JP2726115B2 - Underwater structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is provided adjacent to a dike installed in water,
The present invention relates to an underwater structure for preventing erosion or scouring due to movement of earth and sand.

[Prior Art] As is well known, various measures have been taken to prevent erosion or scouring of rivers and coasts (hereinafter simply referred to as erosion). As one of them, for example, a stone block, a block, a concrete structure, or the like is constructed in water slightly away from a coast. Among such structures, there are breakwaters, breakwaters, jetties, etc., whose tops are constantly exposed to the surface of the water, and submerged embankments whose tops are submerged in the water (hereinafter collectively referred to simply as embankments). Are known.

However, when such a levee is constructed, the earth and sand at the base portion of the levee may be eroded longitudinally by waves or water currents, and as a result, the levee may collapse.

In order to prevent such flow of earth and sand, for example, Japanese Patent Laid-Open Publication No. 61-501215 discloses a technique in which a large number of elongated leaf-like bodies are fixed to a mat and the mat is installed on a riverbed. Laying such an elongated foliate attachment mat is effective in itself,
There is a problem in the way of laying, and the mat is simply fixed with an anchor, so that the mat is torn off or the anchor is detached by the force of the water current or wave at the time of the storm, and the leaf-like body floats and is washed away And the erosion preventing effect is not exhibited.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a mat with the leaf-shaped member attached thereto without peeling or moving due to the force of a water current or a wave caused by a storm or the like, and a stable erosion prevention effect over the longitudinal direction. To provide an underwater structure that can maintain the

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

[Operation] Therefore, since a large number of foliates are fixed between the walls, there is little effect of waves between the walls even in a storm, so that the foliates can be stably installed. . Also, since they are installed in the water in front of the embankment, that is, on the opposite side of the land, their walls are installed in a substantially parallel relationship with the embankment, and are buried underwater, so that sediment and floating Objects accumulate, earth and sand move to or near the base portion of the embankment, and the earth and sand at the base portion of the embankment are not eroded, but rather accumulate.

[Preferred Embodiment] In practicing the present invention, the wall is preferably formed by continuously driving a concrete pile, a steel sheet pile, a steel pipe pile, a steel pipe sheet pile, or the like, and its cross-sectional shape is arbitrary. The leaves are preferably attached to a mesh mat in a known manner and the mat is laid between the walls. In a place where there is a lot of sand drifting, it is preferable to lay a mat near the upper part of the wall in addition to the mat laid near the water bottom to form a two-stage structure.

Further, the foliate body has no toxicity and has seawater resistance, and it is preferable to use a material having a specific gravity of 0.2 to 0.4 g / cm ³ , for example, polypropylene.

Also, the outer wall (anti-land side) farthest from the embankment is easily eroded, so that the eroded sand flows over the outer wall by the waves and flows to the inner mat to accumulate foliar It is preferable to increase the vegetation density of. It is therefore preferred that the leaves are fixed so that they can be freely planted on the mat. When there are mats on the upper and lower sides, it is preferable to fix the upper and lower ends of the leaf-shaped body to the upper and lower mats.

Further, when the erosion rate is high, sand may be scattered on the leaves provided between the walls to bury the leaves.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an underwater structure embodying the present invention,
In the figure, a breakwater 1 is provided near the coast, and on the opposite side of the land, there are four rows of wall bodies 2 substantially parallel to and adjacent to the breakwater 1.
a, 2b, 2c, 2d are provided, and a large number of leaf-like bodies 3 are fixed between their walls. In the figure, L indicates the sea surface, and the top of the breakwater 1 projects above the sea surface L,
The top of the wall is located below the sea level, and the lower part is driven below the sea bottom E.

FIG. 2 shows another embodiment of the present invention, in which a mat 5 is mounted near the tops of the walls 2a to 2d, and another leaf 4 is mounted thereon.

FIG. 3 shows an example in which the wall is made of steel sheet piles, and the wall bodies 2a and 2b are respectively constructed by connecting the sheet piles 6, 6... Alternately, and have another end having the same size at the longitudinal end. They are connected to each other by sheet piles 7 and 7 to form a generally closed rectangular shape. However, the sheet piles 7, 7 need not necessarily be provided. A net-like mat 9 is provided between the interior 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 the leaf-like bodies 3 are attached to the mat 9 and the fixing of the mat 9 can be performed by a known technique, for example, the technique disclosed in the above-mentioned Japanese Patent Publication No. 61-501215. That is, the leaf 3 is attached to the mat via a holding piece (not shown).

Next, an example of the construction method will be described with reference to FIGS. First, as shown in FIG. 5, a wall body such as a sheet pile is driven into the seabed E in a plurality of rows, and then, as shown in FIG. 6, the leaf 3 is laid between the mounting mat 9 and the sheet piles 2a to 2d. Accordingly, a mat 9 is laid on the bank 1a of the sheet pile 2a. The construction is completed as described above. However, as shown in FIG. 7, the space between the sheet piles 2a to 2d may be backfilled with the earth and sand 10 using a soil transport ship or the like as necessary. Even without backfilling, sediment accumulates naturally.

[Effects of the Invention] As described above, according to the present invention, the flow on the non-land side of the base portion of the bank 1 is blocked by the wall, and erosion is prevented.

Further, according to the present invention, as shown in FIG. 8, the earth and sand in the outer portion X of the outermost (anti-land side) wall 2d is scoured. Is deposited between the walls 2d and 2c together with the sand drift Y as shown by arrows A and B. Then, the water gradually accumulates between the walls 2c and 2b, and sequentially moves to the inside (land side) of the wall 2a, so that the base portion of the embankment is not eroded.

As described above, the earth and sand move to the land side by natural energy such as waves and water currents, so that a sandy beach can be formed.

Further, the wall is submerged in the water, so the effect is not impaired.
Adjusting its underwater height will not hinder the vessel's navigation.

Further, if mats are used on the upper and lower sides, even if organisms adhere to the foliate body, the state of being independent in the vertical direction is maintained, which helps to prevent erosion. In the case of a sheet pile, strength is preferred.

[Brief description of the drawings]

FIG. 1 is a side view of a first embodiment of the present invention, FIG. 2 is a side view of a second embodiment of the present invention, FIG. 3 is a plan view showing an example of a wall, and FIG. Perspective view showing the mode of attachment, FIG.
7 are side views sequentially showing the construction method of the underwater structure of the present invention, and FIG. 8 is a side view showing the effect of the present invention. 1 ... breakwater, 2a, 2b, 2c, 2d ... wall, 3, 4 ... leaf, 5, 9 ... mat, L ... sea surface, E ... sea bottom

Claims (1)

(57) [Claims] Claims: 1. An adjoining dike installed in water,
An underwater structure for preventing erosion or scouring due to movement of earth and sand, comprising at least two rows of underwater walls installed in front of a bank, and fixing a number of elongated leaf-like bodies between the two rows of walls. An underwater structure characterized by the following.