GB2138732A

GB2138732A - Anchor with Sleeve

Info

Publication number: GB2138732A
Application number: GB08311918A
Authority: GB
Inventors: Jeffrey George Haigh
Original assignee: Fosroc International Ltd
Current assignee: Fosroc International Ltd
Priority date: 1983-04-30
Filing date: 1983-04-30
Publication date: 1984-10-31
Also published as: GB8311918D0; BR8306657A; GB2138732B; ZA842734B

Abstract

A sleeve is formed on the end of an anchor element B, e.g. rebar, by placing an end of the element in a reusable plastics mould M, having a former for at least one thread R, and containing a self setting shrinking composition. The composition may undergo a colour change on hardening. The moulded article may be removed from the mould by unthreading it. <IMAGE>

Description

SPECIFICATION Anchor with Sleeve The invention concerns an anchor useful in mining, construction and civil engineering, the anchor having at one end an anchor sleeve. The invention also relates to a method and to means for making such a sleeved anchor.

In mining it is known to piace anchors in a drilled substrate to hold the substrate together to prevent roof falls and the like. Often a relatively wide diameter hole is drilled e.g. in a gallery roof and a bolt having at one end an expansion shell mechanical anchor is inserted and fixed following which a load is applied. When drilling in some substrates however, e.g. friable shale, there is a need for a longer anchorage to spread the load on the rock to prevent failure of the rock. In such circumstances it is preferable to use a resin grouted bar as the anchor. Because of the loading pattern only a small diameter bar is required and it is inefficient to grout this into a large diameter hole.

It is known from British patent 1382054 (CBP 23/25) that one can use a relatively narrower diameter anchor bolt in a relatively larger diameter hole by applying a sleeve to the end of the bolt. The sleeved bolt may be anchored by means of a self-setting composition housed in a capsule placed in the hole. The sleeve makes up the annular clearance and forms a mixing end for use in rupturing the capsule housing the interactive components of the self-setting composition to release and mix up those ingredients to form the composition to allow it to set and anchor the bolt. While that patent specification describes the manufacture of a sleeve about the end of the bolt the method is not described in detail and judging by the drawing, Figure 4, is not practical.

In British patent specification 1437339 (CBP 27) it is proposed to cast a polyester sleeve about an anchor cable in a corrugated plastics sheath, the sheath being stripped off so that one can inspect the cast sleeve before the anchor is inserted in the hole. Such a sheath can not be reused and an anchor cable of this type is very large: in the specification mention is made of a sleeve end portion 3.66 metres long and 50.8 mm in diameter.

In British patent specification 1 524524 (CBP 80) there is described a length of concrete reinforcing bar having thread like deformations formed thereon during rolling, a sleeve being retained on the bar, the sleeve being cast of selfsetting composition and extending along a length of the bar. The sleeve may be cast by known techniques which are unspecified.

It is one object of this invention to provide a practical and economic method of casting a sleeve about a bar, and means for use in the method, and also a new form of sleeved bar useful in the circumstances outlined above.

According to one aspect of the invention there is provided a method of placing an anchor sleeve length at the end of an anchor element having at least one keying deformation, the method comprising:- - placing a self-setting composition within a reusable mould, the mould being a preformed body of synthetic resin selected so as not to bond to the composition, the body having a former for at least one thread to be formed on the outside of the anchor sleeve, - pushing the anchor element into the composition within the mould and allowing the composition to set to bond to the element, and - removing the sleeved bolt by unthreading it from the mould.

The anchor element may be a length of concrete reinforcing bar, rod, strand, cable or the like. The element requires a keying deformation to grip the sleeve and the deformation may comprise threading or the spiral or helical deformations formed on a bar during rolling. Where the element is smooth the deformations may be hammered thereon and a nut or collar may be fitted to form the keying deformations.

The self-setting composition is preferably one which shrinks on setting as this will better debond the set sleeve length from within the mould, so enabling easier release of the sleeve from the mould. This is in contrast to the present thinking where one may use an expansive material e.g. an expansive cement. The composition may be cementitious or resinous: polyester or epoxy resin compositions are suitable. It is much preferred that the composition undergo a colour change on setting so that one may detect its presence within the mould and observe a colour change when setting has finished, usually within a matter of minutes, so that it is simple to know when to remove the sleeved anchor.

Typically the sleeved anchor will be secured in a bore-hole by means of a frangible capsule housing in separate compartments the interactive components of a self-setting anchoring composition, and for this reason at least one external thread is required on the sleeve. The thread may take a variety of forms ranging from helical or spiral ribs or shoulders or collars, provided that they will rupture the capsule and intermix the components. The thread is preferably selected so that when the sleeve is rotated within a hole, it tends to urge material deeper in the hole.

The sleeved anchor may also be used with a capsule of the type housing a drying interactive component only within a perforate wall and which, prior to use, is immersed in water.

In a further aspect, the invention includes a reusable mould for forming an anchor sleeve length at the end of an anchor element, the sleeve being formed of a self-setting composition, the length having at least one revolution of a thread, the mould comprising a preformed body of synthetic resin, the body having a former for the one thread, the body being formed of a material to which the self-setting composition will not bond.

In order that the invention may be well understood, it will now be described by way of illusration only, with reference to the accompanying diagrammatic drawings in which Figure lisa side elevation of a mould of the invention, and Figure 2 is a longitudinal sectional view of an anchor element being secured in the hole.

The mould M of Figure 1 comprises a cylinder about 300 mm long and having one end, the left hand end as shown, closed and defining an apex extension about 18 mm long. The average width of the cylinder is 30 mm but four longitudinally spaced apart, helical wound rib formers R are present; the ribs measure about 33 to 34 mm across the cylinder. The mould was blow moulded and made of polyethylene. The mould wall is translucent white.

In use, a quantity of a polyester grout Lokset (Registered Trade Mark) is supplied into the mould. As mixed the grout is green and appears green through the translucent mould. A threaded bar B, about 25 mm in diameter, is pushed into the mix until it reaches the end of the mould. The grout sets in 2 to 3 minutes and changes in colour as it debonds from the inside surface of the mould wall; as a result the apparent colour of the mould wall is then white. The bar B is then rotated to be removed from the mould M; the bar may be used as an anchor and the mould is ready for immediate re-use.

The bar B having a sleeve S moulded using the mould M of Figure 1 is to be anchored in the hole H in the gallery roof G of a friable shale of Figure 2. The hole H measures 40 mm in diameter and yet is to receive the 25 mm diameter bar B, having a sleeve S. A resin capsule C preferably according to British patent specification 1460588 (CBP 65) is pushed up the hole on the bar B which is then spun to rupture the capsule and release and intermix the ingredients. In this way a bar B is anchored in a wide diameter hole; the method is cheap and simple to perform and the sleeve is cheap and simple to make.

Claims

1. A method of placing an anchor sleeve length at the end of an anchor element having at least one keying deformation, the method comprising placing a self-setting composition within a mould, the mould being a preformed body of synthetic resin selected so as not to bond to the composition, the body having a former for at least one thread to be formed on the outside of the anchor sleeve, pushing the anchor element into the composition within the mould and allowing the composition to set to bond to the element, and removing the sleeved bolt by unthreading it from the mould.

2. A method according to Claim 1, in which the anchor element is a length of concrete reinforcing bar, rod, strand, cable or the like.

3. A method according to Claim 1, in which the element has a keying deformation to grip the sleeve and the deformation comprises threading of the spiral or helical deformations formed on a bar during rolling.

4. A method according to any of Claims 1 to 3, in which the self-setting composition is one which shrinks on setting.

5. A method according to any of Claims 1 to 4, in which the composition is selected to undergo a colour change on setting.

6. A method according to Claim 4 or 5, in which the composition is cementitious or resinous.

7. A method according to any preceding Claim, in which the mould is arranged to form at least one external thread on the sleeve.

8. An anchor element having a sleeve which has been formed by the method of any preceding Claim.

9. A reusable mould for forming an anchor sleeve length at the end of an anchor element by a method according to any of Claims 1 to 7, the sleeve being formed of a self-setting composition, the length having at least one revolution of a thread, in which the mould comprises a preformed body of synthetic resin, the body having a former for the one thread, the body being formed of a material to which the self-setting composition will not bond.

9. A reusable mould for forming an anchor sleeve length at the end of an anchor element, the sleeve being formed of a self-setting composition, the length having at lesat one revolution of a thread, in which the mould comprises a preformed body of synthetic resin, the body having a former for the one thread, the body being formed of a material to which the self-setting composition will not bond.

10. A method of forming an anchor sleeve length, substantially as described with reference to the drawings.

11. A reusable mould substantially as described with reference to the drawings.

Superseded Claims 1,9.

New or Amended Claims

1. A method of placing an anchor sleeve length at the end of an anchor element having at least one keying deformation, the method comprising placing a self-setting composition within a mould, the mould being a preformed body of synthetic resin selected so as not to bond to the composition, the body having a former for at least one thread to be formed on the outside of the anchor sleeve, there being an annular clearance between the mould interior and the element whereby a sleeve length having the threads is formed on the anchor element, pushing the anchor element into the composition within the mould and allowing the composition to set to bond to the element, and removing the sleeved bolt by unthreading it from the mould.