WO2022221887A1

WO2022221887A1 - Rock bolt anchoring device

Info

Publication number: WO2022221887A1
Application number: PCT/ZA2022/050017
Authority: WO
Inventors: George WEIDEMAN; Jacob Petrus Stephanus OLIVIER
Original assignee: Weideman George; Olivier Jacob Petrus Stephanus
Priority date: 2021-04-14
Filing date: 2022-04-12
Publication date: 2022-10-20
Also published as: ZA202309312B

Abstract

A rock bolt anchoring device (40) which includes a container (56) which has a first part of a settable composition in the form of a solid member (42), a second part of the composition in fluent form (58), and a barrier (50) between the first part and the second part and wherein the container, the barrier and the solid member are broken, and then mixed, by mechanical action.

Description

ROCK BOLT ANCHORING DEVICE

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to the anchoring of a rock bolt or other rock reinforcing component inside a borehole formed in a body of rock, using an adhesive composition. [0002] An adhesive composition of this kind is usually provided in two-part form with the two parts being mixed together and allowed to react inside a borehole thereby to form an adhesive bond which secures a rock bolt, in the borehole, to a surrounding wall of the rock body.

[0003] One type of an adhesive composition is based on the use of a powdered cementitious material which is mixed with an activator prior to use. This type of settable composition is described, for example, in the specification of South African patent No. 2015/04756.

[0004] It is important that the settable composition should be provided in a packaged form which allows for large-scale production and, thereafter, which can be stored and transported with minimal risk of breakage. Additionally the requirements for mixing and using the composition should be compatible with existing techniques which are employed with other kinds of adhesive compositions.

SUMMARY OF THE INVENTION

[0005] To meet the aforementioned objectives the invention provides a rock bolt anchoring device which includes a frangible container and, inside the container, at least one solid member which comprises a first part of a settable composition, a fluent substance which comprises a second part of said settable composition, and a protective barrier between said first part and said second part which prevents contact between the first part and the second part, wherein said protective barrier and said solid member are breakable by mechanical action to allow said first part to contact, and to be mixed with, said second part. [0006] Said first part may initially be in powdered form and said solid member may be formed by subjecting a quantity of the powdered form of the first part to a compressive force, preferably making use of a mould, so that the quantity of the powdered form of the first part is moulded into said solid member and has a desired shape and size.

[0007] The shape and size of the solid member may vary according to requirement and, subject to operating parameters, are not limited. In one example of the invention, which is preferred, the solid member is circular cylindrical and is elongate to a desired length. The fluent substance (second part) may then circumferentially surround at least some of the solid member.

[0008] In another form of the invention the solid member is tubular cylindrical with a bore and the fluent substance is located inside the bore of the tubular cylindrical member. [0009] It is possible for the solid member to be one of a plurality of elements which may be substantially similar to one another e.g. disc-like or of any other suitable shape.

[0010] The solid member may be encased in the protective barrier which may be in the form of a sheath. The sheath may be made from a material which can be broken, when desired e.g. the sheath may be made from a plastic sheet material. [0011] It thus falls within the scope of the invention for the settable composition to be provided in two-part form with a first part comprising a solid member of a suitable shape and dimension and a second part comprising a fluent substance, and wherein the first part is separated from the second part by means of a frangible protective barrier. [0012] The aforementioned South African patent specification describes a settable composition for use in the anchoring of rock bolts wherein a first part of the composition is a cementitious- based mixture of dry components which may be in powder form, and the second part comprises an activator. The current invention finds particular application in the packaging of this type of settable composition. Nonetheless said application is exemplary and is non-limiting for the principles of the invention can be used with other settable compositions in which one part can be provided in a solid form or can be made into a solid form e.g. through a suitable mechanical process.

[0013] in order to allow the solid member to be mixed, when required, with the activator i.e. the fluent substance, the solid member must be breakable, by means of mechanical force e.g. of the kind which is exerted by a rock bolt which is inserted into a borehole into which the rock bolt anchoring device is inserted. Typically the rock bolt, when inserted into the borehole, causes the frangible container which houses the solid member and the fluent substance to be broken and, thereafter, rotation and other movement of the rock bolt causes the solid member to be broken or crumbled into increasingly smaller fractions which can then effectively be mixed with the second part which is in fluent form. [0014] The invention aiso provides a method of making a rock bolt anchoring device which includes the steps of compressing a first part of a settable composition, which is in powdered form, into a solid member, encasing the solid member in a protective frangible sheath, locating the sheath and the first part in a frangible container, placing a second part of the settable composition which is in a fluent form into a space inside the container which is not occupied by the sheath and the first part, and sealing the container thereby to enclose the second part, the sheath and the first part in the container.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention is further described by way of examples with reference to the accompanying drawings in which :

Figure 1 depicts a technique for making a rock bolt anchoring device according to the invention, Figure 2 is a side view in section of a rock bolt anchoring device made according to the process shown in Figure 1 ,

Figure 3 is a view in cross section of the rock bolt anchoring device taken on a line 3-3 in Figure 2,

Figure 4 is similar to Figure 3 and shows, in cross section, a rock bolt anchoring device according to another form of the invention,

Figure 5 is similar to Figure 2 and shows, from one side and in section, a rock bolt anchoring device according to a further form of the invention, and Figures 6 and 7 are respectively similar to Figures 2 and 3 and show a rock bolt anchoring device according to a different form of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS

[0016] The invention finds particular application in the packaging of the materials which make up the rock bolt anchoring device described in the aforementioned South African patent specification. Nonetheless that application is exemplary and is non-limiting. [0017] The South African patent specification describes the use of a cementitious mixture to which a fluent activator, referred to as sodium liquid glass, is added when appropriate to form an adhesive mixture which is effective at bonding a rock bolt to a wail of a borehole in a body of rock in which the rock bolt is positioned.

[0018] Referring to Figure 1 a first part of a settable composition is initially provided in a powdered form 10. The ingredients in the powdered form by way of example can be of the kind described in the specification of the South African patent. It can be difficult to handle a material which is in powdered form and the invention seeks to address this difficulty. The powdered first part material 10 is directed to a mould 12 of any suitable shape. Through the application of pressure 14 which is produced by means of a mechanically or hydraulically actuated device, not shown, the powdered material 10 is compressed and compacted, and is thereby shaped into a solid member 16 of suitable form and size. Subsequently the solid member 16 is encased, in a step 20, in a protective plastic sheath 22 which acts as a barrier and which totally encloses the solid member to produce a packaged first part 24.

[0019] The adhesive materia! additionally includes a second part 26 which comprises an activator and which is provided in fluent form. Usually the second part is fairly viscous i.e. it is paste-like and does not flow readily. This characteristic nonetheless is exemplary and non- limiting. The packaged first part 24 emerging from the step 20 is directed to a packaging stage 28 in which two steps are carried out. Firstly the first part which is encased in the plastic sheath 22 is inserted into an elongate plastic container 30 and, secondly, a measured quantity of the fluent second part 26 is injected into a space inside the container which is not occupied by the solid first part i.e. the member 16. The container 30 is then sealed to produce a finished product 34.

[0020] The fluent actuator 26 and the solid member 16 are held in a known ratio inside the container 30.

[0021] Figures 2 and 3 are sectional side, and cross sectional, views respectively of a rock bolt anchoring device 40 produced in accordance with the steps shown in Figure 1. The device 40 includes an elongate circular cylindrical solid member 42 which is equivalent to the solid member 16 depicted in Figure 1. The member 42 has an appropriate diameter 44 and is of a chosen standard length 46. The member 42 is produced by means of an extrusion process using the mould 12 and the pressure applicator 14 referred to in connection with Figure 1. During this process sufficient pressure is applied to the powder constituents of the first part to ensure the formation of a solid end product 42 which can be handled with relative ease without fear of breaking the product. The extruded member can be sized to have the length 46 which is chosen according to a particular application.

[0022] The member 42 is then placed inside a frangible circular cylindrical container 50 of plastic or other suitable material, which is equivalent to the plastic sheath 22 referred to in connection with Figure 1. The member 42 is encased in the container which is sealed and thus is protected from inadvertently reacting with external materials. Thereafter, consistent with what has been described in connection with Figure 1, the container-encased member 42 is inserted into an elongate plastic cylindrical container 56, which corresponds to the item marked 30 in Figure 1. The container 56 has a closed lower end 56A and an upper end 56B which initially is open. A fluent material 58 which makes up the second part 24 (Figure 1) is then injected through the open upper end into the annular space surrounding the container-encased first part to fill the cylindrical container 56. Finally the container 56 is sealed at the injection end 56B so that the first part 42 and the second part 58 are securely enclosed in the container 56.

[0023] Figure 4 is similar to Figure 3 and illustrates in cross section a rock bolt anchoring device 40A according to a second form of the invention. In this case though the solid first member, designated 42A, is of tubular circular cylindrical form and defines an internal bore 60. A fluent activator 62A is encased in a protective tubular plastic sheath 64 and is inserted into the bore 60. A frangible cylindrical plastic container 66A encloses the assembly and surrounds the solid member 42A. The container 66A is sealed at both ends so that the assembly is held securely together, in a protected configuration, until such time as installation of the device 40A is to take place. [0024] Figure 5 is similar to Figure 2 and shows from one side and in section a device 40B according to another form of the invention.

[0025] In this instance the device 40B includes a number of segments 70 of solid members interspersed with segments 74 each of which comprises a fluent activator. Each segment 70 comprises a short circular cylindrical section which is encased in a protective sheath 76. The segments 74 are also short cylindrical sections which are encased in respective flexible protective plastic sheaths 78. Each sheath 78 contains a predetermined quantity of the fluent activator. The assembly of segments is held together in an elongate frangible cylindrical enclosure 80 of a flexible plastics material or any other appropriate material.

[0026] Figures 6 and 7 show from one side in section, and in transverse cross section respectively a device 40C according to another form of the invention. A rigid solid section 84 which makes up the first part of the settable composition is elongate and has a roughly semicircular shape in cross section. An activator is provided as a second part 88 which is elongate and also has a semi-circular shape in cross section. The parts 84 and 88 are respectively encased in protective and frangible sheaths 90 and 92 of a suitable plastic or other material. A flexible plastic container 98 of tubular circular cylindrical form holds the parts together so that they make up the device 40C of elongate circular cylindrical form.

[0027] It is apparent from the aforegoing description that various techniques can be used to package the parts which make up the settable composition into usable and different shapes. What is important in this respect is that the first part of the composition comprises one or more solid members which for example are initially of powdered form. If this is the case i.e. the first part is provided in a powdered form then the powder is shaped using a compressive force into a solid first member which can be handled with relative ease. If necessary in this respect use can be made of a binding agent. The first part does not break readily during normal transport and storage processes. When the first part is packaged the fluent second part is separated from the first part by means of one or more protective barriers. The assembled first part and the second part form an end product of a desired cross sectional shape which is sized so that it can be inserted, when required, into a borehole (not shown) which is bored into a body of rock and which has a predefined diameter. [0028] The device 40 (the finished product 34 of Figure 1) should be sufficiently rigid so that it can be inserted into the borehole with relative ease. Also the packaging materials used for the first and second parts must be such that they are capable of withstanding storage, transport and installation processes even in harsh conditions which might prevail underground, without inadvertently breaking.

[0029] Once a rock bolt anchoring device has been inserted into a borehole a conventional installation process is followed in that the materials which house the first part and the second part are pierced by means of a rock bolt which is inserted into the borehole using a placement machine which imparts linear and rotary movement to the rock bolt. [0030] As the rock bolt passes through the packaging materials it encounters the solid first part.

The manner in which the first part was formed, by compressing the powdery starting material, is such that the mechanical action of the moving, and rotating rock bolt causes the first part to crumble and disintegrate into small pieces which are then mixed with the fluent second part in an effective manner to form a fluent adhesive material, in situ, which bonds the rock bolt to a wall of the borehole in which the rock bolt is located.

Claims

1. A rock bolt anchoring device which includes a frangible container and, inside the container at least one solid member which comprises a first part of a settable composition, a fluent substance which comprises a second part of said settable composition, and a protective barrier between said first part and said second part which prevents contact between the first part and the second part, wherein said protective barrier and said solid member are breakable by mechanical action to allow said first part to contact, and to be mixed with, said second part.

2. A rock bolt anchoring device according to claim 1 wherein the solid member is circular cylindrical in form and is elongate to a predetermined length.

3. A rock bolt anchoring device according to claim 2 wherein the fluent substance circumferentially surrounds at least a portion of the solid member.

4. A rock bolt anchoring device according to claim 1 wherein the solid member is tubular cylindrical with a bore and the fluent substance is located inside the bore of the solid member.

5. A rock bolt anchoring device according to claim 1 wherein the solid member is one of a plurality of similar elements.

6. A rock bolt anchoring device according to claim 1 wherein the solid member is encased in the protective barrier which comprises a frangible sheath.

7. A method of making a rock bolt anchoring device which includes the steps of compressing a first part of a settable composition, which is in powdered form, into a solid member, encasing the solid member in a protective frangible sheath, locating the sheath and the first part in a frangible container, placing a second part of the settable composition which is in a fluent form into a space inside the container which is not occupied by the sheath and the first part, and sealing the container thereby to enclose the second part, the sheath and the first part in the container.