JPH0223643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for constructing a stepped seawall in which a wave breaking plate extends from the upright surface of the stepped seawall, leaving drainage channels at regular intervals. According to the present invention, a permanent seawall can be obtained in which the reflected flow of seawater that has washed up on the seawall recedes is brought closer to a steady flow, thereby preventing the phenomenon of scouring and sucking out of the front surface of the seawall.

[Conventional technology]

There have been many accidents in which seawalls, which have traditionally been built on sandy beaches to prevent coastal erosion, are damaged. This is caused by strong reflected waves scouring the front of the embankment foundation, and strong reflected waves that flow down the concrete surface of the embankment as jets, sucking out interstitial water within the embankment from small gaps or cracks in the embankment, accompanied by earth and sand. It is empirically known that this is due to the so-called suction phenomenon.

The inventors discovered that although all of these seawalls are made of strong concrete, they do not have strong walls against the waves that hit the coast with a large amount of energy, and instead attenuate the wave energy. In particular, we focused on the fact that a seawall that weakens the energy of reflected waves and allows free flow of pore water at the back of the embankment body is stronger as a result.
Publication No. 14125, Japanese Patent Publication No. 14126, Publication No. 14125, Japanese Patent Publication No. 1983-14126
- In 168805 and 168806, concrete blocks with a water storage section are placed in advance to temporarily pool seawater that washes up with the waves and slowly release it until the next wave. We proposed a seawall that has a reflective flow control function by covering the dam body with a large number of these concrete blocks.

[Technical problem to be solved by the invention]

The present invention provides a method for constructing a seawall having a reflected flow control function by directly pouring concrete onto the staircase surface without placing such concrete blocks in advance.

[Means of problem solving]

The structure of the present invention is that the slope is leveled in the shape of steps, and a molded body in which a sturdy wave-breaking plate is extended leaving a drainage channel on the rear wall at a height that covers the upright surface of the stairs is installed on the upright surface of the stairs. The method is characterized in that concrete is placed in close contact with the molded body and covered everywhere, and concrete is poured on the horizontal surface of the stairs and hardened integrally with the molded body.

In the present invention, the slope is leveled in advance into a staircase shape, and a molded body forming a rear wall is installed on the upright surface of the staircase prior to concrete pouring. This molded body has a sturdy wave-breaking plate extending from the upper end of the rear wall. The rear wall has a shape, preferably square, that can be joined laterally to completely cover the upright side of the staircase. In addition, a protrusion or a concave shape may be provided on the contact surface between the rear walls in order to make the joint more complete.

The wave-breaking plate does not extend from the entire upper end of the rear wall, but is provided at intervals of the drainage channel. The drainage channel should have a width of at least 70 mm, preferably 100 to 200 mm, so that there is no risk of blockage due to adhesion of shellfish, seaweed, etc.
In some cases, more than this is required. Furthermore, since the wave-breaking plate is the part that receives the strongest wave energy, it is preferable that it has sufficient thickness and is tilted toward the land side. It may be provided at one end of the wave breaking plate, preferably at a portion of the wave breaking plate opposite to the drainage channel.

〔Example〕

FIG. 1 is a perspective view of a molded body that is placed on a staircase surface when concrete is placed on a seawall. 4 is a molded body consisting of a rear wall 1, a wave breaking plate 2 and a side wall 3. The rear wall 1 has a height that matches the sum of the height of the stepped slope and the thickness of the concrete to be poured. The wave breaking plate 2 extends from the upper end of the rear wall leaving a drainage channel 5. There is no problem even if it stands upright, but since it is a structure that protrudes from the seawall, if it is tilted slightly toward the land side as shown in the drawing, the impact from waves can be alleviated to some extent.

Figure 2 shows that the molded bodies shown in Figure 1 are arranged on the vertical surface of a stepped slope, the wave breaking plates 2 are made to protrude, and then concrete is poured on the horizontal surface of the stepped slope, and the molded bodies are integrated with the molded bodies. FIG. 3 is a cross-sectional view of the product after it has been cured. In this case, it is preferable that the side wall 3 contacts the horizontal surface of the stepped slope. FIG. 3 is a plan view of FIG. 2. 6
7 is a concrete pouring surface, 7 is a water reservoir formed by the side wall 3 and the wave breaking plate 2, and 8 is a foot protection work. As shown by the arrow in Figure 2, the waves crashing from the ocean crash into the lowest wave breaking plate, go over the breaking wave plate 2a and fill the water storage part 7a, and then go over the next level wave breaking plate 2b and fill the water storage part 7b. In this way, the waves collide with the wave breaking plates one after another, consuming energy, filling the water storage section 7 with seawater, and reducing the amount of seawater.

When the waves recede, if it is a normal seawall, the water will flow down rapidly in the form of a jet stream, but in the case of the seawall of the present invention, as shown by the arrow in FIG. Since the reflected flow passes through the channel 5 and flows down, it approximates a steady flow and can prevent scouring of the front surface of the embankment body.

According to the construction method of the present invention, all that is required is to level the slope in a step-like manner, arrange the structures 4 in close contact with the upright surface so as to completely cover the upright surface, and then pour concrete on the horizontal surface 6. can be easily constructed.

FIG. 4 is a cross-sectional view of a seawall constructed using a structure without side walls. In the case of this embodiment, since the seawater stored in the water storage section 7 flows horizontally, it has the effect of offsetting the difference in seawater amount due to the local height of waves. Furthermore, the seawater lateral flow phenomenon can prevent the accumulation of earth and sand on the seawall, making the construction easier.

In the above embodiment, the wave breaking plates are arranged in parallel,
Although the drainage channels are arranged so as to be offset between the drainage channels of the next stage and the drainage channels, it is not necessary to shift them in this way, and the drainage channels may be arranged to run perpendicularly to each other.

〔effect〕

The present invention, in which concrete is placed directly on the upright surface of a stepped slope, temporarily stores the energy of waves and seawater, adjusts the flow of reflected waves, avoids a projectile flow, approximates a steady flow, and improves the embankment foundation. prevents scouring of
It is possible to construct a seawall that is stable over a long period of time using a simple method.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a perspective view of a structure arranged in front, FIGS. 2 and 4 are cross-sectional views of a stepped slope, and FIG. 3 is a plan view of FIG. 2. It is a diagram. In the drawings, reference numeral 1 is a rear wall, 2 is a wave breaking plate, 3 is a side wall, 4 is a structure, 5 is a drainage channel, 6 is a horizontal surface, 7 is a water storage part, and 8 is a foot protection work.

Claims (1)

[Claims] 1 The slope is leveled into a staircase shape, and a molded body with a sturdy wave-breaking plate extended from the back wall at a height that covers the upright side of the stairs, leaving a drainage channel, is placed in close contact with the upright side of the stairs. A method for constructing a stair-type seawall, characterized by covering the stairway without covering the stairway, pouring concrete on the horizontal surface of the stairway, and curing it integrally with the molded body.