JP4832328B2 - Wave-dissipating caisson and parapet used for wave-dissipating caisson - Google Patents

Description

  The present invention relates to a parapet used for a wave-dissipating caisson and a wave-dissipating caisson.

  Conventionally, several techniques for improving the wave preventing performance have been proposed. For example, for the purpose of providing a breakwater caisson that can improve the breakwater performance of the breakwater and the water quality improvement function in the harbor, a seawater inlet is formed in front of the caisson on the open sea side, and the inlet is formed on the upper surface of the caisson. An outflow port through which seawater that has flowed in from the water can flow out is formed. The outflow port and the outflow port are connected to each other to form an overall curve, and the rear wall of the outflow side and the caisson There has been proposed a breakwater caisson (see Patent Document 1) that includes at least one water channel having an angle of 90 ° or less with the upper surface and can flow the inflowing seawater back to the open sea.

In addition, on the breakwaters, the seawater and inland seas were designed to ensure that even if the seawater level fluctuates, the water permeability function is activated to improve the flowability of seawater in closed water areas and prevent contamination of seawater in the inland seas. A breakwater main body installed on the sea floor so as to partition, a plurality of backflow prevention walls having different heights provided on the breakwater main body facing the open sea, and provided on the inland sea side of the respective backflow prevention walls. A breakwater (see Patent Document 2) characterized by comprising a plurality of water reserving sections, and a plurality of water guiding sections provided at the lower part of the breakwater main body so as to communicate each recreational section and the inland sea. Has also been proposed.
Japanese Patent Laid-Open No. 7-259045 JP 2004-19279 A

  However, in the conventional caisson, the consideration for reducing the overtopping amount has not been sufficient. Therefore, a technique for efficiently suppressing the overtopping amount at a high tide level has been desired. Then, this invention is made | formed in view of said point, and sets it as the main objective to provide the caisson which show | plays the favorable amount of wave overtopping reduction.

The wave-dissipating caisson of the present invention that achieves the above-described object includes a drinking water chamber in which seawater flows in from the sea through an opening and stays therein, and the water space of the seawater is reduced, an upper space of the watering room, and the sea surface of the sea. A wave-dissipating caisson having a communication path communicating with the parapet, wherein the wave-dissipating caisson includes a parapet that is a superstructure, and the communication path is formed inside the parapet, and is a surface on the sea surface side of the parapet. It is characterized by having an opening . According to this, while the seawater flows into the recreational water chamber, the water flow of the seawater is reduced, and the seawater that rises up along with the water flow narrows the recreational water chamber upper space (not submerged). Thus, an exhaust flow from the communication path toward the sea surface is generated.

  This exhaust flow becomes a flow that opposes the seawater that rushes toward the communication path (the sea side opening) from the sea, and can reduce the momentum of the seawater trying to overtop the caisson. Furthermore, if the seawater flowing into the water reserving chamber is stronger, the sea water rising up the water reserving chamber flows into the communication passage, and a drainage flow from the communication passage toward the sea surface is generated. This drainage flow is a flow that opposes the seawater that rushes toward the communication path (the sea side opening) from the sea, and can reduce the momentum of the seawater trying to overtop the caisson.

  As the water flow of the seawater that strikes the wave-dissipating caisson increases, the momentum of the exhaust flow or the drainage flow discharged from the sea-side opening of the communication path increases, and the amount of overtopping can be reduced efficiently. . Therefore, according to the wave-dissipating caisson of the present invention, there is an excellent effect of reducing the overtopping amount.

Further, the parapet according to the present invention is a parapet that constitutes a wave-dissipating caisson provided with a water-reserving chamber that allows seawater to flow in from the sea through the opening and retains the water, and the opening of the water-reserving chamber top plate And a communication passage that communicates with the opening facing the sea surface. According to this, since the effective overtopping amount reduction by the exhaust flow and the drainage flow is realized, it is possible to adopt a wave-dissipating caisson and a parapet that have a lower levee height than before, and a wave-dissipating caisson. Design / installation cost and environmental load can be reduced. Therefore, it is possible to configure a wave-dissipating caisson that exhibits a good effect of reducing the overtopping amount.

  In addition, the problems disclosed by the present application and the solutions thereof will be clarified by the embodiments of the present invention and the drawings.

  According to the present invention, there is an excellent effect of reducing the amount of overtopping.

--- Structure of wave-dissipating caisson ---
Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1A is a perspective view and FIG. 1B is a side sectional view of a wave-dissipating caisson according to this embodiment. In this embodiment, as an example, a wave-dissipating caisson 100 that faces the open sea 10 and appropriately receives the waves 11 rushing from the open sea 10 to suppress overtopping to the backland 12 is assumed. The wave-dissipating caisson 100 is a structure formed of a concrete frame, and is a columnar reflector 101 arranged at an appropriate interval and a slit-like space between the reflectors 101. 11 is provided with an opening 102 for allowing seawater to flow in, and a water reserving chamber 103 for retaining the seawater 20 flowing from the opening 102 and reducing the water flow of the seawater 20.

  Further, the wave-dissipating caisson 100 includes a communication path 105 that communicates the upper space 104 of the water reserving chamber 103 and the sea surface 13 of the open sea 10. It is preferable that the communication path 105 is provided inside a parapet 106 that is an upper work of the wave-dissipating caisson 100. The communication path 105 in the parapet 106 of such a form serves as a path that communicates the opening 108 of the top plate 107 of the water reserving chamber 103 and the opening 109 facing the sea surface 13 of the open sea 10.

  When the seawater 20 flows into the recreational water chamber 103, the waves of the seawater 20 collide with each other in the recreational water chamber or collide with the reclaimed water indoor wall, thereby reducing the water force of the seawater 20. In addition, the seawater 20 that rises upward in the reclaimed water chamber along with the water force and that has seen a rise in the water level in the reclaimed water chamber serves to narrow the unsubmerged reclaimed water chamber upper space 110, and from the communication path 105 to the sea surface 13. An exhaust flow 111 directed in the direction is generated.

  This exhaust flow 111 becomes a flow that opposes the seawater 21 that rushes from the open sea 10 toward the opening 109 of the communication path 105, and can reduce the momentum of the seawater 21 that is going to wave over the wave-dissipating caisson 100. is there.

  Furthermore, if the seawater 20 flowing into the recreational water chamber is stronger, the seawater 20 that has risen up the recreational water chamber 103 flows into the communication path 105, and a drainage flow 112 is generated from the communication path 105 toward the sea surface 13. Will be allowed to. This drainage flow 112 becomes a flow that faces the seawater 21 that rushes from the open sea 10 toward the opening 109 of the communication path 105, and can reduce the momentum of the seawater 21 that is going to wave over the wave-dissipating caisson 100. .

  As the water force of the seawater 20 that strikes the wave-dissipating caisson 100 increases, the force of the exhaust flow 111 or the drainage flow 112 discharged from the opening 109 of the communication path 105 also increases, and the water force of the seawater 21 efficiently. Therefore, the amount of overtopping can be reduced.

--- Design of wave-dissipating caisson ---
Next, a general design procedure of the wave-dissipating caisson will be described. FIG. 2 is a diagram illustrating an example of a caisson design procedure. The design procedure shown here shows a general design method applied to the design of a conventional wave-dissipating caisson. In designing the wave-dissipating caisson, first, the wave height H ₀ ′ (m) and the period T _1/3 (s) are determined for the design wave at the installation point (design target point) of the wave-dissipating caisson ( s100).

Subsequently, to determine the allowable overtopping quantity _{q a} of the installation point (s101). The allowable overtopping amount is an allowable amount (m ³ ) of water overtopping for 1 second per 1 m of revetment width. That is, the allowable amount of seawater that reaches the hinterland 12 beyond the wave-dissipating caisson 100 is considered. Further, the top height h _c of the parapet is assumed (s102). Further, the offshore wave wavelength L ₀ and the waveform gradient (h / H ₀ ′) are calculated from the specifications (s103).

Next, the amount of wave overtopping q is calculated using the chart of port technical standards (estimated overtopping flow rate of upright revetment: “Technical Standards for Port Facilities / Description” p119, published by Japan Port Association) s104). Here, if the calculated overtopping quantity q is less than the allowable overtopping quantity q _a (s105: Yes), this crest height h _c of the parapet as defined in until is determined to design values, design work is completed.

The inventors of the present application conducted a hydraulic experiment after creating a model of the wave-dissipating caisson 100 of the present embodiment. According to this hydraulic experiment, the wave-dissipating caisson 100 according to the present embodiment including the water reserving chamber 103 and the communication path 105 has the same top end as compared with the conventional wave-dissipating caisson under certain wave conditions. About 40% of the wave overtopping reduction effect was recognized even with the height parapet. A graph 300 in FIG. 3 shows the overtopping amount difference depending on the presence or absence of a communication path or the like in the hydraulic experiment. According to this graph 300, the overtopping amount q in the wave-dissipating caisson 100 of the present embodiment is “0.029 (m ³ / m / s)”, while the conventional wave-dissipating caisson (reservoir chamber) 103 and no communication path 105), the overtopping amount q is “0.049 (m ³ / m / s)”, and it can be seen that the overtopping amount can be reduced by about 40%.

  As described above, in step s104 of the design procedure of the above-described wave-dissipating caisson 100, the overtopping amount q can be reduced by 40% in advance from the conventional type, and the determination in step s105 can be performed.

In addition, the wave-dissipating caisson 100 (reservoir chamber) of the present embodiment under the conditions of design wave height H ₀ ′: 3.97 m, period T _1/3 : 8.6 seconds, water depth 8.52 m, and seabed slope 1/10 103 and the communication path 105) and a conventional wave-dissipating caisson without the water reserving chamber 103 and the communication path 105 were compared and calculated. However, the wave overtopping amount of the wave-dissipating caisson 100 of the present embodiment takes into account the 40% reduction from the conventional type in the chart of the port technical standards (estimated overtopping flow rate of the upright revetment) Application of the overtopping flow estimation diagram is the same as the conventional method).

  FIG. 4 shows the result. According to this, in the wave-dissipating caisson 100 of the present embodiment, the height of the top end of the parapet 106 can be lowered by 1.5 m from that of the conventional type (conventional type: 10.5 m, the extinction of the present embodiment). Wave type caisson: 9.0 m). According to the wave-dissipating caisson 100 of the present embodiment, the effective overtopping amount reduction by the exhaust flow 111 and the drainage flow 112 is realized, and therefore, the parapet 106 that suppresses the height of the top of the conventional type is adopted. It is possible to reduce the design / installation cost and environmental load of the wave-dissipating caisson.

  Therefore, according to this embodiment, there is a good effect of reducing the overtopping amount.

  As mentioned above, although embodiment of this invention was described concretely based on the embodiment, it is not limited to this and can be variously changed in the range which does not deviate from the summary.

It is (a) perspective view and (b) sectional side view of the wave-dissipating caisson in this embodiment. It is a figure which shows the example of a caisson design procedure. It is a graph which shows the overtopping amount difference by the presence or absence of a communicating path. It is a figure which shows the top end height difference by the presence or absence of a communicating path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Outer sea 11 Wave 12 Back ground 13 Sea surface 20, 21 Sea water 100 Wave-dissipating caisson 101 Reflector 102 Opening 103 Reservoir chamber 104 Reservoir upper space 105 Communication path 106 Parapet 107 Top plate 108, 109 Opening 110 Not yet Submerged water chamber upper space 111 Exhaust flow 112 Drain flow

Claims (2)

It is a wave-dissipating caisson comprising a water reserving chamber that allows seawater to flow from the sea through the opening and retains it, and that reduces the water pressure of the sea water, and a communication path that connects the upper space of the water reserving chamber and the sea surface of the sea. And
The wave-dissipating caisson includes a parapet that is a superstructure, and the communication path is formed inside the parapet and opens to a surface on the sea surface side of the parapet . A parapet constituting a wave-dissipating caisson equipped with a water-reserving chamber that allows seawater to flow from the sea through the opening and retains it, and opposes the opening of the water-reservoir top plate and the sea surface of the sea A parapet characterized in that a communication passage communicating with an opening is formed inside .

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