JP2023097274A - Scour prevention structure and scour prevention method of pier structure - Google Patents

Abstract

To provide means for obtaining a sufficient scour prevention effect even for a pier structure in an offshore wind power generation that is subjected to flow in any direction without requiring much work for construction.SOLUTION: There are two sets of four control plates (2) having 0.60 to 0.90 of porosity which is represented by (a total area of openings of the control plate/a total area of the control plate), and symmetrically positioned along a vertical direction of an outer peripheral surface of a pier structure (1).SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an anti-scouring structure and an anti-scouring method for a pier structure, and more particularly to an anti-scouring structure and an anti-scouring method for a pier structure, which is a windmill turbine platform essential for offshore wind power generation.

A technique described in Patent Document 1 is known as an anti-scouring technique for preventing scouring that occurs around underwater structures such as rivers.
This technology is a construction method for preventing scouring that occurs around underwater structures such as rivers. Rubble stones with smaller particle diameters are laid around the underwater structures in the lower layers, and the wires of the mesh are laid. A scouring prevention construction method characterized by covering the riprap with a mesh that is bendable, has a smaller mesh than the surface riprap, and is connected by a connecting member that can rotate vertically and horizontally at grid points of the mesh. be.

Moreover, the technique of patent document 2 is known as a scouring prevention device of a bridge pier foundation structure.
This technology surrounds a pier foundation structure, and includes a sealing plate with a plurality of holes formed therein, one surface of which is connected to one surface of the sealing plate, a predetermined distance from the pier foundation structure, and a plurality of first A first flow guide plate having flow holes formed thereon, and a second flow guide plate having one surface connected to the other surface of the sealing plate, separated from the pier foundation structure by a predetermined distance, and having a plurality of second flow holes formed therein. a guide plate and a block plate connecting the first flow guide plate and the second flow guide plate to prevent the flow of fluid, wherein the first flow guide plate and the second flow guide plate are connected to the pier foundation structure. It is characterized by being symmetrical with each other as a reference.

JP-A-2000-144675 Japanese Patent Publication No. 2011-516756

The technique described in Patent Literature 1 requires work to lay a large amount of rubble, and furthermore, it requires work to cover with a net, so construction is time-consuming.
The technology described in Patent Document 2 is effective for flows in specific directions, typified by unidirectional flows such as ordinary rivers and floods, and uniaxial reciprocating flows such as tidal flows. Sufficient scouring prevention effect was not obtained for the pier structure in the offshore wind power generation under the environment where the flow of unspecified arbitrary direction is received.

Therefore, the problem to be solved by the present invention is to provide a means that does not take much time to construct and that can obtain a sufficient scouring prevention effect even for pier structures in offshore wind power generation that receive flow in any direction. to provide.

Means for solving the problems of the present invention are as follows.

First,
The porosity indicated by (total area of the openings of the control plate/total area of the control plate) is 0.60 or more and 0.90 or less, preferably 0.65 or more and 0.85 or less, more preferably 0.70. 0.80 or more, more preferably 0.73 or more and 0.77 or less control plates are positioned symmetrically along the vertical direction of the outer peripheral surface of the cylindrical pier structure. anti-scouring structure.
Second,
The anti-scouring structure for a pier structure according to the first aspect, characterized in that there are two sets of control plates.
Third,
The pier according to the second aspect, characterized in that the two sets of four control plates make an angle with the adjacent control plate at 90 degrees so as to divide the columnar pier structure into four equal parts. Anti-scouring structures for structures.

Fourth,
Along the vertical direction of the outer peripheral surface of the cylindrical pier structure, the porosity indicated by (total area of the openings of the control plate/total area of the control plate) is 0.60 or more and 0.90 or less, preferably It is characterized by controlling water flow by symmetrically attaching control plates of 0.65 or more and 0.85 or less, more preferably 0.70 or more and 0.80 or less, further preferably 0.73 or more and 0.77 or less. , anti-scouring method for pier structures.
Fifth,
The scouring prevention method for a pier structure according to the fourth aspect, characterized in that two sets of control plates are attached.
Sixth,
The pier structure according to the fifth aspect, wherein the angle between the four control plates mounted in two sets and the adjacent control plates is 90 degrees so as to divide the cylindrical pier structure into four equal parts. Anti-scouring method for objects.

The high-porosity "control plate" in the first to sixth means controls and weakens the horseshoe-shaped vortex generated around the pier structure, thereby reducing vortex crossing and raising water bottom sediment. and reduce local scouring.
That is, the control plate with a high porosity cuts the horseshoe-shaped vortex into pieces, and suppresses the generation of new tissue vortices by changing the action of the crossing flow from "blocking to passing".
A thin mesh flat plate can be used as the high-porosity control plate, but it can also be formed by providing a large number of aperture groups in a thin flat plate.
Here, the "porosity" indicates the proportion of openings penetrating through the control plate, and is expressed by the following equation.
Porosity = (total area of openings in control plate/total area of control plate)

In the means shown in the first to sixth, the positional symmetry of the control plate means that a set of two control plates sandwiching the columnar pier structure includes the center line of the columnar pier structure. It means to be on the extended plane of the longitudinal section.
For example, in the case of a cylindrical pier structure, a plurality of control plates can be arranged at equal angular intervals so as to protrude radially outward from the center of the pier structure, in contact with the cylindrical outer peripheral surface. The position of the control plate can be completely symmetrical.

ADVANTAGE OF THE INVENTION According to this invention, there can exist the following effects.

Since the present invention only requires symmetrical installation of control plates with a high porosity, it does not require much work, and it is sufficient to prevent scouring even for pier structures in offshore wind power generation that receive flow in any direction. effect is obtained.

1 is an explanatory diagram of Example 1 of the present invention; FIG. It is an explanatory view of Example 2 of the present invention. It is explanatory drawing of Example 3 of this invention. 1 is an explanatory diagram of Test Example 1 of the present invention; FIG. It is explanatory drawing of the test example 2 of this invention. It is explanatory drawing of the test example 3 of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated concretely, referring drawings.
Here, in the accompanying drawings, the same members are denoted by the same reference numerals, and redundant description is omitted.
In addition, since the description here is one embodiment of the present invention, the present invention is not limited to the embodiment.

As shown in FIG. 1, the scouring prevention structure of the pier structure of the present embodiment 1 is a mesh flat plate with a porosity of 0.75 in the pier structure 1, which is a windmill turbine platform essential for offshore wind power generation. Four control plates 2 are attached at intervals of 90 degrees (see (A) in FIG. 1).
The anti-scouring structure of the pier structure 1 of Example 1 has two sets of control plates 2 attached at symmetrical positions. .
The control plate 4 has a height substantially equal to the radius of the pier structure 1 and a length substantially equal to the diameter of the pier structure 1 (see (B) in FIG. 1).
In FIG. 1(B), reference numeral 3 denotes the seabed on which the pier structure 1 is installed.

As shown in FIG. 2, the scouring prevention structure of the pier structure of the second embodiment is a mesh flat plate with a porosity of 0.75 in the pier structure 1, which is a windmill turbine platform essential for offshore wind power generation. Six control plates 2 are attached at intervals of 60 degrees.
In the anti-scouring structure of the pier structure of Example 2, three sets of control plates 2 are attached at symmetrical positions. .
Similarly to Example 1, the control plate 2 of Example 2 also has a height approximately equal to the radius of the pier structure and a length approximately equal to the diameter of the pier structure 1 (( B)).

As shown in FIG. 3, the scouring prevention structure of the pier structure of the third embodiment is a mesh flat plate with a porosity of 0.75 in the pier structure 1, which is a windmill turbine platform essential for offshore wind power generation. Eight control plates 2 are attached at intervals of 45 degrees.
In the scouring prevention structure of the pier structure of Example 3, four sets of control plates 2 are attached at symmetrical positions. .
Similarly to Example 1, the control plate 2 of Example 3 also has a height approximately equal to the radius of the pier structure and a length approximately equal to the diameter of the pier structure 1 (( B)).

Next, a scouring prevention method for a pier structure using the scouring prevention structure for a pier structure shown in Example 1-3 will be described.

A control plate 2 having a porosity of 0.75 is symmetrically mounted along the vertical direction on the outer peripheral surface of a columnar pier structure 1 .
By attaching the control plates 2 at symmetrical positions, the horseshoe-shaped vortex generated around the pier structure 1 can be controlled and weakened, thereby suppressing the lifting of sediment from the bottom of the water and reducing local scouring. It becomes possible.
That is, the high-porosity control plate 2 cuts the horseshoe-shaped vortex into chunks and changes the action of the crossing flow in the manner of "blocking → passing", thereby suppressing the generation of new tissue vortices, thereby suppressing the water flow. can be controlled to prevent scouring of the pier structure.

Next, test examples will be described.
First, common test conditions will be described.

Each test was conducted in a straight test channel (horizontal installation).
The straight channel is 6 (m) long, 40 (cm) wide and 25 (cm) high.
The test conditions are sand particle size d≈0.1 (mm), water depth h=(3.3 cm), and flow velocity u=14.8 (cm/s).
In each figure, the white arrow indicates the direction of flow.
The Reynolds number is Re=4.8×10 ³ .

The pier structure in each test has a diameter d=5.0 (cm).
The control plate in each test has a length L=5.0 (cm), a height H=1.0 (cm), and a porosity Φ=0.75.

As shown in FIG. 4, the anti-scouring structure of the four-plate pier structure of Example 1 is arranged such that one control plate matches the flow direction, as shown in (1) in FIG. installed.
(2) in FIG. 4 is mounted so that one control plate has an angle of 45 degrees with respect to the flow direction.
(3) in FIG. 4 shows the case where no control plate is attached, and A, B, C, and D in the figure show measurement points of data common to each test example.

As shown in FIG. 5, the anti-scouring structure of the six-plate pier structure of Example 2 is arranged such that one control plate matches the flow direction, as shown in (1) in FIG. installed.
(2) in FIG. 5 is mounted so that one control plate has an angle of 30 degrees with respect to the flow direction.
(3) in FIG. 5 shows the case where no control plate is attached, and A, B, C, and D in the figure show measurement points of data common to each test example.

As shown in FIG. 6, the scouring prevention structure of the eight-piece pier structure of Example 3 is arranged such that one control plate matches the flow direction, as shown in (1) in FIG. installed.
(3) in FIG. 6 shows the case where the control plate is not attached at all, and A, B, C, and D in the figure are measurement points of data common to each test example (hereinafter abbreviated as "measurement point" ) is shown.

Each test time was 5 minutes, and the scouring depth was measured at measuring points A, B, C, and D after 5 minutes and expressed in cm.
In addition, the reduction rate (unit: %) of scour depth at measuring point A on the front side and measuring points B and D on the lateral side was determined.
Note that measurement point C was excluded from the evaluation because it was "accumulation".

The results of the test example shown in FIG. 4 are as follows.
The scouring depth in case (1) was 0.61 at survey point A, 1.23 at survey point B, -0.30 at survey point C, and 1.08 at survey point D (unit: cm).
The scouring depth in case (2) is 0.69 at measuring point A, 1.05 at measuring point B, -0.50 at measuring point C, and 1.19 at measuring point D (unit: cm).
The scouring depth in case (3) was 1.38 at survey point A, 1.79 at survey point B, -0.15 at survey point C, and 1.31 at survey point D (unit: cm).
In the case of (1), the reduction rate was 56 at the measuring point A and 25 at the average of the measuring points B and D (unit: %).
In the case of (2), the reduction rate was 50 at the measuring point A and 28 at the average of the measuring points B and D (unit: %).

The results of the test example shown in FIG. 5 are as follows.
The scouring depth in case (1) was 0.75 at survey point A, 1.23 at survey point B, -0.04 at survey point C, and 1.57 at survey point D (unit: cm).
The scouring depth in case (2) is 1.20 at survey point A, 1.38 at survey point B, -0.49 at survey point C, and 1.50 at survey point D (unit: cm).
The scouring depth in case (3) was 1.38 at survey point A, 1.79 at survey point B, -0.15 at survey point C, and 1.31 at survey point D (unit: cm).
In the case of (1), the reduction rate was 46 at the measuring point A and 10 at the average of the measuring points B and D (unit: %).
In the case of (2), the reduction rate was 13 at the measuring point A and 7 at the average of the measuring points B and D (unit: %).

The results of the test example shown in FIG. 6 are as follows.
The scouring depth in case (1) was 0.72 at survey point A, 0.96 at survey point B, -0.53 at survey point C, and 1.28 at survey point D (unit: cm).
The scouring depth in case (3) is 1.38 at measuring point A, 1.79 at measuring point B, -0.15 at measuring point C, and 1.31 at measuring point D (unit: cm).
In the case of (1), the reduction rate was 48 at the measurement point A and 28 at the average of the measurement points B and D (unit: %).

According to the test results, it was confirmed that the scouring of the front surface of the pier structure (measurement point A) was reduced by approximately 50% or more for each test example in which the control plate was installed.
It was also confirmed that the scouring of the side surfaces of the pier structure (measurement points B and D) was reduced by 25% or more for each test example in which the control plate was attached.

1 pier structure 2 control plate 3 sea floor

Claims (6)

Control plates having a porosity of 0.60 or more and 0.90 or less shown by (total area of openings in control plate/total area of control plate) are arranged symmetrically along the vertical direction of the outer peripheral surface of the pier structure. An anti-scouring structure of a pier structure, characterized in that it is located at: Anti-scouring structure for pier structure according to claim 1, characterized in that there are two sets of said control plates. 3. The method according to claim 2, wherein the two sets of four control plates have an angle of 90 degrees with respect to the adjacent control plate so as to divide the cylindrical pier structure into four equal parts. Anti-scouring structures for pier structures. A control plate having a porosity of 0.60 or more and 0.90 or less, indicated by (total area of openings of the control plate/total area of the control plate), is arranged symmetrically along the vertical direction of the outer peripheral surface of the pier structure. A method for preventing scouring of a pier structure, characterized by controlling water flow by installing. The scour prevention method for a pier structure according to claim 4, characterized in that two sets of said control plates are attached. 6. The pier structure according to claim 5, wherein the two sets of four control plates are attached at an angle of 90 degrees to an adjacent control plate so as to divide the pier structure into four equal parts. Anti-scouring method.

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