JPH0220213B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an upwelling current generating artificial method for generating an upwelling current from the sea floor to the upper layer in order to artificially improve the living conditions of fish. Regarding reefs.

(Prior Art) In recent years, the development of large-scale artificial fish reefs has been actively promoted, but conventional mechanisms for collecting fish on reefs have placed emphasis on their function as feeding grounds or spawning grounds.

However, in addition to these fish-attracting functions, in flowing waters, turbulence, eddies, or upwelling currents that occur in the wake of fish reefs advection-diffusion of rich nutrients from the seabed to the upper layers, and the photosynthetic action of sunlight. This has the effect of promoting the proliferation of plankton and increasing the basic productivity of the sea area. In fact, all over the world, sea areas with upwelling currents and eddies are good fishing grounds without exception.

In an attempt to improve the habitat conditions of fish by generating upwelling currents, conventional methods have involved installing a small number of flat shielding plates on the seabed facing the tidal currents (for example, Japanese Patent Publication No. No. 101630 (1982) was developed.

(Problems to be solved by the invention) Even with such conventional artificial reefs, upwelling currents occur and fishing grounds are improved, but
In order to obtain an effective upwelling flow that reaches the upper layer in deep water areas, a shielding plate of great height is required, and installing this shielding plate facing the tidal current requires extensive support. There was a problem.

In view of these conventional problems, the present invention aims to provide an upwelling current generating artificial reef that is small in size, can generate large upwelling currents, and is easy to install.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention aims to install a main block for an artificial reef having a long tidal current shielding plate on the seabed in a direction substantially perpendicular to the tidal current. In front of the center of the main block for the artificial reef,
1/3 of the tidal current shielding plate of the main block for the artificial reef
Artificial reef sub-blocks equipped with tidal flow shielding plates with a length of ~1/2 are arranged parallel to each other, and the interval between the artificial reef main block and the artificial reef sub-block is
The artificial reef main blocks are arranged at intervals so that the tidal currents flowing from both sides of the artificial reef sub-blocks meet just before the artificial reef main block.

(Function) In the upwelling flow generating artificial reef of the present invention having such a configuration, due to the presence of the artificial reef sub-block, a dead area (region of weak flow) is created on the downstream side, and the rear end of the dead area (area where the flow is weak) is created. At point), the water flows from both sides of the artificial reef sub-block merge diagonally at the central position on the downstream side, generating a vortex. By placing the artificial reef main block at this confluence position, the vortex has no place to escape in the horizontal direction and collides with the artificial reef main block, generating an upwelling flow that rises upward.

(Example) Next, an example of implementation of the present invention will be described in detail with reference to the drawings.

In the figure, A is the main block for the artificial reef (hereinafter simply referred to as the main block), and B is the sub-block for the artificial reef (hereinafter simply referred to as the sub-block).
The main block A has a tidal current shielding plate 2 erected on the upper surface of a bottom plate 1 installed on the seabed, and is installed on the seabed with the tidal current shielding plate 2 facing approximately perpendicular to the direction of the tidal current. . Similarly to main block A, sub-block B also has a tidal current shielding plate 4 that is integrally installed on the upper surface of the bottom plate 3 installed on the seabed, and is placed parallel to main block A and located in front of the center of the main block. It is located and installed.
In addition, 2a and 4a in the figure are retaining wall boards.

Main block A is formed into a long piece, whereas sub-block B is 1/3 to 1/3 of main block A.
It is molded to a short length of about 1/2.

The distance between both blocks A and B is determined by the attachment point 6 at the rear end of the dead area 5 that occurs on the back side of block B, as shown in FIG.
The spacing is such that main block A is located slightly behind the main block A. The distance from the sub-block B to the attachment point 6 is almost unaffected by the speed of the current and is approximately proportional to the width of the shielding plate 4. According to experiments, the distance L to the attachment point 6 is equal to the width b of the shielding plate, as shown in FIG.
It turned out to be approximately twice as large.

Furthermore, if the height of main block A is particularly large among both blocks A and B, the shielding rate becomes large and the scale of the upwelling flow becomes large. However, according to experiments, as shown in FIG. 4, even if the shielding rate is doubled, the strength of the vortex does not double. Therefore, the optimal shielding rate needs to be determined based on the water depth of the installation sea area and investment efficiency. As a result, a shielding rate of about 20% is generally sufficient, and therefore the height of the main block A is preferably about 1/5 of the water depth.
The strength of the eddy current Φ in FIG. 4 was determined by measuring the flow velocity and using the following equation.

Φ=∫ _x ∫ _y ∫ _z (b/u*)dzdydx In the formula, q indicates turbulence intensity and U* indicates friction speed.

In artificial reefs installed in this way, the first
As shown in Fig. 2, when a current exists in the direction of arrow a, a dead area 5 is created downstream due to the existence of sub-block B, and at the attachment point 6 at the rear end of the dead area 5, the sub-block Water flows from both sides of B merge diagonally at the center position. Since main block A is located at this merging position, the water flow has no place to escape in the horizontal direction, collides with main block A, is pushed upward, and becomes an upwelling flow.

When installing this artificial reef, in sea areas where the tidal current changes with the ebb and flow of the tide, as shown in Figure 5, the main blocks A are lined up in a straight line at appropriate intervals, and each main block is A pair of sub-blocks B, symmetrically located around this
Install B. Further, when the direction of the current is only one direction, the sub-block B is installed only on the upstream side.

The interval between a set of artificial reef sets consisting of one main block and one or two sub-blocks should be such that changes in tidal current caused by each set do not affect changes in tidal current caused by other sets. It is necessary to set the direction of flow of the current,
It is preferable to separate them by at least 20 times the height of the main block.

Each of the blocks in the above-mentioned embodiments has an inverted T-shaped cross section and an integrated bottom plate and tidal current shielding plate, but in the present invention, in addition to this,
As shown in Figures 6a to 6c, the overall cross section is H-shaped,
Various shapes such as a triangular shape and an inverted Y shape may be used.

Note that subblock B shown in the above-mentioned embodiment
As shown in Figures 1 and 2, when rectangular retaining wall plates 4a are attached to both ends, when compared with triangular retaining wall plates and those without buttresses, It has a high ability to generate upwelling flow, and when used in combination with main block A, a more effective upwelling flow can be obtained.

(Effects of the Invention) The upwelling current generating artificial reef of the present invention has the following effects by being configured as described above.

In front of the central part of the main block for artificial reef, 1/3 to 1/3 of the tidal current shielding plate of the main block for artificial reef is installed.
By arranging the artificial reef sub-blocks equipped with 1/2-length tidal current shielding plates parallel to each other, water flows from both sides of the artificial reef sub-blocks merge diagonally at the downstream center, creating an artificial reef. A vortex can be generated just in front of the reef main block.

The interval between the artificial reef main block and the artificial reef sub-block is such that the artificial reef main block is placed at a position where the tidal currents flowing from both sides of the artificial reef sub-block meet just before the artificial reef main block. As a result, the eddy current generated just before the main block for the artificial reef loses its escape in the horizontal direction, collides with the main block for the artificial reef, and rises, generating an upward upwelling flow. For example, Japanese Patent Application Publication No. 58
- Compared to the case where one type of block is simply installed in a straight line as described in Publication No. 101630, two types of blocks act in a complex manner to effectively control large upwelling flows reaching the upper layer in deep sea areas. This makes it possible to improve the habitat conditions of fish over a wide range of areas.

The interval between the main block for an artificial reef and the sub-block for an artificial reef is such that the main block for an artificial reef is placed at a position where the currents flowing from both sides of the sub-block for an artificial reef meet just before the main block for an artificial reef. As a result, it is possible to know in advance the number of blocks required to effectively generate a large upwelling flow reaching the upper layer, which allows effective installation on the seabed and is economical.

[Brief explanation of drawings]

The drawings show an example of the implementation of the present invention.
The figure is a perspective view of the main parts showing the state of installation on the seabed.
Figure 3 is a graph showing the relationship between the tidal current shielding plate and the attachment point distance, Figure 4 is a graph showing the relationship between the shielding rate of the tidal current shielding plate and the strength of the eddy current, and Figure 5 is a graph showing the relationship between the tidal current shielding plate and the strength of the eddy current.
The figures are perspective views showing specific installation conditions, Figures 6 a to c
3A and 3B are perspective views showing other examples of tidal current shielding plates, respectively. A... Main block for artificial reef, B... Sub-block for artificial reef, 1, 3... Bottom plate, 2, 4... Current shielding plate, 5... Dead area, 6... Attachment point.

Claims (1)

[Claims] 1. A main block for an artificial reef having a long tidal current shielding plate is installed on the seabed in a direction substantially perpendicular to the tidal flow, and a main block for an artificial reef is installed in front of the central part of the main block for an artificial reef to prevent the tidal flow of the main block for an artificial reef. Artificial reef sub-blocks equipped with tidal current shielding plates with a length of 1/3 to 1/2 of the shielding plates are arranged parallel to each other, and the interval between the artificial reef main block and the artificial reef sub-block is An upwelling current generating artificial reef characterized in that main blocks for an artificial reef are arranged at intervals such that tidal currents flowing from both sides of the sub-blocks for an artificial reef meet just before the main block for an artificial reef.