EP0739442B1 - Tensionable gfp rock anchor - Google Patents

Abstract

A rock anchor (1), which can be secured in any position by fitting a tensioner, has a securing section (4) consisting of a tensioning sleeve (6) with a counter taper (7) and a wedge (8) matching the tensioning sleeve (6) which can be fitted over the anchor pin (2). The wedge slope is about 3 DEG , as is that of the taper (7), so that it is possible not only to insert the wedge (8) reliably into the taper (7) but also to apply the tensional forces evenly without peak tensions and consequent wear on the GFP anchor pin. The GFP anchor pin does not have to be slotted; rather, securing is effected by suitably fitting the securing section (4) and fixing the wedge (8) by a tensioner (9) or a tensioning screw (16), so that the fixing may be made at virtually any point on the anchor pin (2).

Description

The invention relates to a rock bolt with the GRP anchor rod, the tension element that can be braced deepest in the borehole, and the clamping element on the borehole mouth side that consists of a calotte plate and a fixing part that bears against the anchor rod.

Rock anchors are used in rock construction as well as in underground mining where the mountains themselves have sufficient stability, but where the layers close to the cavity created are to be secured together. Rock anchors made of steel are known, as are those made of GRP material. EP-A 94 908 discloses a glass fiber reinforced plastic anchor, this material being characterized not only by its very high tensile strength but also by its low weight. The anchor rod as such cannot corrode, so that it also has a long service life. For bracing, the GRP pipe is provided with a thread on which the anchor screw is moved. A GRP anchor is known from EP-A 188 174, in which a corresponding thread is applied to the end protruding from the borehole. The anchor nut with spherical washer can be moved on this thread, so that the anchor can be braced. It is disadvantageous, however, that a large production outlay is required for the thread and that special importance must be attached to the formation of the thread in order to ensure the necessary power transmission. It has been shown that the thread, which is preferably glued to the GRP pipe, does not withstand high loads, but rather tears off. In order to prevent this tearing off, according to DE-OS 29 03 694, the GfK pipe end is slotted and an insertion of a corresponding wedge is provided, so that tensioning is possible without fear of tearing off the thread. However, the prerequisite is that appropriate wedges are attached to both ends, since otherwise it is not possible to secure them with sufficient security. Another disadvantage is that resinification of the borehole is theoretically possible, but can only be achieved with considerable effort. Finally, it is disadvantageous that an approximately right-angled arrangement between the anchor rod and the rock face is required in order to enable the calotte washer to be properly clamped over the anchor nut. In addition, a multi-wedge arrangement is provided, which not only requires a complex manufacturing process, but also difficult assembly. The wedge or the wedges attached at both ends have a large slope to prevent them from being pressed out of the GRP pipe during the tensioning process. A similar solution is known from EP-A 14 426, in which the fixing of the armature is achieved in that an expanding sleeve which grips in the borehole is placed on the end of the tension element arranged in the borehole. At the opposite end, a tension nut is provided which can be clamped to the outer end of the tension element when rotating via tension means. The spreading apart of the slotted end of the GRP pipe is achieved in that the expansion sleeve has a corresponding inner bore, which, according to a special embodiment, even runs conically in the upper region, so as to enable the expansion mandrel to be driven completely into the expansion sleeve. The disadvantage here is that tension peaks form in the transition area, ie where the wall of the GRP pipe is pressed against the inner wall of the expansion sleeve, which can lead to tearing, so that the effectiveness of the anchor is then excluded. The distribution of the forces predetermined by the shape of the expanding mandrel on the one hand and the expanding sleeve on the other hand is unfavorable and, moreover, cannot be determined exactly, so that precise work with such a GRP anchor design not possible. Finally, from DE-PS 39 02 727 a GRP rock anchor is known, in which the expanding mandrel and the inner wall of the conical sleeve are correspondingly conical, so that stress peaks cannot occur in this area. In this as well as in the other solutions described, an expanding wedge must be inserted, which requires a cross-shaped splitting of the GRP anchor rod. The tensioning element can thus only be attached to predetermined ends of the anchor rod, and it is in particular not possible to ensure the effectiveness of the rock anchor even after application of shotcrete by re-tensioning or the like.

The invention is therefore based on the object of providing a fixing part which can be easily and securely attached to the end of the borehole mouth and which at the same time can also absorb high tensile loads and which is to be fixed more or less at any point on the anchor rod.

The object is achieved in that the fixing part is displaceable in the longitudinal direction of the counter cone by a clamping sleeve with a counter cone and a correspondingly designed wedge which can be pushed onto the anchor rod and which is displaceable via a clamping device which can be displaced on the anchor rod and partially inserted into the clamping sleeve or counter cone, is formed and that the wedge on the inner surface is designed to have a greater coefficient of friction than on the outer surface.

In the case of such a rock anchor, the disadvantageous splitting of the GRP pipe or the GRP anchor rod, which precisely defines the fixing location, can be dispensed with entirely. Rather, the adapter sleeve with the counter cone is pushed onto the anchor rod, whereupon the wedge is then also pushed onto the anchor rod and inserted into the adapter sleeve with counter cone. This insertion of the wedge into the adapter sleeve and counter cone is supported or effected by means of a tensioning device, which quasi pulls into the tensioning sleeve or the counter cone and thereby pushes the wedge in front of it. Since the wedge has a greater coefficient of friction on the inner surface than on the outer surface, it can accordingly be inserted into the clamping sleeve or the counter cone. At the same time, it fixes itself and thus the entire fixing part in the correspondingly provided area on the GRP anchor rod, so that an effective and permanent connection is created without voltage peaks occurring in any area. Rather, the tensile forces are applied evenly over the entire length of the adapter sleeve to the GRP anchor rod, so that there is no fear of tearing off. If re-tensioning is then to be carried out, for example because shotcrete is subsequently applied, the previously removed adapter sleeve with counter cone can be applied again after hardening of the shotcrete and fixed as described. This creates a very versatile solution that is adapted to the operational conditions, which is characterized by a long service life and, as mentioned, the absorption of high tractive forces. It is particularly advantageous here that the GRP anchor rod can be cut to any position in order to complete the rock anchor by applying the tensioning element or fixing part. Due to the special design of the wedge used, slipping is prevented because, as mentioned, the inner surface has a greater coefficient of friction than the outer surface.

According to an expedient embodiment of the invention, it is provided that the fixing part is made of fiber composite material, the clamping sleeve consisting of radially wound plastic material. This fiber composite material has a significantly more favorable property than the previously used fiber-reinforced plastic, so that the term GRP anchor rod or GRP rock anchor is no longer applicable per se. The fixing part can be adjusted to the expected tensile loads via material variations can be advantageously adapted, in the end, for example, by using aluminum for the wedge tensile forces of well over 10 t can be applied. In addition, the material of the clamping sleeve is important, fiber composite material being applied according to the invention. The adapter sleeve consists of radially wound fiber-reinforced plastic material. This material, but in particular also that of the wedge, can be designed such that the glass fibers used in each case are arranged approximately perpendicular to the anchor rod. The appropriately designed adapter sleeve in particular allows more than 16 t tensile load.

In order to facilitate the arrangement of the wedge, it is provided according to the invention that the wedge of the fixing part is formed in two parts and thereby represent two half-shells. These two half-shells are placed around the anchor rod and then pushed along it into the clamping sleeve or the counter cone until there is a lock due to the slope of the wedge. This is then overcome as far as possible and necessary via the tensioning device and gives the certainty that the two-part wedge assumes the necessary and correct end position.

The counter cone and the wedge are aligned with each other with regard to their shape, but also with regard to the material used. In order to enable a respective coordination here, the invention provides that the counter cone is molded onto the adapter sleeve and has a different material mixture. While the adapter sleeve must absorb high pressure forces as such, the material and shape of the counter-cone should ensure that the wedge can also be pushed in or pressed far enough to then apply correspondingly high frictional forces and thus enable fixing. It is also conceivable that the wedge consists of a plurality of wedges to be arranged one behind the other in the longitudinal direction of the clamping sleeve, which, depending on the length, increases Tensile forces u. Ä. May be appropriate.

As already mentioned, the effectiveness of the clamping element at the mouth of the borehole can be achieved by adapting the wedge and counter wedge and, of course, also via the respective slope. It has been found to be optimal that the wedge has a wedge slope of 1 - 7.5 °, preferably 3 - 4 °. This and the specific choice of material prevent the wedge from pulling through and ensure a secure fit in the counter cone and thus in the adapter sleeve.

If, for certain reasons, the choice of material is to be changed, this is possible without great effort, also with regard to the material used, by appropriately selecting the corresponding wedge or specifying the material. This is particularly advantageous if the wedge has 25-35% of the total amount of material of the wedge and counter cone.

It was pointed out earlier that in any case the wedge should have a higher coefficient of friction on the inner surface than on the outer surface, which can be achieved according to an expedient embodiment of the invention in that the friction surface between the anchor rod and the inner surface of the wedge is enlarged by an adapted shape. For example, it is conceivable to effectively enlarge the surface of the anchor rod by means of corresponding arcuate recesses or the like.

According to an appropriate design, it is also possible to roughen the inner surface of the wedge or to assign a similar surface design to it in order to specifically change, ie to increase, the coefficient of friction in this way. As a rule, the surface of the wedge is changed and not that of the counter cone; this is simply because the corresponding inner surface of the Keils and that of the anchor rod lie against each other.

The rock anchor according to the invention can also be used as an adhesive anchor or can be used for grouting work if the anchor rod has an internal bore as provided according to the invention. The same is achieved during the manufacturing process when the long glass fibers are placed next to one another and shaped, which then embedded in the appropriate material dictate the dense wall of the anchor tube. Solidification material is pressed deep into the borehole via the inner bore, so that the anchor can be glued over its entire length, with simultaneous gluing of the adjacent rock layers.

If you want to ensure that synthetic resin or other solidifying material can emerge at several points along the length of the anchor rod, it is advantageous if the inner bore is oval and / or has sections that extend to the outer surface. This particular embodiment then leads to the bulges in the predetermined areas allowing the adhesive material to pass through, so that the desired effect occurs. The disadvantage here is that the tensile strength of the anchor rod may suffer, especially if these bulges are provided more or less regularly over the length.

If tensioning of the rock bolt is necessary, this can be achieved with the aid of a further development of the invention in that the clamping sleeve is designed to be displaceable in the longitudinal direction of the anchor rod relative to the calotte plate. A sufficiently high prestress can thus be applied so that the effectiveness of the rock anchor is increased in a targeted manner. This is made possible in particular by the fact that the clamping sleeve has an external thread at the end facing the cap plate, the cap plate having a corresponding thread formation.

In order to further simplify the clamping element, the invention provides that the clamping sleeve or the counter-cone is pivotally mounted in the spherical cap only in one direction. The spherical design of the clamping sleeve can thus be dispensed with entirely, which enables simpler production and which nevertheless allows the clamping element to be fixed practically at any point on the anchor rod. Since variations in the wide range are possible due to the design of the anchor rod and also of the clamping element, the clamping sleeve and the calotte plate can also be mounted at the same time, which is particularly facilitated by the fact that the calotte plate is connected to the cone for transport and thus to the clamping sleeve via shear pins is. If assembly and a first movement against each other now take place, these shear pins are sheared off and the counter cone or the clamping sleeve can pivot and move as desired with respect to the calotte plate.

The wedge is driven into the counter cone by means of a clamping device. It is particularly expedient here if the tensioning device is designed as a tensioning screw which is displaceable on the anchor rod and which has an external thread corresponding to an internal thread assigned to the tensioning sleeve. This training, d. H. So the clamping screw, which can be screwed onto the anchor rod in the clamping sleeve, gives the opportunity to insert the wedge evenly and effectively so that an effective fixing of the clamping element or fixing part is achieved on the anchor rod.

The invention is characterized in particular by the fact that a rock bolt is created which can be fixed effectively and absorbing high tensile forces at the end of the borehole mouth, this being done with relatively simple means and being so simple that even inexperienced people can be employed with it. The fixing part is delivered as a complete unit and then onto the protruding part from the borehole mouth The anchor rod is pushed on, whereupon ultimately only the wedge has to be tightened via the tensioning screw in order to achieve an effective connection between the fixing part or tensioning element and the anchor rod. The clamping screw has a thread that corresponds to a thread in the counter cone, so that a uniform retraction or a uniform displacement of the wedge is ensured. The special design of the wedge and counter cone ensures uniform force transmission and thus a permanent and secure connection between the anchor rod and the fixing part described. By appropriate choice of material, tensile forces of 13 t and more can be applied, so that an adaptation to the respective circumstances is also possible without having to change to another type of anchor. The fixing part can advantageously be attached practically at any point on the anchor rod, so that readjustment or re-tensioning can also be achieved without any problems, especially since the bracing can be achieved by appropriate design of the fixing part.

Fig. 1

einen Gebirgsanker am bohrlochmundseitigen Ende im Schnitt,

Fig. 2

den Gegenkonus im Schnitt,

Fig. 3

die Spanneinrichtung bzw. Spannschraube im Schnitt,

Fig. 4

eine perspektivische Darstellung des Keils,

Fig. 5

einen Querschnitt durch die Ankerstange und

Fig. 6

eine perspektivische Darstellung der Kalottenplatte.

Further details and advantages of the subject matter of the invention emerge from the following description of the accompanying drawing, in which a preferred exemplary embodiment is shown with the details and individual parts required for this. Show it:

Fig. 1

a rock bolt at the end of the borehole mouth on average,

Fig. 2

the counter cone in section,

Fig. 3

the clamping device or clamping screw in section,

Fig. 4

a perspective view of the wedge,

Fig. 5

a cross section through the anchor rod and

Fig. 6

a perspective view of the calotte plate.

Fig. 1 shows a rock anchor 1 in side view, with the end protruding from the borehole mouth. It is clear in the section shown here that the anchor rod 2, here consisting of a GRP pipe, is effectively connected between the calotte plate 3 and the end area with a fixing part 4, shown here in section.

This fixing part 4 consists of the clamping sleeve 6 and the counter-cone 7 and the wedge 8. The clamping sleeve 6 consists of a radially wound GRP material, which clamping sleeve can hold 17-18 t.

The counter cone 7 is injection molded onto the clamping sleeve 6 and consists of a material corresponding to the material of the wedge 8.

About the clamping device 9, the wedge 8 is pushed along the anchor rod 2 into the counter-cone 7, so that the uniform and effective forces act on the anchor rod 2 without leading to problem areas and thus tearing.

The coefficient of friction of the inner surface 10 is greater than the coefficient of friction of the outer surface 11, so that an effective "adhesion" of the wedge 8 on the anchor rod 2 is ensured. The wedge 8 has an incline of 3 - 4.5 °, the optimum being 3 °. A slope of the wedge 8 can be prevented in any case by means of the slope and choice of material, and an effective fixing of the fixing part 4 on the anchor rod 2 can be ensured.

The inner wall 12 of the counter cone 7 and the outer surface 11 of the wedge 8 have a corresponding slope, so that the uniform application of the forces is ensured. A further safe absorption of the forces is ensured via the collar ring 13, the clamping sleeve 6 at the end facing the calotte plate 3, on the opposite side End of the counter cone 7 is provided with an extension 14, so that when the counter cone 7 is injected into the clamping sleeve 6, an intensive connection is obtained despite the different choice of materials.

At the end of the counter cone 7 opposite the collar ring 13, the cone has an internal thread 15 which is designed to correspond to the external thread 17 of the clamping screw 16 serving as a clamping device 9. This clamping screw 16, which expediently has a hexagon 18 or the like, can be screwed securely into the counter cone 7 in order to simultaneously press the wedge 8 into the counter cone 7.

2 shows a section through the counter-cone 7, the collar ring 13 being apparent at the end 31 facing the spherical plate 3 and the extension 14 at the opposite end with the internal thread 15. The clamping sleeve 6, not shown here, is made of radially wound GRP material quasi embedded in this counter cone 7 or more correctly the counter cone 6 is injection molded into the adapter sleeve or onto the adapter sleeve 6.

Fig. 3 shows the clamping screw 16 with the external thread 17 and the hexagon 18, it being clear that this clamping screw 16 is characterized by a simple structure.

The wedge 8, which is important for the effectiveness of the rock bolt 1, is shown in perspective in FIG. 4. The outer surface 11 is characterized by the gradient of 3 - 4.5 ° already mentioned. 4 it is clear that the inner surface 10 of the wedge 8 consisting of two half-shells 20, 21 has been given an enlarged friction surface 22 by a special shape 23. This shape 23 corresponds to the shape of the anchor rod 2 shown in FIG. 5, so that the desired much higher friction surfaces 22, 22 'result here.

5, as mentioned, shows a section through an anchor rod 2, the outer surface 25 being characterized by the shape 23 already mentioned with the enlarged friction surface 22 '. An inner bore 26 is provided in the center, this inner bore being able to have an oval shape if lateral exits are desired in certain areas. Then it is expedient to provide the inner bore 26 with lateral bulges 27, 28, so that, as already mentioned, the compression material pressed up through the inner bore 26 can emerge laterally from the anchor rod 2 in certain areas.

FIG. 6 finally shows a perspective illustration of the spherical cap plate 3, specifically from the side facing the clamping sleeve 6 and the counter cone 7. Here it is clear that the dome plate 3 equipped with the bore 32 specifies a sliding surface 30 which only allows the clamping sleeve 6 or the counter cone 7 to move in one direction. The counter cone 7 and the clamping sleeve 6 are not spherical, so that taking into account the special design of the calotte plate 3, the described limited mobility arises.

Claims (16)

1. Rock anchor with the anchor bolt made of glass fibre-reinforced plastic, the tension element which may be clamped in the lowest point of the drill hole, and the clamping element on the mouth side of the drill hole comprising a crown plate and a securing part abutting against the anchor bolt, characterised in that the securing part (4) is formed from a clamping sleeve (6) with a counter-cone (7) and a correspondingly constructed wedge (8), which may be slid onto the anchor bolt (2) and is displaceable in the longitudinal direction of the counter-cone via a clamping means (9), which may slide on the anchor bolt (2) and may be partly inserted into the clamping sleeve or the counter-cone; and that the wedge (8) is constructed so as to have or provide a higher coefficient of friction on the inside surface (10) than on the outside surface (11).
2. Rock anchor according to Claim 1, characterised in that the securing part (4) is made from composite fibre, in which case the clamping sleeve (6) is made of radially wound plastic material.
3. Rock anchor according to Claim 1 and Claim 2, characterised in that the wedge (8) of the securing part (4) is constructed in two parts, thus forming two half shells (20, 21).
4. Rock anchor according to Claim 1, characterised in that the counter-cone (7) is injected onto the clamping sleeve (6) and has a material mixture different therefrom.
5. Rock anchor according to Claim 1, characterised in that the wedge (8) comprises several wedge sections arranged one behind the other in the longitudinal direction of the clamping sleeve (6).
6. Rock anchor according to Claim 1 to Claim 5, characterised in that the wedge (8) has a wedge gradient of 1-7.5°, preferably 3-4°.
7. Rock anchor according to Claim 1 to Claim 6, characterised in that the wedge (8) has 25-35% of the total amount of material of the wedge (8) and counter-cone (7).
8. Rock anchor according to Claim 1, characterised in that the friction surface (22) between the anchor bolt (2) and the inside surface (10) of the wedge (8) is increased by adapted shaping (23).
9. Rock anchor according to Claim 1, characterised in that the inside surface (10) of the wedge (8) is roughened or has a similar surface structure.
10. Rock anchor according to Claim 1, characterised in that the anchor bolt (2) has an inside bore (26).
11. Rock anchor according to Claim 10, characterised in that the inside bore (26) is oval and/or in sections has bulges (27, 28) extending as far as the outside surface (25).
12. Rock anchor according to Claim 1, characterised in that the clamping sleeve (6) is constructed to be displaceable in relation to the crown plate (3) in the longitudinal direction of the anchor bolt (2).
13. Rock anchor according to Claim 12, characterised in that the clamping sleeve (6) has an external thread at the end (31) facing the crown plate (3).
14. Rock anchor according to Claim 1, characterised in that the clamping sleeve (6) or the counter-cone (7) is mounted in the crown plate to swivel only in one direction.
15. Rock anchor according to Claim 1 and Claim 14, characterised in that for transport, the crown plate (3) is connected via shearing pins to the counter-cone (7) and therefore to the clamping sleeve (6).
16. Rock anchor according to Claim 1 to Claim 15, characterised in that the clamping means (9) is constructed in the form of a clamping screw (16), which may be displaced on the anchor bolt (2) and which has an external thread (17) corresponding to an internal thread (15) allocated to the clamping sleeve (6).

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