EP3336258A1 - End anchoring for a floor and/or rock anchor - Google Patents

Abstract

The end anchorage for a ground and / or rock anchor comprises a tension member (2) of at least one tensioning strand (12). Their wires (13) have emerged to an upsetting head (6) as an end, which is held on an anchor plate (5).

Description

The invention relates to an end anchor for a ground and / or rock anchor, which comprises a tension member of at least one tension cord.

Advantageously, the tension member is anchored in the final anchorage slip-free as possible, so that in the displacement measurements in anchor tests and clamping samples for determining and controlling the sustainability of the ground no mixing of reactions of the ground and slippage takes place in the final anchorage.

For end anchors, it is known to anchor the tension strands purely mechanically with clamping wedges or pressing sleeves on an anchoring plate. However, this anchorage is unfavorable because of the space requirements of the anchoring plate, in which the clamping wedges stuck or the press sleeves, since the diameter of the well compared to the common diameters used in normal anchoring anchors without pressure tube, must be increased, resulting in significant additional costs leads.

An object of the present invention is to propose an end anchorage for a ground and / or rock anchor with a compact construction.

An end anchorage which achieves this object is specified in claim 1. The further claims indicate preferred embodiments of the inventive end anchorage as well as an anchor with such an end anchorage.

By providing a compressed Spannlitzenendes the end anchorage can be made compact. It is therefore not necessary to provide a borehole which has a diameter in excess.

Fig. 1

einen Längsschnitt durch die Endverankerung;

Fig. 2

den Schnitt A - A aus Fig. 1;

Fig. 3

den Stauchkopf am Litzenende im Detail;

Fig. 4

den Schnitt B - B durch die Spannstahllitze aus Fig. 3;

Fig. 5

den Schnitt C - C durch den Stauchkopf aus Fig.3 ohne Verfüllung; und

Fig. 6

den Schnitt C - C durch den Stauchkopf aus Fig.3 mit Verfüllung.

The invention will be further explained with reference to an embodiment with reference to figures. Show it:

Fig. 1

a longitudinal section through the end anchorage;

Fig. 2

the section A - A off Fig. 1 ;

Fig. 3

the swaging head at the end of the strand in detail;

Fig. 4

Cut B - B through the prestressing steel strand Fig. 3 ;

Fig. 5

Cut C - C through the head Figure 3 without backfilling; and

Fig. 6

Cut C - C through the head Figure 3 with backfilling.

Fig. 1 shows a longitudinal section through the end anchorage 1, z. B. on a pressure pipe of a pressure pipe anchor or generally on a support 11 of a rock and / or ground anchor by means of a transfer plate 3 is supported. The tension member 2 of the armature is formed from tension strands 12, for example prestressing steel strands. These pass through bores in the transfer plate 3, then extend along a connection path and finally pass through bores in an anchor plate 5 (also referred to below as the "end plate"). The transfer plate 3 has a support surface, which bears against the support 11. The tension strands 12 are provided at their ends with upset heads 6, which are supported on the end plate 5 and are pressed by means of the pressure plate 10 to this. For this purpose, the pressure plate 10 is bolted to the end plate 5 or connected in any other way with this.

Between the end plate 5 and the pressure plate 10, the compression heads 6 are surrounded by the potting 8. This is made for example of a material based on cement, plastic and / or metal. The forces of the compression heads 6 on the end plate 5 are transmitted to the transfer plate 3 via a steel tube 4, which is arranged between the plates 3 and 5 and surrounds the tension member 2.

In the steel pipe 4 between the end plate 5 and the transfer plate 3, the prestressing steel strands 12 of the tension member 2 in a backfill 7, cast grout, for example, by composite on skin friction on the inner surface of the steel pipe 4 and upsetting the backfill 7 on the transfer plate 3 forces from the Tension member 2 on the transfer plate 3 on the support 11 ablate. For the production of filling 7 diverse materials are conceivable, for example, cement-water mixture with the possible addition of one or more additives, such as. As propellants, plasticizers and setting accelerators, mortars based on plastic, etc.

The in the Fig. 1 illustrated end anchorage is designed for a dismantling of the tension member 2. For this purpose, a separating device is provided to weaken or cut through the tensioning strands 12 as required. For example, the Separating device, an induction coil 16 which surrounds the tension member 2 and this inductively heated during removal to the break. The temperature required for this can be kept below the melting point of the tension member 2 if it is sufficiently pre-stressed during the heating process, typically with a force of at least 10%, preferably at least 25% and more preferably at least 50% of the tensile strength of the tension member 2 at 0 degrees Celsius.

The induction coil 16 is arranged closer to the plate 3 than to the plate 5, preferably subsequently to the plate 3, and is cast in the backfill 7.

For energizing the induction coil 16 is a (not shown) frequency converter, such as a static frequency converter, which is connected via a along the tension member 12 extending power supply cable 17 to the induction coil 16. This is preferably formed by a winding which is single or multi-layered and consists of a cable. In Fig. 1 it can be seen that the power supply cable 17 is passed through an opening in the pipe 4. Alternatively, it is conceivable to pass the cable 17 from the interior of the support 11 through the transfer plate 3.

Preferably, the induction coil 16 extends spaced around the tension member 2 so as to prevent the heat generated in the tension member 2 during the heating process from melting the electrical insulation of the induction coil 16 and thus causing an electrical short circuit. The induction coil 16 may, for. B. be arranged on or in a pipe section through which the tension member 2 extends and which is embedded in the backfill 7.

Fig. 2 shows a section through the composite section with the existing of the prestressing steel strands 12 tension member 2, which is connected via the grout 7 with the steel pipe 4. There are four prestressing steel strands 12 shown here. The number can also be different and be one, two or more. If the number is greater than one, then the prestressing steel strands 12 are preferably arranged symmetrically around the center, so that in each case the angle between two adjacent compression heads 6 is equal in the circumferential direction. It is also conceivable to provide at least one tension cord 12 in the center and to arrange the remaining, if present, as explained above symmetrically around the center.

Furthermore, here for each strand 12 seven individual wires 13 are shown. This number can also be different and be two, three or more. The respective wire 13 of the strand 12 has a solid cross-section. Preferably, the respective strand 12 in Center on a wire 13 as a soul to which wires 13 are wound whose respective diameter is smaller than the diameter of the soul.

• -- zementöser Vergussmörtel,
• -- Kunststoffvergussmörtel,
• -- metallischer Verguss, beispielsweise Flüssigmetall wie Wirelock^®.

Fig. 3 shows in detail the end portion of a prestressing steel strand 12 of the final anchorage. The individual wires 13 of the prestressing steel strand 12 are filled in the swaging head 6 as upset individual wires 14 with the interspaces 15 through the potting 9 and are surrounded by the potting 8. Preferably, the potting 9 is made of the same material as the potting 8. The following materials are suitable for the potting 8 or 9:

• - cementitious grout,
• - plastic grout,
• - Metallic encapsulation, such as liquid metal such as Wirelock ^® .

The pressure plate 10 presses the compression head 6 against the end plate 5 in order to cancel a possible game. Subsequent to the end plate 5, the prestressing steel strand 12 extends in the steel tube 4 which is filled with the grouting 7.

To produce an upset end of a single wire, the method according to Birkenmaier, Brandestini, Ros and Vogt is known (BBRV method), cf. CH 300 486. This method can be transferred here to produce for anchoring a strand 12 with an upsetting head 6 as an end. In this case, the end of a strand 12 is plunged in the cold state with a compression machine during manufacture. The ends 14 of the individual wires 13 of a strand 12 are thereby compressed, so that they form a total of an upsetting head 6, whose diameter is increased compared to the diameter of the strand 12. The swaging head 6 is therefore an integral part of the strand 12 and surprisingly has a high load capacity. This is typically at least 40% of the breaking load of the strand 12, preferably at least 50%.

By providing the pressure plate 10 and the potting 8, 9 can be prevented that a yielding of the compression heads 6 takes place by changing the geometry of the compressed individual wires of their initial shape under load. As a result, the carrying capacity of the compression heads 6 can be increased, as a result of which the upstream connection section is shortened and the slippage overall can be further reduced. Typically, this carrying capacity is at least 70%, preferably at least 90% and particularly preferably 100% of the breaking force of the strand 12.

Fig. 4 shows the section through the prestressing steel strand 12 with the here seven individual wires 13 in the region of the end plate 5. It can be seen the bore 5a in the end plate 5, through which the prestressing steel strand 12 extends.

Fig. 5 shows the section through a compression head 6, before the interstices 15 have been filled and poured around.

Fig. 6 shows the section through the upturned by the potting 8 upset head 6 with the individual wires 14, the interstices 15 are filled with the potting 9.

The end anchoring described here can be used in many ways as part of a ground and / or rock anchor. In use, the prefabricated anchor end anchor is inserted into a wellbore in the ground. The anchor is z. B. formed as a pressure tube anchor. In this case, the tension member over the entire anchor length freewheeling in a piping, z. B. out of PE and anchored in the borehole deepest by means of the final anchorage. To initiate the anchor force in the ground, the end anchorage is based on the pressure tube, which is typically 1.5 to 4 meters long and is connected non-positively by casting with cement mortar for anchoring purposes to the ground. The pressure tube may be made of one or more materials.

The anchorage can be used for anchors with retractable tension member or for permanently installed anchors, ie anchors without removable tension member. In the latter case, the separating device for separating or weakening the tension member (see, for example, the in Fig. 1 shown elements 16 and 17) may be omitted.

If the final anchoring designed for decommissioning, so the tension member by means of the separator, which z. B. is designed for heating by induction, so weakened that it breaks under the upcoming clamping forces.

Soil anchors and rock anchors with a retractable tension member are used in particular for securing construction pits. The forces held in equilibrium by the anchors, mainly due to active earth pressure, can usually be taken over by the construction of the structures, so that the function of the anchors becomes obsolete. The anchors usually extend under neighboring properties, so that they represent an obstacle in the construction site there when left in construction. In particular, the tension member made of prestressing steel strands is difficult to cut because of the high strength and toughness of the steel. Therefore, in many cases, the demand for a dismantling of anchors is charged.

The end anchoring described here has, among others, the following advantages:

The end anchor has a compact construction.

Thus, the end anchorage can be designed to be slim transversely to the direction of the well. A stranded head has a smaller lateral extent than e.g. a strand, which is anchored with wedges or a compression sleeve. Typically, the Litzenstauchkopf has a diameter which is smaller than 2 times the strand diameter and is z. B. 1.5 times the strand diameter. It is therefore possible to arrange the strands space saving than usual. Compared to the commonly used anchoring anchors without pressure pipe no larger diameter boreholes are required.

The end anchorage can also be kept short in the direction of the borehole. Thus, the distance between the support 11 and the swaging head 6 or the swaging heads 6 is typically less than 1 m, preferably less than 0.50 m.

The tension member can be anchored in the final anchorage as possible slip-free, so that takes place in the displacement measurements in anchor tests and clamping samples for determining and controlling the sustainability of the ground no mixing of reactions of the ground and slippage in the final anchorage. Typically, the slip that results in the final anchorage during tensioning of the tension member is less than 0.5 mm, preferably less than 0.2 mm and particularly preferably less than 0.1 mm.

From the foregoing description, numerous modifications will be apparent to those skilled in the art without departing from the scope of the invention, which is defined by the claims.

For the production of the individual parts and other materials are conceivable as explained above. For example, in addition to steel, other materials are also suitable for providing the tube 4 and / or a tensioning strand 12.

Depending on the application, a different number of strands 12 is provided for forming the tension member than shown in the figures. In a simple embodiment, a single strand 12 may be provided as a tension member having an upsetting head 6 for anchoring. Generally, the number of strands may be one, two or more.

Also, the number of wires 13 of a single strand 12 may be different than shown in the figures and be two, three or more.

The length of the composite route through the backfill 7 depends i.a. from the load bearing capacity of the BBRV strand dipping heads, i. the higher the load capacity of the compression heads, the shorter the connection distance can be. It is also conceivable to provide no connection line and to anchor the compression heads, for example, directly on the support, so that the anchor plate 5 rests on the support 11.

reference numeral

1

end anchorage

2

Tension member from tension strands, for example prestressing steel strands

3

transfer plate

4

Pipe, for example steel pipe

5

Anchor or end plate

5a

Hole in the anchor plate

6

Forming head

7

Backfilling on compound line, z. B. grout

8th

Grouting for strapping the compression heads

9

Potting for filling a compression head

10

pressure plate

11

Pressure tube or support for the final anchorage

12

Single tension cord, for example 7-wire prestressing steel strand

13

Single wire of the tension cord

14

Upset individual wires in the swaging head

15

Interspaces between the individual wires in the swaging head

16

induction coil

17

Power cable

Claims (10)

End anchorage for a ground and / or rock anchor, comprising a tension member (2) of at least one tensioning strand (12), characterized in that the wires (13) of the tensioning strand (12) have emerged as end to a compression head (6) is held on an anchor plate (5). End anchorage according to claim 1, which has a pressure plate (10) which presses the swaging head (6) against the anchor plate (5). End anchorage according to one of the preceding claims, wherein the swaging head (14) in a casting (8, 9) is embedded, preferably also the mutual interstices (15) of the compressed single wires (14) of the swaging head are filled. An end anchorage according to claim 3, wherein the encapsulation (8) or the backfill (9) in the intermediate spaces (15) is made of at least one of the following materials: - cementitious grout, - plastic grout, - metallic potting. End anchorage according to one of the preceding claims, in which a part of the tension member (2), which is located in front of the anchor plate in the direction of the swaging head (6), embedded in a potting (7) and / or surrounded by a tube (4) is. An end anchorage according to claim 5, comprising a transfer plate (3) spaced from the anchor plate (5) and for transmitting forces acting on the tension member (2) to a support (11), the tension member (2) passing through the transfer plate (3) passes, preferably, the transfer plate (3) has a bearing surface for resting on a pressure tube as a support (11). An end anchorage according to any one of the preceding claims, wherein the tensioning strand (12) has at least one of the following features: - the tension cord is made of prestressing steel, the prestressing strand has a single wire (13) as a core around which individual wires (13) are wound whose respective diameter is smaller than the diameter of the core, - The tension cord has seven individual wires (13). An end anchorage according to one of the preceding claims, comprising a separating device (16, 17) for weakening and / or separating the tension member (2) for dismantling. End anchorage according to claim 8, wherein the separating device comprises an induction coil (16), by means of which the tension member (2) is inductively heated. An anchor for anchoring in soil and / or rock, with an end anchorage according to one of the preceding claims and preferably with a pressure tube (11), on which by means of the end anchorage on the anchor plate (5) acting forces are transferable.

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