JP5798629B2 - Seawall - Google Patents

Description

  The present invention relates to a tide embankment installed on a coast, and more particularly to a tide embankment that prevents damage from a tsunami.

Tsunami by the Tohoku Pacific Yooki earthquake that occurred on March 11, 2011, took an enormous amount of human life, and destroyed the property. There is now a strong demand for seawalls that effectively prevent damage from such massive tsunamis.

  Simply put, a traditional seawall is a wall that pushes back a tsunami, and even if pushed back by a seawall, the energy of the tsunami does not decrease. The tsunami pushed back to the seawall is superposed on the second and third waves that invades, increasing the energy and returning to the seawall again.

  The seawall must be strong enough to withstand the impact of a tsunami collision. However, there is a limit to improving the strength by changing the structure and dimensions.

  Therefore, a seawall has been proposed that attenuates tsunami energy at the seawall. For example, in Patent Document 1, an overflow opening is provided by cutting out a substantially central position of the top end surface of a levee body, a serrated roughness surface is formed at the bottom of the overflow opening, and the overflow opening is formed. It describes a tsunami breakwater that attenuates the energy of the tsunami that overflows. In addition, the embankment described in Patent Document 2 is intended to reduce the damage by arranging energy dissipating elements (projections) on the top surface of the embankment to attenuate the energy of the tsunami that crosses the embankment. Have

  Certainly, if the tsunami energy is attenuated, the impact on buildings on land can be reduced, so damage may be reduced somewhat. However, inundation damage caused by overflowing seawater is not resolved. Therefore, to prevent damage from the tsunami, it is still necessary to dam the seawater with a seawall.

Therefore, Patent Document 3 includes a slope having an upward slope from the sea side to the land side in a cross-sectional shape, and the slope of the slope increases in a parabolic manner toward the land side. A protective bank that is inverted toward the sea side to form an overhang portion is disclosed. According to Patent Document 3 , with such a configuration, the movement direction of seawater hitting the slope gradually changes upward, so that the impact received by the levee body can be mitigated, and the seawater hitting the slope is scattered in the air And return to the sea level. In other words, it claims to be able to prevent seawater overtopping.

Japanese Patent Laid-Open No. 07-113216 Japanese Examined Patent Publication No. 6-63210 Special table 2011-500998 gazette

  Patent Document 3 claims that the direction of movement of seawater colliding with the protective bank can be changed by curving the cross-sectional shape of the protective bank to the land side to prevent seawater from overflowing. Certainly, the seawater that collides first may be the same, but since the energy of the tsunami does not decay, the seawater surface rises in front of the protective levee, and it is thought that it will eventually cross over.

  The present invention has been made in view of the background as described above, and an object of the present invention is to provide a seawall that can attenuate tsunami energy and prevent seawater overtopping.

  In order to achieve the above-mentioned object, the tide embankment of the present invention has, in a planar shape, alternately arranged bulging portions protruding to the sea side and ridges arranged between the bulging portions and recessed to the land side. Configured.

Contour of the cross section of the bulging portion is rising from the bottom an arc convex to the sea side, culminated in the arc, with its after, overhangs draw a convex curve landside, the troughs of the cross section of the contour, rise from the bottom draw a convex curve to the sea side, gradually falling to the land side, then you overhang draw a convex curve landside.

  The end of the contour line of the overhang portion in the cross section of the bulging portion is closer to the sea than the end of the contour line of the overhang portion in the cross section of the contour line of the cross section of the flange portion, and the bulge The elevation angle of the tangent line at the end of the contour line of the overhang portion in the cross section of the overhang portion may be smaller than the elevation angle of the tangent line at the end of the outline line of the overhang portion in the cross section of the contour line of the cross section of the flange portion. Good.

  The elevation angle of the tangent at the end of the contour line of the overhang portion in the transverse section of the bulge is about 30 °, and the elevation angle of the tangent at the end of the contour line of the overhang portion in the transverse section of the buttock is about 60 degrees. You may make it be °.

  Moreover, you may make it form many dimples on the surface of a seawall.

  According to the present invention, it is possible to attenuate the energy of a tsunami by shifting the phase of a tsunami carrier and causing the carriers to interfere with each other. In addition, the tsunami movement direction can be changed to the direction toward the sea side to prevent tsunami overtopping. Therefore, the loss of human life and property due to the tsunami can be reduced.

It is a notional top view of a seawall showing an example of an embodiment of the present invention. It is a top view which shows the detailed form of a seawall. FIG. 3 is a cross-sectional view of the tide embankment taken along line AA ′ of FIG. 2. It is a top view explaining the effect | action of a seawall. It is a top view explaining the effect | action of a seawall. It is a figure which shows the shape of the dimple formed in the surface of a seawall, (a) is a top view, (b) is sectional drawing cut | disconnected by the BB 'line | wire of (a).

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual plan view of a seawall 1 showing an embodiment of the present invention. As is clear from FIG. 1, the tide bank 1 is provided with a predetermined distance from the coastline 2 and includes a bulging portion 4 that protrudes toward the sea 3. A large number of the bulging portions 4 are arranged in the length direction of the seawall 1 with a predetermined interval. There is a flange 5 between the bulging portion 4 and the bulging portion 4 adjacent to the bulging portion 4 and is recessed on the land 6 side. The seawall 1 is generally configured as described above, blocks the tsunami 7 approaching the land 6 from the sea 3, prevents the tsunami 7 from landing, and protects the building 8 installed on the land 6.

  FIG. 2 is a plan view showing a detailed form of a part of the seawall 1 cut out. The bulging part 4 has a three-dimensional shape similar to the spherical bow of a ship, that is, a hemisphere at the tip (may be called a quadrisphere because it lacks the lower half), so the contour of the tip of the bulging part 4 is In the plan view (FIG. 2), it is semicircular. The flange portion 5 is between the bulging portion 4 and the bulging portion 4 adjacent thereto, and is lower than the bulging portion 4. That is, if the bulges 4 and the ridges 5 are alternately arranged on the seawall 1 and the bulges 4 are compared to comb teeth, the ridges 5 correspond to gaps between the teeth. Or if the bulging part 4 is compared with a ridgeline, the collar part 5 will correspond to a valley line.

  FIG. 3 is a cross-sectional view of the seawall 1 taken along the line A-A ′ of FIG. 2. Here, in order to avoid complication of the figure, only the shape of the portion protruding on the seabed 9 is shown, but the foundation structure is buried in the seabed 9 so that the seawall 1 is connected to the seabed. Needless to say, it is firmly fixed to 9. As shown in FIG. 3, the contour line of the cross section of the bulging portion 4 rises from the bottom a by drawing a convex arc b on the sea side, reaches the apex c of the arc b, and then protrudes on the land side. An overhang is formed by drawing a curve d and reaches the end e. Further, the tangent line of the contour line of the overhang portion has an elevation angle of 30 ° at the terminal end e. On the other hand, the outline of the cross section of the ridge 5 rises from the bottom f with a convex curve g on the sea side, gradually falls to the land side, rises to the land side, and then protrudes to the land side. Is drawn to form an overhang portion, and the end i is reached. Further, the tangent line of the contour line of the overhang portion has an elevation angle of 60 ° at the terminal end i.

  Note that the radius of curvature of each of the arc b, the curve d, and the curve h is r, and r is equal to the height of the tsunami assumed at the location where the seawall 1 is installed.

  Moreover, although it is hard to express in a figure, the surface by the side of the sea 3 of the seawall 1 is comprised by the smooth and continuous curved surface. The bulging portion 4 and the flange portion 5 are also connected by a smooth and continuous curved surface, and there are no steps or discontinuities. However, “smooth and continuous curved surface” is a design goal, and it goes without saying that there are distortions due to errors in work and rough surfaces due to the properties of materials on the actual surface. . For practical purposes, it is sufficient to have a curved surface that can be regarded as smooth and continuous.

  Next, the function of the seawall 1 will be described. When the first tsunami wave traveling from the sea 3 toward the land 6 reaches the seawall 1, a part of the seawater collides with the bulging part 4, and the rest flows directly into the ridge part 5. The seawater that has collided with the bulging portion 4 flows into the flanges 5 on both sides of the bulging portion 4. The seawater that has flowed from the bulging portion 4 into the heel portion 5 merges with the seawater that directly flows into the heel portion 5 and rises along the contour line of the heel portion 5 (see FIG. 3). That is, the seawater that has been flowing horizontally from the sea 3 to the land 6 gradually flows upward, and further reaches the overhang portion (curve h) and flows obliquely upward from the land 6 toward the sea 3. And after the terminal i, it is dissipated high in the air. Seawater is released into the air while swirling, so the seawater diverges in the air as a splash. The splash eventually falls to the sea surface, but no longer causes a wave traveling in a specific direction because it no longer has a velocity in a specific direction (for example, a direction from the land 6 to the sea 3).

  In addition, the dimension of the seawall 1 is determined according to the conditions of an installation place. For example, when the height of the tsunami assumed at the place is r, the interval between the bulging portions 4 is selected from 2r to 4r. The width of the flange 5 is selected between r and 2r (see FIG. 2). Select the height of the seawall 1 from the seabed between 3r and 4r (see Fig. 3)

By the way, the tsunami is generally regarded as a single water surface wave with a very long wavelength, but a large number of waves generated by the behavior of the sea floor caused by an earthquake It is appropriate to consider that this phenomenon is caused by the superposition of “subcarriers”. Further, "carrier" is a pressure fluctuation caused by the behavior of the seabed, because affected by water depth during propagation, the period T _P of the "carrier" is given by the following equation. However, h is the depth of water and _Cw is the speed of sound in seawater (≈1500 m / s).

T _P = 4h / C _w (Formula 1)

The tsunami propagation velocity V is given by the following equation. However, h is water depth (m) and g is gravitational acceleration (m / s ² ).

  V = √ (g * h) (Formula 2)

  The wavelength λ (m) of the “carrier wave” is given by the following equation.

λ = V * _TP (Formula 3)

  As described above, the wavelength λ of the “carrier wave” can be estimated. For example, when h = 100 m, λ≈8 m.

  The tsunami energy is the sum of the energy of the “carrier wave”. If the “carrier wave” is attenuated, the energy of the tsunami can be attenuated.

  Now, as shown in FIG. 4, the difference (d2−d1) between the stroke d1 reaching directly from the sea 3 to the ridge 5 and the stroke d2 reaching the ridge 5 via the bulging portion 4 is “carrier wave”. If the shape of the seawall 1 is selected so as to be ½ of the wavelength λ, that is, λ / 2, the phase of the “carrier wave” that has reached the heel part 5 by following the stroke d1 and the stroke d2 are traced by the heel part 5 Since the phase of the “carrier wave” arriving at is reversed, the “carrier wave” disappears in the flange 5. In this way, the tsunami energy can be extinguished by eliminating the “carrier waves” one after another. Of course, (d2-d1) cannot be reduced to λ / 2 for all “carrier waves”, so the tsunami energy cannot be completely eliminated, but if (d2-d1) is optimized, Many parts of the energy can be attenuated.

  Further, as shown in FIG. 5, seawater flows into the heel part 5 from the bulging parts 4 adjacent to the left and right sides and collides and scatters, so that the seawater is oblique to the tide bank 1 (that is, the tide bank). Even if it flows in (with a velocity component parallel to 1), the seawater stays in a vortex in the heel part 5 so that the sea level does not rise.

  Further, if the surface of the seawall 1 (the bulging portion 4 and the ridge portion 5) is formed with a dimple 10 as shown in FIG. 6, that is, a number of depressions having a depth d = 10 to 20 mm and a diameter D = 100 to 200 mm, Viscous frictional resistance can be reduced by disturbing the boundary layer of seawater flowing on the surface of the seawall 1. For this reason, seawater can be dissipated more highly and a splash can be spread | diffused more widely.

  Thus, the seawall 1 divides the propagation path of the tsunami into two, gives a phase difference to the tsunami that reaches the buttock 5 through each propagation path, and causes the two to interfere to attenuate the energy of the tsunami. be able to. Moreover, since the seawater which collided with the seawall 1 is scattered high in the air, the energy of the tsunami remaining without being attenuated can be diffused. As a result, life and property on land can be effectively protected.

  In addition, the said embodiment illustrates the specific embodiment of this invention, Comprising: The technical scope of this invention is not limited to what was illustrated by the said embodiment. The present invention can be freely applied, modified or improved within the scope of the technical idea shown in the claims.

  For example, FIG. 1 shows an example in which the seawall 1 is installed on the sea 3 side away from the coastline 2, but the position where the seawall 1 is installed is not limited to this. The seawall 1 may be installed on the coastline 2 or may be installed at a position on the land 6 side of the coastline 2.

  Moreover, although the seawall 1 shown in FIG. 1 has an arcuate planar shape as a whole, the planar shape of the seawall 1 is not limited to an arcuate shape. It can be designed freely according to the terrain of the installation location.

  Moreover, in FIG. 3, although the example which sets the elevation angle of the tangent of the end of an overhang part in the outline of the cross section of the bulging part 4 and the collar part 5 to 30 degrees and 60 degrees was shown, respectively, In this case, an error caused by a limit of the machining accuracy is allowed. However, this does not mean that the range of 30 ° or 60 ° is expanded without limit. The allowable error range follows the common general knowledge of those skilled in the art.

  The material, structure, and construction method of the seawall 1 are not particularly limited. The optimum material, structure, and construction method may be selected according to design constraints. The material of the seawall 1 is generally concrete, but if there is an alternative material, it may be selected. In addition, concrete may be placed on site, or precast concrete lumps may be stacked on site.

  The tide embankment of the present invention can be used as a tide embankment installed on the coast to prevent tsunami damage.

DESCRIPTION OF SYMBOLS 1 Seawall 2 Coastline 3 Sea 4 Swelling part 5 Ridge part 6 Land 7 Tsunami 8 Building 9 Seabed 10 Dimple

Claims (4)

In the planer shape, in the tide bank constructed by alternately arranging the bulging part protruding to the sea side and the ridge part that is disposed between the bulging part and recessed into the land side,
Contour of the cross section of the bulging portion is rising from the bottom an arc convex to the sea side, culminated in the arc, with its after, overhangs draw a convex curve landside,
The contour line of the cross section of the buttock draws a convex curve on the sea side and rises from the bottom, gradually falls to the land side, and then overhangs with a convex curve on the land side,
A tide embankment characterized by that. The end of the contour line of the overhang portion in the cross section of the bulging portion is on the sea side from the end of the contour line of the overhang portion in the cross section of the contour line of the cross section of the flange portion,
The elevation angle of the tangent at the end of the contour line of the overhang portion in the cross section of the bulge is smaller than the elevation angle of the tangent of the end of the contour line of the overhang portion in the cross section of the contour line of the cross section of the flange The seawall according to claim 1. The elevation angle of the tangent at the end of the contour line of the overhang portion in the transverse section of the bulge is about 30 °, and the elevation angle of the tangent at the end of the contour line of the overhang portion in the transverse section of the buttock is about 60 The seawall according to claim 2, wherein The seawall according to claim 1, wherein a number of dimples are formed on the surface.

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