JP3915537B2 - How to place ground anchor on the retaining wall - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for placing a ground anchor on a retaining wall at the time of root cutting in retaining work.
[0002]
[Prior art]
When excavating the ground to build an underground structure, it is usual to construct a mountain retaining wall and then perform rooting work on the inner ground. In this case, the retaining wall is deformed by the surrounding earth pressure at the root cutting portion, and there is a possibility that a large-scale deformation such as subsidence may occur in the surrounding ground. Therefore, conventionally, in order to prevent such ground deformation during the root cutting work, root cutting is performed while placing a ground anchor on the retaining wall.
[0003]
FIG. 10 is a perspective view showing an outline of a conventional root cutting work using the ground anchor 12. As shown in the figure, after the construction of the retaining wall 10, the root cutting of the inner ground is divided into a plurality of layers (such as (1) to (4) shown in the figure) in a stepwise manner. Then, the ground anchor 12 is driven in the portion where the root cutting of each layer is completed. Then, when root cutting is finished for a certain layer and placement of all ground anchors 12 to be provided in that layer is completed, ground anchor 12 is driven by performing root cutting for the next layer. Since the deformation of the retaining wall 10 becomes larger as the root cutting portion becomes deeper, the root anchoring can be advanced while suppressing the deformation of the retaining wall 10 by sequentially placing the ground anchor 12 from the upper layer to the lower layer.
[0004]
[Problems to be solved by the invention]
Thus, conventionally, attention is paid to deformation in the depth direction of the retaining wall (that is, deformation in the vertical plane), and ground anchors are placed in order from the upper layer to the lower layer so that the deformation does not increase. . However, since the retaining wall extends two-dimensionally in the depth direction and the width direction and the deformation occurs three-dimensionally, in order to more effectively suppress the deformation of the retaining wall, the width direction of the retaining wall Considering this deformation (that is, deformation in the horizontal plane), a method for setting the placement order of the ground anchors can be considered. In this regard, the conventional construction method in which the ground anchor placement order is set only in consideration of the deformation in the depth direction of the retaining wall is not optimal for suppressing the deformation of the retaining wall.
[0005]
The present invention has been made in view of the above points, and an object thereof is to provide a method for placing a ground anchor on a retaining wall capable of effectively suppressing deformation of the retaining wall during root cutting. To do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is a method for placing a ground anchor on a retaining wall,
A first step of partially rooting the ground inside the retaining wall with respect to the width direction of the retaining wall and placing a ground anchor on the retaining wall at the rooted portion;
Subsequent to the first step, there is a second step of rooting the root cutting portion in the depth direction and placing a ground anchor on the retaining wall at the root cutting portion.
[0007]
According to the first aspect of the present invention, in the first step, a ground anchor is driven by partially rooting in the width direction of the retaining wall, and subsequently, further in the depth direction in the second step. Then place the ground anchor. For this reason, when the ground anchor is placed on the retaining wall in the first step, the deformation of the retaining wall is small because both sides of the placement position are restrained by the unexcavated ground. And after placing the ground anchor in such a small deformation state, since the ground anchor is driven by rooting in the depth direction in the second step, the deformation of the retaining wall is effectively suppressed. Can cut roots.
[0008]
Further, the invention described in claim 2 is a method of placing a ground anchor on a retaining wall,
A first step of partially rooting the ground inside the retaining wall with respect to the width direction of the retaining wall, and placing a ground anchor on the retaining wall at the rooted portion;
And a second step of cutting the ground on both sides and the lower side of the part where the root cutting has been completed, and placing a ground anchor on the retaining wall at the root cutting part.
[0009]
According to the second aspect of the present invention, in the first step, the ground anchor is driven by partially rooting with respect to the width direction of the retaining wall, and in the second step, both sides of the portion where root cutting has been completed and Cut the bottom ground and place ground anchors. For this reason, when the ground anchor is placed on the retaining wall in the first step, the deformation of the retaining wall is small because both sides of the placement position are restrained by the unexcavated ground. Then, after placing the ground anchor in such a small deformation state, in the second step, the root cutting on both sides and the lower side of the root cutting part and the ground anchor are driven, so that the deformation of the retaining wall is effective. It is possible to proceed with root cutting while restraining.
[0010]
According to a third aspect of the present invention, in the method for placing a ground anchor on the retaining wall according to the second aspect, the second step is repeated until the root cutting work is completed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing an embodiment of the present invention. As shown in FIG. 1, in this embodiment, after the mountain retaining wall 10 is constructed, the ground inside the mountain retaining wall 10 is sequentially rooted in a substantially V shape from the center in the width direction of the mountain retaining wall 10. The ground anchor 12 is driven to 10.
[0012]
FIG. 2 is an enlarged cross-sectional view for explaining an example of the construction work of the local board anchor 12. The ground anchor placing method used in the present invention is not limited to that shown in FIG. As shown in the figure, when the ground anchor 12 is driven, first, the anchor hole 16 is cut to a predetermined depth of the hard ground 14 obliquely downward from the inner surface of the retaining wall 10 exposed by root cutting toward the back. Make a hole. Next, the wire-like anchor member 22 inserted through the sheath 20 is inserted into the anchor hole 16 until it reaches the bottom of the anchor hole 16, and grout (cement milk) 18 is injected. The distal end of the anchor member 22 is exposed from the sheath 20, and the anchor member 22 is in direct contact with the grout 18 at this exposed portion. Therefore, when the grout 18 is cured, the tip of the anchor member 22 is fixed to the hard ground 14 by the grout 18. After the anchor member 22 is fixed to the hard ground 14 in this way, the anchor member 22 is pulled from the inside of the retaining wall 10 with a jack or the like to apply tension to the anchor member 22, and the end of the anchor member 22 is fixed to the fixing member 24. Thus, the anchoring of the ground anchor 12 is completed.
[0013]
The construction method of this embodiment is characterized by the placement order of the ground anchors 12. That is, as shown in FIG. 1, first, the ground in the center in the width direction of the retaining wall 10 is rooted to a predetermined depth, and the ground anchor 12 is placed on a portion A1 of the retaining wall 10 exposed by this root cutting. Next, the substantially V-shaped portions on both sides and the lower side of the portion where the root cutting has been completed are rooted, and the ground anchor 12 is placed on the portion A2 of the retaining wall 10 newly exposed by this root cutting. Thereafter, similarly, the process of rooting both sides and the lower part of the part where root cutting has been completed in a substantially V shape and driving the ground anchor 12 to the root cutting part is repeated.
[0014]
In the present embodiment, by placing the ground anchor 12 in this order, the deformation of the retaining wall 10 can be suppressed as compared with the above-described conventional technique. The reason will be described with reference to FIG.
[0015]
The construction method of the above prior art is to perform root cutting of a certain layer and driving all ground anchors 12 to be provided in the layer, and then perform root cutting of the next layer and driving of the ground anchor 12. It is. In this construction procedure, for each layer, root cutting is advanced in the width direction of the retaining wall 10, and the ground anchor 12 is installed from the portion where excavation has been completed. In this method, as shown by a broken line in FIG. 3, the retaining wall 10 is deformed in a horizontal plane such that the central portion in the width direction is largely displaced.
[0016]
On the other hand, in the present embodiment, the central portion in the width direction of the retaining wall 10 is partially rooted and the ground anchor 12 is driven, and then the ground on both sides and the lower side is rooted to form the next layer. The process of placing the ground anchor 12 is repeated. For this reason, at the time when the ground anchor 12 is driven in the center portion in the width direction of the retaining wall 10 where deformation is greatly increased in each layer, both sides of the placement position are restrained by the unexcavated ground. The deformation is small. As described above, after the ground anchor 12 is driven in a state where the deformation in the central portion in the width direction of the retaining wall 10, which is greatly deformed by the conventional method, is laid, the ground anchor 12 is cut by rooting the ground on both sides and the lower side. As shown by the solid line in FIG. 3, the root cutting can be advanced while suppressing the deformation of the retaining wall 10 to be small.
[0017]
Next, the results of verifying the deformation restraining effect of the retaining wall 10 according to the present invention by simulation calculation using the finite element method will be described.
[0018]
FIG. 4 is a diagram illustrating three-dimensional modeling of the retaining wall 10 and the ground in the simulation calculation. 5 and 6 show the ground anchor placement position and placement order used in the simulation calculation of the present invention and the prior art on the front view of the retaining wall 10, respectively. The ground anchor placement position is shown on the vertical cross section of the retaining wall 10.
[0019]
As shown in FIGS. 4 to 6, in this simulation calculation, the width of the retaining wall 10 is 27 m, the depth is 18 m, the depth of the soft ground is 14 m, and the depth of the hard ground below the soft ground is 18 m. The depth is 4 m. The ground inside the retaining wall 10 is divided into elements of 1.5 m (width direction) × 1.5 (depth direction) × 1 m (depth direction) to perform calculation. Further, as shown in FIG. 5 and FIG. 6, the root cutting is divided into four layers and divided into areas each having a width of 3 m, and the first stage root cutting depth is 2 m and the second to fourth stages. The root cutting depth of each is 4m. The ground anchor 12 is placed at a position 1 m upward from the bottom surface at the center in the width direction every time the root cutting is completed.
[0020]
FIG. 8 shows a result of simulation calculation of the deformation amount of the retaining wall 10 under the above-described conditions as a displacement distribution in the depth direction at the center position in the width direction of the retaining wall 10. FIG. 9 shows the calculation result as a horizontal displacement distribution at the top of the retaining wall 10. 8 and 9, the calculation results for the present invention are indicated by ▲ and the calculation results for the conventional technique are indicated by ●.
[0021]
From the calculation results shown in FIGS. 8 and 9, it is possible to suppress the deformation of the retaining wall 10 to be smaller when the ground anchor 12 is driven in the driving order of the present invention than in the case where the ground anchor is driven in the conventional driving order. I understand that I can do it.
[0022]
【The invention's effect】
As described above, according to the ground anchor placement method for the retaining wall of the present invention, deformation of the retaining wall during root cutting work can be effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view for explaining an example of ground anchor placement work. FIG. 3 is a diagram for explaining an effect of suppressing deformation of a retaining wall according to the present embodiment.
FIG. 4 is a diagram showing three-dimensional modeling for calculating a deformation of a retaining wall.
FIG. 5 is a diagram showing the ground anchor placement position and placement sequence in the simulation calculation of the present invention on the front view of the retaining wall.
FIG. 6 is a diagram showing the ground anchor placement position and placement order in the simulation calculation of the prior art on the front view of the retaining wall.
FIG. 7 is a diagram showing a ground anchor placement position on a vertical section of a retaining wall in the simulation calculation.
FIG. 8 is a diagram showing a result of simulation calculation of the deformation amount of the retaining wall as a displacement amount distribution in the depth direction at the central portion in the width direction of the retaining wall.
FIG. 9 is a diagram showing a result of simulation calculation of the deformation amount of the retaining wall as a horizontal displacement distribution at the top of the retaining wall.
FIG. 10 is a perspective view showing an outline of conventional root cutting work using a ground anchor.
[Explanation of symbols]
10 Mountain retaining wall 12 Ground anchor

Claims (3)

A method of placing a ground anchor on a mountain retaining wall,
A first step of partially rooting the ground inside the retaining wall with respect to the width direction of the retaining wall and placing a ground anchor on the retaining wall at the rooted portion;
And a second step of rooting the root cutting portion in the depth direction following the first step and placing a ground anchor on the mountain retaining wall at the root cutting portion. . A method of placing a ground anchor on a mountain retaining wall,
A first step of partially rooting the ground inside the retaining wall with respect to the width direction of the retaining wall, and placing a ground anchor on the retaining wall at the rooted portion;
And a second step of rooting the ground on both sides and the lower side of the root cut portion and placing a ground anchor on the retaining wall at the root cut portion. The method of placing a ground anchor on a retaining wall according to claim 2, wherein the second step is repeated until the root cutting work is completed.

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