JP2000154518A - Reflected wave reducing structure having different draft type double curtain wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preclude the possibility of a disaster of a fishing boat by efficiently attenuating a transmitted wave and a reflected wave, and to reduce washing excavation of a sandy beach by shallowing draft of an offing side front curtain wall more than draft of a land side rear curtain wall. SOLUTION: An offing side front curtain wall 11 and a land side rear curtain wall 12 are arranged at an interval to constitute a reflected wave reducing structure having a double curtain wall. In this constitution, draft d1 of the offing side front curtain wall 11 is shallowed more than draft d2 of the land side rear curtain wall 12. These both curtain walls 11, 12 are respectively installed on a front steel pipe pile 1 and a rear steel pipe pile 2 driven into the water bottom ground 3. Or both curtain walls 11, 12 are constituted as a floating body type bank body, and may be vertically movably fitted/arranged along the piles 1, 2 driven into the water bottom ground 3 to thereby efficiently attenuate a transmitted wave and a reflected wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for reducing reflected waves having double curtain walls with different drafts spaced apart.

[0002]

2. Description of the Related Art Generally, in a breakwater facility installed for the purpose of effectively utilizing a coastal sea area, it is desired that a wave energy is dissipated by a structure to reduce both reflected waves and transmitted waves. This is provided to reduce the reflected wave disaster in the surrounding sea area and the secondary impact on the surrounding sea area environment due to the installation of the breakwater facility. For example, there is a risk of disaster due to reflected waves on raft such as oysters in front of structures such as breakwaters and fishing boats at anchor, or scouring sandy beaches due to reflected waves reflected from breakwaters, or entering small and medium-sized fishing boats or small and medium-sized vessels. This is provided to eliminate the possibility that the operation of a ship such as a transport ship becomes difficult due to reflected waves.
Curtain breakwater, which is a pile breakwater (breakwater structure),
It has advantages such as being able to be constructed on soft ground and having a seawater exchange function through the lower part of the embankment.
Further, since only the vicinity of the water surface where the wave motion is dominant is blocked by the curtain wall, the transmitted wave can be efficiently reduced. However, the effective reduction of transmitted waves requires a deeper draft of the curtain wall, which in turn increases the reflected waves and has a relatively large effect on the surrounding waters as described above. .

Conventionally, as a curtain type breakwater for reducing both transmitted and reflected waves, a double curtain type breakwater in which the front and rear curtain walls have the same draft is known. In the case of this double curtain type breakwater, the energy dissipation due to vortex formation at the lower end of the embankment is made using the resonance phenomenon of the water area in the embankment sandwiched between two curtains (partitions) arranged at an interval. It is known to have a function of promoting dispersion and reducing both transmitted and reflected waves.

It is known that the wave resonance state includes both a first-order or higher resonance mode in which an antinode and a node occur, and a piston mode resonance which occurs when the embankment interval is narrower than the wavelength. Considering the effective use of the harbor waters and the construction cost, the distance between the front and rear curtain walls should not be long, assuming the primary or higher resonance mode. It is desired to suppress the width to about the width.

[0005]

In the case of the conventional double curtain breakwater, transmitted waves can be reduced as compared with the case of a single curtain breakwater, but the drafts on the front and rear curtain walls are the same, so that the draft is the same. There is a problem that the effect of reducing the reflected wave cannot be expected to a great extent. SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and promotes energy dissipation due to vortex formation at the lower end of a curtain wall, and attenuates energy due to transmitted and reflected waves, so that it is in front of a structure such as a breakwater. It is possible to eliminate the danger of disaster due to waves reflected on rafts such as oysters and fishing boats at anchor, and to reduce scouring of sandy beaches due to waves reflected from breakwaters,
A double-draft double curtain wall that can prevent obstacles due to reflected waves, such as the possibility that ships such as small and medium-sized fishing boats or small and medium carriers that enter the port may become difficult to operate due to reflected waves. It is an object of the present invention to provide a reflected wave reducing structure provided with the above.

[0006]

In order to achieve the above object, in the structure for reducing reflected waves by the double-draft type double curtain wall according to the present invention, a front curtain wall on the offshore side and a rear curtain wall on the land side are provided. In the reflected wave reduction structure provided with the double curtain wall in which the distance between the front curtain wall and the rear curtain wall on the land side is smaller than that on the land side, the draft is reduced. In addition, the front curtain wall and the rear curtain wall are attached to a pile driven into the underwater ground. In addition, a floating type levee body having a front curtain wall and a rear curtain wall at intervals, and having a draft of the front curtain wall shallower than a draft of the land side rear curtain wall, is cast on the underwater ground. Up and down along the set pile.

[0007]

1 to 8 show a double curtain type reflected wave reduction structure (breakwater) having a blind type front curtain wall in front of a first embodiment of the present invention. The front steel pipe pile 1 is driven into the submarine ground 3 so that the lower part inclines toward the offshore side, and the rear steel pipe pile 2 is mounted on the submarine ground 3 so that the lower part inclines toward the land side.
The front and rear pair of front steel pipe piles 1 and the rear steel pipe piles 2 are mounted on the underwater ground 3 at intervals in the left-right direction. And the like, and the front PC plate support member 5 having a hollow rectangular cross section is fitted on each of the waterproof / supporting bands 4 in a state of being fitted to the front steel pipe pile 1. The lower end of the front PC plate supporting member 5 is water-stopped by a water-stopping buffer (not shown) provided on the upper surface of the water-stopping / supporting band 4, and the front steel pipe pile is provided. A filler 6 such as mortar is filled between the first and the front PC plate supporting members 5 through holes.
The front PC plate support member 5 is fixed to the front steel pipe pile 1. A lateral slit (gap) across the front side (offshore side) of the front PC plate bearing member 5 adjacent in the left-right direction
13, a plurality of front PC plates 7 made of precast concrete plates such as lightweight concrete are arranged at intervals in the vertical direction, and bolts and reinforcing bars (not shown) through which each front PC plate 7 is inserted. ) Is fixed to the front PC plate support member 5. The first
Although the embodiment has shown the case where the blind is provided, it is also possible to appropriately change to the slit type, the closed type, and the like by adjusting the mounting angle and the mounting position of each front PC plate 7.

A water-stopping / supporting band 4 made of steel or the like is fixed to an intermediate portion of the rear steel pipe pile 2, and a rear-surface PC plate supporting member 8 having a hollow rectangular cross section is attached to the water-stopping / supporting band 4. It is placed in a state fitted to the steel pipe pile 2, and the lower end of the rear PC plate support member 8 is provided with a water-stopping buffer material (not shown) provided on the upper surface of the water-stopping / supporting band 4. The space between the rear steel pipe pile 2 and the through hole of the rear PC plate support member 8 is filled with a filler material 6 such as mortar, and the rear steel pipe pile 2 is filled with the rear PC plate support member. 8 is fixed. From a precast concrete plate such as lightweight concrete, a small vertical gap is provided across the rear surface (land side) of the rear PC plate bearing member 8 adjacent to the left and right direction so as to provide a small slit in the vertical direction. The rear PC plate 9 is fixed to the rear PC plate support member 8 with bolts and reinforcing bars (not shown) inserted therein.

A connecting member 4 made of H-shaped steel is disposed over the upper ends of the front steel pipe pile 1 and the rear steel pipe pile 2 and fixed to the front steel pipe pile 1 and the rear steel pipe pile 2 by welding or bolts. An upper structure 10 having a wave return 10a is embedded so as to embed the upper portions of the plurality of front steel pipe piles 1 and the rear steel pipe piles 2 adjacent in the left-right direction and the connecting member 4. In the upper structure 10, a plurality of precast concrete girder (PC girder) 15, which are open on the front side and the lower side and are closed on the rear side, have a substantially inverted U-shaped cross section and are buried at intervals in the left-right direction.

A plurality of front PC plates 7 arranged at intervals in the vertical direction constitute a blind type front (offshore) curtain wall 11 and are arranged at small intervals in the vertical direction. A plurality of the rear PC plates 9 form a slit-type rear (land side) curtain wall 12, and a lower end level (draft) d1 of the front (offshore) curtain wall 11 from the water surface is the rear surface from the water surface. The side (land side) curtain wall 12 is provided at a level higher than the lower end level (draft) d2 of the curtain wall 12.

As described above, the draft (d1) of the front (offshore) curtain wall 11 and the draft (d2) of the rear (land) curtain wall 12 are made different from each other to make a different draft, that is, the front (open). The draft d1 of the curtain wall 11 (offshore side) is made shallower than the draft d2 of the rear (land side) curtain wall 12 so that waves having a longer wavelength and particularly waves having a shorter wavelength than between the curtain walls 11 and 12 can be prevented. Utilizing the wave resonance in the piston mode due to the folding of the wave between the curtain walls 11, 12, that is, the front and rear curtain walls 11, 1
In addition to utilizing the wave resonance accompanying the piston motion of the wave occurring between the two, a vortex is generated at the lower end of the front side (offshore side) curtain wall 11, and the vortex is formed (in this embodiment,
Energy dissipation (due to vortex formation at each lower end of each front PC plate 7) is promoted, and as a result, transmitted waves and reflected waves can be efficiently attenuated.

FIGS. 9 to 16 show a floating type double curtain type reflected wave reduction structure according to a second embodiment of the present invention, in which a front steel pipe pile 1 and a rear steel pipe pile 2 are front and rear. The pair of front and rear steel pipe piles 1 and the rear steel pipe piles 2 are vertically installed on the underwater ground 3 at intervals in the direction, and the front and rear pair of front steel pipe piles 1 and the rear steel pipe piles 2 are installed on the underwater ground 3 at right and left intervals. I have. A floating body 16 is fitted along the front steel pipe pile 1 and the rear steel pipe pile 2 so as to be movable vertically.

The floating embankment body 16 has a substantially rectangular tubular front lower guide member 17, a substantially tubular rear PC plate lower support and guide member 18, and a hollow lower connecting beam for integrally connecting them at the same level. A lower floating unit 20 composed of a material 19, a substantially square tubular front PC plate intermediate bearing member 22, a substantially tubular rear PC plate intermediate bearing member 21, and a hollow intermediate connecting beam for integrally connecting them at the same level. Floating body unit 24 consisting of a member 23, a front upper floating beam member 25 extending in the left-right direction and having an intermediate portion opened downward and having an inverted U-shaped cross section, and the same cross section arranged in parallel at a distance therefrom A flat ladder-like upper floating unit 28 comprising a rear floating beam 26 having a same shape and a plurality of upper connecting beams 27 having the same cross-sectional shape for integrally connecting them at the same level. Float unit 20, the members constituting the intermediate floating body unit 24 and the upper floating unit 28, the connecting member 29 is inserted over the hole extending in the longitudinal direction provided on these corners (not shown)
And are fixed sideways together.

The lower floating unit 20, the intermediate floating unit 24, and the upper floating unit 28 are connected to each other by a connecting member inserted through a vertical through hole (not shown) provided at a corner thereof. (Not shown)
As a result, the buoyancy is adjusted so that the water surface is located at the intermediate portion of the upper floating unit 28.

A plurality of or a single front PC plate 7 made of a precast concrete plate such as lightweight concrete is attached to the front upper floating beam member 25 over the front side (offshore side) of the front PC plate intermediate bearing member 22 adjacent in the left-right direction. The front PC plate 7 is arranged in a contact state, and the front PC plate 7 is fixed to the front PC plate intermediate support member 22 by bolts and reinforcing bars (not shown) inserted therein.

A rear PC intermediate support member 21 and a rear PC lower support / guide member 1 adjacent to each other in the left-right direction.
A rear PC plate 9 composed of a precast concrete slab such as lightweight concrete is densely vertically arranged over the front side (land side) of the rear PC plate 8 by bolts and reinforcing bars (not shown). It is fixed to the support member 21 and the lower support / guide member 18 of the rear PC plate. The uppermost rear PC plate 9 is in contact with the lower part of the rear floating beam member 26.

A notch is provided in the upper part on the front side of the front PC plate intermediate support member 22, that is, the PC plate 7
The dimension in the front-rear direction is set smaller by the thickness of the
In a state where the plate 7 is arranged, the plate 7 is set to be substantially the same vertical plane as the front side of the front upper floating beam 25. Also,
The front-side sides of the rear PC-plate intermediate support member 21 and the rear PC-plate lower support / guide member 18 are set to be smaller in the front-rear direction by the thickness of each of the PC plates 7 and 9. Are arranged so as to be substantially the same vertical plane as the front side of the rear floating beam 26.

A front side (offshore side) curtain wall 11 is constituted by the front side PC version 7, and a plurality of rear side PC versions 9 arranged in a state of being contacted in the vertical direction are provided on the rear side (land side). A curtain wall 12 is formed, and the front side (offshore side) curtain wall 11 from the water surface is configured similarly to the first embodiment.
The lower end level (draft) d1 is provided at a higher level than the lower end level (draft) d2 of the rear side (land side) curtain wall 12 from the water surface.

A front upper floating beam 25 and a rear floating beam 26
, A front steel pipe pile insertion through-hole 31 and a rear steel pipe pile insertion through-hole 32 are provided at intersections with the upper connecting member 27, respectively. In the hollow grooves of the floating beam members 25 and 26 and the connecting beam members 19, 23 and 27,
The styrofoam 30 is filled with styrofoam 30 having a closed cell or the like so as to impart buoyancy to the floating body 16.

A plurality of guide members 33 are arranged at equal angular intervals around the upper end of the through hole 31 for inserting the front steel pipe pile and the lower end of the through hole 32 for inserting the steel pipe pile. The floating embankment 16 is configured to be vertically slidable along each of the steel pipe piles 1 and 2. With this configuration, the floating levee body 16 can slide up and down while following not only the ebb and flow of the tide but also the vertical movement of the sea surface due to the waves. In addition, it is possible to sequentially reduce the input wave in accordance with the sea level without exerting the wave, and to deal with a wave having a longer wavelength than that between the curtain walls 11 and 12 and particularly a wave having a shorter wavelength. Like curtain wall 1
Utilizing the wave resonance of the piston mode due to the folding of the wave between the first and second curtain walls 12, that is, the front and rear curtain walls 11, 12
In addition to utilizing the wave resonance accompanied by the piston motion of the waves occurring between them, a vortex is generated at the lower end of the front (offshore) curtain wall 11 to promote energy dissipation due to the formation of the vortex, resulting in transmission. Waves and reflected waves can be efficiently attenuated.

A connecting member 4 made of steel H-shaped steel is disposed over the upper end of the front steel pipe pile 1 and the rear steel pipe pile 2 at a position above and away from the floating levee body 16. It is fixed to the steel pipe pile 1 and the rear steel pipe pile 2 by fixing means such as welding or bolts. The connecting member 4 is
The floating type levee body 16 also functions as a stopper when it rises above a design value.

The above-mentioned floating embankments 16 are arranged at intervals in the left-right direction, and are inserted into a pair of front and rear steel pipe piles 1, 2 arranged at intervals in the left-right direction. Steel pipe piles 1, which are arranged according to the level of sea or water surface
2 so as to be slidable in the vertical direction.

In the case of the first embodiment, the case where the blind is provided is shown. However, the blind is not provided, and the closed curtain is not provided with a gap as shown in the second embodiment. It may be a wall, or the front and rear steel pipe piles may be vertically driven into the underwater ground, and the front and rear curtain walls may be arranged in a vertical plane.

By carrying out the present invention, the lower end level (draft) d1 of the front (offshore) curtain wall 11 is changed to the lower end level (draft) d2 of the rear (land) curtain wall 12 from the water surface.
If it is shallower, the draft d1 of the front (offshore) curtain wall 11 will be about 1/4 of the draft d2 of the rear (land) curtain wall 12, depending on the number of PC plates 7 and 9 installed. ~ 3 /
4 may be set.

[Experimental Example] FIG. 17 is a longitudinal sectional side view of the embankment model used in the hydraulic experiment, and shows two front and rear waterproof plywood plates 11a, 12a (front curtain walls 11, 1).
2 (corresponding to 2) is shown on a double curtain wall breakwater model supported on the upper cross beam 36 via cantilever beams 35a and 35b. Was carried out. The draft d2 of the curtain wall was fixed to a draft depth (d2 = 27.5 cm) that would provide an effective transmitted wave control effect when a single curtain plate was used. In addition, the draft d1 of the front wall is changed gradually in three stages (d1 = 27.5 cm, 12 cm, 6 cm) from the same draft depth as the rear wall, and the reflected wave / transmitted wave and the wave height distribution between the curtain walls are measured. Then, the reflection rate, transmittance, energy dissipation rate, and the fluctuation characteristics of the amplitude of the wave height in the embankment due to the wave height at the time of drafting each front wall were grasped. Among these results, FIG. 18 and FIG. 18 show typical examples (in the case of d1 = 12 cm) of the verification results of the reflectance Cr and the transmittance Ct in the case of the breakwater model of the single curtain wall and the breakwater model of the double curtain wall. FIG. 19 shows the result of verification of the energy dissipation rate Ed of the wave, and FIG. 20 shows the result. Note that L is the wavelength of the wave, H1 is the wave height of the incident wave, and fc is the linear resistance coefficient in the equation of motion assuming a virtual fluid in which a resistance proportional to the flow velocity acts in the attenuation wave region. is there. As for the data of the model of the breakwater with a single curtain wall, the data performed under the same scale and the same wave conditions as in this experiment are used. From these results, the reflectivity of the breakwater of the double curtain wall has a characteristic of temporarily decreasing at a specific d2 / L, and the effect of the rear wall is dominant on the transmitted wave. It was found that the target variation was small and fit well with the analysis result. Energy dissipation rate E
d (Ed = 1−Cr × Cr−Ct × Ct) is an experimental value
Both the calculated values correspond to the draft conditions of each front wall, and a specific d
The condition of d2 / L at which the peak is shown at 2 / L and the energy dissipation ratio Ed is at the peak almost coincides with the condition of d2 / L at which the reflectance once drops. Therefore, it can be inferred that the reflectivity once decreases due to an increase in energy dissipation. Further, it can be assumed that the decrease in the reflectivity is directly caused by the increase in the vortex flow at the lower end of the front curtain wall. From these, the following has been found. (1) In a double curtain wall breakwater, the draft of the rear wall is kept at the same level as the breakwater of a single curtain wall, and the shallow draft of the front wall is more effective than the breakwater with a single curtain wall. The reflected wave can be reduced effectively. Also, the effect of reducing transmitted waves is about the same as or slightly higher than the breakwater with a single curtain wall. At this time, the distance between the front and rear curtain walls may be about the width of the superstructure of the conventional breakwater. At this time, if the draft of the front curtain wall is made shallower, the period in which the reflectance can be reduced sequentially shifts to the shorter period side. (2) The reflection wave is reduced by maximizing the vortex flow at the lower end of the front curtain wall due to the resonance of waves in the embankment. The energy dissipation of the wave shows the maximum value under this condition, and the cycle condition shifts to the short cycle side when the draft of the front curtain wall becomes shallow. (3) In the case of the double curtain wall breakwater with the same draft draft on the front and rear curtain walls and the distance between them is equal to the width of the superstructure, the transmitted wave is smaller than that of the single curtain wall breakwater. Although it can be reduced, the effect of controlling the reflected wave can hardly be expected. (4) Using damping wave theory that approximately considers the dissipation effect due to the generation of vortex flow, the effect of reducing transmitted and reflected waves at the breakwater of a double curtain wall under various conditions is roughly estimated. it can.

[0026]

According to the present invention, the draft d1 of the curtain wall 11 on the front side (offshore side) is made shallower than the draft d2 of the curtain wall 12 on the rear side (land side).
For waves having a longer wavelength than between the two, and particularly for waves having a shorter wavelength, the wave resonance in the piston mode due to the folding of the wave between the curtain walls 11, 12 is used, that is, the front and rear curtain walls 11 In addition to utilizing the wave resonance accompanying the piston motion of the waves occurring between the, the vortex is generated at the lower end of the front (offshore) curtain wall 11, and the energy dissipation due to the vortex formation is promoted. Thus, the transmitted wave and the reflected wave can be efficiently attenuated.
Therefore, it is possible to eliminate the risk of disasters caused by waves reflected on rafts such as oysters in front of structures such as breakwaters and fishing boats at anchor, and to reduce scouring of sandy beaches due to waves reflected from breakwaters. It is also possible to eliminate the risk that a boat such as a small or medium-sized fishing boat or a small or medium-sized carrier entering the port may become difficult to operate due to reflected waves.
In addition, by appropriately setting the draft of the front wall for the wave period of the reflected wave, the reflected wave can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a wave-proof structure provided with a double-draft double curtain wall slab according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view of the wavebreak structure shown in FIG.

FIG. 3 is a longitudinal sectional side view cut in the vicinity of a curtain wall slab shown in FIG. 1;

FIG. 4 is a front view of the breakwater structure shown in FIG.

FIG. 5 is a rear view of the wave preventing structure shown in FIG. 1;

FIG. 6 is a sectional view taken along line AA of FIG. 3;

FIG. 7 is a sectional view taken along line BB of FIG. 2;

FIG. 8 is a sectional view taken along line CC of FIG. 2;

FIG. 9 is a perspective view showing a wave-proofing structure provided with a double-draft double curtain wall slab according to a second embodiment of the present invention.

FIG. 10 is a longitudinal sectional side view of the wave preventing structure shown in FIG. 9;

11 is a vertical sectional side view cut in the vicinity of the curtain wall slab shown in FIG. 9;

FIG. 12 is a plan view showing a state in which a large number of wave-breaking structures provided with a double draft wall curtain of a different draft type according to the second embodiment of the present invention are installed.

FIG. 13 is a front view of the breakwater structure shown in FIG.

FIG. 14 is a rear view of the wave preventing structure shown in FIG.

FIG. 15 is a sectional view taken along line AA of FIG. 11;

FIG. 16 is a sectional view taken along line BB of FIG. 11;

FIG. 17 is a longitudinal sectional side view of a bank body model used in a hydraulic experiment.

FIG. 18 is a diagram showing a typical example of verification results of the reflectance Cr in the case of a double curtain breakwater model and a single curtain breakwater model.

FIG. 19 is a diagram showing a typical example of verification results of the transmittance Ct in the case of a double curtain breakwater model and a single curtain breakwater model.

FIG. 20 is a diagram showing a wave energy dissipation rate Ed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front steel pipe pile 2 Rear steel pipe pile 3 Underwater ground 4 Coupling means 5 Front PC plate support member 6 Filler 7 Front PC plate 8 Rear PC plate support member 9 Rear PC plate 10 Upper structure 11 Curtain wall 12 Curtain wall 13 Slit ( Gap) 14 Small slit 15 PC girder (Precast concrete girder) 16 Floating body 17 Lower PC plate lower support member 18 Front lower support member 19 Lower connecting beam 20 Lower floating unit 21 Rear PC plate middle support member 22 Front PC plate Intermediate bearing member 23 Intermediate beam 24 Intermediate floating unit 25 Front upper floating beam 26 Rear floating beam 27 Upper connecting beam 28 Upper floating unit 29 Connecting beam 30 Styrofoam 31 Through-hole for front steel pipe pile insertion 32 Rear steel pipe pile insertion Through-hole 33 Guide member for guide

Continued on the front page (72) Inventor Toru Kono 2-10-11 Hikaricho, Higashi-ku, Hiroshima City, Hiroshima Pref. 10-11 Reconstruction Investigation Design Co., Ltd. (72) Inventor Yoshimitsu Morita 2-1-1, Hirakawacho, Chiyoda-ku, Tokyo Oriental Construction Co., Ltd. F-term (reference) 2D018 BA16

Claims (3)

[Claims] 1. A reflected wave reduction structure comprising a double curtain wall in which an offshore front curtain wall and a land side rear curtain wall are spaced apart from each other, wherein an offshore front curtain wall is provided. The structure for reducing reflected waves by a double-draft type double curtain wall, characterized in that the draft is made shallower than the draft of the rear curtain wall on the land side. 2. The double-drafted double curtain wall according to claim 1, wherein the front curtain wall and the rear curtain wall are attached to a pile driven into the underwater ground. Structure to reduce reflected waves. 3. A floating type embankment having a front curtain wall and a rear curtain wall at an interval, wherein the draft of the front curtain wall is shallower than that of the rear curtain wall on the land side. A structure for reducing reflected waves by a double-draft double curtain wall, which is vertically movably fitted along a stake that has been driven into the building.