JP2894223B2 - Adhesion transfer method ground anchor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an adhesion transmitting type ground anchor.

[0002]

2. Description of the Related Art A ground anchor supporting a retaining wall or a building is an adhesion transmission system in which a tensile force applied to a tensile material is transmitted to an anchor fixing body by an adhesive resistance between the tensile material and a grout material, and a tension applied to the tensile material. It is roughly classified into a bearing transmission system in which the force is transmitted to the anchor fixing member by a bearing resistance force of a bearing plate (also referred to as a load-bearing body) attached to the tip end of the tension member, or a combination of both. In the adhesion transmission method, a method of embedding the tension material as it is in the grout material, and a method in which a reinforcing bar or a steel or plastic sheath is wound around the entire length of the adhesion of the tension material to increase the adhesion resistance A method of embedding in grout material is known.

[0003]

In a conventional adhesion transmission type anchor, when a reinforcing bar or the like is wrapped around the entire length of the tension member to increase the adhesion resistance, the grout material is filled in the adhesion portion. In some cases, the adhesiveness is deteriorated and the adhesion resistance is not improved as expected.

[0004] In the adhesion transmission type anchor, (1) due to the repetitive load of the tensile force, the adhesion breakage occurs first in the upper portion of the adhesion length portion, and this propagates sequentially to the lower portion of the adhesion length portion, and finally the tensile material comes off. Occurs. (2) When a large-diameter tensile material or a plurality of tensile materials are bundled, a crack is generated in the grout material around the upper part of the attached long part where the largest tensile stress occurs, and the split propagates rapidly to the lower part. Loses anchor support. The phenomenon described above stops the function as an anchor. Therefore, it is possible to cope with the phenomenon (1) by increasing the adhesion length,
With respect to the phenomenon (2), it is necessary to increase the adhesion resistance of the grout material around the upper portion of the adhesion length so that the grout material does not split even under a long-time large tensile load. .

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a reinforcing rod which is spirally wound into a spindle shape and is attached to an upper portion of an attached length of a tensile material so as to prevent splitting of the grout material and to provide the tensile material and the grout material. The present invention relates to a structure of a ground anchor that improves the adhesion performance of the anchor and improves the tensile resistance of the anchor fixing body.

That is, the present invention is an adhesion-transmitting ground anchor in which a tension member in which a reinforcing reinforcing bar formed into a spiral shape and processed into a spindle shape is attached to an upper portion of an adhesion long portion is buried in a grout material in the ground.

As the tensile material of the present invention, a PC steel rod or P
Rods and strands made of fiber reinforced plastic (FRP) are used in addition to PC steel such as stranded C steel. One of the tension members may be embedded in a grout material (cured to become an anchor fixing member), or a plurality of the tension members may be bundled and embedded. The spindle-type reinforcing bar attached to this tension member is manufactured by spirally winding a reinforcing bar having a diameter of several mm to 10 mm and simultaneously processing it into a spindle shape. The diameter of the spindle shape is set to a size corresponding to the magnitude of the tensile force, and the spindle shape is The shape does not hinder the filling of the grout material into the reinforcing steel. The spindle-shaped reinforcing steel bar is fixed by caulking one end or both ends thereof to the outer periphery of the tensile member via a fitting.

[0008] The grout material used in the present invention is:
In addition to the hardened body of cement milk and mortar injected into the ground after installing the tensile material, the hardened body of cement milk, mortar, concrete, etc. injected or poured into the ground before installing the tensile material, For the sake of simplicity, it is collectively called grout material. When the grout material is injected or poured into the ground before the tension material is installed, it is needless to say that the tension material must be embedded in the grout material before the grout material hardens.

[0009] In the ground anchor of the present invention, a spindle-shaped reinforcing bar is attached to the upper part of the attached length of the tensile material,
The restraining effect prevents the splitting of the grout material and improves the adhesion performance between the tension material and the grout material, so that the length of the adhesion length portion of the tension material can be shortened.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a ground anchor according to an embodiment of the present invention;

FIG. 1 (a) is a longitudinal sectional view of an example in which the adhesion transmitting type ground anchor of the present invention is used to support a retaining wall, and FIG. 1 (b) is an example of a spindle type reinforcing steel bar attached to a tension member. It is a perspective view of.

FIG. 2 is an example of a distribution diagram of a tensile stress generated in a tensile material of the ground anchor of the adhesion transmitting method.
The drawing shows a comparison between the present invention (a) and the conventional one (b).

As shown in FIG. 1 (b), the spindle-shaped reinforcing steel bar 1 is manufactured by spirally winding a reinforcing bar having a diameter of several mm to 10 mm and simultaneously processing it into a spindle shape having a length of about 1 m. As shown in FIG. 1A, the tension member 2 has a free length portion M covered with a sheath 3 on the ground surface side and an attached length portion L on the anchor fixing body side.
The spindle-shaped reinforcing steel bar 1 is attached to the outer periphery of the upper part of the attachment length L of the tension member 2. After the construction of the retaining wall 5, drilling of the ground according to the usual anchor anchoring method,
The grout material 4 is injected, and the tension material 2 is inserted and set in the drilled hole while the grout material 4 is not cured. After the grout material 4 is hardened, the tension material 2 is applied while applying tension to the tension material 2.
Is fixed to the retaining wall 5 via the fixing device 8, the support plate 7, and the pedestal 6. In this way, the retaining wall 5 is supported by the adhesion-transmitting ground anchor.

As shown in FIG. 2 (a), in the ground anchor having the structure of the present invention, the tensile stress f generated in the tensile member 2 naturally increases as the tensile force P increases. Since the adhesion resistance of the reinforcing bar 1 is improved, it becomes possible to resist the increasing tensile force P only at the attachment portion of the spindle-shaped reinforcing bar 1, and the tensile stress distribution does not spread much downward.

On the other hand, in the conventional ground anchor to which the spindle type reinforcing bar 1 is not attached, the tensile stress f generated in the tensile member 2 increases as the tensile force P increases, and the length L of the tensile member 2 adheres. Due to the decrease in the adhesive force due to the splitting of the grout material on the upper part of the adhesive, the adhesive resistance at the upper part of the adhesive long part L cannot resist the increasing tensile force P. As the tensile force P increases, the tensile stress distribution becomes It rapidly spreads downward, and finally reaches the state of resisting the tensile force P over the entire length of the attached length L.

[0016]

According to the ground anchor of the present invention, a spindle-shaped reinforcing bar is attached to the upper portion of the attached length of the tensile material, and the restraining effect prevents the splitting of the grout material, and also reduces the occurrence of splitting of the grout material. Since the adhesion performance of the tension member is improved, it is possible to shorten the length of the adhesion length portion of the tensile material.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of an example in which an adhesion transmitting type ground anchor of the present invention is used for supporting a retaining wall,
(B) is a perspective view of an example of a spindle-shaped reinforcing steel bar attached to a tension member.

FIG. 2 is an example of a distribution diagram of a tensile stress generated in a tensile material of a ground anchor of an adhesion transmitting type, in which (a) according to the present invention and (b) are compared.

[Explanation of Signs] 1. Spindle-shaped reinforcing steel bar, 2. Tension material, 3. Sheath, 4 Grout material, 5 Retaining wall, 6, Pedestal,
7 ··· Support plate, 8 ··· Fixing tool, P ·· Tension force, f ···
Tensile stress, L ... Length of attached tensile material, M..Free length of tensile material.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E02D 5/80

Claims (1)

(57) [Claims] 1. An adhesion-transmitting ground anchor in which a reinforcing material spirally wound into a spindle shape and attached to an upper portion of an attached long portion is embedded in a grout material in the ground.