JP2021127573A - Earth anchor structure - Google Patents

Abstract

To provide an earth anchor structure allowing overturn of a building receiving eccentric earth pressure caused by difference of insertion depths of external walls on both sides.SOLUTION: An earth anchor structure 10 is provided with a building 12 receiving eccentric earth pressure UEP caused by difference of insertion depths D1, D2 on external walls and earth anchors 22 inserted on an outer wall 20A side deeper in insertion from a center of the building 12, secured in a spread foundation 18 of the building 12, and extended along a vertical direction in the foundation 30.SELECTED DRAWING: Figure 1

Description

The present invention relates to an earth anchor structure.

Patent Document 1 discloses a method of constructing a foundation that stably supports a structure on an inclined support base. Here, in order to stably support the structure at a predetermined ground height against the inclined support base, the soft stratum between the construction surface of the structure and the support base was excavated and removed over the entire area. Later, a foundation concrete constructed at a predetermined height by placing lapple concrete in close contact with a support base is disclosed.

Japanese Unexamined Patent Publication No. 9-316891

However, in the invention described in Patent Document 1, for example, when applied to a building that receives unbalanced earth pressure due to a difference in the depth of penetration of the building, it is assumed that the construction surface of the building can be stably supported by the foundation concrete. However, it is not easy to prevent the building from tipping over due to unbalanced earth pressure.

In consideration of the above facts, it is an object of the present invention to obtain an earth anchor structure capable of preventing the building from tipping over in a building subject to unbalanced earth pressure due to different rooting depths of the outer walls on both sides.

The earth anchor structure of the first aspect is provided on the outer wall side where the rooting depth is deep from the center of the building and the building which receives unbalanced earth pressure because the rooting depths of the outer walls on both sides are different, and is fixed to the direct foundation of the building. It also has an earth anchor that extends along the vertical direction in the ground.

According to the earth anchor structure of the first aspect, the earth anchor is provided on the direct foundation on the outer wall side deeply rooted from the center of the building. Buildings that are rooted in the ground, such as steps, are difficult to slide laterally. However, if the embedding depths of the outer walls on both sides are different, the building may receive unbalanced earth pressure, and a pulling force may be generated on the outer wall side where the embedding is deep, causing a force to overturn the building. For this reason, it is possible to prevent the building from tipping over by providing an earth anchor directly on the foundation on the outer wall side, which is deeply rooted from the center of the building.

In the earth anchor structure of the second aspect, in the earth anchor structure of the first aspect, the tensile force applied to the foundation directly by the earth anchor is designed by the weight of the building and the penetration depth of the outer walls on both sides.

According to the earth anchor structure of the second aspect, the number of economical earth anchors can be calculated by designing the tensile force directly applied to the foundation from the weight of the building and the depth of penetration of the outer walls on both sides.

In the earth anchor structure of the third aspect, in the earth anchor structure of the second aspect, the tensile force can be adjusted by the prestress applied to the earth anchor.

According to the earth anchor structure of the third aspect, since the tensile force can be adjusted by prestress, for example, in a building such as a small building where the area of the bottom is relatively small and it is difficult to fix a large number of earth anchors. Even if there is, the tensile force can be adjusted efficiently.

As described above, the earth anchor structure according to the present invention has an excellent effect that it is possible to prevent the building from tipping over in a building that receives unbalanced earth pressure due to the difference in the depth of penetration of the outer walls on both sides.

It is a block diagram of the building to which the earth anchor structure which concerns on embodiment of this invention is applied. It is a block diagram which showed the process of drilling the hole for fixing the earth anchor in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the process of temporarily inserting the earth anchor assembly into the hole for fixing the earth anchor in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the process of filling the injection material in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the process which once lifted the earth anchor assembly to the outside of a hole in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the process of injecting an injection material in a state where the earth anchor assembly is lifted in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the step of main-inserting the earth anchor assembly into the hole for fixing the earth anchor in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the first step of pulling up a casing pipe and pressure-injecting an injection material in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the last step of pulling up a casing pipe and pressure-injecting an injection material in the construction of the earth anchor which concerns on embodiment of this invention. It is a block diagram which showed the process of constructing the building foundation after installing the earth anchor in the ground in the construction of the earth anchor which concerns on embodiment of this invention. It is a vertical sectional view of the earth anchor which concerns on embodiment of this invention. It is an enlarged sectional view of the earth anchor which concerns on embodiment of this invention.

Hereinafter, an embodiment of the earth anchor structure 10 according to the present embodiment will be described with reference to FIGS. 1 to 12. In the figure below, the arrow UP indicates the upper side of the building.

FIG. 1 shows a building 12 in which the earth anchor structure 10 according to the present embodiment is adopted. The building 12 has, for example, a three-story structure composed of columns 14 and beams 16 made of reinforced concrete. Further, the building 12 is composed of a flat area that is almost the same as the area of the site where it is installed. For this reason, for example, it is a so-called small-scale building located on a narrow site where it is difficult to construct foundation structures such as piles, cloth foundations, and footings on the outer periphery of the building 12.

The building 12 is directly used as the foundation 18, and the load is directly transmitted to the bottom surface 31 of the good ground 30. Further, the building 12 has different rooting depths D1 and D2 in the ground 30 of the outer walls 20A and 20B. Therefore, the earth pressure EP1 acting on the outer wall 20A on the deep side of the ground 30 and the earth pressure EP2 acting on the outer wall 20B on the shallow side with the embedding depth D2 are different. As a result, an unbalanced earth pressure UEP that is the difference between the earth pressures EP1 and EP2 on both sides is generated, and the pulling force (tilt) is in the direction of tilting from the side where the embedding depth D1 is deep to the side where the embedding depth D2 is shallow. Moment) is generated.

The direct foundation 18 is fixed to the ground 30 via an earth anchor 22 extending along the vertical direction (vertical direction) of the building. The earth anchor 22 is centrally arranged on the outer wall 20A side deeply embedded from the central CL of the building 12 in order to cancel the tilting moment generated by the unbalanced earth pressure UEP and stabilize the building 12. The upper end of the earth anchor 22 is directly fixed to the foundation 18, and the lower end of the earth anchor 22 is embedded in the ground 30.

(Earth anchor)
FIG. 12 shows a cross-sectional view of the earth anchor 22 installed in the building 12. The earth anchor 22 is constructed in the following steps. As shown in FIG. 2, for example, a drilling machine 32 such as a rotary percussion is installed directly on the foundation 18, and a hole 36 for fixing the earth anchor is drilled by performing a middle digging using the casing pipe 34. do. As shown in FIG. 3, a casing pipe 34 is provided (inserted) in the drilled hole 36, and the earth anchor assembly 38 is temporarily inserted into the casing pipe 34.

As shown in FIG. 12, the earth anchor assembly 38 is a free body formed of an unbonded PC steel stranded wire 44, a load-bearing body 46 formed in a thick steel tubular shape, and a synthetic resin pipe made of thin-walled polyethylene or the like. It is configured to include a long sheath 48. The unbonded PC steel stranded wire 44 extends along the vertical direction of the building, and the tip bearing plate 42 provided on the lower end side is fastened to the crimping grip 40. The load-bearing body 46 is formed along the outer peripheral portion of the unbonded PC steel stranded wire 44 on the lower side of the building. Further, the outer peripheral surface of the load-bearing body 46 is projected outward in the radial direction (outside in the horizontal direction of the building) of the earth anchor assembly 38, and becomes effective when a tensile force acts toward the upper side of the building (vertically upward). A plumb bob is formed to make it. The free length sheath 48 extends directly from the upper end of the load bearing body 46 toward the foundation 18 along the vertical direction of the building and covers the unbonded PC steel stranded wire 44.

The crimp grip 40 is provided with a tip cap 50 fixed to the tip pressure plate 42 so as to cover the crimp grip 40, and a rust preventive filler such as rust preventive oil is provided between the crimp grip 40 and the tip cap 50. 52 is injected and filled. As a result, the crimping grip 40 is doubly rust-proofed.

As shown in FIG. 3, the free length sheath 48 (see FIG. 12) of the synthetic resin pipe is configured to have a higher specific gravity than the drilled water filled in the hole 36. Therefore, the earth anchor assembly 38 can be constructed to be lightweight and temporarily inserted into the hole 36 without floating due to the buoyancy of the drilled water.

As shown in FIG. 4, the tip bearing plate 42 (see FIG. 12) is inside the free length sheath 48 and the load bearing body 46 (see FIG. 12) of the earth anchor assembly 38 temporarily inserted into the hole 36. The grout hose 56 is inserted. An injection material 58 (see FIG. 12) such as cement milk is filled from the lower end side of the ground anchor assembly 38 of the inserted grout hose 56. Therefore, the airtightness in the earth anchor assembly 38 can be improved, and the unbonded PC steel stranded wire 44 has an unbonded sheath provided on its own, a free long portion sheath 48 or a load bearing body 46, and an injection material 58. , Is triple rustproof. Since the weight of the earth anchor assembly 38 is increased by the injection material 58, it can be arranged in the hole 36 without being lifted by the buoyancy of the drilled water.

As shown in FIG. 5, the temporarily inserted earth anchor assembly 38 is once vertically suspended (lifted) toward the outside of the hole 36 (directly on the foundation 18 side) by, for example, a tow truck. As shown in FIG. 6, the grout hose 56 is inserted into the hole 36 from which the earth anchor assembly 38 (see FIG. 12) is suspended until the grout hose 56 reaches the bottom of the hole 36, and cement milk is inserted from the bottom side of the hole 36. Etc. 58 is injected. The injection material 58 is filled in the hole 36 and replaced with the drilled water.

As shown in FIG. 7, the suspended earth anchor assembly 38 is actually inserted into the hole 36 filled with the injection material 58. Since the injection material 58 is also filled in the earth anchor assembly 38, the earth anchor assembly 38 can be inserted without being lifted by the buoyancy generated by the injection material 58 filled in the holes 36.

As shown in FIG. 8, the pressure head 60 is connected to the upper end of the casing pipe 34 after the main insertion of the earth anchor assembly 38 is completed. Further, the casing pipe 34 is pulled up by approximately 1/2 of the earth anchor fixing length LT, and the injection material 58 is pressurized and injected into the hole 36 through the grout hose 62. As a result, the inner wall surface of the hole 36 is expanded by the injection pressure of the injection material 58, and the large-diameter root portion 64 is formed at the lower end portion.

As shown in FIG. 9, the casing pipe 34 is further pulled up by approximately 1/2 of the earth anchor fixing length LT, and the injection material 58 is pressure-injected. As a result, a large-diameter root portion 64 is formed at the lower end of the earth anchor assembly 38, and the load-bearing body 46 (see FIG. 12) receives a reaction force from the surrounding ground 30 through the large-diameter root portion 64, thereby causing the earth anchor 22. Is fixed to the ground 30.

As shown in FIG. 10, the tension steel material 66 (unbonded PC steel stranded wire 44) is directly fixed (fixed) to the foundation 18 in a state where a predetermined initial tension is applied. As a result, a downward reaction force (compressive force) acts directly from the tensile steel material 66 on the foundation 18, and the foundation 18 is fixed in a state of being in pressure contact with the bottom surface 31 of the ground 30. That is, the tension steel 66 directly introduces prestress into the foundation 18. A head cap 68 formed in a substantially hat shape having an outer shape larger than the outer shape of the tensile steel material 66 is arranged at a portion of the tension steel material 66 projecting upward from the fixed direct foundation 18 (covering). Will be). As a result, the upper end of the earth anchor assembly 38 is rust-proofed.

As shown in FIG. 11, a head sheath 70 is fitted in the upper end of the free length sheath 48 of the earth anchor assembly 38, and the foundation 18 is directly driven up to the upper surface of the head sheath 70. .. Further, a packing 72 is arranged between the upper end of the free length sheath 48 and the head sheath 70, and a head bearing plate 74 is arranged above the building of the packing 72 and the head sheath 70. As a result, air and water are blocked from entering the inside of the free length sheath 48 through the gap between the head sheath 70 and the free length sheath 48.

A fixing metal fitting 76 is arranged on the upper side of the building of the head bearing plate 74, and a fixing wedge 78 is arranged between the fixing metal fitting 76 and the tension steel material 66. The unbonded PC steel stranded wire 44 is fixed to the fixing metal fitting 76 by the fixing wedge 78. The unbonded PC steel stranded wire 44 is fixed to the fixing metal fitting 76 after being applied with a predetermined amount of tension by, for example, a control setting method in the so-called strong hold method using a strong hold jack (not shown). ing. As a result, the tensile force F for the earth anchor 22 to pull the building 12 downward (vertically downward) can be set.

The rust preventive filler 80 is filled so as to fill the hollow portion of the free length sheath 48 on the upper side of the building from the injection hole (not shown) formed in the fixing metal fitting 76. As a result, the inside of the free long portion sheath 48 is filled with the rust preventive filler 80. Further, the PC steel stranded wire 44 is cut leaving an extra length portion of a length required for re-tensioning. As a result, the tension steel material 66 and the fixing metal fitting 76 of the PC steel stranded wire 44 are covered with the head cap 68.

An O-ring 82 is arranged along the outer peripheral shape of the abutting portion of the head cap 68 in contact with the head bearing plate 74 on the lower side of the building, and a bolt 84 is inserted along the vertical direction of the building. ing. As a result, the head cap 68 is fixed to the head bearing plate 74 in a state of being sealed by the O-ring 82. Further, the inside of the head cap 68 is filled with a rust preventive filler 80. Therefore, the PC steel stranded wire 44 and the fixing metal fitting 76 come into contact only with the rust preventive filler 80 without coming into contact with air. Since the head cap 68 is configured to be removable, the tension applied to the tensile steel material 66 can be changed by removing the head cap 68 and discharging the rust preventive filler 80.

The tensile force F directly applied to the foundation 18 by the earth anchor 22 is designed by the weight (own weight) of the building 12 and the embedding depths D1 and D2 of the outer walls 20A and 20B on both sides. First, the tilting moment generated by the unbalanced earth pressure UEP is calculated. Next, the earth anchor 22 from the center CL of the building 12 can generate a predetermined moment that exceeds the tilting moment and can stably construct the building 12 against external forces such as wind pressure and earthquake. The downward force of the building is calculated from the horizontal distance DT of the building up to. The tensile force F can be calculated by removing the component M due to the weight of the building 12 from the downward force of the building calculated in this way. When a plurality of earth anchors 22 are provided, the tension of the individual earth anchors 22 and the distance DT from the center of the building 12 are set so that the tensile force F becomes a predetermined size as a whole.

(Action and effect)
Next, the operation and effect of the earth anchor structure 10 according to the present embodiment will be described.

According to the earth anchor structure 10 according to the present embodiment, the earth anchor 22 is provided on the direct foundation 18 on the outer wall 20A side where the penetration depth D1 is deep from the central CL of the building 12. The building 12 rooted in the ground 30 such as a stepped ground is difficult to slide laterally. However, if the embedding depths D1 and D2 of the outer walls 20A and 20B on both sides are different, the building 12 may receive the unbalanced earth pressure UEP, and the building 12 may be tilted toward the outer wall 20A where the embedding depth D1 is deep due to the tilting moment. Occurs. Therefore, the tilting of the building 12 can be suppressed by intensively arranging the earth anchors 22 on the direct foundation 18 on the outer wall 20A side where the rooting depth D1 is deep from the center CL of the building 12.

Further, according to the earth anchor structure 10 according to the present embodiment, it is economical to design the tensile force F directly applied to the foundation 18 from the weight of the building 12 and the rooting depths D1 and D2 of the outer walls 20A and 20B on both sides. The number of earth anchors 22 can be calculated.

Further, according to the earth anchor structure 10 according to the present embodiment, since the tensile force F can be adjusted by prestress, for example, the area of the bottom is relatively small as in a small building, and a large number of earth anchors can be fixed. The tensile force F can be adjusted efficiently even in a difficult building.

As described above, the earth anchor structure 10 according to the present embodiment prevents the building 12 from tipping over in the building 12 that receives unbalanced earth pressure due to the different rooting depths D1 and D2 of the outer walls 20A and 20B on both sides. be able to.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be carried out without departing from the gist of the present invention.

In the embodiment of the present invention, the earth anchor 22 is driven along the vertical direction in relation to the building 12 and the site, but the present invention is not limited to this, and when the site is wide, the rooting depth is deeper in the vertical direction. On the other hand, the earth anchor may be driven diagonally. As a result, the number of earth anchors can be reduced.

10 Earth anchor structure 12 Building 18 Direct foundation 20 Outer wall (outer wall)
20A outer wall (outer wall)
20B outer wall (outer wall)
22 Earth Anchor D1 Rooting Depth D2 Rooting Depth

Claims (3)

Buildings that receive unbalanced earth pressure with different depths of penetration of the outer walls on both sides,
An earth anchor that is provided on the outer wall side that is deeply rooted from the center of the building, is fixed to the direct foundation of the building, and extends along the vertical direction in the ground.
Earth anchor structure with. The earth anchor structure according to claim 1, wherein the tensile force applied directly to the foundation by the earth anchor is designed by the weight of the building and the penetration depth of the outer walls on both sides. The earth anchor structure according to claim 2, wherein the tensile force can be adjusted by the prestress applied to the earth anchor.

Images