JP2001348832A - Breakwater structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a breakwater structure 11 having the low upper bed and with sufficiently required breakwater performance by considering that the waves rising over by an offshore side wall surface 21 are blown back by strong winds. SOLUTION: An arch-inclined wall surface part 211 is provided on the offshore side wall surface 21, and the parameter X of the following formula indicating the rising height of the waves with respect to the upper bed height is set in the relationship to the breakwater performance required for the installation sea area of the breakwater structure 21. [Formula 1] X=2.19+0.466h/Ho-1.63 Ho/ho-36.4S/HoLo)-0.334Lh/B, where Ho is the maximum offshore wave height, Lo is the offshore wave length, ho is the offshore wave depth, h is the installation water depth of the structure, S is the sectional area of an area held between the offshore side wall surface 21 and the calm sea water depth, Lh is the length of the offshore side wall surface 21 above the calm water level, and B is the height of the offshore side wall surface 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a breakwater and a breakwater structure for revetment installed in a harbor or the like.

[0002]

2. Description of the Related Art Breakwaters and seawalls installed in harbors and the like include ships and buildings located on the land side of the wavebreaking structures (waves over the body of the wavebreaking structure). Phenomena). In addition, in order to prevent hindrance to the landscape and reduce the construction cost of foundations required for installation,
It is required to keep the height of the top of the breakwater structure (height from the still water surface to the top surface of the breakwater structure body) as low as possible. Therefore, such a breakwater structure is provided with an inclined part protruding offshore at the upper part of the offshore wall surface, and the waves running up the offshore wall surface are bounced offshore, so that overtopping occurs at a low crown height There has been proposed a breakwater structure capable of preventing the occurrence of a wave.

Conventionally, in such a breakwater structure,
There has been proposed a method of obtaining a top height that can theoretically prevent overtopping of a wave having a maximum wave height assumed at an installation location (Japanese Patent Application Laid-Open Nos. 11-241324 and 11-3504).
No. 48).

[0004]

However, even at a peak height that can theoretically prevent overtopping, at the actual construction site, waves bounced offshore and blown back to the land by strong winds. And, as a result, overtopping may occur. Heretofore, the top height and the like required to prevent overtopping due to such a phenomenon have not been quantitatively clarified.

[0005] Therefore, in the conventional wave-breaking structure, in order to cope with such uncertain factors that are not quantitatively evident, a margin must be provided to the top end height, and the overtopping wave obtained as a result is required. The top height was higher than necessary for performance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made to quantitatively clarify the shape condition of the offshore wall surface for obtaining a necessary and sufficient overtopping performance, so that a low crown is obtained. It is an object of the present invention to provide a wave-breaking structure having a necessary and sufficient overtopping performance at a height.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a wave-breaking structure erected facing offshore, wherein at least the upper part of the offshore wall surface is protruded offshore. And a parameter X defined by the following equation, which is an index of a wave launch height from the height of the still water surface with respect to the height of the top of the offshore wall surface, is set within a predetermined range. Is set to

[0008]

(Equation 2)

However, Ho is the maximum offshore wave height, Lo is the offshore wave wavelength, ho is the offshore wave depth, h is the installation depth of the structure, and S is the distance between the offshore wall surface and the still water surface as viewed from the width direction of the breakwater structure. The cross-sectional area of the sandwiched area, Lh, is the length of the portion above the still water surface of the offshore wall viewed from the width direction of the breakwater structure, and B is the height of the offshore wall surface.

Note that the maximum offshore wave height Ho is set in order to assume the largest wave reaching this breakwater structure when designing a breakwater structure or the like. Considering the service life of the structure, etc., it refers to the maximum wave height of a wave that is expected to occur during this service life.

Here, the offshore wave means a wave in a region where the wave is not affected by the sea floor, a wave reaching the coastal area where the breakwater is installed passes, and a water depth is deeper than half the wavelength. (Toru Sawaragi and Ichiro Deguchi, "New Ocean Engineering" Kyoritsu Shuppan 19
Published in 1996, page 14).

In addition, the service life of such a breakwater structure is often assumed to be 50 years in civil engineering facilities (“Example of Design Calculation of Harbors and Offshore Structures”, Civil Engineering Special Edition, 1987.1, January 2001). VOL.28, NO.2, page 5).

Therefore, in the present invention, in consideration of the above circumstances, the maximum offshore wave height Ho refers to the maximum wave height of waves generated in the past 50 years from the time of construction in the sea area where the breakwater structure is installed. Shall be.

However, if there is no survey data for the past 50 years from the time of construction, the above-mentioned document “Example of Design Calculation of Ports and Offshore Structures”, page 54, “3.1.4 Calculation of Design Wave Height” is described. Based on the method of estimating the stochastic wave height, the probability is calculated from the obtained survey data with a reproducibility period of 50 years.
The calculated maximum wave height is defined as the maximum offshore wave height Ho.

The offshore wave wavelength Lo refers to the wavelength of a wave having the maximum offshore wave height Ho.

The offshore wave depth ho is the maximum offshore wave height Ho.
Refers to a water depth that is not affected by the sea floor, and specifically, refers to 1/15 of the offshore wave wavelength Lo.

The installation depth h of the structure is the height from the sea bottom to the still water surface.

The hydrostatic surface is the sea level at an average height over one year of the highest high tide surface and the lowest low tide surface of each month observed within 5 days from the day of the new moon (Shuo) and the full moon (Noboru). The average high tide surface (HWL) is set based on observation data made in the past year from this reference date, with a date within one year from the construction of the breakwater structure as a reference date. Shall be.

The parameter X calculated based on each value defined as described above is, as described later in detail, in such a breakwater structure with respect to the top height of the offshore wall surface. It is a value that is an index of the wave launch height from the still water level.

In a strong wind, the wave rebounded offshore by the offshore wall surface is blown back to the land side. The ratio of the wave launch height to the top height of the offshore wall surface was blown back. It is an indicator that indicates whether a wave will overshoot a breakwater structure. For this reason, the parameter X is a more practical index obtained by quantifying the likelihood of occurrence of the overtopping phenomenon in consideration of a strong wind.

Therefore, by setting the shape of the offshore wall surface and the height of the crown so that this parameter X falls within a predetermined range satisfying the overtopping performance according to the purpose of installing the structure, it is necessary and sufficient. The top edge height is as low as possible while obtaining the overtopping performance.

Specifically, in the present invention, the parameter X is set within a range of 0.7 or more and 2.0 or less.

If the parameter X is set to 2.0 or less, when the wave having the maximum wave height arrives, the height launched from the offshore surface is twice or less the height of the top of the breakwater structure. Height. As a result, even in strong winds,
It is possible to suppress the amount of wave overtopping to a moderate level, which is equivalent to the overtopping performance required in a coastal area such as a seaside park away from densely populated areas such as houses and general roads.

On the other hand, if the parameter X is set to 0.7 or more, the launch height of the wave having the maximum wave height is 0.
Since it is 7 or more, it is possible to prevent the top height from becoming higher than necessary for the required overtopping rejection performance, and to obtain a low top height.

Further, in such a wave-preventing structure, it is desirable that the protruding inclined wall portion has its lower end positioned above the still water level.

In this way, the cross-sectional area S of the region sandwiched between the offshore wall surface and the still water surface, as viewed from the width direction of the breakwater structure, is ensured to be large. The value of the parameter X indicating the launch height of the wave from the still water level with respect to the height can be reduced, and a lower top height can be realized.

Further, if the parameter X is set to a range of 1.5 or less, when the wave having the maximum wave height arrives,
The height that is launched from the offshore wall can be suppressed to a height slightly higher than 1.5 times or less the height of the top of the breakwater structure. As a result, it is possible to suppress the overtopping amount to a small amount corresponding to the overtopping prevention performance required in the coastal area adjacent to the coastal airport or the like which is not used during a storm or the like.

Further, if the parameter X is set to a range of 1.0 or less, when the wave having the maximum wave height arrives,
The height launched from the offshore wall can be kept below the height of the top of the breakwater. As a result, even when the houses, public facilities, general roads, and the like are densely located adjacent to the revetment, it is possible to suppress the amount of overtopping that is permissible to a small amount.

Further, if the parameter X is set to a range of 0.9 or less, even if the wave having the maximum wave height arrives, the height that is launched from the offshore wall surface is equal to that of the wave-breaking structure. The height can be kept sufficiently lower than the top height. This completely prevents overtopping even during high waves,
It can also satisfy the extremely high overtopping performance required in the coastal area where particularly important facilities for security such as nuclear power plants are installed.

[0030]

FIG. 1 is a sectional view showing the structure of a wave-proof structure 11 according to a first embodiment of the present invention. This breakwater structure 11, like the conventional breakwater structure, digs down the sea floor and replaces it with sand, improves the ground, and provides a rubble mound on it to form a foundation. The structure body is installed.

The wave-breaking structure 11 is formed in a concave curved shape in which almost the entire offshore wall surface 21 faces offshore. In the upper part of the offshore side wall surface 21, a protruding inclined wall portion 211 which is inclined so as to protrude offshore is provided. On the other hand, a footing 214 protruding offshore is formed below the protruding inclined wall portion 221. Also, the lower end portion 212 of the protruding inclined wall portion 211
Is located above a height position 213 that intersects the still water surface.

The wave W arriving at the breakwater structure 11 collides with the offshore wall surface 21 and rises along the offshore wall surface 21.
By 1, the direction of movement is guided diagonally upward on the offshore side, and is rebounded offshore. Thereby, in this breakwater structure, the motion direction of the wave W is changed to the offshore side using the kinetic energy of the wave W, and the wave overtopping is effectively prevented.

Further, the downward water pressure acting on the footing 214 cancels the force of lifting the breakwater structure 11 upward, thereby enhancing the stability of the breakwater structure 11.

As will be described later, the shape and size of the offshore wall surface 21 of the breakwater structure 11 depend on the assumed wave size, the intended use of the sea area in which the wave is installed (the purpose of installation of the breakwater structure, etc.). ), An appropriate range of various values can be obtained by the overtopping rejection performance. The same applies to the following second to fifth embodiments.

FIG. 2 is a sectional view showing a wave-proof structure 12 according to a second embodiment of the present invention. The offshore wall surface 22 of the breakwater structure 12 has a smaller curvature than that of the breakwater structure of the first embodiment, and the portion corresponding to the footing is very small,
21 is located at a height position 22 intersecting the still water surface.
3 above. Then, the wave W arriving by the protruding inclined wall portion 221 is bounced upward offshore to prevent overtopping.

FIG. 3 is a sectional view showing a wave-proof structure 13 according to a third embodiment of the present invention. The offshore side wall surface 23 of the breakwater structure 13 also has an inclined wall portion 231 that protrudes upward and the lower end portion 232 is located above a height position 233 crossing the still water surface. Also,
A flat footing 234 is provided below the protruding inclined wall portion 231. In addition, the wave W arriving by the protruding inclined wall portion 231 is repelled upward offshore to prevent the wave from overtopping, and the downward water pressure acting on the footing 234 cancels the force of lifting the breakwater structure 13 upward. Thus, the stability of the breakwater structure 13 is enhanced.

FIG. 4 is a sectional view showing the structure of a wavebreak structure 14 according to a fourth embodiment of the present invention. The offshore wall surface 24 of the breakwater structure 14 is provided at its upper part with a flat protruding inclined wall portion 241 that is inclined so as to protrude offshore. , A flat footing 244 protruding offshore.
Each of these parts 241, 245, and 244 is a plane part, and therefore is easy to manufacture.
The lower end portion 242 of the protruding inclined wall portion 241 is located above a height position 243 intersecting with the still water surface.

Offshore wall surface 1 combining such planes
4 also has an inclined wall part 2 protruding offshore on top of it.
Since 41 is provided, the wave arriving here can be bounced upward offshore to prevent overtopping. In addition, the downward water pressure acting on the footing 244 cancels the force of lifting the breakwater structure 14 upward, thereby improving the stability of the breakwater structure 14.

FIG. 5 is a sectional view showing a wave-proof structure 15 according to a fifth embodiment of the present invention. The offshore wall surface 25 of the breakwater structure 15 is also provided with a flat protruding inclined wall surface portion 251 that is inclined so as to protrude offshore on the upper portion thereof, and a substantially vertical surface portion 255 is provided on the lower side thereof. Since it is provided and has a planar wall surface, it is easy to manufacture. Further, the lower end portion 252 of the protruding inclined wall portion 251 is located above a height position 253 intersecting with the still water surface.

Offshore wall surface 1 combining such planes
5 also has a sloped wall part 2 protruding offshore above it
Since 51 is provided, the wave arriving here can be bounced upward offshore to prevent overtopping.

According to the breakwater structures 11 to 15 according to the first to fifth embodiments configured as described above, the waves W arriving from the offshore side are bounced off the offshore wall surfaces 21 to 25 to the offshore side. Overtopping is prevented.

However, in a strong wind or the like, the waves bounced off the offshore wall surfaces 21 to 25 may be blown back to the land side by the strong wind again, resulting in an overtopping phenomenon. Whether or not such overtopping has occurred depends on the offshore wall surface 2
It depends on whether or not the wave bounced upward at 1 to 25 exceeds the top of the breakwater structures 11 to 15. That is, the ratio of the height at which the wave is launched upward on the offshore wall surfaces 21 to 25 and the top height of the wavebreak structures 11 to 15 is one index.

In the following, focusing on this point, the wave condition is changed while changing various external conditions such as the water depth of the sea area where the breakwater structure is installed, and the shape condition of the offshore wall surface of the breakwater structure. The launch height of the wave is measured, and the quantitative relationship between each of these conditions and the launch height of the wave is examined.

Therefore, the scale models I and II of the wave-proof structure main body corresponding to the first embodiment (FIG. 1) and the scale model of the wave-break structure main body corresponding to the fourth embodiment (FIG. 4). A series of experiments were performed using III and the two-dimensional wave-making water tank shown in FIG. In this experiment, an impervious slope having a 1/20 gradient simulating a seabed gradient was installed in a two-dimensional wave-making water tank (length 30 m, height 1.2 m, width 0.6 m) shown in FIG. A scale model of the breakwater structure was installed on the opaque slope, and various waves generated by the wave maker were made to collide with the scale model.

Table 1 shows the results of this series of experiments.

[0046]

[Table 1]

In Table 1, each row shows one experimental condition and its result. In each experiment, the model shown in the second column of each row was installed on the opaque slope at the position of water depth h shown in the sixth column, and the offshore wave height Ho and the offshore wave wavelength Lo shown in the second and third columns were set. Waves were generated, and the wave launch height R shown in the tenth row was obtained.

The "cross-sectional area S" shown in the seventh column of Table 1 refers to the offshore wall surfaces 21 to 2 as shown by oblique lines in FIGS.
The area sandwiched between 5 and the still water surface is defined as a breakwater structure 11-1.
5 shows the cross-sectional area as viewed from the width direction, and the “cross-sectional length Lh” shown in the eighth column of Table 1 is the static length of the offshore wall surfaces 21 to 25 as shown by the curved arrows in FIGS. 1 to 5. The length above the water surface when viewed from the width direction of the wavebreak structures 11 to 15 is shown.

Next, a numerical analysis based on the experimental results shown in Table 1 shows a quantitative relationship between the shape conditions and external conditions of the wavebreak structures 11 to 15 and the wave launch height R. A theoretical formula was derived.

Specifically, based on all the data shown in Table 1, the ratio R of the wave launch height R to the top height hc is given by R
/ Hc as the objective variable, the ratio h / Ho of the installed water depth to the offshore wave height Ho, the ratio S / (HoLo) of the area of the area between the offshore wall surface and the still water surface to the wave area, and the offshore wave for the offshore wave depth ho The ratio ho / Ho of the wave height Ho, the ratio Ho / B of the height of the offshore wall surface to the wave height, and the ratio Lh / B of the length Lh of the offshore wall surface on the still water surface to the wall height B are described as explanatory variables x1 to x4. And multiple regression analysis was performed. From these four explanatory variables x1 to x4, an estimation formula for estimating the ratio R / hc of the wave launch height R to the top height hc, which is the target variable, was obtained. When the estimated ratio R / hc is represented by a parameter X, the estimation formula is as follows.

[0051]

(Equation 3)

Table 2 shows the parameter X (estimated value R / hc) estimated by this estimation formula.

[0053]

[Table 2]

In Table 2, the second to fifth columns represent explanatory variables x1 to x4, respectively, and the fifth column represents parameter X.
And the sixth column shows the actual measurement values measured in the experiment.

Next, the accuracy of this estimation formula will be verified.

FIG. 7 is a graph obtained by plotting the parameter X (predicted value R / hc) calculated from the estimation formula on the vertical axis and the measured value R / hc from the experiment on the horizontal axis for each of the above experiments. 4 is a graph showing the relationship between the two. According to this graph, each plot is placed on a straight line having a slope of 1 substantially passing through the origin, and the correlation coefficient between the two is sufficiently high at 0.8987, indicating that the accuracy of the estimation formula is sufficiently high.

Next, according to the purpose of installing the wavebreak structure and the like,
An appropriate range required for the parameter X will be examined.

In the sea area where the breakwater is installed, the required overtopping performance differs depending on the purpose of use of the sea area.

For example, in the case of a seawall such as a seaside park, when a large wave is expected, the park is not used in principle, so that a wave having a maximum offshore wave height Ho is allowed as much as possible while allowing a medium overtopping wave. It is required that the top height hc be reduced to provide a hydrophilic revetment that prevents the landscape from being hindered. For this reason, in the case of a strong wind, an overtopping wave of a moderate level or less is allowed to occur, and the launch height R of the wave is set to about twice or less the top height hc, that is, the parameter X is set to 2.
What is necessary is just to set it in the range of 0 or less.

Also, at seawalls at airports and the like, airports and the like are closed during typhoons and the like, so that a small amount of overtopping is allowed for waves with the maximum offshore wave height Ho so as not to obstruct the pilot's view. It is required to lower the top height hc. Therefore, in a strong wind, a small amount of overtopping is allowed to occur, and the launch height R of the wave is set to about 1.5 times or less the top height hc, that is, the parameter X is set to a range of 1.5 or less. Just set it.

In the revetment adjacent to an area where people, public facilities, and general roads are dense, it is required that almost no overtopping occurs even by strong winds. hc, that is, the parameter X may be set to a range of 1.0 or less.

In the coastal area where the most important facilities for security such as nuclear power plants are installed, the assumed maximum offshore wave height H
Also for o, since it is required to surely prevent overtopping, if the wave launch height R is sufficiently lower than the top height hc, that is, if the parameter X is set to a range of 0.9 or less, Good.

On the other hand, even in the coastal area where the most important facilities for security are installed, if the crown height hc is set higher than necessary,
In addition to hindering the landscape, the foundation for installing the breakwater structure becomes large, and the construction cost increases. Therefore, the parameter X is set so that the wave launch height R with respect to the top end height hc is not excessively low.
What is necessary is just to set in the range of 0.7 or more.

As described above, the present invention has been described based on the embodiments. However, the wave preventing structure according to the present invention may be configured as follows.

For example, a top plate made of a plate-like member projecting substantially horizontally toward the offshore side may be provided on the top surface. In this way, the wave lifted upward along the offshore wall surface is repelled toward the sea surface by the top plate, so that more excellent overtopping performance can be obtained.

Further, a wave-returning structure projecting upward on the top end surface may be provided. In this way, the water that separates from the main flow of the waves lifted along the offshore wall surface and flows to the top end surface can be dammed on the top end surface.

Alternatively, a drainage means for draining such water flowing on the top end surface so as not to reach the land side may be provided on the top end surface.

[0068]

As described above, according to the present invention, the overhanging slope wall portion is provided on the offshore wall surface, so that excellent overtopping performance can be obtained. The quantitative relationship between the wave launch height and the external conditions such as the offshore wall surface condition and the offshore wave height was clarified, and based on this relationship, the shape of the breakwater structure was set up. Because we set the launch height of the waves required in the sea area to be necessary and sufficient,
It is possible to provide a wave protection structure having a low top end height while satisfying the required wave overtopping performance and keeping the wave overtopping amount within a desired range.

Therefore, while maintaining the view of the coastal area where the breakwater structure is installed, the body of the breakwater structure is reduced in weight, thereby reducing the required foundation and reducing the cost and labor required for ground improvement. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram showing a first embodiment of a wavebreak structure according to the present invention.

FIG. 2 is a cross-sectional configuration diagram illustrating a second embodiment of a wavebreak structure according to the present invention.

FIG. 3 is a cross-sectional configuration diagram illustrating a third embodiment of a wavebreak structure according to the present invention.

FIG. 4 is a cross-sectional configuration diagram illustrating a fourth embodiment of a wavebreak structure according to the present invention.

FIG. 5 is a cross-sectional configuration diagram showing a fifth embodiment of a wavebreak structure according to the present invention.

FIG. 6 is a cross-sectional view showing a two-dimensional wave-making water tank used in a series of water tank experiments.

FIG. 7 is a graph showing a relationship between an estimated value by an estimation formula and an actually measured value by an experiment with respect to a ratio of a wave launch height R to a top height hc.

[Explanation of symbols]

 11 to 15 Breakwater structure 21 to 25 Offshore wall surface 211 to 251

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhito Kataoka 1-5-5 Takatsukadai, Nishi-ku, Kobe, Japan Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Yasuo Ichikawa Wakihama-cho, Chuo-ku, Kobe City 1-3-18 Kobe Steel, Ltd.Kobe Head Office (72) Inventor Naoto Takehana 1-3-18, Wakihama-cho, Chuo-ku, Kobe Kobe Steel Co., Ltd.Kobe Main Company (72) Inventor Yoshihiro Hamasaki Kobe 1-3-18, Wakihama-cho, Chuo-ku Kobe Steel, Ltd.Kobe head office (72) Inventor Fujihiko Hashino 1-3-18, Wakihama-cho, Chuo-ku, Kobe Kobe Steel, Kobe main office (72) Inventor Katsu Numata 1-3-18, Wakihama-cho, Chuo-ku, Kobe Kobe Steel, Ltd. Kobe Head Office (72) Inventor Takefumi Yamada 1-5-5, Takatsukadai, Nishi-ku, Kobe Company Kobe Steel, Kobe Technical Research Institute in (72) inventor Kenichi Sugii, Chuo-ku, Kobe, Wakinohama-cho 1-chome No. 3 No. 18 stock company Kobe Steel, Kobe headquarters in the F-term (reference) 2D018 BA18

Claims (5)

[Claims] 1. A wave-breaking structure erected facing offshore, wherein at least an upper portion of an offshore wall surface is provided with a protruding slope wall portion inclined so as to protrude toward offshore, and The parameter X defined by the following equation, which is an index of the launch height of the wave from the still water level with respect to the top height of the wall surface, was set within a range of 0.7 or more and 2.0 or less. A wave-breaking structure characterized by the above-mentioned. (Equation 1) However, Ho is the maximum offshore wave height, Lo is the offshore wave wavelength, ho is the offshore wave depth, h is the installation depth of the structure, and S is sandwiched between the offshore wall surface and the still water surface viewed from the width direction of the breakwater structure. The cross-sectional area of the area, Lh, is the length of the portion of the offshore wall above the hydrostatic surface viewed from the width direction of the breakwater structure, and B is the height of the offshore wall. 2. The wavebreak structure according to claim 1, wherein a lower end of the projecting inclined wall portion is located above a still water level. 3. The wavebreak structure according to claim 1, wherein the parameter X is set in a range of 1.5 or less. 4. The wavebreak structure according to claim 1, wherein the parameter X is set in a range of 1.0 or less. 5. The wavebreak structure according to claim 1, wherein the parameter X is set in a range of 0.9 or less.