EP0094908B1 - Anchor bolt for ground strengthening - Google Patents

Description

The present invention relates to a tie rod for rock protection according to the preamble of independent claim 1.

When building cavities in the mountains or when building rock walls, it is known that forces are released through which rock migrates against free space. To prevent this, rock anchors are installed in boreholes that are anchored at the end of the borehole and tensioned at the beginning of the borehole or on the free rock wall using an anchor plate and lag screw.

One problem that needs to be solved is anchoring at the end of the borehole. Some suggestions have already been published. According to DE-B-1 117 071, a fixed crescent-shaped wedge rests on the tension member or the anchor bolt, which is held in the axial direction by positive and frictional engagement. The outer surface of the wedge is inclined to the axis of the tension member and interacts with the inner lateral surface of a loose wedge, also with a crescent-shaped cross-section, such that the tensile force on the tension member displaces the fixed wedge relative to the loose wedge and thus presses it against the rock. The two wedges are connected to each other by an elastic member so that they can be pushed together into the borehole. It is disadvantageous that the tension member is bent because the wedge acts only on one side, so that bending forces act on the tension member in addition to the functional tension forces, by means of which the possible tension load is reduced.

According to another proposal in CH-A-564 654, the anchoring member is designed as a deformable body which is supported in the borehole in the deformed state. The anchoring member is designed as a hollow body and the tension member is fastened in an end plate below the hollow body. A viscous mass is pressed into the hollow body by the tension member, which is designed as a tube, so that it lies precisely against the borehole. With such a tie rod, the tensile force is limited by the friction of the hollow body on the one hand on the tension member and on the other hand in the borehole. The hollow body consists of a deformable shell, so there is a further force limitation due to the strength of this shell, and the tension member can under no circumstances be stressed to its own capacity.

Finally, reference is made to the rock anchor according to DE-A-2 903 694. Accordingly, an expanding sleeve which is clawed in the borehole is placed on the tension member and can be clamped by means of a tensioning bolt by means of rotation by means of the tension nut. For this purpose, the ends of the tension member are flared to accommodate an expanding wedge. If the expansion bolt is designed with a star-shaped cross section and the tips engage in the gaps in the tension member which cause the conical expansion, the material, in particular the glass fibers in the case of a glass fiber synthetic resin tube, cannot escape and the strength is increased. However, it has been shown that such a glass fiber synthetic resin pipe (GRP) is not sufficiently supported by a radial pressure between an expansion bolt and an expansion sleeve and can slide out. Even an additional potting with epoxy resin is not a significant improvement.

Another problem is the threaded part of the tension rod for exerting a tensile force by means of a tension nut.

«In a tie rod known from US-A-3 469 407 according to the preamble of claim 1, expansion bolts with an internal thread sit on a tension member provided with a corresponding thread. The latter is connected with a screw bolt as a clamping arrangement, the head of which is supported on the mountain wall via a flat anchor plate. Tensioning is carried out by turning the bolt and the tension member, which - at least towards the end of the tensioning process - must therefore transmit considerable torques in addition to the tensile force. In addition, the anchor plate is often not perpendicular to the bolt axis on the rock face, which means that the bolt and tension member are additionally subjected to bending. »

It is therefore an object of the invention to provide a tie rod in which a high tensile force can be exerted regardless of the material used for the tension member and which is simple to manufacture and consists of few parts.

According to the invention this is achieved by the features in the characterizing part of independent claim 1.

• Fig. 1 einen Aufriss eines Verankerungsgliedes mit einer Schnittansicht der Spreizhülse und Draufsicht auf den Spreizbolzen und mit einer Schnittansicht durch Spreizbolzen und Spreizhülse,
• Fig. 2 eine Schnittansicht des Spreizbolzen allein gemäss der Schnittlinie 11-11 in Fig. 1,
• Fig. 3 eine Schnittansicht des Spreizbolzens allein gemäss der Schnittlinie 111-111 in Fig. 1,
• Fig. 4 eine Schnittansicht des Ausschnittes IV in Fig. 1 in stark vergrössertem Massstab,
• Fig. 5 eine Draufsicht auf die Spreizhülse,
• Fig. 6 eine Schnittansicht gemäss der Schnittlinie VI-VI in Fig. 1 (5),
• Fig. 7 eine Schnittansicht gemäss der Schnittlinie VII-VII in Fig. 1 (5),
• Fig. 8 eine Schnittansicht gemäss der Schnittlinie VIII-VIII in Fig. 1 (5),
• Fig. 9 eine schematisierte Schnittansicht durch Zugstab und Zugmutter zur Erläuterung des Prinzips,
• Fig. 10 eine Schnittansicht eines achsial geschnittenen Ankerstabes mit Gewindehülse unter Verwendung der anhand von Fig. erläuterten Prinzips,
• Fig. 11 eine Ausschnittsvergrösserung der Stelle XI in Fig. 10,
• Fig. 12 eine Ausschnittsvergrösserung der Stelle XII in Fig. 10,
• Fig. 13 eine Schnittansicht einer Zugmutter zur Verwendung mit dem Zuganker nach Fig. 10,
• Fig. 14 eine Stirnansicht der Zugmutter nach Fig. 13, und
• Fig. 15 eine Schnittansicht durch das freie Ende des Zugankers mit Zugmutter und auf das Gebirge aufgesetzter Ankerplatte.

An embodiment of the invention is explained below with reference to the drawing. Show it:

• 1 is an elevation of an anchoring member with a sectional view of the expansion sleeve and top view of the expansion bolt and with a sectional view through expansion bolt and expansion sleeve,
• 2 is a sectional view of the expansion bolt alone along the section line 11-11 in Fig. 1,
• 3 is a sectional view of the expansion bolt alone along the section line 111-111 in Fig. 1,
• 4 is a sectional view of section IV in FIG. 1 on a greatly enlarged scale,
• 5 is a plan view of the expansion sleeve,
• 6 is a sectional view according to the section line VI-VI in Fig. 1 (5),
• 7 is a sectional view along the section line VII-VII in Fig. 1 (5),
• 8 is a sectional view according to the section line VIII-VIII in Fig. 1 (5),
• 9 is a schematic sectional view through tension rod and tension nut to explain the principle,
• 10 is a sectional view of an axially cut anchor rod with a threaded sleeve using the principle explained with reference to FIG.
• 11 is an enlarged detail of the point XI in Fig. 10,
• 12 is an enlarged detail of the point XII in Fig. 10,
• 13 is a sectional view of a tension nut for use with the tie rod of FIG. 10,
• Fig. 14 is an end view of the pull nut of Fig. 13, and
• Fig. 15 is a sectional view through the free end of the tie rod with tie nut and anchor plate placed on the mountains.

According to FIG. 1, the anchoring member 1 consists of a number of expansion bolts 10 which are fastened on the tension member 3 and an equal number of expansion sleeves 20. The expansion bolts 10 are formed from holding wedges 15 which form an angle with the axis of the tension member 3. According to the example shown, this angle is 9 °. In the area of the largest diameter of the expansion bolts 10 there is a sectional view according to FIG. 2, in which the outline formed by the abutting surfaces of triangular wedges can be seen. At the smallest circumference of the expansion bolts 10, an image according to FIG. 3 is shown, according to which the expansion bolts 10 practically encircle the tension member 3.

For the non-positive connection between the expansion bolts 10 and the tension member 3, the surface of the tension member 3 according to FIG. 4 is provided with sawtooth-shaped circumferential ribs 11 at least in the area of these expansion bolts 10. Of these ribs 11, the steep flank 11a is directed towards the end 12 of the tension member 3, and the flat flank 13 faces it. A tensile force in the direction of arrow a, which acts on the tension member 3, is thus transmitted to the respective expansion bolt 10 via the flat flanks 13. Thus, the power transmission takes place gradually and decreases gradually in the tension member and for this the expansion bolts 10 have to absorb a gradually increasing force. However, since the expansion bolts 10 also have an increasing circumference towards the end 12 of the tension member 3, these forces can be absorbed without overstressing the material.

Advantageously, the tension member 3 consists of a glass fiber synthetic resin tube with an axial bore 14, and the expansion bolts 10 can consist of thermoplastic material and can be molded directly onto the tension member.

According to the six triangular holding wedges 15, the expansion sleeves 20 each consist of six lamellae 21, each of which comprises an expansion bolt 10. According to the sectional view in FIG. 1, the lamellae 21 are wedge-shaped and rest on a holding wedge 15 of an expansion bolt 10 with a surface 25 that is also triangular in cross section. This configuration has the effect that when the expansion bolt 10 and the lamella 21 of the expansion sleeve 20 are displaced relative axially, there is always area-like contact. This allows the tensile force to be distributed over a surface and the surface pressure does not exceed an admissible level at any point.

The lamellae 21 are connected to one another circumferentially, for example by means of a hook-shaped tongue and groove, in order to allow relative lateral freedom of movement. This is for the purpose that the expansion sleeves 20 can be widened by axial displacement on the expansion bolts 10.

As clearly shown in cross-section in FIG. 8, the lamellae 21 have a T-shaped design with a transverse web 22 which tapers with increasing distance from the supporting rib 23. This exerts pressure on the mountain above all in the middle of the lamellae 21 and is less on the outside, so that the mountain bulges more in the middle, and the force can be applied evenly to the rock. This prevents the mountains from erupting next to the segments.

The cross section according to FIG. 7 is created at a point between two axially following slats 21. This shows that the longitudinal connection between the following slats 21 is formed with a bark-like bridge section 26.

1, 5 and 6 it can be seen that the parts 26 are formed with tongues 27 projecting outwards between each of two successive expansion sleeves 20. These tongues 27 have the task of ensuring that the expansion sleeves 20 are in contact with the rock at all times.

The proposed arrangement shows significant advantages: by dividing the expansion bolt 10 into, for example, three holding wedges 15, the force transmission can take place uniformly over a greater length than was the case with only one wedge of the previously known embodiments. The ridge-shaped surfaces 15a, 15b arranged distributed around the circumference of the holding wedges 15 allow the lamellae 21 to always lie on the holding wedges with a constant surface over their entire axial displacement path, so that the same surface pressure always arises. By increasing the length of the power transmission by dividing the expansion bolts 10, larger diameter differences can be mastered, for example a borehole can now vary between 34-40 mm instead of the previous 34-36 mm.

The outer surface of the slats can be ribbed or otherwise roughened in order to achieve better adhesion to the rock.

Tests have shown that an anchoring member 1 of the type described can withstand forces in the order of magnitude of the tensile strength of the tensile member 3. By using a tube as a tension member 3, epoxy resin or mortar can be injected, which can also spread outside the tension member 3 without additional injection tubes due to the shape of the lamella 21 with the tapered support rib 23.

Instead of holding wedges 15 of the type described above, cylindrical surfaces could also be provided. 2 would then look cycloid-like. The cylindrical surfaces should advantageously have the same diameter as the tension member 3.

In FIG. 9, the two elements 91 and 92 are superimposed on one another with their surfaces 93 and 94 visible in section, and they are pressed together according to the arrows P perpendicular to these surfaces 93, 94. If the first element 91 has a tensile force K1 to the right in the drawing and / or the second element 92 has a tensile force K2 to the left in the drawing, this gives the same arrangement as in the transition point from a tension member to the sleeve.

The idea on which the flanks 96 of different lengths are based, with a constant burr height, is to keep the force transmission per unit of tooth length constant. For this reason the elongation of the material was introduced with increasing force from left to right and the lengths of the flanks 96 compared to the assumed original and unloaded length of a comparison rod V corresponding to the tensile force of a force unit, e.g. 1 T on the far left gradually up to ten force units, e.g. B. 10 T far right, stretched. As a result of the constant surface pressure on the flanks 96, the force K1 decreases uniformly with each step and the second element 92, on the right in the drawing, to which no force acts, pulls on the left in the drawing with the total force K1 on a fictitious fastening, so that conversely the force K2 on this fictitious attachment is effectively the force K1. The force curve in the first element 91 is shown with dotted lines.

According to the exemplary embodiment shown in detail in FIGS. 10-15, this knowledge is transferred to the tension member 3. At its end, this tension member 3, for example made of fiber-reinforced plastic, is provided with teeth like the first element 91 in FIG. 9. The long flanks 96 and the short flanks 97 are peripheral surfaces. The tension member 3 prepared in this way is provided with a threaded sleeve 40 in an injection mold. This threaded sleeve naturally assumes a complementary shape in the toothed area of the tension member 3 and shows a sectional view according to the second element 92 in FIG. 9. A thread 41 was formed on the outer circumference of the threaded sleeve 40.

• a = f(X)

The toothed part is clearly shown in FIG. 11 in an enlarged detail of the detail XI. The angle of inclination of the longer flank 45 (corresponding to flank 96 in FIG. 9) is a function of the distance X between the rod end 42 and the point in question, ie:

• a = f (X)

The axial length t of a flank 45 between two adjacent steep flanks 46 results from this angle a.

The shape of the external thread 41, which is a saw thread, is shown in the detail enlargement FIG. 12 of the detail XII in FIG. 10. The angle of inclination of the steep tooth flank 43 with respect to the vertical is, for example, β = 5 ° and the flat tooth flank 44 y = 40 ° with a distance between the steep tooth flanks 43 of 3.5 mm and a tooth height of 1.84 mm. Through the combination of the toothing shown between tension member 3 and threaded sleeve 40 on the one hand and a saw thread, which is known to be designed for large forces from the same direction, on the other hand, the tensile force from the tension member 3 is transferred in sections to a tension nut 60 on the threaded sleeve 40, whereby the Pull nut 60 is claimed over its entire length.

A tie nut 60 for use with a tie rod of the type described above is described in FIGS. 13 and 14. The tension nut 60 is designed as a sleeve 61 with an internal thread 62. On the circumference of the sleeve 61 there are a plurality of ribs 63, 66 arranged in a distributed manner. At the foot end 67, the sleeve 61 is provided with a support flange 64 which is annular and which has a spherical zone-like outer surface 65. Ribs 66 are also present between the support flange 64 and the sleeve 61. The ribs 63, 66 along the sleeve 61 have, for example, a pitch of 15 °, so that there are 24 ribs and the ribs 63, 66 on the flange 64 have, for example, the same pitch.

The installation of a tension member 3 of the type described in a hole 80 in the rock 81 is shown in Fig. 15. An anchor plate 70 with its central hole 74 is placed on the rock 81 on the borehole 80. This anchor plate 70 is annular. The support surface 77 on which the outer surface 65 of the tension nut 60 rests is concavely curved and shaped as a spherical zone with the same radius as the outer surface 65.

On the outside and on the inside of the wing there are ribs 71, 72 which are concentric with one another. The area between these ribs 71, 72 is at least partially filled by slats 75. Such lamellae can be designed as platelets which are arranged in axially parallel planes. These axially parallel planes can be arranged radially or intersect in a honeycomb shape, an arrangement of cylindrical planes and radial planes would also be conceivable. These lamellae 75 form a crumple zone and can be compressed by protruding points 82 on the surface of the rock 81. It can thus be achieved that the anchor plate 70 lies evenly on the rock.

The area determined by the free end faces of the lamellae can be curved, by means of which the edge parts of the ribs 71, 72 are connected to one another.

15 also clearly shows the purpose of the hood 68 of the pull nut 60. This serves to cover the central hole 74 in the anchor plate.

With the proposed arrangement, the lines of force 91 are accordingly guided in discrete bundles over the long flanks 45 of the toothing onto the threaded sleeve 40 and transmitted practically uniformly via the saw thread 41 to the tension nut 60, where they are concentrated on the outer surface 65 and further onto the anchor plate 70 be transmitted.

Tests have shown that with this special design a tension member 3 in the form of a glass fiber reinforced plastic tube, in which the glass fibers are parallel and run longitudinally, can be subjected to its own breaking load without the anchoring member 1 loosening in the borehole or the molded threaded sleeve 40 would be blasted off the tension member 3.

Claims (12)

1. Tension bolt for supporting rock, having a tension member (3) which is anchored in the drill hole by means of an anchoring member (1) which comprises, connected to the tension member (3), at least one expansion bolt (10), connected to the tension member (3), consisting of a plurality of retaining wedges (15) which encompass the tension member (3) and are spaced apart axially, and an expansion sleeve (20) assigned to each retaining wedge, in order to bear as a deformably body in the deformed state on the wall of the drill hole and to retain fixedly in the rock, by means of frictional force, the tension member (3) which is connected to the anchoring member (1) by positive fitting, and having a clamping arrangement which is supported against a bolting plate (70) bearing on the rock wall and engages over a thread provided at the free end of the tension member (3), characterized in that the expansion sleeves (20) are mutually connected and encompass the tension member (3), in that furthermore a threaded sleeve (40) encompassing the tension member (3) is present at the free end (42) of the bolt, in that the outer surface of the tension member (3) in the region of this threaded sleeve (40), and the inner surface of the threaded sleeve (40), possess a number of raised portions (95, 96, 97) which encompass the tension member (3) and engage each other with positive fitting, which raised portions are of saw-toothed design when observed in a diametral plane of cross-section, the flanks with the lower angle of inclination (96) facing the tensile force applied and the height of the ridge (95) above the axis of the tension member being the same, and in that a nut (60) engaging over the thread (41) of the threaded sleeve (40), and the bolting plate (70) in the region in which the nut (60) bears on the bolting plate (70), each have a curved surface (65, 77) of identical shape.

2. Tension bolt according to Patent Claim 1, characterized in that the retaining wedges (15) and the tension member (3) are connected to each other with positive fitting by means of mutually engaging radial ribs (11, 11a).

3. Tension bolt according to Patent Claim 2, characterized in that the ribs (11, 11a) are of saw-toothed design, and those flanks (13) with the lower angle of inclination are arranged on the side on which the force acts.

4. Tension bolt according to Patent Claim 3, characterized in that the surface of each retaining wedge (15) is of pyramid-shaped design having at least two surfaces (15a, 15b) forming at least one edge, in that the said edges of all retaining wedges (10) are arranged equidistantly on a conical surface, and in that all surfaces (15a, 15b) in combination encompass the tension member (3) continuously.

5. Tension bolt according to one of Patent Claims 1 to 4, characterized in that each expansion sleeve (20) comprises a number of lamellae (21) which are connected to each other at at least one point of their axial length and possess internally a surface of pyramid-shaped design in the same manner as the surface of the retaining wedges (15) and externally a roughened surface, and in that each lamella (21) possesses a T-shaped cross-sectional surface, whereof the crossbar (22) is designed to thicken from the outer edge towards the supporting rib (23), the supporting rib (23) of the said lamella (21) being of rhomboid design.

6. Tension bolt according to Patent Claim 5, characterized in that vanes (26) provided on one side with two outward-projecting tongues (27) are present in an axial connecting part (26) between two consecutive expansion sleeves (20), distributed on the periphery.

7. Tension bolt according to one of Patent Claims 1 to 6, characterized in that the tension nut (60) is designed as a cylindrical sleeve (61) which is provided with radially outward projecting ribs (63, 66), in that moreover the cylindrical sleeve (61) is provided at the foot end (67) with an encompassing support flange (64) whose outer surface (65) has a convex curvature, and in that the thread (62) of the tension nut (60) and the corresponding thread (41) of the said threaded sleeve (40) are buttress threads.

8. Tension bolt according to Patent Claim 7, characterized in that the supporting flange (64) is of annular design and is covered, at a distance from the cylindrical sleeve (61) and the supporting flange (64), by an encompassing hood (68).

9. Tension bolt according to one of Patent Claims 1 to 8, characterized in that the bolting plate (70) is of annular design and possesses an encompassing rib (71, 72) on both sides, and in that moreover the area between the said ribs (71, 72) is at least partly filled by lamellae (75).

10. Tension bolt according to Patent Claim 9, characterized in that the lamellae (75) are designed as radially oriented platelets.

11. Tension bolt according to Patent Claim 10, characterized in that the bearing surface (77) for the outer surface (65) of the supporting flange (64) has a concave curvature.

12. Tension bolt according to Patent Claim 11, characterized in that the curvature of the bearing surface (77) and the outer surface (65) is of spherical design.

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