JPH0359211A - Structure under water - Google Patents

Abstract

PURPOSE:To stably prevent encroachment extending for a lengthwise embank ment by providing at least two rows of underwater wall bodies in front of the embankment built in the water, and fixing many slender leaf-like bodies between the respective rows. CONSTITUTION:At least two rows of underwater wall bodies 2a - 2d are pro vided in front of an embankment 1, adjoining to the embankment 1 built in the water. Many slender leaf-like bodies 3 are fixed between respective rows of respective wall bodies 2a - 2d. Hereby, water flow against the water side of the base part of the embankment 1 is obstructed with the wall bodies 2a - 2d, and encroachment extending for the lengthwise embankment 1 can be stably prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an underwater structure that is installed adjacent to an embankment installed underwater to prevent erosion or scouring caused by movement of earth and sand.

[Prior Art] As is well known, various measures have been taken to prevent erosion or scouring (hereinafter simply referred to as erosion) of rivers and coasts. One known example is one in which a stone mass, block, or concrete structure is constructed underwater a little distance from the coast. Among such structures, there are offshore breakwaters, breakwaters, jetties, etc. whose tops are always exposed above the water surface, and submerged levees whose tops are submerged underwater (hereinafter collectively referred to as simply levees). Are known.

However, when such an embankment is constructed, the earth and sand at the base of the embankment are eroded over its length by waves or water currents.
As a result, the embankment may collapse.

In order to prevent such flow of earth and sand, for example, Japanese Patent Publication No. Sho 61-501215 discloses a technique in which a large number of elongated leaves are fixed to a mat and the mat is installed on the river bed. Although it is effective in itself to install mats by attaching elongated leaves, there is a problem with the manner in which the mats are installed, and because the mats are simply fixed with anchors, they are susceptible to water currents and waves during storms. The problem is that if the mat is torn or the anchor is dislodged due to the force of the fronds, and the fronds become floating and are washed away, the erosion prevention effect cannot be achieved.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a mat with fronds attached thereto that will not peel off or move due to the force of water flow or waves caused by storm winds, etc., and that will have a stable erosion prevention effect over its length. The aim is to provide underwater structures that can maintain the

[Means for Solving the Problems] According to the present invention, in an underwater structure that is installed adjacent to a dike installed underwater to prevent erosion or scouring due to movement of earth and sand, a structure is provided in front of the dike. At least two rows of underwater walls are installed, and a number of elongated leaves are fixed between the two rows of walls.

[Effects] Therefore, since many leaves are fixed between walls, the space between the walls is less affected by waves even during stormy winds, so the leaves can be installed stably. . Also, since it is installed in front of the embankment, that is, in the water against land,
These walls are installed almost parallel to the embankment and are buried underwater, so as a result, sediment and suspended matter accumulate between the walls and move to the base of the embankment or its vicinity. However, the soil at the base of the embankment is not eroded, but rather accumulates.

[Preferred embodiment] When carrying out the present invention, the wall is made of concrete piles, steel sheet piles,
It is preferable to continuously drive steel pipe piles, steel pipe sheet piles, etc., and the cross-sectional shape is arbitrary.

Preferably, the fronds are attached in a known manner to a reticulated mat, which is placed between the walls. In addition, in areas where there is a lot of drifting sand, it is preferable to install a mat near the top of the wall in addition to the mat near the bottom of the water to create a two-tiered structure.

In addition, the thallus is non-toxic and has seawater resistance, and its specific gravity is 0.2-04g/cII! It is preferable to use a material such as polypropylene.

In addition, the outer wall that is farthest from the embankment (on the opposite land side) is easily eroded, so the eroded sand is washed over the outer wall by waves and flows onto the inner mat, where it is deposited.
It is preferable to increase the vegetation density of the thallus. Therefore, the fronds are preferably fixed to the mat so that they can be planted freely. Further, if there are mats on the upper and lower sides, it is preferable that the upper and lower ends of the leaf-like bodies are fixed to the upper and lower mats, respectively.

Furthermore, if the erosion rate is high, sand may be spread on the lobes provided between the walls and the lobes may be buried.

[Example code] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of an underwater structure in which the present invention is implemented. In the figure, a breakwater 1 is provided near the coast, and on the opposite land side there are four rows of walls adjacent to and substantially parallel to the breakwater 1. 2a
, 2b, 2c, and 2d are provided, and a number of leaf-like bodies 3 are fixed between these walls. The middle part of the figure shows the sea surface, and the top of the breakwater 1 protrudes above the sea surface, but the top of the wall is located below the sea surface, and the lower part is driven below the ocean floor E.

FIG. 2 shows another embodiment of the present invention, in which a mat 5 is attached near the top of the walls 2a to 2d, and another leaf-like body 4 is attached thereon.

Fig. 3 shows an example in which the walls are constructed of steel sheet piles, and each of the walls 2a and 2b is constructed by connecting sheet piles 6, 6, etc. in an alternating manner. They are connected to each other by sheet piles 7.7 and have a generally closed rectangular shape. However, the sheet piles 7.7 do not necessarily need to be provided.

A net-like mat 9 is installed in the internal space 8, that is, between the wall 2a and the wall 2b. As shown in FIG. 4, a large number of leaf-like bodies 3 are attached to the mat 9. The manner in which these leaf-like bodies 3 are attached to the mat 9 and the fixing of the mat 9 can be carried out using known techniques, for example, the technique disclosed in the above-mentioned Japanese Patent No. 61-501215. That is, the leaf-shaped body 3 is attached to the mat via a holding piece (not shown).

Next, an example of the construction method will be explained with reference to FIGS. 5 to 7. First, as shown in FIG. 5, multiple rows of walls, such as sheet piles, are driven into the seabed E. Then, as shown in FIG. A mat 9 is laid on the embankment 1 side of the sheet pile 2a according to the requirements. The construction work is completed above, but if necessary, the space between the sheet piles 2a to 2d may be backfilled with earth and sand 10 using an earth carrier or the like as shown in FIG. Also, earth and sand will accumulate naturally without backfilling.

[Effects of the Invention] As described above, according to the present invention, the counter-land flow of the foundation portion of the embankment I is blocked by the wall body, and erosion is prevented.

Moreover, according to the present invention, as shown in FIG. 8, the earth and sand in the outer part X of the outermost wall 2d (on the opposite land side) is scoured, but this scoured earth and sand Z is deposited together with alluvial sand Y between the walls 2d and 2a as shown by arrows A and B. Then, due to the water flow, it is gradually deposited between the walls 2C and 12b, and is sequentially moved to the inside (land side) of the wall 2a, so that the foundation part of the embankment is not eroded.

In this way, natural energy such as waves and water currents moves the earth and sand toward the land, making it possible to form a nourished beach with a lot of sand.

Furthermore, the walls are submerged in water, so the impact is not compromised. If the height below the water surface is adjusted, it will not interfere with the navigation of ships.

Additionally, if mats are used on the top and bottom, even if organisms attach to the fronds, they will remain vertically independent, helping to prevent erosion. Sheet piles are preferable in terms of strength.

[Brief explanation of drawings]

Fig. 1 is a side view of the first embodiment of the present invention, Fig. 2 is a side view of the second embodiment of the invention, Fig. 3 is a plan view showing an example of a wall body, and Fig. 4 is a side view of a leaf-shaped body. Perspective view showing the manner of installation, No. 5
7 to 7 are side views sequentially showing the construction method of an underwater structure according to the present invention, and FIG. 8 is a side view showing the effects of the present invention. 1@116 Breakwater 2a, 2b, 2c, 2d--Wall 3.4J... Foliage 5.9... Mat
L... Sea surface E... Seabed surface Figure 5 Figure 6

Claims (1)

[Claims] In underwater structures installed adjacent to banks installed underwater to prevent erosion or scouring due to movement of earth and sand,
1. An underwater structure comprising at least two rows of underwater walls installed in front of an embankment, and a large number of elongated leaves fixed between the two rows of walls.