JPS60126412A - Breakwater and revetment caisson - Google Patents

Abstract

PURPOSE:To dissipate wave through effective reduction against a wave force, by a method wherein a wave absorbing surface is formed on the front of a caisson body, a retardation basin for overflow is formed on the body, and drainage holes, being open to the inshore side, are provided. CONSTITUTION:A wave absorbing surface is formed on the front on the inshore side of a caisson body 1, and a wave dissipation chamber A covered with an upper surface slit wall body is formed. A retardation basin, having a capacity enough to allow for retardation of overflow and being formed with concrete structure at the upper part thereof, is formed on the caisson body 1. Drainage holes 7, which are of sufficient size and number to complete retardation of the retardation basin 6 during a time in which a subsequent wave breaks upon, are formed to interconnect the retardation basin 6 and the inshore side. This enables provision of wave dissipation structure having a high wave dissipation effect, and permits economical design of a breaker and a revetment.

Description

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

The disadvantages of regular breakwaters and seawalls are that they have a high wave reflectivity and are subject to strong wave force. As a countermeasure, for example, as shown in the cross-sectional view shown in Figure 1, a wave-dissipating block (2) is placed in front of the caisson (1) that forms a breakwater or seawall to reduce wave force and reduce reflected overflow. This has been widely practiced for a long time. 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 amount of professional equipment is 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 Figure 2, a caisson (
1) with a wave-dissipating structure has been proposed. As shown in Figure 2, this is located on the open sea side of the caisson body (1).
This is a so-called upright wave-dissipating structure in which waves are dissipated by forming a rectangular water play space (4) with a rectangular section (3) on the front surface. According to this method, the disadvantages of the method using wave-dissipating plots, such as the stability of wave-dissipating plots mentioned 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 inevitably leads to disadvantages 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 levee body than before, which is effective against long-period waves. By making it possible to dissipate waves by reducing the force, it was possible to create economical columns.

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 Figure 2, waves are introduced into the retarding space (4), which reduces reflection due to energy loss and reduces reflection and overflow into the harbor. It is designed with an attitude of trying. For this reason, it is necessary to increase the size of the water retarding space (4) to prevent it from being filled with water in response to the longer wave period. On the other hand, in the present invention, as shown in the sectional view shown in FIG. While converting the force downward, it allows reflection towards the open sea side and overflow on the caisson body (1). And the caisson body (1) at the rear of the slope (5) that controls overflow, -1
- After the water is received by the water retention pond (6) provided in At the same time, it prevents the floating water space from increasing in size during long periods of waves, and at the same time provides sliding motion to the caisson.

This is designed to reduce the force of falling.

FIG. 4 is a bird track diagram showing an example of a practical wave-dissipating structure of the present invention, and its features are as follows. That is, the first is a wave control slope (5) that stands on the front surface of the caisson body (1) on the open sea side, facing toward the caisson body (1).
a front slit wall body (8) having a plurality of vertical slits (8a) on its front and upper surfaces;
Multiple horizontal lines extending from the front to the rear
A wave-dissipating chamber A is formed, which is covered with a top slit wall (9). and vertical pickpocket, 1 (8a
) and fill wave slope (5), the wave force is gradually reduced by causing energy loss one after another.

Even with this, the remaining waves that were not completely dissipated are removed by the wave control slope (5) through the upper surface slit and the slit 1-(9a) of the wall body (9) to the outside rear ((discharge). In addition to this, the upward toppling force exerted on the caisson body (1) due to the impact of waves on the upper plane of the retarding space (4) as in conventional upright wave-dissipating structures is aimed at further energy loss. The second reason is that there is a top surface slit, and the front part (
6a) is made thicker and heavier to resist the force of falling.
At the same time, a water retention pond (6) is installed with an upper concrete structure that has the capacity to retain overflow waves.
) and the open sea side, one end of which opens at a point above the water level when the waves recede, and until the next wave hits, drains the stagnant water in the reservoir (6). Provide drainage holes (7) of a thickness and number that can complete the process. The discharge water that has overflowed through the horizontal slit (9a) of the upper slit wall (9) is received by the water reservoir (6) to prevent overflow into the inner side of the port.

In other words, in the standing wave structure described in 1 above with reference to FIG. 2, the wave entering the retarding space (4) is not designed to reduce energy loss due to turbulence when passing through the slit (3). By colliding with the upright surface of the basin and causing the resulting upward flow to collide with the upper plane again, a downward flow is created and the water is circulated in the retarding space (4).

After the wave force is reduced by causing energy loss due to successive collisions, the receding waves cause the floating water space (4
) to prepare for the next wave dissipation. This reservoir water storage space (4) needs to be large enough to circulate and drain the water that enters during one cycle of the wave, from the wave's arrival to the wave's retreat. When the period becomes longer and the wavelength between the waves hitting and receding becomes larger than the size of the water retarding space (4), the water retarding space (4) is filled with water. Therefore, we cannot expect a wave-dissipating effect due to circulation. Therefore, in order to avoid this, if the wave period is long, it is necessary to increase the size of the water retarding space (4) accordingly. In addition, even when the wave-dissipating effect is being performed by the retarding water circulation, in the conventional wave-dissipating structure, a strong upward movement occurs on the upper surface of the retarding space (4) due to the collision of waves with the upper surface of the retarding space (4). Uplift force acts.

However, if a horizontal slot (9a) is provided on the top surface to allow water to escape as in the present invention, the internal space 00 of the wave-dissipating chamber A can be filled with water even if the wave period becomes longer. Therefore, there is no loss of wave-dissipating function. As a result, even if the cycle becomes longer, there is no need to enlarge the water retentive 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 secondary slit (8a).

In addition to this, exit the wave control slope (8a) (8a)
The wave force (Pr) colliding with the caisson body (1) is converted into two directions (PH, Pv) as shown in Fig. 4, and the downward conversion causes sliding and overturning force on the caisson body (1). The water passes through the horizontal pickpocket 7) (9a) with little energy and is discharged after further loss of energy due to the turbulence of the water flow that occurs at this time. Therefore, wave dissipation by reducing wave force is often performed. In addition to this, a part of the discharged water whose energy has been greatly weakened by the above-mentioned water flows over the top wall (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 with that of a conventional upright wave-dissipating structure through model experiments.

Figure 5 shows the underwater weight at the sliding limit of the caisson under wave action, and the weight of the caisson itself when the water depth above the stone mound l-01) is 20 cm and the wave height H is constant at 10z as shown in Figure 4. The coefficient of friction between the and rubble mount is 053.
The water/F wave force (g) was determined by a regular wave cross-section experiment, with the horizontal axis representing the ratio of the wave height H to the wavelength. 1. Figure 6 shows the ratio of water depth to wavelength, that is, the reflectance KrO value determined by the following method with relative water depth as the horizontal axis; in this case, water depth and wave height H are Since it is constant, only the period of the wave 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 becomes longer, the horizontal wave force (0 means 0), the wave-dissipating force decreases, so the play space becomes larger. In contrast, in the present invention, as shown by curve 8 in the figure, the horizontal wave force is approximately % of that of the conventional structure, and is almost constant despite changes in wavelength. 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 will lead to the design of economical embankment bodies in the future. Furthermore, 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, as shown in Fig. 7 (the same reference numerals as in Fig. 4 indicate the same parts), the top of the front part (6a) of the reservoir (6) is raised to prevent waves from overtopping. This provides resistance, thereby making it possible to reduce the capacity of the water reservoir (6). Further, as shown in FIG. 8, the directions of the vertical slit (8a) and the horizontal slit (9a) may be changed.

8- As is clear from the above explanation, the present invention has the excellent effect of enabling economical design of breakwaters and seawalls, and its practical effects are remarkable.

[Brief explanation of drawings]

1 and 2 are sectional views showing conventional wave-dissipating structures, respectively. FIG. 3 is a sectional view for explaining the principle of the present invention. FIG. 4 is a sectional view of an embodiment of the present invention. FIG. 6 is a diagram showing the experimental results, and FIGS. 7 and 8 are sectional views and perspective views showing modified examples of the present invention. (1)...caisson, (2)...wave dissipation block, (3
)...Pickpocket. (4)... Retarding space, (5)... Wave control slope, (
6)... Reservoir, (6a)... Its front part, (7)...
...Drain hole, (8)...Front slit wall, (8a)
...Vertical direction, (9)...Top slit wall, (9a)...Horizontal slit, A...Wave-dissipating chamber, OI...Inner space thereof, Q+) ...a stone mount.

Claims (1)

[Claims] (1) A wave control slope is provided on the front side of the caisson body, and an overflow water retention pond is provided on the caisson body. A breakwater and a seawall caisson are characterized by being provided with a drainage hole opening to the open sea side and having a capacity capable of completely discharging water. (2. A breakwater and seawall caisson according to the invention set forth in claim 1, characterized in that a wave-dissipating chamber is formed by covering the front and upper surfaces of the wave-controlling slope with a slit wall body.