CA2764585A1

CA2764585A1 - Sliding anchor

Info

Publication number: CA2764585A1
Application number: CA2764585A
Authority: CA
Inventors: Richard Podesser; Frank Schmidt
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2011-03-10
Filing date: 2012-01-18
Publication date: 2012-09-10
Also published as: AU2012200555A1; EP2497901A2; DE102011005361A1; US20120230774A1

Abstract

A chemical sliding anchor (1), in particular for use in mining, for the firm bonding to the rock (18) in a borehole (19) using a fixing agent (20), comprises an anchor pipe (2), preferably an anchor nut (7), anchor plate (8) preferably supported by the anchor nut (7), for lying on the rock (18), involving little technical effort by effectively using a sliding function of the sliding anchor (1) in the case of a large change in length of the sliding anchor (1) on absorbing dynamic loads.

This problem is solved in that an elastic element (9), in particular a spring (9), is integrated in the sliding anchor (1) and an increase in length of the sliding anchor (1) is effected for a given sliding function with a spring deflection of the elastic element (9).

Description

Sliding Anchor DESCRIPTION
The present invention relates to a sliding anchor according to the preamble of claim 1.

In mining and tunnelling, rock bolts are used to prevent or slow down movement of the bedrock, or to avoid greater spalling of the bedrock and thus ensure safe operation. Two functional principles are known, which can also be partially combined. In the case of mechanical systems, anchoring of the anchor means is achieved by frictional interaction, whereby the mechanical rock anchors also generally have an expansion sleeve. In the case of chemical rock anchors, anchor pipes are firmly bonded to the substrate or the bedrock using mortar or a hardening resin as a fixing agent. The rock bolts are installed in the bedrock either with or without preloading. Rock bolts used in mining, such as in underground coal mining and unlike those used for tunnelling, are only used for temporary support of the rock because, in general, the temporarily supported rock is mined in a subsequent operation and so the rock bolts are removed from the rock.

When sliding anchors are used as rock bolts, a sliding of the sliding anchor on an anchor plate in a longitudinal direction is possible above a certain compressive force. In this case, an anchor plate generally lies on the anchor nut while a female thread engages in a male thread of a rod protrusion of an anchor pipe. Above a given tension in the anchor pipe or a compressive force on the anchor plate, where the rock is lying on the anchor plate, the anchor nut like the rod protrusion can move a certain sliding distance on the anchor pipe and thereby enable an increase in the length of the sliding anchor. The sliding anchor thus requires a large rod protrusion in the working space for the sliding function outside the rock, such as in tunnels. However, this freedom of movement and the working space in the gallery of a mine is severely limited. Furthermore, considerable technical effort is required to enable the sliding movement of the anchor nut on the rod protrusion. As an alternative, the sliding function. i.e. the change in length of the sliding anchor, can also be effected by an elastic elongation of the anchor pipe. Because of the rigidity of such sliding anchors, there is a risk of an unforeseen anchor rupture and an anchor failure under dynamic loads, e.g. due to rock bursts.

DE 29 04 778 Al shows a monitoring device for detecting and displaying roof movements by means of a supporting device anchored and extending longitudinally above the roof, to whose lower end at the roof surface is attached a sensing device that is responsive to changes in length and displays roof movements, and where there is a holding device that is supported on, and movable with respect to, the supporting device for the sensing device that is suspended from it and automatically swings down under the effect of gravity, along with a locking device for automatic locking of a sensing device in a highly tilted position, and a release mechanism mounted at the lower end of the supporting device to release the locking on the occurrence of a predetermined relative movement with respect to the holding device.

The object of the present invention is therefore to provide a sliding anchor which, featuring low technical complexity, enables an effective sliding function of the sliding anchor in the event of a large longitudinal change of the sliding anchor by the absorption of dynamic loads.

This object is achieved by means of a chemical sliding anchor, in particular for use in mining, for firm bonding to rocks in a borehole using a fixing agent, comprising an anchor pipe, preferably an anchor nut, and preferably an anchor plate to rest against the rock and supported by the anchor nut, whereby an elastic element, in particular a spring, is integrated in the sliding anchor enabling a longitudinal movement of the sliding anchor for a sliding function with a spring deflection, i.e. an elastic deformation of the elastic element is effected.

The elastic element, in particular the spring, can absorb both static and dynamic forces as a separate component independently of the anchor pipe. Thus the static and dynamic forces acting on the anchor pipe can be absorbed by the spring. In particular, this enables dynamic loads to be damped and, in the case of static forces acting on the anchor pipe, enables a longitudinal extension of the sliding anchor due to a spring deflection of the spring and thus the tensile forces to be absorbed by the sliding anchor can be reduced. Thus this offers an effective way to avoid an unexpected breakdown of the sliding anchor and, due to the good absorption ability of dynamic loads as well, the risk of failure under dynamic loads can be reduced considerably by means of sliding anchors, for example, under the effect of the rock bursts or tremors. In addition, the spring deflection of the sliding anchor is advantageously limited and thus the possible sliding path of the sliding anchor is also limited. Thus the possible deformation path and the possible deformation of the rock on the sliding anchor may be limited in an advantageous manner.

In particular, the sliding anchor has a sleeve and the elastic element is arranged inside the sleeve, and/or any change in length of the elastic element is aligned in the direction of a longitudinal axis of the anchor pipe and/or the sliding anchor is provided with a damper to absorb dynamic forces and/or the elastic element is an additional component in addition to the anchor pipe.
The damping element is used for additional absorption of dynamic forces and can be designed, for example, as a folding plate, a spring or an elastic plastic, such as a thermoplastic, thermosetting or elastomeric plastic, as well as especially a damping element with a movable piston inside a cylinder with a fluid, such as oil or water. Such a damping element with a piston and cylinder corresponds in its technical design and its function to a damping element as used, for example, as a shock absorber in a car.

In a further embodiment, the anchor pipe is arranged inside the sleeve while the elastic element is preferably arranged between the anchor pipe and the sleeve.

In an additional embodiment, the elastic element lies on a sleeve bearing element connected at one end with the sleeve, while the other end lies on an anchor pipe bearing element connected with the anchor pipe and/or the sleeve is closed in the area of the anchor pipe bearing element by a closure cap.
Preferably, the sleeve bearing element is designed as a plate with an opening and the anchor pipe is arranged in the opening of the plate. The anchor pipe is thus supported to be axially movable in the opening of the plate in the direction of a longitudinal axis of the anchor pipe and radially to the opening of the plate.

In one embodiment, the anchor pipe bearing element is designed as a support ring. The support ring may be designed to be integral with the anchor pipe or separate and connected to the anchor pipe as a material, shaped and/or frictionally bound component. The support ring causes the forces absorbed by the anchor pipe to be transmitted from the elastic element, in particular the spring, to the anchor pipe.
It is expedient to arrange the anchor pipe bearing element inside the preferably cylindrical sleeve space that is enclosed, in particular completely, inside the sleeve.

In another embodiment, the sleeve is arranged in the area of a rear end of the anchor pipe in order to position the sleeve within a borehole in the rock while the anchor nut is directly or indirectly attached to the anchor pipe and preferably the sleeve forms the material connection between the fixing agent and the rock of a borehole or the sleeve is arranged in the area of the front end the anchor pipe to position the sleeve outside the borehole in the rock while the anchor plate lies directly or indirectly on the sleeve or the sleeve bearing element, whereby the anchor plate lies against the rock on a rock side and lies on a sleeve side on the sleeve or sleeve bearing element while the rock side is formed opposite the sleeve side on the anchor plate or the sleeve is arranged in the area of the front end of the anchor pipe to position the sleeve inside the borehole in the rock and the sleeve is connected to the anchor plate and/or the anchor nut.

In particular, the anchor pipe is at least partially, preferably completely, made of metal such as steel or, preferably, fiber-reinforced plastic.

In another embodiment, the spring is in the form of a coil spring, a volute spring, an annular spring, a folding plate or an elastic plastic, such as a rubber spring.

It is useful to have the sliding path mainly effected by a spring deflection of the elastic element, i.e. by at least 50%, 80% or 90%.

In an additional variant the sliding path, i.e. the increase in length of the sliding anchor, is a function that is, for example, directly proportional to the change in length, particularly compression, of the elastic element, in particular where the elastic element is coupled with a mechanism with a component of the sliding anchor, in particular the anchor plate. Preferably, the mechanism includes an axially-movable sleeve.

In a further embodiment, the anchor pipe has an inner space in the form of a hollow pipe while the fixing agent is arranged inside the anchor pipe, e.g. in a bag or a cartridge.
The fixing agent is, for example, a two-component resin with an adhesive component and a hardening component. The adhesive and a hardening components are first separately stored in the inner space, e.g. in a bag or a cartridge, and then mixed prior to extrusion from the inner space, and then the mixed resin is extruded into a space between the anchor pipe and the rock in the borehole to make a material connection between the anchor pipe and the rock.

Appropriately, the elastic element, especially the spring, is integrated into the hollow pipe as the anchor pipe, whereby the elastic element is arranged between two parts or sections of the hollow pipe and connected to two parts or sections, whereby the elastic element is preferably arranged outside an area with the fixing agent.

In an additional embodiment, the sliding anchor has at least one means, e.g. a dispensing device, to extrude the fixing agent from the inner space enclosed by the anchor pipe into a space between the anchor pipe and the rock in a borehole with a sliding anchor inserted. The dispensing device, for example, comprises a piston and a pressure is exerted on the piston by water under high pressure, so that the piston moves within the inner space and forces the fixing agent out.
To this end, the anchor pipe has at least one opening through which the fixing agent can be extruded.
Preferably, for this, a mixing device is provided which enables the mixing of a fixing agent before being extruded.

Embodiments according to the invention are described in more detail below with reference to the accompanying drawings. The figures show:

Fig. I shows a longitudinal section of a sliding anchor in a first embodiment in a borehole in the rock, Fig. 2 shows a longitudinal section of the sliding anchor in a second embodiment in a borehole in the rock, and Fig. 3 shows a longitudinal section of the sliding anchor in a third embodiment in the borehole in the rock.

A sliding anchor shown in Figure 1 as a rock anchor l is a mine anchor that is used in mining for temporary support of tunnels. The sliding anchor I can absorb tensile forces, and thus stop outer rock layers from detaching in tunnels in the mining industry by transferring these forces into deeper layers. Furthermore, shear forces on the rock 18 are absorbed by the sliding anchor 1 and thus there is additional assurance with respect to the outer layers of rock in the tunnel in the mine.

Sliding anchor I comprises an anchor pipe 2 made of metal such as steel or glass fiber reinforced plastic as a solid profile with no cavities. To secure a tunnel in a mine, a borehole 19 is first drilled in the rock 18 in the tunnel and subsequently a fixing agent 20 such as a resin in a cartridge or concrete is introduced into the hole 19. Then the sliding anchor 1 is introduced in the borehole 19 and then the fixing agent 20 is extruded into a space 21 between the sliding anchor 1 and the rock 18.

Figure l illustrates a first embodiment of the sliding anchor 1. The sliding anchor I is already inserted into the borehole 19 in the rock 18 and is firmly bonded to the rock 18 with the fixing agent 20. The anchor pipe 2 has a front end 3 in a working chamber 22 and a rear end 4 in the area of the rear end 4 of the borehole 19. At the rear end section of the anchor pipe 2, a cylindrical sleeve 11 is coaxially pushed onto the anchor pipe 2. Between the sleeve 11 and the anchor pipe 2, a spring 9 in the form of a coil spring 10 serves as an elastic element 9 made of steel that is arranged in an inner space 12 enclosed by the sleeve 11. An anchor pipe bearing element 16 in the form of a support ring 17 is arranged at the rear end 4 of anchor pipe 2. The support ring 17 is then connected with the anchor pipe 2 so that it is not movable along a longitudinal axis 6 of the anchor pipe 2.
A plate 15 is formed integrally with the sleeve 11 as a sleeve bearing element 14 at a front end of the sleeve 11. The sleeve bearing element 14 or the plate 15 has an opening and the anchor pipe 4 is mounted axially in this opening. Thus it is possible that in the axial direction, i.e. along the longitudinal axis 6 of the anchor pipe 2, to move the anchor pipe 2 relative to the plate 15 and thus also to the sleeve 1 1 . The sleeve 11 is firmly bonded by the fixing agent 20 to the rock 18. To allow such axial movement of the anchor pipe 2 even in the area of the anchor pipe 2 with fixing agent 20, the anchor pipe 2 is provided with a sliding coating 5 so that effectively no forces are transferred between the anchor pipe 2 and the fixing agent 20. Between the coil spring 10 and the plate 15, an additional damping element 23 is provided to absorb dynamic loads. The sleeve 11 is closed in the area of a rear end of the sleeve 11 by a closure cap 13.

In the area of the front end 3. the anchor pipe 2 is provided with an external thread. An anchor plate 8 and an anchor nut 7 are displaced towards the anchor pipe 2 in the working chamber 22, i.e. pushed out of the hole 19. Here, the anchor nut 7, presents a non-illustrated female thread which engages with the male thread of the anchor pipe 2. The anchor plate 8 thus lies against the rock 18 in the area of the borehole mouth, so that it is secured by the rock 18, whereby forces are applied by the anchor plate 8 on the rock 18 and these are transferred as tensile forces to the anchor pipe 2 with the anchor nut 7. The tensile forces in the anchor pipe 2 are applied to the coil spring 10 via the support ring 17 and from the coil spring 10 to the damping element 23 and from the damping element 23 to the plate 15 or the sleeve bearing element 14. The axial forces acting on the sleeve member 14 in the direction of the longitudinal axis 6 are transferred to the sleeve I I and from the sleeve 11 to the rock 18 by means of the fixing agent 20. This enables the outer layers of rock 18 to be held by the sliding anchor 1 and the transfer of the forces required to hold the outer layers of rock 18 to deeper rock layers 18 in the area of the fixing agent 20. In addition to another component, for example anchor pipe 2, of the sliding anchor 1, spring 9. as an elastic element 9, is elastically deformable according to Hooke's law where F = - c x s, where c is the spring constant of the spring 9 and s the spring deflection in the form of elongation or compression of the spring 9. The force F thus corresponds to the tensile force acting on anchor pipe 2 and which acts as a compressive force on the spring 9. The sliding anchor 1 thus has a sliding function and, in the case of deformations of the outer layers of rock 18, it is possible to avoid a breakdown or a failure of the sliding anchor 1 due to an increase in length of the sliding anchor I because of a change in length or a compression of the spring 9, even in the case of larger separations or deformation of the rock 18 in the area of the anchor plate 8. The spring 9 can thus also absorb or dampen dynamic loading.

In Fig. 2, a second embodiment of the sliding anchor 1 is shown. In what follows, only the essential differences with respect to the first embodiment shown in Figure 1. are described. The sleeve 11 is arranged outside the fixing agent 20 in the borehole 19 in the rock 18 and the transfer to the rock 18 of tensile forces absorbed by the anchor pipe 2 is effected by the direct contact of the fixing agent 20 with the anchor pipe 2. The anchor nut 7 is not connected to the anchor pipe 2, but the sleeve II has a non-illustrated male thread which engages in a non-illustrated female thread of the anchor nut 7. This allows transfer of the forces acting on the anchor plate 8 to be transferred as tensile forces to the anchor nut 7 and from the anchor nut 7 to the sleeve 11. These tensile forces are transferred from the sleeve i l to the sleeve bearing element 15 and from this to the screw spring 10. The coil spring 10 transfers these tensile forces as compressive forces to the damping element 23 and the second support ring 17 as tensile forces in the anchor pipe 2. Upon movement of the outer layers of rock 18 or the anchor plate 8 to the right as shown in Figure 2, the sleeve 11 is also moved to the right. The anchor pipe 2 remains unchanged in its axial position and there is thus a relative movement between the sleeve 11 and the fixed anchor pipe 2.

Figure 3 shows a third embodiment of the sliding anchor 1. In what follows, only the essential differences with respect to the first embodiment shown in Figure 1 are described. The sleeve 11 is arranged outside the borehole 19 in the working chamber 22. The transfer of the tension forces acting on the anchor pipe 2 to the rock 18 is effected through direct contact between the anchor pipe 2 and the fixing agent 20. The sliding anchor I has no anchor nut 7 and the plate 15 rests on the anchor plate 8 as a sleeve bearing element 14. Upon movement of the outer layers of rock or the anchor plate 8 to the right as shown in Figure 3, then the anchor plate 8 as well as the sleeve 11 move to the right also.
The position of the anchor pipe 2 remains unchanged with respect to deeper, fixed rock layers due to the fixing with the fixing agent 20, so that any movement of the anchor plate 8 to the right as shown in Figure 3 compresses the spring 9 (length reduction) i.e. it has a smaller deflection in the direction of the longitudinal axis 6 because the stationary anchor pipe 2 is connected at the front end 3 of the anchor pipe 2 of the support ring 17 and thus the damping element 23, and thus the spring 9, is compressed.

In addition to the anchor pipe 2 and the spring 9, the sleeve 11, the sleeve bearing element 14 and the anchor pipe bearing element 16 are also made of metal such as steel.

Overall, there are significant advantages connected with the sliding anchor 1 according to the invention. The spring 9 built into the sliding anchor 1 in the form of an elastic element 9 can accept large deformations or changes in length thereby effecting a change in length or a sliding of the sliding anchor I. Thus spring 9 can also absorb dynamic loads well in addition to static loads. The risk of a failure of the sliding anchor I can be reduced significantly, while the use of springs 9 with different spring constants in the presence of an otherwise identical sliding of the sliding anchor I enables the sliding anchor I also to be used in a variety of applications and with different types of rocks 18.

Claims

1. Chemical sliding anchor (1) especially for use in mining for a firmly bonded fixing to rock (18) in a borehole (19) with fixation equipment (20), comprising - an anchor pipe (2), - preferably an anchor nut (7), - an anchor plate (8) preferably supported by the anchor nut (7) for positioning on the rock (18), characterized in that an elastic element (9), in particular a spring (9), is integrated in the sliding anchor (1) whereby an increase in the length of the sliding anchor (1) is achieved by means of a sliding movement on deflection of the elastic element (9).

2. Sliding anchor according to claim 1, characterized in that the sliding anchor (1) has a sleeve (11) and the elastic element (9) is arranged inside the sleeve (11), and/or a change in length of the elastic element (9) is aligned in the direction of a longitudinal axis (6) of the anchor pipe (2), and/or the sliding anchor (1) is provided with a damping element (23) for absorbing dynamic forces, and/or the elastic element (9) is an additional component in addition to the anchor pipe (2).

3. Sliding anchor according to claim 2, characterized in that the anchor pipe (2) is arranged within the sleeve (11), and the elastic element (9) is preferably arranged between the anchor pipe (2) and the sleeve (11).

4. Sliding anchor according to claim 2 or 3, characterized in that the elastic element (9) at one end lies on the sleeve bearing element (14) connected to the sleeve (11) while at the other end it lies on the anchor pipe support element (16) connected to the anchor pipe (2), and/or the sleeve (11) is closed in the area of the anchor pipe support element (16) by a closure cap (13).

5. Sliding anchor according to claim 4, characterized in that the sleeve bearing element (14) is designed as a plate (15) with an opening and the anchor pipe (2) is arranged in the opening of the plate (15).

6. Sliding anchor according to claim 4 or 5, characterized in that the anchor pipe bearing element (16) is in the form of a support ring (17).

7. Sliding anchor according to one or more claims 4 to 6, characterized in that the anchor pipe bearing element (16) is enclosed, in particular completely, inside a preferably cylindrical sleeve space (12) in the sleeve (11).

8. Sliding anchor according to one or more claims 2 to 7, characterized in that the sleeve (11) is arranged in the area of a rear end (4) of the anchor pipe (2) in order to position the sleeve (11) within a borehole (19) in the rock (18) while the anchor nut (7) is directly or indirectly attached to the anchor pipe (2) and preferably the sleeve (11) forms the material connection between the fixing agent (20) and the rock (18) of a borehole (19) or the sleeve (11) is arranged in the area of the front end (3) the anchor pipe (2) to position the sleeve (11) outside the borehole (19) in the rock (18) while the anchor plate (8) lies directly or indirectly on the sleeve (11) or the sleeve support member (14), whereby the anchor plate (8) lies against the rock (18) on a rock side and lies on a sleeve side of the sleeve (11) or sleeve bearing element (14) while the rock side is formed opposite the sleeve side on the anchor plate (8) or the sleeve (11) is arranged in the area of the front end (3) of the anchor pipe (2) to position the sleeve (11) inside the borehole (19) in the rock (18) and the sleeve (11) is connected to the anchor plate (8) and/or the anchor nut (7).

9. Sliding anchor according to one or more of the preceding claims, characterized in that the anchor pipe (2) is at least partially, preferably completely, made of metal such as steel or, preferably fiber-reinforced plastic.

10. Sliding anchor according to one or more of the preceding claims, characterized in that the elastic element (9), in particular the spring (9), is in the form of a coil spring, a volute spring, an annular spring, a folding plate or an elastic plastic, such as rubber spring.