EP0094908A2 - Anchor bolt for ground strengthening - Google Patents

Abstract

The tie rod consists of a tension member (3) in the form of a plastic rod. The anchoring member (1) for anchoring in the mountain consists of a plurality of expansion bolts (10) each with a plurality of holding wedges (15) comprising the tension member (3) and an expanding sleeve (20) assigned to each holding wedge (15). The expansion sleeves (20) are axially connected to one another and each consist of lamellae (21) assigned to the holding wedges (15), which are connected to one another by means of grooves and springs. The thread (62) for the tension nut (60) is attached to the inner surface of a threaded sleeve (61). The threaded sleeve (40) is integrally formed on the tension member (3) by means of radial ribs. The ribs are sawtooth-shaped and the flanks with the smaller angle of inclination are on the force application side. The tension nut (6) is provided with an annular support flange (64) at its foot end for resting on an anchor plate (70). The superimposed surfaces are spherical surfaces. The side of the anchor plate (70) facing the rock is laminated in order to create a crumple zone for protruding rock peaks. A tie rod designed in this way can be stressed up to the breaking limit of the tension member (3).

Description

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

As is known, when cavities are built in the mountains or when rock walls are dismantled, 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 element 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 in addition to the functional tension forces, bending forces act on the tension member, which reduces the possible tension load.

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 it is Traction 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 up to its own resilience.

Finally, reference is made to the rock anchor according to DE-A 29 03 694. 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.

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.

_E rfindungsgemäss this is achieved by the features in the characterizing part of the 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 Spreizbolzens allein gemäss der Schnittline II-II in Fig. 1,
• Fig. 3 eine Schnittansicht des Spreizbolzens allein gemäss der Schnittlinie III-III 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. 9 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. 15, 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,
• _F ig. 2 shows a sectional view of the expanding bolt according to section line II-II in FIG. 1,
• 3 is a sectional view of the expansion bolt alone along the section line III-III 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 threaded sleeve using the principle explained with reference to FIG. 9,
• 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. 15, 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.

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 sawed at least in the area of these expansion bolts 10 toothed circumferential ribs 11 are provided. 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 this. 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 in the direction 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, with a surface 25 that is also triangular in cross section, each rest on a holding wedge 15 of an expanding bolt 10. This training will cause relative axial displacement of the expansion bolt 10 and the lamella 21 of the expansion sleeve 20 always takes place over a large area. 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 slats 21 are circumferentially connected to one another, for example by means of a hook-shaped tongue and groove, in order to enable 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 support rib 23. This exerts pressure on the rock, especially in the middle of the lamellae 21, and is less on the outside, so the rock 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 outwardly projecting tongues 27 between each of two subsequent expansion sleeves 20. These tongues 27 have the task of ensuring that the expansion sleeves 20 are in contact with the mountains 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 is always produced. 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. The multi-fold outline according to FIG. 2 would then look similar to cycloxides. 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 Kl 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 at the transition point from a tension member to the sleeve.

The idea underlying the differently long flanks 96 with a constant ridge height 95 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. 10 T far right, stretched. As a result of the constant surface pressure on the flanks 96, the force Kl decreases uniformly with each step, and the second element 92, 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 Kl. The force curve in the first element 91 is shown with dotted lines.

According to the 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 in an injection mold with a Provided threaded sleeve 40. 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.

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:
«= F (X)

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

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 inclination angle of the steep flank 43 with respect to the vertical is, for example, β = ⁰ 5 and the flat tooth flank 44 γ 40 = ⁰ at a distance between the steep tooth flanks 43 of 3.5 mm and height of 1.84 mm a tooth. Through the illustrated combination of the teeth between the tension member 3 and the threaded sleeve 40 on the one hand and a saw thread, which is known for large Forces from the same direction is designed, 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 tension nut 60 is stressed 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 wing 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.

Experiments 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 that molded threaded sleeve 40 would be blasted off the tension member 3.

Claims (12)

1. Tension anchor for rock securing with a tension member, which is anchored in the borehole with an anchoring member, which is designed as a deformable body, which rests in the deformed state on the wall of the borehole and by means of frictional force holds the tension member firmly connected to the anchoring member in the mountains and from which tie rod the free anchor end has a thread overlapped by a tie nut which is supported against an anchor plate resting against the rock face, characterized in that the anchoring member (1) consists of an expansion bolt (10) connected to the tension member (3) and consists of several, the tension member (3) comprising axially spaced-apart holding wedges (15) and each holding wedge (15) associated with expansion sleeve (20), which expansion sleeves (20) are connected to one another and comprise the tension member (3) that furthermore at the free anchor end (42 ) there is a threaded sleeve (40) surrounding the tension member (3) that the outer surface of the tension member s (3) in the area of this threaded sleeve (40) and the inner surface of the threaded sleeve (40) have a number of interlocking elevations (95, 96, 97) comprising the tension member (3), which elevations are sawtooth-shaped when viewed in a diametrical section plane, in which the flanks with the smaller angle of inclination (96) are directed against the attacking tensile force , and have the same height of the ridge (95) over the axis of the tension member (3), and that the tension nut (60) and the anchor plate (70) in the contact area of the tension nut (60) on the anchor plate (70) each have an arched surface of the same shape ( 65, 77). 2. Tie rod according to claim 1, characterized in that the holding wedges (10) and the tension member (3) are non-positively connected to one another by means of interlocking radial ribs (11, 11a). 3. Tie rod according to claim 2, characterized in that the ribs (11, lla) are sawtooth-shaped, and those flanks (13) with the smaller angle of inclination are arranged on the force application side. Tie rod according to claim 3, characterized in that the surface of each retaining wedge (15) is pyramid-shaped with at least two surfaces (15a, 15b) forming at least one edge, that said edges of all holding wedges (10) are arranged equidistantly on a conical surface, and that all surfaces (15a, 15b) together comprise the tension member (3) without gaps. 5. Tie rod according to one of the claims 1 to 4, characterized in that each expansion sleeve (20) consists of a number of lamellae (21) which are interconnected at least at one point along their axial length, on the inside the same as the surface of the holding wedges (15) pyramid-shaped surface and on the outside have a roughened surface, that each lamella (21) has a T-shaped cross-sectional area, of which the crossbar (22) from the outer edge against the support rib (23) is too thick and with which lamella (21) the support rib (23) is diamond-shaped. 6. Tie rod according to claim 5, characterized in that in an axial connecting part (26) between two successive expansion sleeves (20) distributed around the circumference, on the one hand with two outwardly projecting tongue (27) provided with flags (26). 7. Tie rod according to one of the claims 1 to 6, characterized in that the tension nut (60) is designed as a cylindrical sleeve (61) with radially outwards projecting ribs (63, 66) is provided that the cylindrical sleeve (61) at the foot end (67) is provided with a comprehensive support flange (64), the outer surface (65) of which is convex, and that the thread (62) of the tension nut (60) and the corresponding thread (41) of said threaded sleeve (40) are saw threads. 8. Tie rod according to claim 7, characterized in that the support flange (64) is annular and at a distance from the cylindrical sleeve (61) and the support flange (64) is covered by a comprehensive hood (68). 9. tie rod according to one of the claims 1 to 8, characterized in that the anchor plate (70) is annular and has on both sides a comprehensive rib (71, 72), that further the area between said ribs (71, 72) by lamellae (75) is at least partially completed. 10. Tie rod according to claim 9, characterized in that the lamellae (75) are designed as radially arranged plates. 11. Tie rod according to claim 10, characterized in that the bearing surface (77) for the outer surface (65) of the support flange (64) is concavely curved. 12. Tie rod according to claim 11, characterized in that the curvature of the bearing surface (77) and the outer surface (65) is spherical.

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