JP7509481B1 - Retaining wall protection fence and construction method thereof - Google Patents

Abstract

[Problem] To provide a protective fence for a retaining wall that can be constructed in a stable position directly above the top surface of an existing retaining wall with simple construction, and to provide a construction method thereof.
[Solution] The system comprises an expanded support layer 30 made of concrete constructed on-site on the top surface of the existing retaining wall 10, and a number of anchor materials 40 which penetrate the expanded support layer 30 and are fixed to the back ground G to position the expanded support layer 30. The expanded support layer 30 has an expanded top surface 31 which is wider than the top surface 11 of the existing retaining wall 10, and an expanded portion 32 which extends from the top surface 11 of the existing retaining wall 10 towards the mountainside. The heads of the anchor materials 40 are fixed to a biased position on the mountainside side of the expanded portion 32 of the expanded support layer 30 to position the expanded support layer 30 so that it cannot be displaced, and the lower part of the support pillar 21 is fixed to the expanded top surface 31 of the expanded support layer 30 and erected.
[Selected figure] Figure 2

Description

The present invention relates to a protective fence that captures collapsed soil, avalanches, falling rocks, and other debris, and in particular to a protective fence for a retaining wall that is constructed on top of an existing retaining wall such as a leaning retaining wall, and a method for constructing the same.

2. Description of the Related Art A protective fence equipped with a plurality of posts and a protective net is known as a protective facility for preventing disasters caused by falling objects such as avalanches, falling rocks, and collapsed soil.
The kinetic energy of the collapsed debris acting on the protective net is ultimately supported by pillars.
One known method of erecting the posts of these protective fences is to embed the lower part of the post in a concrete fence foundation, with the fence foundation supporting the kinetic energy acting on the post (Patent Document 1).

On the other hand, a leaning type retaining wall, which resists earth pressure by leaning on it with its own weight, is known as a gravity type retaining wall for protecting slopes.
In some cases, an additional protective fence may be installed on top of this existing lean-type retaining wall.
As a method of building a protective fence on top of an existing lean-type retaining wall, it has been proposed to raise the height of the top of the existing retaining wall by constructing a large concrete fence foundation that is wider than the top surface, and then erecting posts on the newly raised fence foundation to construct a protective fence (Patent Document 2).

JP 2014-29070 A Japanese Patent Application Laid-Open No. 8-134849

Conventional protective fence construction technology has the following areas that need improvement:
<1> In addition to the need to excavate the mountain side slope of the existing retaining wall and carry out ground improvement work, a large fence foundation will have to be added to the top of the existing retaining wall.
Therefore, constructing a protective fence on top of an existing retaining wall requires a lot of cost and construction time.
<2> It is also possible to consider erecting a support pillar on the top of an existing lean-type retaining wall, but since the depth-width of the top surface of an existing retaining wall is generally very narrow, at around 50 cm, it is technically difficult to erect a support pillar while maintaining a stable position on the top surface of the retaining wall.
<3> Even if a protective fence could be constructed by erecting supports on the top of an existing lean-type retaining wall, the top of the existing retaining wall would not be able to withstand the impact load when an attack is received and would be damaged.

The present invention was made in consideration of the above points, and its purpose is to provide a protective fence for a retaining wall that can be constructed in a stable position directly above the top surface of an existing retaining wall with simple construction, and a method for constructing the same.

The present invention is a protective fence for a retaining wall that comprises a plurality of posts and a protective net and is constructed on top of an existing retaining wall to capture falling material. The fence comprises an expanded support layer made of concrete constructed on-site on the top surface of the existing retaining wall, and a plurality of anchor materials that penetrate the expanded support layer and are fixed to the ground behind it to position the expanded support layer. The expanded support layer has an extended top surface that is wider than the top surface of the existing retaining wall, and an extended portion that protrudes from the top surface of the existing retaining wall toward the mountainside. The heads of the anchor materials are fixed to an offset position on the mountainside of the extended portion of the expanded support layer to position the expanded support layer so that it cannot be displaced. A base plate provided at the bottom of the posts is seated on the extended top surface of the expanded support layer , and the heads of the anchor materials are fixed to the offset position on the mountainside of the base plate to erect the post .
In another embodiment of the present invention, the depth width of the expanded support layer is greater than the depth width of the top surface of the existing retaining wall.
In another embodiment of the present invention, a plurality of anchor bolts may be implanted in the expanded support layer in accordance with the erection positions of the support columns, and the base plate at the lower part of the support column may be bolted to the base plate via the plurality of anchor bolts to erect the support column.
In another aspect of the invention, one or more bearing plates are embedded within the expanding support layer, and the anchor bolts are secured to the bearing plates.
In another embodiment of the present invention, the expanded support layer is formed continuously along the top surface of the existing retaining wall .

The present invention is a method for constructing a protective fence for a retaining wall, in which a protective fence equipped with a number of posts and a protective net is constructed on top of an existing retaining wall, wherein an extended support layer made of concrete is constructed on-site on the top surface of the existing retaining wall, the extended support layer having an extended top surface wider than the top surface of the existing retaining wall and an extended portion that extends from the top surface of the existing retaining wall toward the mountainside, the heads of anchor materials are fixed to the extended portions of the extended support layer to position the extended support layer so that it cannot be displaced, and a base plate provided at the bottom of the post is seated on the extended top surface of the extended support layer , and the heads of anchor materials are fixed to a biased position on the mountainside of the base plate to erect the post .
In another form of the present invention, when constructing the extended support layer, a plurality of anchor bolts may be implanted in the extended support layer in accordance with the erection positions of the supports, and the base plate of the lower part of the support may be bolted in place via the plurality of anchor bolts.
In another embodiment of the present invention, one or more bearing plates may be embedded in the expanded support layer, and the anchor bolts may be fixed to the bearing plates .

The present invention has at least one of the following advantages.
<1> In the present invention, by combining an expanded support layer constructed on the top surface of the existing retaining wall with anchor materials that position the expanded support layer, the top surface of the existing retaining wall can be effectively utilized, allowing the protective fence posts to be erected in a stable position.
<2> By utilizing anchor material fixed to the rear ground without connecting the expanded support layer to the top surface of the existing retaining wall, the expanded support layer can be positioned so that it cannot be displaced.
Therefore, a protective fence can be easily constructed on top of an existing retaining wall.
<3> By fixing the head of the anchor material to the extension part that is off the top surface of the existing retaining wall, the anchor material can be installed quickly and easily without penetrating the top surface of the existing retaining wall.
<4> The impact force transmitted to the support pillar is supported by the back ground through the anchor material, so that excessive stress is not concentrated on the extended support layer or the top surface of the existing retaining wall, effectively avoiding damage to the extended support layer or the upper part of the existing retaining wall.

FIG. 1 is a front view of a protective fence for a retaining wall according to a first embodiment of the present invention, with a portion omitted; A cross-sectional view of the retaining wall guardrail shown in FIG. Plan view of the retaining wall guardrail shown in FIG. Diagram of how to build a protective fence for a retaining wall Diagram of how to build a protective fence for a retaining wall Enlarged cross-sectional view of the erected part of the support post of the retaining wall protective fence Cross-sectional view of the expanded support layer positioned by the anchor material FIG. 11 is an enlarged cross-sectional view of a part of a support post of a protective fence for a retaining wall according to a second embodiment of the present invention, with a portion omitted. FIG. 9 is a plan view of the retaining wall guardrail shown in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Example 1]

<1> Leaning-type existing retaining wall Referring to Figures 1 to 3, the leaning-type existing retaining wall 10 is a gravity-type retaining wall installed on a slope, and includes a cast-in-place concrete structure, a laminated structure of precast concrete blocks, etc.
In the present invention, when installing a protective fence 20 on top of an existing retaining wall 10, an extended concrete support layer 30 is added on-site onto the top surface 11 of the existing retaining wall 10, and the posts 21 of the protective fence 20 are erected using this extended support layer 30 as a support base.

<1.1> Expanded support layer The expanded support layer 30 is a base layer made of mortar or concrete for supporting the pillars 21, and has an extended top surface 31 that is wider than the top surface 11 of the existing retaining wall 10, and an extension portion 32 that extends from the top surface 11 toward the slope.
As shown in FIG. 4, a plurality of anchor bolts 33 are implanted in the expanded support layer 30 in accordance with the erected positions of the posts 21.
If necessary, the expanded support layer 30 may be reinforced by embedding a metallic or fibrous reinforcing material therein, or by mixing short or long fibers therein.

The expansion section 32 of the expansion support layer 30 has multiple through holes 35 along the longitudinal direction of the expansion support layer 30, and the expansion support layer 30 can be positioned by the anchor material 40 inserted into each through hole 35.

<1.1.1> Total length of expanded support layer The expanded support layer 30 is formed continuously along the top surface 11 of the existing retaining wall 10, but the expanded support layer 30 may also be formed partially (completely) to match the erected positions of the supports 21.

<1.1.2> Thickness of the expansion support layer (Fig. 5)
The thickness of the expansion support layer 30 is uniform over its entire length, and a layer thickness of about 400 mm is sufficient for practical purposes.

<1.1.3> Depth dimension of the extended support layer (Fig. 6)
If the depth width of the top surface 11 of the existing retaining wall 10 is B ₁ and the depth width of the extended top surface 31 of the expanded supporting layer 30 is B ₂ , the depth width B ₂ of the extended top surface 31 is dimensionally greater than the depth width B ₁ of the top surface 11.
The reason for this dimensional relationship is to substantially expand the depth width _B1 of the top surface 11 of the existing retaining wall 10.

The depth width _B2 of the expanded support layer 30 is the depth width _B1 of the top surface 11 plus the protruding dimension of the expansion portion 32 (approximately 100 to 150 mm).
That is, if the depth _B1 of the top surface 11 is, for example, 500 mm, the depth _B2 of the extended top surface 31 is 600 to 650 mm.

<1.2> Anchor Material The anchor material 40 is a fixing member for positioning the expanded support layer 30 by obtaining a reaction force from the rear ground G of the existing retaining wall 10.
The anchor material 40 is inserted through the through hole 35 provided in the expansion portion 32 of the expandable support layer 30 .
The length of the fixing portion of the anchor material 40 is appropriately selected depending on the site.
The anchor material 40 is made of an inexpensive tensile material such as a steel bar or a ground anchor.

<1.3> Anchor material fixing position (Fig. 3, 6)
The through hole 35 may be provided at any position in the expanded support layer 30, but if it is formed within the formation area of the top surface 11 of the existing retaining wall 10, a new through hole must be drilled in the top surface 11 to insert the anchor material 40.
By forming the through hole 35 in the expansion portion 32 of the expanded support layer 30 extending toward the slope side, the anchor material 40 can be fixed to the back ground G while avoiding the top surface 11 of the existing retaining wall 10.
By biasing the fixing position of the anchor material 40 relative to the expanded support layer 30 toward the slope, not only can the horizontal movement of the expanded support layer 30 be effectively prevented, but the effect of preventing the expanded support layer 30 and the support pillars 21 from tipping over is also improved.

<2> Overview of the Protection Fence The following will be described with reference to Figures 1 and 2. The protection fence 20 is a protective facility for protecting against avalanches, collapsed soil, or falling rocks, and is appropriately selected depending on the purpose.
The protective fence 20 comprises a plurality of posts 21 erected on an extended support layer 30 and a protective net 25 provided between adjacent posts 21.
In FIG. 1, a shape-maintaining rope 29 is laid horizontally between the heads of the posts 21, but the shape-maintaining rope 29 is not essential.

2.1 Supports The supports 21 include end supports, intermediate supports, or intermediate end supports.
The support 21 includes a base plate 22 that is integrally provided at the lower part of the support 21 .
The pillar body constituting the pillar 21 may be made of a known pillar structure such as a steel pipe, a column, a mortar-filled steel pipe, or an H-shaped beam.
The base plate 22 is a steel plate having a size larger than the cross-sectional shape of the support column 21, and is fixed integrally to the support column 21 by welding or the like.
The base plate 22 has a plurality of bolt holes 22a on its periphery (FIG. 4).

<2.2> Means for erecting the support pillars When the expanded support layer 30 is formed, a plurality of anchor bolts 33 and one or more support plates 34 are embedded in the expanded support layer 30 (FIG. 5).
In order to increase the bearing strength of the anchor bolts 33 , the heads of each anchor bolt 33 are fixed to a bearing plate 34 within the expanded bearing layer 30 .
The support columns 21 are fixed to the base plate 22 by a plurality of anchor bolts 33 and nuts 37 protruding upward from the expanded support layer 30 .
The number of support plates 34 to be installed is not limited to two, and can be selected as appropriate.

<2.3> Protective net The protective net 25 includes at least a plurality of rope materials 26 and a net material 27 .
The safety net 25 may additionally include shock absorbing devices as known in the art.

In this example, a rope material 26 that can be laid horizontally across multiple spans is combined with a diamond-shaped wire mesh net material 27.
Both ends of each rope material 26 are connected to a terminal support or an intermediate terminal support, and the intersections of the intermediate supports 21b and each rope material 26 are anchored by the intermediate supports in a state in which each rope material 26 can slide.
Furthermore, a plurality of spacing members 28 are attached between the plurality of rope materials 26 arranged in multiple stages to maintain the spacing between the rope materials 26.
The configuration of the protective net 25 is appropriately selected depending on the type and amount of collapsed material, etc.

[How to build a protective fence]
Next, a method for constructing a protective fence 20 on top of an existing retaining wall 10 will be described.

<1> Preparation As shown in FIG. 4, the top surface 11 of an existing retaining wall 10 is often covered with foreign matter such as deteriorated concrete fragments, moss, salt from snow-melting agents, etc.
Therefore, these foreign objects are removed using a known scraping tool, brush, etc., and the top end surface 11 is cleaned.

<2> Formation of expanded support layer Assemble formwork on top of the existing retaining wall 10.
After setting a support plate 34 and a plurality of anchor bolts 33 within the formwork in accordance with the intended position of the support pillar 21, mortar or concrete is poured into the formwork to construct the expanded support layer 30.
When constructing the expanded support layer 30, a box punching pipe or the like is set in the expanded portion 32 of the expanded support layer 30 to form a through hole 35 (FIG. 7).
Since the expanded support layer 30 has an area expanded compared to the top surface 11 at the top of the existing retaining wall 10, multiple anchor materials 40 can be planted within the expanded support layer 30 without being affected by the area of the top surface 11.

<2.1> Formation of Adjustment Layer An adjustment layer 36 made of non-shrink mortar is formed on the upper surface of the expandable support layer 30 at the intended position where the support column 21 is to be erected (FIG. 4).
For practical purposes, the thickness of the adjustment layer 36 may be about 30 mm, and the plane area of the adjustment layer 36 may be the minimum size that allows the base plate 22 to be placed on it.
The adjustment layer 36 is not essential and may be omitted.

<3> Fixing the anchor materials Multiple anchor materials 40 are fixed to the rear ground G of the existing retaining wall 10 along the expanded support layer 30, and after setting a washer 41 on the head of each anchor material 40, the fixing nut 42 is tightened to fix the expanded support layer 30 (Figure 7).

It is possible to penetrate the anchor material 40 into the top surface 11 of the existing retaining wall 10 and secure it there, but drilling holes in the existing retaining wall 10 requires a lot of time and effort.
Therefore, by forming a through hole 32 in the expansion portion 32 off the top surface 11 of the existing retaining wall 10, the anchor material 40 can be installed quickly and easily without penetrating the top surface 11.

<4> Assembling the protective fence Through the following steps, the protective fence 10 is assembled on the extended support layer 30.

<4.1> Installation of Support Posts The base plate 22 is fixed by tightening nuts 37 onto each anchor bolt 33 protruding directly upward from the adjustment layer 36, and the support posts 21 are installed at predetermined positions on the expanded support layer 30 (FIGS. 5 and 6).

<4.2> Installation of protective net As shown in FIG. 1, a plurality of rope materials 26 are laid horizontally in multiple stages between the posts 21 erected on the extended support layer 30, and the ends of each rope material 26 are fixed to the terminal posts 21a.
A spacing member 28 is attached to cross a plurality of rope materials 26 arranged in multiple stages.
The slope side of the multiple rope materials 26 is covered with net material 27 to assemble the protective net 25.
The intersections of the rope material 26 and the net material 27 are connected by a coil material 23 or the like.

If necessary, connect a backing rope (not shown) between the head of each support 21 and the anchor on the mountain side of the slope, or between the head of each support 21 and the anchor on the valley side of the slope.

[Self-supporting structure of protective fence]
Next, the self-supporting structure of the safety fence 20 will be described.

<1> Relationship between the top surface of the existing retaining wall and the expanded support layer As shown in Figures 1 and 2, the protective fence 20 is erected so as to be able to stand on its own on the upper surface of the expanded support layer 30 formed on the top of the existing retaining wall 10.
Regarding the relationship between the top surface 11 of the existing retaining wall 10 and the extended support layer 30, the extended support layer 30 is simply placed on the top surface 11 of the existing retaining wall 10, and there are no components directly connecting the extended support layer 30 and the top surface 11.

<2> Fixing means for the expanded support layer The expanded support layer 30 is positioned in a state where it cannot be displaced horizontally by a plurality of anchor materials 40 fixed to the rear ground G through through holes 35 formed biased toward the slope side of the expanded support layer 30, and load can be transmitted between the expanded support layer 30 and the rear ground G through the anchor materials 40.

<3> Relationship between the extended support layer and the pillars The lower parts of the pillars 21 that make up the protective fence 20 are rigidly connected to the extended support layer 30 by a number of anchor bolts 33 and nuts 37, allowing load transmission between the pillars 21 and the extended support layer 30 (Figure 6).

<4> Support of impact load In FIG. 2, when a collapsed object W such as a rock falls from the slope mountain side and collides with the protective net 25 of the protective fence 20, the protective net 25 absorbs the kinetic energy of the collapsed object W while deforming toward the valley side.
The impact force acting on the protective net 25 is transmitted to the support pillars 21.
The impact force transmitted to the support 21 is supported by the frictional resistance of the contact surface between the underside of the expanded support layer 30 and the top surface 11 of the existing retaining wall 10, and the shear strength and tensile strength of the multiple anchor materials 40 connected to the expanded support layer 30.
Therefore, the impact force transmitted through the protective net 25 and finally to the support pillar 21 is supported by the back ground G through the anchor material 40.
As a result, excessive stress is no longer concentrated on the expanded support layer 30 or the top surface 11 of the existing retaining wall 10, and damage to the expanded support layer 30 and the upper part of the existing retaining wall 10 can be effectively avoided.

<5> Overturning moment of extended support layer (pillars) When an impact force acts on the protective net 25, a counterclockwise overturning moment acts on the pillars 21.
The overturning moment acting on the support column 21 is transmitted to the expanded support layer 30 via the anchor bolt 33 and the support plate 34 .

When a counterclockwise overturning moment acts on the extended support layer 30, it attempts to rotate around the front end P of the extended support layer 30, which abuts against the top surface 11 of the retaining wall 10, as a fulcrum, but the anchor material 40 provided at the rear end of the extended support layer 30 effectively restrains the rotation of the extended support layer 30.

The anchor material 40 is fixed at a position offset toward the slope with respect to the erected position of the support pillar 21, so the support reaction force of the anchor material 40 during an impact is smaller than in a configuration in which the anchor material 40 is fixed at a position aligned with the erected position of the support pillar 21.

[Example 2]
Other embodiments will be described below. In the description, the same parts as those in the above-mentioned embodiment will be given the same reference numerals and detailed description thereof will be omitted.

<1> Configuration With reference to Figs. 8 and 9, another embodiment in which the head of the anchor material 40 is fixed to a part of the end plate 22 will be described.
In the above embodiment 1, the heads of the anchor materials 40 are fixed to the expandable support layer 30 , but the heads of the anchor materials 40 may also be fixed to the sloped mountain side of the base plate 22 of the support 21 .
An anchor hole 22 b is formed on the slope side of the base plate 22 of the support 21 , and an anchor material 40 is inserted through the anchor hole 22 b and the through hole 35 of the expanded support layer 30 .
The head of the anchor material 40 is fixed to the base plate 22 via a washer 41 and a fixing nut 42 .

<2> Effects of this Example In this example, in addition to obtaining the same effects as in the previous Example 1, the slope side of the base plate 22 of the support 21 is fixed with the head of the anchor material 40, which further improves the stability of the posture of the support 21 and improves the effect of preventing damage to the expanded support layer 30 and the upper part of the existing retaining wall 10 at the erection position of the support 21.

G... Rear ground of existing retaining wall 10... Existing retaining wall 11... Top surface of existing retaining wall 20... Protective fence 21... Support 21a... Terminal support 21b... Intermediate support 22... Base plate 22a... Bolt hole in base plate 22b... Anchor hole in base plate 23... Coil material 25... Protective net 26... Rope material 27... Net material 28... Spacing retaining material 29... Shape-retaining rope 30... Expanded support layer 31... Expanded top surface 32... Expanded part of expanded support layer 33... Anchor bolt 34... Support plate 36... Adjustment layer 37... Nut 40... Anchor material 41... Washer 42... Fixing nut

Claims (8)

A protective fence for a retaining wall is constructed on top of an existing retaining wall, and includes a plurality of posts and a protective net to capture collapsed objects.
A concrete expansion support layer constructed on-site on the top surface of the existing retaining wall,
and a plurality of anchor materials which penetrate the expansion support layer and are fixed to the back ground to position the expansion support layer;
The expanded support layer has an expanded top surface wider than the top surface of the existing retaining wall, and an expanded portion extending from the top surface of the existing retaining wall toward the slope mountain side,
The head of the anchor material is fixed to a biased position on the slope side of the expansion portion of the expansion support layer so that the expansion support layer is positioned so as not to be displaced;
A base plate provided at the lower part of the support is placed on the extended top surface of the extended support layer ,
The head of the anchor material is fixed to a position offset toward the slope side of the base plate to erect the support .
Protective fence for retaining walls. A protective fence for a retaining wall as described in claim 1, characterized in that the depth width of the expanded support layer is greater than the depth width of the top surface of the existing retaining wall. The protective fence for a retaining wall according to claim 1, characterized in that a plurality of anchor bolts are planted in the extended support layer in accordance with the erection positions of the posts, and the base plate at the bottom of the posts is bolted and erected via the plurality of anchor bolts. The protective fence for a retaining wall according to claim 3, characterized in that one or more bearing plates are embedded in the expanded support layer, and the anchor bolts are fixed to the bearing plates. The protective fence for a retaining wall according to claim 1, characterized in that the extended support layer is formed continuously along the top surface of the existing retaining wall. A method for constructing a protective fence for a retaining wall, the method comprising: constructing a protective fence having a plurality of posts and a protective net on the upper part of an existing retaining wall,
A concrete expansion support layer is constructed on-site on top of the existing retaining wall.
The expanded support layer has an expanded top surface wider than the top surface of the existing retaining wall, and an expansion portion extending from the top surface of the existing retaining wall toward the slope mountain side,
While fixing the head of the anchor material to the expansion portion of the expansion support layer to position the expansion support layer so that it cannot be displaced,
A base plate provided at the lower part of the support is placed on the extended top surface of the extended support layer ,
The head of the anchor material is fixed to a position offset toward the slope side of the base plate to erect the support .
How to build a retaining wall guardrail. A method for constructing a protective fence for a retaining wall as described in claim 6, characterized in that when constructing the extended support layer, a plurality of anchor bolts are implanted in the extended support layer in accordance with the erection positions of the supports, and the base plate of the lower part of the support is bolted in place via the plurality of anchor bolts. The method for constructing a protective fence for a retaining wall according to claim 7, characterized in that one or more bearing plates are embedded in the expanded support layer and the anchor bolts are fixed to the bearing plates.

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