JPH04136312A - Riprap type breakwater - Google Patents

Abstract

PURPOSE:To increase the functionality of a breakwater by forming a trapezoidal riprap mound under a water level, drilling a recess through the widthwise center of widthwise mound top, and so housing a float body in the recess as to project from the top of the mound. CONSTITUTION:A riprap mound 2 is so formed as to be continuous to the end of a breakwater 1, and a concrete block 3 extended in a lengthwise direction is buried in the center of mound top 2b at the center of the mound 2 with the upper surface exposed. Thereafter, a float body 6 having a center box form is housed in the recess 3a of the block 3. In this case, the vertical length of the body 6 is so set as to keep the lower end thereof within the recess 3a, and the weight of the body 6 is so determined as to keep the upper surface 6a thereof near a water level respectively, even when afloat due to buoyancy. At the time of a high tide level, the float body 6 becomes afloat due to buoyancy, and the top of the underwater riprap mound 2 nominally increases, thus alleviating a wave with the top of the mound 2 to some extent, and then completely dissipating the wave with the float body 6. According to the aforesaid construction, the functionality of the breakwater 1 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubble type breakwater whose height can be changed according to the tide level.

(Conventional technology) Conventional rubble-type breakwaters (hereinafter referred to as artificial reefs) are
It is formed by a roughly trapezoidal rubble mound with a gentle slope on the coast, etc., and is installed with the top widened to some extent, and the height of the top is set at or below the low tide level so that it does not rise above the water surface. It is set. This arrangement suppresses waves and keeps the water surface calm.

(Problem to be solved by the invention) However, in the ocean, the tide level is thick (and fluctuates), so an artificial reef with a fixed crown height will have a reduced wave-dissipating effect at high tide. Even if the width is widened, there is a limit to its effectiveness, and if the top width is widened, the utility value of ports or coasts will be halved.

Floating breakwaters have a good wave-dissipating effect against fluctuations in tidal levels, but they are generally built in areas where it is difficult to construct rubble mounds due to soft ground, or offshore, and they are used in areas with long ocean wavelengths. It is quite large to withstand waves, and requires careful consideration in mooring and fixing methods.

Therefore, it is technically difficult to use this floating breakwater in combination with artificial reefs installed in ports, coasts, etc., and the problem arises that space in ports, coasts, etc. cannot be used effectively.

An object of the present invention is to provide a rubble-type breakwater that solves the above problems and can effectively cope with fluctuations in the tide level.

(Means for Solving the Problems) In order to achieve the above object, the present invention installs a trapezoidal rubble mound under the water surface, and places a trapezoid in the widthwise center of the top of the rubble mound in the longitudinal direction of the rubble mound. The present invention is characterized in that a recess extending from the top is formed, and a floating body protruding from the top is housed in the recess.

(Function) Since the present invention is configured as described above, the floating body is supported by the concave portion, and at high tide, the floating body rises due to its buoyancy and its actual top becomes high.

In this configuration, the waves are somewhat relaxed at the top of the underwater rubble mound, and can be completely dissipated by the floating body. Furthermore, when the tide level is low, the floating body is stored in the recessed part, and waves can be sufficiently reduced in this state. Furthermore, even if the wavelength of the wave is long, it can be sufficiently attenuated because the top width of the rubble mound is wide.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in Figure 2.3, an artificial reef is installed at the tip of a breakwater l in a port. As shown in Figure 1, it is formed into a trapezoidal shape with a gently sloped surface 2a extending both inside and outside the port. rubble mound 2
The top end 2b is formed wide, and a concrete block 3 extending in the longitudinal direction is buried in the center thereof with the top surface exposed, and a recess 3a is bored in the top surface. Further, the block 3 is fixed to the upper part of the rubble mound 4, which is the base of the center of the rubble mound 2, to prevent it from sinking, and the height of the top end 2b is approximately adjusted to the low tide level. Note that the top end 2b is covered with a rubble mound 4 by a concrete block 5.

Further, a hollow box-shaped floating body 6 is housed in the recess 3a on the upper surface of the block, and its vertical length is such that its lower end is located within the recess 3a even when it floats due to buoyancy, and its upper surface 6a
The weight is set so that it is close to the water surface.

In the artificial reef having the floating body 6 configured in this way, the floating body 6 is freely displaced by buoyancy, so when the tide level rises, the floating body 6 also rises to form a wall surface 6b underwater, and the waves hit the wall surface 6b and are weakened. As a result, the Uranami effect can be obtained.

Next, details of the operation will be explained with reference to FIGS. 4 to 6.

As an example, high tide level: H,=,=H,W,L, child 2. IQ Wei (Low tide level: L, W, L, +0.14m) Water depth: h=1
5m #j wave: Tl/! = 7.6- (Lo=9(1
, 1 m) Consider the condition of H1/-= 3.2 m. In addition, the numerical value at the high tide level is a water level at which the wave-dissipating effect when only the rubble mound 2 is used is significantly reduced.

At high tide, the cross section of the rubble mound 2 has a shape in which the center protrudes toward the water surface due to the floating body 6, as shown in Figure 4.
As shown in FIG. 5, the width of two parts of the rubble mound is 81, and as shown in FIG. 6, the width of six parts of the floating body is 82.

In addition, the wave transmittance when the crest width is BI and the crest water depth R is 196 m is Ktl, and the crest width is B2 and the crest water depth R is O.
Let the transmittance when m be 2. Further, the transmittance KT of the artificial leaf of the present invention is IXKT2.

Table 1 Wave-dissipating effect of the embodiment According to Table 1, a sufficient wave-dissipating effect can be obtained by setting CASE 3 or higher.

In addition, the upper surface 6a of the floating body 6 incorporated in the rubble mound 2
can be set either underwater or above the water surface, as required. This is the upper surface 6 as shown in FIGS. 7 and 8.
By attaching small buoyant bodies 7 to key points on a,
The portion that sinks below the water surface becomes larger, and only a portion of the buoyant body 7 is visible above the water surface. This configuration has high utility value in resort areas and seaside parks because it does not spoil the scenery.

In addition, since the top of the artificial reef is below the water surface, its wave-dissipating function is similar to that of a natural beach, so it has little impact on the surrounding area, maintains the habitat of fish, and has a fish-attracting effect and the reproduction of organisms. You can expect it.

(Effects of the Invention) Since the present invention is configured as described above, the rubble mound makes the water surface calm against periodic fluctuations of waves, and the floating body follows the water level against the tide level. The floating body rises to the high tide level and forms a wall (V4 wave action, making it an efficient rubble type breakwater. In addition, the external force is small because the waves softened by the rubble mounds of the rubble type breakwater act on the floating body. The thickness of the floating body in the width direction can be reduced, and the method of supporting the floating body is simply by storing it in a recess, so it is economical and does not take up much space.

[Brief explanation of the drawing]

Fig. 1 shows a rubble type breakwater according to an embodiment of the present invention, and is a cross-sectional view taken along line II in Fig. 2. Fig. 2 is a plan view of the rubble type breakwater shown in Fig. 3. Fig. 3 is an implementation example. A perspective view of a port in which a rubble type breakwater is installed according to an example. Figure 4 is a schematic diagram showing the external shape of a rubble type breakwater when a floating body according to an example is applied. Figure 5 explains the rubble mound shown in Figure 4. Schematic diagram; Figure 6 is a schematic diagram illustrating the embankment with floating bodies shown in Figure 4; Figure 7 is a perspective view of a rubble-type breakwater with floating bodies according to another embodiment; Figure 8 is the rubble-stone breakwater shown in Figure 7. It is a sectional view of a type breakwater. 2... - Stone mound 2b... Top end 3a... Concavity 6... Floating body Figure 3

Claims (1)

[Claims] (1) A trapezoidal rubble mound is installed below the water surface, a recess extending in the longitudinal direction of the rubble mound is bored in the widthwise center of the top of the rubble mound, and a floating body protrudes from the top into the recess. A rubble-type breakwater characterized by storing.