Device, method and system for loading fixatives for rock bolts

Abstract

The present invention relates to a device, method and system for the installation of a fixative in a drill-hole, such as to secure rock bolts. The device comprises (a) a chamber adapted to hold the fixative, and (b) a thrust member, wherein the fixative is displaced from the chamber into the drill-hole following application of force to the thrust member.

Claims

1. A device for loading a fixative into a drill hole in a region to be stabilized, the device comprising: a. a chamber adapted to hold a fixative, and b. a thrust member, wherein the fixative is configured to be displaced at least partially from the chamber positioned external of a drill hole, into the drill hole, following application by a rod member of a first predetermined force to the thrust member to move the thrust member through the chamber, wherein the thrust member comprises at least one frangible section and the rod member in use applies a second predetermined force to the thrust member to rupture the at least one frangible section, and wherein the chamber has a fixed internal transverse dimension greater than that of the drill hole whereby, in use, the chamber is maintained entirely external of the drill hole.

2. A device according to claim 1 wherein the chamber comprises a front wall and peripheral wall with an exit port for said fixative formed in said front wall, said thrust member comprising an externally facing guide tube to engage, in use, with an end zone of said rod member.

3. A device according to claim 2 wherein said thrust member is independent of said peripheral wall of said chamber and, in use, moves through said chamber towards said exit port to displace the fixative at least partially from said chamber.

4. A device according to claim 1 wherein the chamber comprises a front wall, an exit port for said fixative formed in said front wall, and an exit spout leading from said exit port externally from said chamber, said exit spout having outer dimensions permitting said exit spout to, in use, fit into said drill hole.

5. A device according to claim 4 wherein said fixative is contained within said chamber.

6. A device according to claim 5 wherein the fixative comprises: a. a resin, and b. a catalyst for curing said resin, said resin and said catalyst being separated within the chamber.

7. A device according to claim 5 wherein the fixative comprises: a. cementitious grout, and b. water, said cementitious grout and said water being separated within the chamber.

8. A device according to claim 5 wherein the fixative comprises activated or activatable cementitious grout.

9. A device according to claim 1 wherein the chamber comprises a front wall, an exit port for said fixative formed in said front wall, and an exit spout leading from said exit port externally from said chamber, said exit spout having outer dimensions permitting said exit spout to, in use, fit into said drill hole.

10. A method of installing a rock bolt and a fixative therefor in a region to be stabilized, said method comprising the steps of: a. drilling a drill hole in a region, b. providing a device for loading a fixative in said drill hole, said device comprising a chamber holding said fixative, an exit port leading from said chamber in communication with said fixative, and a thrust member with an externally facing guide tube engageable with an end zone of a rock bolt, c. engaging said guide tube with said end zone of said rock bolt to position said exit port overlying said drill hole and maintain said chamber entirely external of said drill hole, d. applying force to said rock bolt to move said thrust member such that at least some of said fixative is displaced from said chamber through said exit port into said drill hole, and e. applying a second force to said rock bolt whereby said rock bolt passes through said thrust member into said drill hole, wherein during steps d and e, said exit port is positioned overlying said drill hole and said chamber is maintained entirely external of said drill hole.

11. A method according to claim 10 whereby said end zone of said rock bolt passes through said chamber of the device and through said exit port into said drill hole.

12. A method according to claim 10 wherein said rock bolt is rotated to mix components of said fixative.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which:

(2) FIG. 1 is a drawing depicting the components of a typical grouted rock bolt.

(3) FIG. 2 is a drawing depicting a typical set-up for a resin anchored and grouted rock bolt; and

(4) FIG. 3 is a drawing depicting one embodiment of a device according to the present invention.

(5) FIG. 4 is a drawing depicting one embodiment of fixative used to anchor a rock bolt.

(6) FIG. 5 is a drawing depicting a drill hole for receiving fixative and a rock bolt, in a region to be stabilized.

(7) FIG. 6 is a drawing depicting a rock bolt installation according to one aspect of the invention.

DETAILED DESCRIPTION

(8) FIG. 1 is a drawing depicting the components and set up for a typical grouted rock bolt (1) of the prior art. A variety of types of rock bolts are commercially available but the basic principle of operation is the same in all. As shown in FIG. 1 the typical components are a tapered cone (9) with an internal thread and a pair of wedges held in place by a bail (13). The cone (9) is screwed onto the threaded end of the elongated body (12) of the rock bolt and the entire assembly is inserted in to a drill hole. The length of the drill hole is usually at least 100 mm longer than the bolt otherwise the bail (13) will be dislodged by being forced against the end of the drill hole. Once the assembly is in place a sharp pull on the end of the bolt will seat the rock bolt. Tightening the bolt forces the cone further into the wedge, thereby increasing the anchoring force.

(9) These rock bolts work well in hard rock but are not very effective in closely jointed rock and soft rock because rock in contact with the wedge grips tends to fail. Grout or resin cartridges are often inserted to alleviate this problem.

(10) At the end of the rock bolt projecting from the drill hale there is a fixed head or threaded end and nut (2). A faceplate (1) distributes the load form the bolt onto the rock face. In addition a tapered washer or conical seat (4) compensates for the fact that the rock face is typically at right angles to the bolt. Tensioning of rock bolts is important to ensure that all the components are in contact and that a positive force is applied to the rock.

(11) Traditionally, grouting is carried out by using a short grout tube (5) to feed the grout into the drill hole. A smaller diameter breather tube (3) to bleed air is taped (7) to the rock bolt and extends to the end of the hole.

(12) FIG. 2 illustrates in cross-section a typical set-up of the prior art for creating a resin anchored and grouted rock bolt. Slow setting grout cartridges (21) are located behind fast setting anchor cartridges (19) in a drill hole. The rod of the rock bolt (23) is then spun through the cartridges (19) to mix the resin and catalyst, thus initiating the chemical reaction. The rock bolt (23) is tensioned using a faceplate (17) and nut (15) applied to the end of the rock bolt (23) after the fast setting anchor resin has set. The cartridges of slow setting grout (21) subsequently set and lock the rod in place. The slow setting grout is timed to set in about 30 minutes, so the rock bolt (23) can be tensioned within two or three minutes of installation after the fast anchor resin has set. This tension is then locked in by the later setting grout cartridges and the resulting installation is a fully tensioned, fully installed rock bolt.

(13) FIG. 3 depicts a device according to the present invention for loading a chemical anchor in a drill hole. In this embodiment, the device includes a generally cylindrical chamber (31) adapted to hold the chemical anchor. One end of the chamber (31) is open, and adapted to receive a thrust member (33) comprising a flat disk, with a skirt (45) associated with a cylindrical inlet port (39). The skirt assists in aligning the thrust member (33) in the chamber and helps to avoid misalignment. It will be appreciated that other means for aligning the thrust member (33) such as a keyway type arrangement could also be used. The other end of the chamber comprises a front wall (32) and an exit port (50) leading to a cylindrical exit spout (30) associated with the front wall (32).

(14) FIG. 4 depicts fixative used to anchor a rock bolt according to one aspect of the invention. The fixative comprises resin (51) and catalyst (52). FIG. 5 depicts a drill hole (53) for receiving fixative and a rock bolt, in a region to be stabilized (54). FIG. 6 depicts a rock bolt installation according to one aspect of the invention.

(15) In use, the chamber (31) is filled with or contains a sufficient dose of the component(s) of the fixative. In this illustration, the fixative is a chemical anchor comprising resin (51) and catalyst (52), but as one alternative the fixative could be a grout comprising cement and water. The thrust member (33) is then inserted to close the chamber (31). The end of a rock bolt (41) is then inserted into the inlet port (39) which fits over the end of the rock bolt like a sleeve. The device, supported on the end of the rock bolt (41), is then inserted in a drill hole. The rock bolt (41) is pushed along into the drill hole, preceded by the device until the chamber (31) abuts the end of the drill hole and can move no further. Further force applied to the rock bolt (41) pushes the thrust member (33) along the immobilised chamber (31), urging the chemical anchor out the exit port (50), through the exit spout (30) and into the gap between the rock bolt (41) and the drill hole wall.

(16) With continued application of force, the thrust member (33) is pushed all the way through the chamber (31) until it abuts the front wall (32). In this embodiment, the thrust member (33) includes a circular rupture disk frangible section (37) defined by a series of perforations, splits or pre weakened components (35). When the thrust plate contacts the front wall (32), the end of the rock bolt ruptures (41) the perforations and both the rupture disk and the end of the rock bolt (41) pass through the exit port (50). The rock bolt can then be rotated to mix the components of the chemical anchor.

(17) When the thrust plate contacts the front wall (32), the end of the rock bolt ruptures (41) the perforations and both the rupture disk and the end of the rock bolt (41) pass through the exit port (30). The rock bolt can then be rotated to mix the components of the chemical anchor.

(18) In one embodiment, the present invention may be rendered in a form in which the “spout” 30 may be used to locate the device in the drill hole, the drill hole typically varies from 33 mm to 45 mm but can be as large as approx 64 mm. The chamber 31, typically 100 mm to 125 mm in diameter and 100 to 125 mm in length (note these dimensions will depend on the annular volume of the rock hole and the bolt length and may further vary on the dose of fixative to be delivered) and is adapted to hold the fixative. The chamber 31 also may be modified to be conical or hemispherical or otherwise shaped toward the spout end 32, and may be designed so that the device of the present invention may appropriately meet and/or match any inconsistencies in the surface variation of the rock proximate the hole in the rock. In use, the fixative is displaced from the chamber 31 into the drill hole following application of force to the thrust member 33. The thrust member 33 may match the shape of the chamber. The thrust member 33 is appropriately weakened to be frangible 35, 37 so that the rock bolt 41, upon application of a sufficient force, moves the thrust member 33 to cause the fixative to extrude out of the chamber 31 and into the hole via the spout 30, and after the fixative has been extruded into the rock hole, and the thrust member 31 comes to a position where it is no longer able to move in the chamber, the force can enable fracture of the frangible section(s) 35 and/or 37 and enable the bolt 41 to penetrate through the thrust member 33, pass through the spout 30 and enter the rock hole. Upon entering the rock hole, the rock bolt can be spun to mix the resin and allow the resin to secure the rock bolt in the hole in the rock. While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

(19) As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

(20) Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

(21) “Comprises/comprising” and “includes/including” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, ‘includes’, ‘including’ and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.