AU2016100070A4 - Grout Anchored Rock Bolt - Google Patents

Abstract

The invention provides a grouted rock bolt which includes, an elongate body of a suitable steel material having, a first distal end and an opposed second 5 proximal end, a threaded portion at the second end, a first end portion extending from the first end of the body which is adapted with a first plurality of integrally formed anchors, at least one integrally formed anchor on the body, between the threaded portion and the first end portion, a first stem portion between the first end portion and the at least one integrally formed 10 anchor, wherein the first stem portion has a smooth cylindrical surface; wherein each integrally formed anchor is a flattened formation that exceeds the diameter of the body and which defines a plane; and wherein each integrally formed anchor is adapted to be harder than the stem portion. - 1/2 3cFIGR I B'

Description

Our Ref: 71551nno P/00/009 Regulation 3.2 AUSTRALIA Patents Act 1990 INNOVATION SPECIFICATION FOR AN INVENTION ENTITLED Invention title: Grout Anchored Rock Bolt Name of Applicant: NCM Innovations (Pty) Ltd Address for Service A.P.T. Patent and Trade Mark Attorneys PO Box 833 Blackwood, S.A. 5051 The invention is described in the following statement: 1 BACKGROUND OF THE INVENTION [0001] This invention relates to a grouted rock bolt. [0002] The rock bolts which include a mechanical anchor or a composite anchor, located on a distal end portion of the bolt body, are well known in the 5 mining industry. [0003] The mechanical anchor can be an expansion shell type anchor which is actuated to radially expand into contact with walls of the rock hole into which it is inserted by axial retraction of the bolt body. [0004] The composite anchor can include a mechanical anchor and an 10 integrally formed passively loaded anchor arranged in series with the mechanical anchor, or spaced apart on the bolt body. [0005] Such rock bolts, initially, can be mechanically anchored within the rock hole and placed in active pre-load between a faceplate and the mechanical anchor before grout is injected into the rock hole, around the rock 15 bolt, through a grout tube. [0006] These rock bolts are not suitable for being grouted with a grout or resin released from grout or resin capsules that are introduced into the rock hole ahead of the rock bolt. Nor are such bolts suitable for being spun to break the capsules to release the resin or grout. 2 [0007] Hereinafter the terms "resin" and "grout" are used interchangeably to describe an adhesive material used to adhere a rock bolt within a rock hole. [0008] The term "grouted" is used to describe a rock bolt that is bonded in a rock hole by means of an adhesive material such as, for example, a resin or a 5 grout. [0009] The present invention at least partially addresses the shortcoming of the rock bolts briefly described above. SUMMARY OF THE INVENTION [0010] The invention provides a grouted rock bolt which includes: 10 a) an elongate body of a suitable steel material having; b) a first distal end and an opposed second proximal end; c) a threaded portion at the second end; d) a first end portion extending from the first end of the body which is adapted with a first plurality of integrally formed anchors; 15 e) at least one integrally formed anchor on the body, between the threaded portion and the first end portion; 3 f) a first stem portion between the first end portion and the at least one integrally formed anchor; g) wherein the first stem portion has a smooth cylindrical surface; wherein each integrally formed anchor is a flattened formation that exceeds the 5 diameter of the body and which defines a plane; and wherein each integrally formed anchor is adapted to be harder than the stem portion. [0011] Each integrally formed anchor of the first plurality of integrally formed anchors may lie in a plane which is orthogonal to a plane of an adjacent anchor. 10 [0012] The first plurality of integrally formed anchors may be serially arranged on the first end portion. [0013] Preferably, the rock bolt includes a second plurality of integrally formed anchors between the threaded portion and the first end portion. [0014] Each integrally formed anchor of the second plurality of integrally 15 formed anchors may lie in a plane which is orthogonal to a plane of an adjacent anchor. [0015] The second plurality of integrally formed anchors may be serially arranged on the body. [0016] Preferably the second plurality of integrally formed anchors is 4 positioned between a location were the threaded section ends on the body and 700mm from the second end. [0017] The rock bolt may have a second stem portion between the at least one integrally formed anchor or a first anchor of the second plurality of 5 integrally formed anchors and the threaded portion. [0018] The first and the second stem portions are adapted to elongate under a tensile load. BRIEF DESCRIPTION OF THE DRAWINGS [0019] The invention is further described by way of example with relevance 10 to the accompanying drawings in which: Figure 1A is a view in perspective of a rock bolt in accordance with invention; Figure 1B is a view in perspective of a pair of integrally formed anchors as part of the rock bolt of Figure 1A; and Figures 2A to 2C illustrate, in chronological sequence, the rock bolt of the of 15 Figure 1 in use. DESCRIPTION OF PREFERRED EMBODIMENT [0020] Figure 1 of the accompanying drawings illustrates a rock bolt 10 in accordance with a non-limiting embodiment of the invention. The rock 5 bolt 10 has a solid cylindrical steel body 12, which extends between a first distal end 14 and a second proximal end 16 which end, in use, projects out of a rock hole in which it is placed as will be described more fully below. [0021] A section of the rock bolt body 18, extending from the second end 16, 5 is threaded to define a threaded portion 20. At an opposed end, a section of the body is adapted with, in this particular non-limiting example, two pairs of serially consecutive integrally formed anchors, each pair respectively designated 22A and 22B. The section of the body so adapted defines an anchor portion 24. 10 [0022] A pair of integrally formed anchors 26, of the same construction as the anchor pairs 22, is located between the threaded end section 20 and the anchor pairs (22A, 22B) in a position that is biased towards the second end 16. [0023] The anchor pair 26 and the anchor pairs 22 are integral with the body 15 in that they are formed from the same blank as the body 12. [0024] With reference to Figure 1 B, which illustrates the single anchor pair 26 (although the anchor pair in this illustration is equally relevant to each anchor pair 22), an anchor comprises a pair of end-to-end integrally formed paddle formations, each paddle formation is respectively designated 26A and 20 26B. Each paddle formation 26A and 26B substantially defines a plane with each plane of each paddle formation being perpendicular to its counterpart. 6 [0025] Each paddle formation 26 is formed by flattening the rod such that the rock bolt body 12 expands in opposed directions which are orthogonal to the direction of the flattening force (these directions of expansion are designated X and Y respectively). This flattening process is a cold forming process that 5 strain hardens the steel material along the length of the body 12 so adapted. This process also adapts the cylindrical rock bolt body 12 to locally exceed its diameter in radial directions X and Y respectively providing extensions or paddles which are resistive to pull through a grouted borehole and which can function to mix a resin material as will be further described below. 10 [0026] In a typical high stress, deep level, mine excavation, the rock is most densely fractured within the first 300mm or so, from a rock face 30. The anchor pair 26 therefore is optimally and preferably positioned on the rock bolt body 12 about 500mm from the second end 16. The reason for this will be explained below. 15 [0027] Between the anchor pairs 22, the anchor pair 26 and the threaded section 24, first and second, smooth surfaced, stem portions 28 and 30 are respectively defined. [0028] Referring to Figures 2A to 2C, a nut 32 and faceplate 34 are provided, located on the threaded section 20 of the rock bolt body 12, prior to use. 20 [0029] In use, the rock bolt 10 is inserted into a rock hole 36, first end 14 7 leading, behind at least one resin cartridge 38 as illustrated in Figure 2A. [0030] As the rock bolt 10 advances, it penetrates the cartridge 38 (the first end can be adapted to a point or blade to facilitate cartridge puncture. Thereafter, the bolt is spun by action of a bolter (not shown), attached to the 5 nut 32 so that the resin that is released from the cartridge 38 is fully mixed, aided by the anchor pairs 22. This step is illustrated in Figure 2B. [0031] When the bolt 10 is fully inserted, a part of the threaded portion 20, which carries the nut 32 and faceplate 34, projects from the rock hole 36. The faceplate abuts the rock wall 39. 10 [0032] The resin is mixed by the spinning anchor pairs 22 as the resin flows into the annular space 35 between the walls of the rock hole 36 and the bolt 10. As the resin hardens around the bolt to adhere the bolt within the rock hole, torque is experienced by the bolt through action of the bolter. This results in the nut 32 advancing along the threaded portion 22 to bear and 15 tighten against the faceplate 34, forcing the plate against the rock face 38. [0033] Figure 2C illustrates a highly fractured layer of the rock mass 40 beneath the rock face 39 which dilates about surface parallel stress fractures to impart a force on the faceplate 34 which is translates into a pulling force on the rock bolt 10 out of the rock hole 12. This pulling force is resisted by the 20 anchor pairs 22 and the anchor pair 26, each of which is adapted, due to their paddle formations (26) exceeding the diametric dimension of the cylindrical 8 rock bolt body 12, to resist passage through the now hardened resin, providing anchor locations (illustrated by a dotted lines respectively designated 42 and 44). [0034] Thus, the dynamic forces of the rock, being forces that result from 5 movement of the surrounding rock mass relatively to the rock bolt 10, cause the anchor pairs (22, 26) to experience passive loading and local anchoring as they resist movement through the grouted annular space 35. [0035] The rock bolt 10 can stretch along respective first and the second stem portions (28 and 30) to accommodate this dynamic loading movement, 10 between the rock face 39 and anchor location 42 and between location 42 and anchor location 44. [0036] The ability of the stem portions (28, 30) to stretch is resistively unhindered due to the smooth surface of the stem portions. This allows relative movement within the grouted confines of the rock hole 12 by de 15 bonding from the grout. [0037] Should the rock face 39 fall away due to the highly fractious rock mass below, leaving the faceplate 34 removed from a rock surface, the rock bolt 10 can still provide load support of the rock mass within which it is located due to the preload maintained between the anchor locations 42 and 44. 20 9

Claims (8)

1. A grouted rock bolt which includes: an elongate body of a suitable steel material having a first distal end and an opposed second proximal end, 5 a threaded portion at the second end, a first end portion extending from the first end of the body which is adapted with a first plurality of integrally formed anchor, at least one integrally formed anchor on the body, between the threaded portion and the first end portion, a first stem portion between the first end portion and the at least one 10 integrally formed anchor, wherein the first stem portion has a smooth cylindrical surface, wherein each integrally formed anchor is a flattened formation that exceeds the diameter of the body to define a plane, and wherein each integrally formed anchor is adapted to be harder than the stem portions. 15

2. A grouted rock bolt according to claim 1 wherein each integrally formed anchor of the first plurality of integrally formed anchors lies in a plane which is orthogonal to a plane of an adjacent anchor.

3. A grouted rock bolt according to claim 1 or 2 wherein the first plurality of integrally formed anchors is serially arranged on the first end portion. 20

4. A grouted rock bolt according to any one of claims 1 to 3 which includes a second plurality of integrally formed anchors between the threaded portion and the first end portion. 10

5. A grouted rock bolt according to claim 4 wherein each integrally formed anchor of the second plurality of integrally formed anchors lies in a plane which is orthogonal to a plane of an adjacent anchor.

6. A grouted rock bolt according to claim 4 or 5 wherein the second 5 plurality of integrally formed anchors is serially arranged on the body.

7. A grouted rock bolt according to any one of claims 4 to 6 wherein the second plurality of integrally formed anchors is positioned between a location were the threaded section ends on the body and 700mm from the second end. 10

8. A grouted rock bolt according to any one of claims 1 to 7 which includes a second stem portion between the at least one integrally formed anchor or a first anchor of the second plurality of integrally formed anchors and the threaded portion. 15 11