JP2001003360A - Ground anchor having buffer action - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the rupture and slipping-off of a tendon by impulsive load to a ground anchor. SOLUTION: A buffer body 2 in which rubbers 21 and steel plates 22 are laminated at the front end of a tendon composed of an unbonded prestressing steel stranded wire 11 and a bearing plate 23 and a stationary plate 24 are installed before and behind is housed in a corrugated steel pipe 26. Since impulse force working to a structure is transmitted to the prestressing steel stranded wire 11 and transmitted gradually to an anchor body 3 by the buffer body 2 at that time, the rupture of the tendon is prevented. The deformation of the rubbers 21 and a belleville spring constituting the buffer body 2 is added to the elongation of the prestressing steel stranded wire, the elongation of a ground anchor is increased, and the breaking of the anchor is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground anchor having a function of buffering an impact load.

[0002]

2. Description of the Related Art A conventional ground anchor, whether it is a tension type anchor or a compression type anchor, has a tendon and an anchor body that transmits a tensile force to the ground in a rigid state, so that a repeated load such as an earthquake is generated. It could not respond to the impact load when it acted.

[0003] Further, when examining the situation of ground anchor destruction, a lot of damage was found on the lower ground anchor installed in multiple steps on the slope to prevent landslides, but this was due to the assumed distance to the slip layer. Is shorter on the lower side, so that the free length of the ground anchor is shorter, and therefore, it is estimated that the elongation is small and the deformation cannot be absorbed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to prevent damage to a ground anchor such as breakage of a tendon and breakage of an anchor body by damping an impact load so as not to directly act on the anchor body. . Another object of the present invention is to compensate for the extension of a ground anchor having a short free length and insufficient extension.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a shock absorber is provided between an anchor body and a tendon, and the shock is absorbed by transmitting an impact force from the tendon to the anchor body via the shock absorber. Compensate for elongation by deforming and moving the body,
The purpose is to prevent the tendon from breaking and the anchor body from coming off.

An impact force acts on the structure on which the ground anchor is fixed, and is transmitted to the underground anchor body via the tendon. However, since the cushion is interposed between the tendon and the anchor body, the impact force is applied. Since the force is not transmitted directly to the anchor body and the duration of the impact force is extended and transmitted, the tendon is prevented from breaking.

[0007] In addition, the same effect as extending the free length portion by deforming or moving the cushioning member is obtained, and the amount of elongation up to breakage of the anchor is increased. The escape is prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 shows an embodiment of a ground anchor according to the present invention.
The tendon is an unbonded PC steel strand 11 with a buffer 2 attached to the tip. The buffer 2 has a cylindrical rubber 21 having a hole in the center thereof through which a PC steel wire passes. The rubber 21 is alternately passed through the steel plate 22. If the rubber 21 is long, there is a possibility of buckling. Therefore, the tensile force is transmitted by shortening the rubber 21 with the steel plate 22 interposed therebetween. To prevent buckling, a steel rod may be passed through the rubber 21 to suppress lateral deformation. As the tendon, a steel rod or a steel wire other than the stranded wire can be used, and is selected according to the purpose of the ground anchor.

A support plate 23 and a fixing plate 24 are provided at both ends of the rubber 21, and a crimping grip 25 is fixed to the end of the PC steel stranded wire 11. The buffer 2 is housed in a steel pipe 26 having a corrugated surface. The steel pipe 26 is filled with a material that does not deteriorate rubber as necessary.

[0010] The buffer 2 is inserted into a boring hole, and grout is filled in the hole to complete a compression-type ground anchor. The tensile force is applied from the crimping grip 25 to the fixing plate 2.
4, transmitted to the rubber 21 and the support plate 23,
3 to the steel pipe 26, and from the front surface of the support plate 23 and the outer peripheral surface of the steel pipe 26 to the grout of the anchor body 3 and the ground 4 in this order. The impact force is absorbed by the deformation of the rubber 21 to prevent the PC strand 11 from being cut due to excessive stress. Further, since the deformation amount of the buffer 2 is added to the elongation of the PC steel strand, the shortage of the elongation amount of the ground anchor is compensated.

Embodiment 2 In this embodiment, as shown in FIG. 2, a spring steel material is cut out in a circular shape between a support plate 23 and a fixing plate 24, and a PC stranded wire 11 is passed through the center. A bowl-shaped disc spring 27 having holes is provided in parallel in the same direction.
7, a steel plate 28 is interposed. Other parts are the same as in the first embodiment. Embodiment 3 In this embodiment, as shown in FIG. 3, a plurality of disc springs 27 are provided in opposite directions. Other parts are the same as in the first embodiment. Embodiment 4 In this embodiment, as shown in FIG.
And a predetermined number of disc springs 27 are arranged in the opposite direction. In a space formed between the adjacent disc springs 27, a circular reversal prevention plate 29 is attached so as to vertically cross the outer peripheral edge of the disc spring. This reversal prevention plate 2
9 is a material having high rigidity and the same diameter as the diameter of the disc spring, and when one of the pair of opposed disc springs reaches the contact point earlier than the other disc spring, prevents further deformation, The other deformation is continued. Other parts are the same as in the first embodiment.

[0012] If a PC steel stranded wire whose surface is coated with an epoxy resin is used, high corrosion resistance and durability can be obtained. In particular, the PC steel strand (SC strand: trade name) obtained by returning the PC strand and covering the element wire with an epoxy resin coating or the like and re-twisting the strand is excellent in corrosion resistance.

In the ground anchor of the present invention, in a normal state, a tension is introduced while leaving a margin for deformation of the shock absorber 2, so that the ground anchor can be deformed when a sudden excessive load is applied.

[0014]

According to the present invention, the shock load is alleviated by the buffer, and the tendon is prevented from breaking and coming out of the anchor. In addition, since the deformation amount of the buffer is added to the elongation amount of the ground anchor, the total elongation amount is large even for a ground anchor having a short free length, and breakage such as slipping out of tendons is prevented. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment in which rubber is used as a buffer.

FIG. 2 is a sectional view of a second embodiment in which a disc spring is used as a buffer;

FIG. 3 is a sectional view of a third embodiment in which a disc spring is used as a buffer;

FIG. 4 is a sectional view of a fourth embodiment in which a disc spring is used as a buffer;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 PC steel strand 2 Buffer 21 Rubber 23 Support plate 24 Fixing plate 25 Crimping grip 26 Steel pipe 27 Disc spring 3 Anchor body

Claims (7)

[Claims] 1. A ground anchor in which a buffer is provided on the tip side of a tendon, and a tensile force is transmitted to the anchor through the buffer. 2. The ground anchor according to claim 1, wherein the buffer is rubber. 3. The ground anchor according to claim 1, wherein the buffer is a laminate of rubber and a plate. 4. The ground anchor according to claim 1, wherein the buffer is a spring. 5. The ground anchor according to claim 4, wherein the spring is a disc spring. 6. A ground anchor according to any one of claims 1 to 5, wherein the buffer is housed in the pipe, and a tensile force is transmitted from the support plate to the pipe. 7. The ground anchor according to claim 6, wherein the outer peripheral surface of the pipe is formed with irregularities.