JPS633084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to breakwaters and seawall caisson installed in deep water areas, and particularly to improvement of wave-dissipating function.

Disadvantages of regular breakwaters and seawall caisson embankments are:
This can be due to high wave reflectance or strong wave force. As a countermeasure, for example, as shown in the cross-sectional view shown in Figure 1, it has conventionally been possible to install a wave-dissipating block 2 in front of a caisson 1 that forms a breakwater or seawall to reduce wave force and reduce reflected overflow. It is widely practiced. However, in this method, stabilization of the wave-dissipating block 2 becomes a problem when the water depth is deep, and in addition, a large number of blocks are required, which is economically disadvantageous. For this reason, this method is mostly used for breakwaters and seawalls in relatively shallow waters.

Therefore, as shown in Fig. 2, a caisson 1 equipped with a wave-dissipating structure has been proposed for use in deep water. This is the caisson body 1 as shown in Figure 2.
This is a so-called upright wave-dissipating structure in which waves are dissipated by forming a rectangular cross-sectional water play space 4 with a slit 3 on the front surface on the open sea side. According to this method, the disadvantages of the method using a wave-dissipating block, such as the stability of the wave-dissipating block described above, can be eliminated. On the other hand, however, with this structure, the wave-dissipating function decreases as the wave period becomes longer, so the retarding space 4 must be made larger to accommodate this. As a result, the cross-section of the embankment cannot be avoided, which is an unavoidable disadvantage in terms of economical design.

The present invention provides a wave-dissipating structure that has a greater wave-dissipating effect than the upright wave-dissipating structure described above, and has a smaller cross-section of the embankment body than before, which is effective against long-period waves. This enables economical design by making it possible to dissipate waves by reducing force. Next, the present invention will be explained in detail using the drawings.

The gist of the present invention is as follows. In other words, in the conventional upright wave dissipating structure, as shown in Fig. 2, an attempt is made to reduce reflections and overflow into the harbor by reducing reflections due to energy loss due to the introduction of waves into the retarding water space 4. It is designed with an attitude in mind. Therefore, as the wave period becomes longer,
It is necessary to enlarge the water play space 4 to prevent it from being filled with water. On the other hand, in the present invention, as shown in the cross-sectional view shown in FIG. while allowing reflection to the open sea side and overflow over the caisson body 1. After the overflow is received by the reservoir 6 provided on the caisson body 1 at the rear of the wave control slope 5, the water is discharged to the open sea side through the drainage hole 7 when waves recede, thereby preventing overflow into the inner side of the port. This is designed to prevent the floating water space from increasing in size during long periods of waves, as in conventional upright wave-dissipating structures, and at the same time to reduce the sliding and overturning forces exerted on the caisson.

FIG. 4 is a bird's-eye view showing an example of the practical wave-dissipating structure of the present invention, and its features are as follows. Specifically, the first method is to provide a wave control slope 5 rising toward the caisson body 1 on the front surface of the caisson body 1 on the open sea side, and at the same time, a front slit with a plurality of longitudinal slits 8a is formed on the front and upper surfaces of the wave control slope 5. A wave-dissipating chamber A is formed covered by a wall 8 and an upper slit wall 9 having a plurality of lateral slits 9a extending from the front to the rear. The vertical slits 8a and the wave control slope 5 sequentially cause energy loss to reduce wave force.
In addition, even with this, the remaining waves that have not been completely dissipated are discharged to the rear of the outside through the horizontal slits 9a of the upper slit wall 9 by the wave control slope 5, and further energy loss is achieved. In addition, it is designed to reduce the upward toppling force applied to the caisson body 1 due to waves colliding with the upper plane of the retarding space 4, as in the conventional upright wave-dissipating structure. Second, the upper concrete structure has a thick and heavy front part 6a on the caisson body 1 at the rear of the upper slit wall 9 to resist overturning force, and has a capacity to retain overflow waves. At the same time as the water retention pond 6 is provided, one end of the drainage hole 7 connecting the water retention pond 6 and the open sea side is opened at a point above the water level when the waves recede, and until the next wave hits. Reservoir 6
Drain holes 7 are provided with a thickness and number that can complete the drainage of stagnant water. The discharge water overflowing through the lateral slit 9a of the upper slit wall 9 is received by the water reservoir 6, thereby preventing overflow into the inner side of the port.

That is, in the upright wave-dissipating structure described above with reference to FIG. 2, waves entering the retarding space 4 first collide with the upright surface of the water retarding space 4 while reducing energy loss due to turbulence when passing through the slit 3. By causing the generated upward flow to collide with the upper plane again, a downward flow is created and the water is circulated within the water retarding space 4. After the wave force is reduced by causing energy loss due to successive collisions, the water in the retarding space 4 is drained by the receding wave to prepare for the next wave dissipation. For this reason, the water retarding space 4 needs to have a size that can circulate and drain the water that enters during one wave cycle, from the wave's arrival to its retreat.If this is not satisfied, that is, the wave cycle is If the wave length increases and the wavelength from the wave's arrival to its retreat becomes larger than the size of the water retarding space 4, the water retarding space 4 will be filled with water, and the waves will be dissipated by circulation. You can no longer expect it to work. Therefore, in order to avoid this, if the wave period is long, it is necessary to increase the size of the water play space 4 accordingly. Furthermore, even when the wave-dissipating effect is being carried out by the retarding water circulation, in the conventional wave-dissipating structure, a strong upward lifting force acts on the upper surface of the retarding space 4 due to the collision of waves against the upper surface of the retarding space 4. do.

However, as in the present invention, there is a horizontal slit 9 on the top surface.
If a is provided to allow water to escape, the internal space 10 of the wave-dissipating chamber A will not be filled with water even if the wave period becomes longer, so the wave-dissipating function will not be lost. do not have. As a result, even if the cycle becomes longer, there is no need to enlarge the water retarding space as in the past, making it economical. Moreover, in the present invention, since water is discharged to the outside, energy is often lost due to turbulence in the water flow when passing through the vertical slit 8a. In addition to this, the wave force (Pr) that exits the slit 8a and collides with the wave control slope 5 is converted into two directions P _H and P _V as shown in Fig. 4, and is converted downward. The caisson body 1 passes through the lateral slit 9a without applying sliding and overturning force to the caisson body 1,
The turbulence of the water flow that occurs at this time further causes energy loss and the water is discharged. Therefore, wave dissipation by reducing wave force is often carried out. In addition to this, a part of the discharged water whose energy has been greatly weakened as described above flows on the upper surface slit wall body 9 and flows out to the open sea side, and the remaining overflow water flows to the reservoir side. Therefore, the amount of water is small, and this water is retained in the reservoir 6 and drained through the drain hole 7 as the waves recede. Therefore, if the capacity of the water retention pond 6 is selected, water will not overflow into the inner side of the port and disturb the tranquility of the anchorage pond in the port.

Next, the wave-dissipating effect of the present invention will be compared and explained with that of a conventional upright wave-dissipating structure through a model experiment.
Figure 5 shows the stone mount 11 as shown in Figure 4.
A regular wave cross-section experiment was carried out to detect horizontal waves, assuming that the upper water depth h was 20 cm, the wave height H was constant 10 cm, and the underwater weight at the sliding limit of the caisson during wave action and the coefficient of friction between the caisson bottom and the rubble mount were 0.53. The force (F) is determined using the ratio of the wave height H to the wavelength L as the horizontal axis. Figure 6 shows the ratio of water depth h to wavelength L, that is, the value of reflectance Kr determined by Healy's method with relative water depth as the horizontal axis; in this case, water depth h and wave height H are constant. Only the wave period is changed.

As is clear from Fig. 5, in the conventional upright wave-dissipating structure shown by curve A in the figure, as the wavelength L becomes longer, the horizontal wave force (F) increases, that is, the wave-dissipating force decreases, so the floating water While it is necessary to increase the space,
In the present invention, as shown by curve B in the figure, the horizontal wave force (F) is approximately half that of the conventional structure, and is almost constant despite changes in the wavelength L. Furthermore, as is clear from Fig. 6, the same can be said about the reflectance (Kr), and these experimental results show that the present invention has a remarkable effect on upright wave-dissipating caisson embankments, and from now on, economical embankment bodies will be developed. It turns out that the design is possible. Further, from the above explanation, it can be seen that similar effects can be obtained when the present invention is applied to a seawall.

Although the present invention has been explained above, for example, FIG.
The same symbols as in the figures indicate equivalent parts. ), the top of the front portion 6a of the reservoir 6 is raised to provide resistance to overtopping waves, thereby reducing the capacity of the reservoir 6. Further, as shown in FIG. 8, the directions of the vertical slit 8a and the horizontal slit 9a may be changed.

As is clear from the above description, the present invention has an excellent effect of making it possible to economically design breakwaters and seawalls, and its practical effects are remarkable.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing conventional wave-dissipating structures, and FIG. 3 is a cross-sectional view for explaining the principle of the present invention.
FIG. 4 is a cross-sectional view of one embodiment of the present invention, FIGS. 5 and 6 are diagrams showing experimental results thereof, and FIGS. 7 and 8 are cross-sectional views and perspective views showing modified examples of the present invention. . 1...Caisson, 2...Wave dissipating block, 3...Slit, 4...Water control space, 5...Wave control slope, 6...Water retention pond,
6a... Front part thereof, 7... Drain hole, 8... Front slit wall, 8a... Vertical slit, 9... Top slit wall, 9a... Horizontal slit, A... Wave-dissipating chamber, 10
...The interior space, 11...a discarded stone mount.

Claims (1)

[Claims] 1 A wave control slope is provided on the front side of the caisson body, and a wall body with a plurality of slits is provided at the front and upper part of this wave control slope, so that the wave control slope forms one side. Cross section is right angle 3
A wave overtopping chamber is formed with a rectangular wave-dissipating chamber, and is equipped with a drainage hole on the caisson body that opens toward the open sea and has a capacity that allows the discharge of standing water to be completed before the next wave hits. A breakwater and seawall caisson characterized by the provision of a retention pond.