tension on each rock bolt until the indicator has adopted the inverted 25 state. In further forms disclosed is a method of reviewing an array of rock bolt assemblies for levels of tension, the method comprising positioning a tension indicator on each rock bolt shaft of the array of rock bolt assemblies configured to be at least partially located 30 in bores formed in a rock substrate, the indicator being positioned between a bearer configured to engage with the rock bolt shaft and bear against the surface of the rock substrate and a tensioning nut, the indicator comprising a body having a cavity adapted to allow the shaft to extend therethrough; and, a plurality of locators configured to locate the body in position with respect to the bearer, the body being 4119355_1 (GHMatters) P89016.AU.1 28/02/13 6 configured to adopt an inverted state upon application of a predetermined load on the washer; inspecting the tension indicator on each rock bolt shaft to determine if it has adopted the inverted state. 5 Referring to Fig. 1, disclosed in some forms is a rock bolt assembly 1 for use in supporting rock strata such as a rock wall, roof or floor within a tunneling or mining operation. The rock bolt assembly 1 comprises an elongate shaft 2 adapted to be located in a bore hole (not illustrated) in a rock surface which is being rock bolted. 10 The rock bolt assembly 1 further comprises a nut 4 which, in some forms, is adapted to function with and apply pressure to a bearing plate 5 to impart tension upon the elongate shaft within the bore. The bearing plate 5 includes in some forms a cavity 6 extending from a surface of the bearing plate through the bearing plate 5. 15 The nut 4 extends from a leading end 7 which in some forms is positioned in use proximal the plate 5 to a trailing end 8 positioned in use distal the plate 5. In some forms the rock bolt assembly 1 further comprises a dome washer 9 which is adapted to be positioned adjacent the bearing plate 5 and be retained at least partially 20 in the cavity 6. The rock bolt assembly further comprises a tension indicator 10 which is configured in some forms to be positioned intermediate the nut 4 and the bearing plate 5 and to bear against the bearing plate 5 under pressure from the nut 4 toward the rock substrate. 25 The indicator 10 in some forms is separate from the nut 4 and plate 5 and positioned intermediate the nut 4 and the plate 5. The indicator 10 in the illustrated forms is composed of a metal such as spring steel. In alternative not illustrated forms the indicator 10 is integral to the nut 4 and extends 30 therefrom toward the rock substrate or is integral to the plate 5 and extends outwardly therefrom to meet the nut 4. In other alternative forms the extension element is positioned between the nut and the rock substrate and the bearing plate is absent. In some illustrated forms the indicator 10 comprises a body 11 having a cavity 12 35 which extends through the body 11 and is sized to allow the rock bolt shaft 2 to be 4119355_1 (GHMatters) P89016.AU.1 28/02/13 7 inserted therethrough. In the illustrated forms the cavity 12 is positioned in the centre of the indicator 10. In some forms the cavity 12 is sized such that clearance between the body 11 of the indicator 10 and the shaft 2 of the rock bolt assembly 1 is sufficient to allow clearance of between approximately 4mm and 8mm. In some forms the 5 clearance is approximately 6mm. The sizing of the cavity is constrained by creating the desired clearance about the rock bolt shaft and limiting off-centre inversion of the indicator 10. The body 11 of the indicator 10 in the illustrated forms comprises a sheet material 10 formed into a frusto-conical or volcano shape such that the cavity 12 is positioned centrally and side portions 14 slope away from the cavity to form sloping side walls of the body 11. The indicator further includes a base 16 which is in the form of a skirt extending outwardly from the frusto-conical body 11 of the indicator 10. 15 In some forms illustrated, the base 16 includes a bearing portion 24 positioned internally to the base 16. The bearing portion 24 is configured in some forms such that it bears against the dome washer 9 in use. The indicator 10 further comprises a plurality of locators 20 which extend from the base 20 24 and are adapted to locate the indicator 10. In some forms the locators 20 are adapted to locate the indicator 10 with respect to the bearing plate 5. In the forms illustrated in Fig 1, the locators 20 are adapted to locate the indicator with respect to the dome washer 9. The locators 20 are positioned such that they are spaced apart about the cavity 12 at the periphery 18 of the indicator and maintain the indicator 10 in 25 position with respect to the dome washer within the plane of the locators 20. The locators 20 are, in the illustrated forms, in the form of a locator portion of the base 16. The locators 20 are turned out of plane of the base 16. The locators 20 therefore are adapted to centralize the indicator 10 with respect to either the dome washer 9 or 30 the bearing plate 5. A washer 26 is positioned between the indicator 10 and the nut 4. The washer is shaped so as to have sufficient surface area to extend beyond the cavity and not be taken into the cavity. In the illustrated form the washer 26 is in the form of a flat 35 washer. 4119355_1 (GHMatters) P89016.AU.1 28/02/13 8 In some not illustrated forms the locators comprise a single tab folded out of plane. In some forms the locators comprise four locators extending from the base. Referring to Figs 2 through 6 details of the indicator are illustrated. 5 Fig 2 shows a top view of one embodiment of the indicator 10. In some forms the cavity 12 extends through the indicator 10 at a centrally located position and with sufficient clearance from the shaft 2 to have approximately 4mm to 8mm of space divided between space on one side of the shaft and the other through the diameter. 10 Fig 3 shows a base view of the indicator which illustrates the locator 20 comprising turned in sections of the base 16 at the corners 19 of the periphery 18. Fig 4 shows a cross sectional view of the indicator through Y-Y illustrating the locators 15 20 positioned at the corners 19 of the base 16. The turned in sections of the locators 20 results in the periphery 18 of the indicator 10 having a profile in side view such that the locators extend a shorter distance in this plane from the cavity 12 than does the remainder of the base 16. 20 Fig 5 shows a front view of the indicator showing the periphery 18 of the indicator 10 and the locators 20 positioned at the corners 19 of the indicator 10. Fig 6 shows a cross sectional view of the indicator through X-X showing sloped portions 23 which form the edges of the body 11 and the base 16. 25 Figs 7 and 8 show the indicator 10 in use. In Fig. 7 the indicator is in its normal position; in Fig. 8 the indicator is in its inverted position. In use in some forms, the indicator 10 is positioned intermediate the dome washer 9 30 which is adjacent the bearing plate 5 and the tensioning nut 4. The shaft 2 of the rock bolt assembly 1 extends through the cavity 12 of the indicator 10 and the locators 20 act to locate the indicator 10 with respect to the dome washer 9 and therefore the bearing plate 5. 4119355_1 (GHMatters) P89016.AU.1 28/02/13 9 Tension is placed on the rock bolt assembly 1 through rotation and tensioning of tensioning nut 4. In some forms such as that illustrated in Fig 1, the nut 4 bears against the indicator 10 which in turn bears against the dome washer 9 at its bearing portion 24. In position in some illustrated forms the periphery 18 of the indicator 10 is in a 5 facing relationship with the bearing plate and extends toward the bearing plate 5. Figs 7 and 8 illustrate that the indicator 10 is configured to be moveable between a normal state as shown in Fig 7 and an inverted state as shown in Fig 8 upon a given load being placed upon the indicator. In the illustrated forms the indicator 10 is 10 configured such that upon load of greater than a predetermined level being applied to the indicator through tensioning, the indicator 10 will invert such that the periphery 18 of the indicator 10 extends toward the nut 4 and away from the bearing plate 5. This inversion presents a visual indication of sufficient tensioning load upon the rock bolt assembly and allows for a visual check to be performed simply. 15 The indicator 10 is visually distinguishable from the rock bolt assembly. In some forms the indicator is coloured to provide visual differentiation from the remainder of the rock bolt assembly 1. In some forms the colour of the indicator 10 is indicative of 20 characteristics of the rock bolt assembly 1 or the positioning of the rock bolt assembly within the rock strata. In some forms the indicator is coloured to emphasise the distinction between the inverted configuration and the normal configuration. In some forms the indicator is two-toned, the frusto-conical body having a first colour and the base or skirt having a second colour such that inversion of the indicator serves to cover 25 over the first colour. In some forms the indicator 10 is visible from a distance of greater than 1 metre. In some forms the indicator 10 is visible in low light. 30 While the assembly has been described in reference to its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and that changes may be made without departing from its scope as defined by the appended claims. 4119355_1 (GHMatters) P89016.AU.1 28/02/13 10 It is to be understood that a reference herein to a prior art document does not constitute an admission that the document forms part of the common general knowledge in the art in Australia or in any other country. 5 In the claims which follow and in the preceding description of the assembly, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the 10 assembly. 4119355_1 (GHMatters) P89016.AU.1 28/02/13

Claims (12)

1. A tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a rock substrate 5 and a bearer configured to engage with the rock bolt shaft and bear against the surface of the rock substrate when tension is applied to the rock bolt shaft, the indicator comprising: a body having a cavity adapted to allow the shaft to extend therethrough; and, 10 a base, the base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing section. 15

2. A tension indicator as defined in claim 1, wherein the body is substantially frusto-conical.

3. A tension indicator as defined in claim 1 or 2, wherein the cavity extends through the body and the bearing portion. 20

4. A tension indicator as defined in any of the preceding claims wherein the at least one locator comprises a plurality of locators spaced apart around the cavity. 25

5. A tension indicator as defined in any of the preceding claims, wherein the bearing portion comprises a skirt extending outwardly from the body.

6. A tension indicator as defined in any of the preceding claims, wherein the locators comprise turned in projections extending from the bearing portion. 30

7. A tension indicator as defined in any of the preceding claims, wherein the bearing section is shaped to bear against the bearer.

8. A tension indicator as defined in any one of claims 1 through 6, wherein the 35 bearing section is configured to bear against a nut positioned intermediate the bearer and the indicator. 4119355_1 (GHMatters) P89016.AU.1 28/02/13 12

9. A tension indicator for use with a rock bolt assembly having a rock bolt shaft configured to be at least partially located in a bore formed in a rock, the indicator comprising a frusto-conical body having a cavity adapted to allow the 5 shaft to extend therethrough and a bearing portion, the indicator being configured to adopt an inverted state upon application of a predetermined load on the body, wherein in the inverted state clearance is maintained between the rock bolt shaft and the body.

10 10. A tension indicator as defined in claim 9, wherein the cavity is sized to allow clearance of between 4mm and 8mm between the shaft and the body.

11. A tension indicator as defined in claim 9 or 10, wherein the indicator is adapted to be positioned between a bearer and a tensioning nut, the indicator further 15 comprising a plurality of locators adapted to locate the indicator with respect to the bearer.

12. A method of tensioning an array of rock bolt assemblies configured to be at least partially located in bores formed in a rock substrate to one or more 20 predetermined levels of tension, the method comprising: positioning a tension indicator on each rock bolt shaft of the array of rock bolt assemblies, the indicator being positioned between a bearer configured to engage with the rock bolt shaft and bear against the surface of the rock substrate and a tensioning nut, the indicator comprising a body having 25 a cavity adapted to allow the shaft to extend therethrough; and, a base comprising a bearing portion and at least one locator configured to locate the indicator in position with respect to the bearer, the indicator being configured to adopt an inverted state upon application of a predetermined load on the bearing portion; 30 placing tension on each rock bolt until the indicator has adopted the inverted state. 4119355_1 (GHMatters) P89016.AU.1 28/02/13