JP4775738B2 - Long-period wave reduction structure - Google Patents

Description

  The present invention is a long-period wave reduction measure for reducing long-period waves by installing it inside a marine structure such as a quay, a pier, a seawall and a breakwater in a harbor where ship handling operations etc. are mainly performed. Concerning structures.

  Conventionally, wave height reducing structures installed on embankments, coasts, etc., are provided with wave-dissipating blocks stacked on the front (sea side) of the structure (see Patent Document 1, for example) A so-called slit caisson (see, for example, Patent Document 2) is known.

  The wave-dissipation by the wave-dissipating work is a structure in which wave-dissipating blocks are stacked on the front part of the structure to form the wave-dissipating work, and energy is lost when the wave passes through the wave-dissipating work. . On the other hand, the wave height reducing structure made of slit caisson has a shielding wall in which a plurality of vertically oriented slit-shaped water-permeable holes are formed, and a water retentive part consisting of sufficient space behind the shielding wall, and the waves are water-permeable holes. It is a structure that causes wave energy loss when passing through the wave and quenches the wave.

  At this time, the faster the flow velocity when passing through the shielding wall, the more the wave energy is attenuated, and the incident wave overlaps with the reflected wave to form a double wave that becomes a belly in the back of the water retentive part. By installing a shielding wall at a position where the maximum node position, that is, the distance between the shielding wall and the back of the water reserving part is ¼ wavelength of the overlapping wave, the most wave-dissipating effect is obtained. It has become.

  A wave that rushes from the sea side includes a long-period wave along with a normal wave, and this long-period wave has a period that is long from several tens of seconds to several minutes. When entering the harbor, this long-period wave is reflected multiple times depending on various conditions such as the shape of the harbor and the position of the quay, and the ship touching the quay may be greatly shaken, which may hinder cargo handling work. In addition, damage such as the mooring line that moored the ship is cut off has occurred.

  In particular, when a large ship (tens of thousands to hundreds of thousands DWT) is moored using a mooring line made of a synthetic fiber having a high breaking strength, the natural frequency of the mooring line is several tens of seconds to several minutes. Since the mooring line and the period band of the long-period wave coincide with each other, the mooring line is resonated to greatly shake the hull.

  For this reason, there is a demand for countermeasures for quenching or reducing long-period waves. However, since long-period waves have a long wavelength of several hundred m to several km, the above-described conventional extinction using a quenching block or slit caisson is required. In order to obtain a sufficient wave-dissipating effect by countermeasures against waves, it is necessary to use a large-scale structure having a depth of 100 m or more for the water reclaiming section and the wave-dissipating work, and there is a problem that the feasibility is poor.

  On the other hand, a long-period wave reduction countermeasure structure having the structure shown in FIGS. 7 and 8 has been developed as means for reducing this long-period wave (Patent Document 3).

  The structure shown in FIG. 7 includes a so-called double-sided slit caisson 3 in which a barrier wall 1 and 2 each having a slit-shaped permeation hole are provided on the sea side and the land side, and the back side of the slit caisson 3 is backed. It has a structure in which a stone layer 4 in which large stones are laminated as a material is provided.

Further, the structure shown in FIG. 8 includes a water permeable portion 5 having a slit-like opening 5a on the sea side, a water reserving portion 7 disposed on the back side (land side) with a partition wall 6 therebetween, and the water permeable portion 5 And a wave-dissipating material layer 8 made of crushed stone or the like stacked on the water-permeable portion 5, and water between the water-permeable portion 5 and the reclaimed water portion 7 through the water-permeable holes 6 a formed in the partition wall 6 as the water level in the water-permeable portion 5 varies. Is designed to suppress the fluctuation of the water level at the sea side of the water permeable portion 5.
JP 2000-204528 A JP 2002-146746 A Japanese Patent Laid-Open No. 2005-42528

  Although the long-period wave reducing means or the wave-dissipating means of the structure shown in FIGS. 7 and 8 are effective, both require a depth of about 50 m in order to obtain a sufficient wave-reducing effect. There is a problem that it is difficult to make a smaller structure.

  The present invention solves the above-mentioned problems observed in the conventional countermeasures for reducing the long-wave wave, and provides a structure capable of sufficiently reducing the influence of the long-cycle wave even on a small scale. With the goal.

The feature of the invention described in claim 1 for solving the conventional problems as described above and achieving the intended purpose is that it is provided on the inner surface of the harbor of a marine structure such as a ship berth quay, a breakwater or a seawall in the harbor. has a front wall, through water outlet on said front wall is open, vent Minakuchi long period wave reduction measures structures intended for long-period waves over periods of 30 seconds with a retarding portion communicating with this behind the Because
The structure is made of a precast concrete in which a front wall surrounding both the water retentive part, a side wall, a peripheral wall composed of a rear wall, and a bottom plate are integrated, and the front wall is formed with a water passage opening in the form of one vertical slit . The structure main body is installed on the bottom of the water, a compartment is provided at the bottom of the water retentive part in the structure main body, and the inside of the compartment is filled with sliding friction.

  According to a second aspect of the present invention, in addition to the structure of the first aspect, a plurality of compartments partitioned by a partition wall are provided at the bottom of the water retentive part of the structure body, and the filling is provided in each compartment. It is in giving.

  The feature of the invention described in claim 3 is that, in addition to the configuration of claim 1 or 2, the height of the compartment of the water reserving part is not more than half of the water depth.

  According to a fourth aspect of the present invention, in addition to the structure of the first, second, or third aspect, the front wall of the structure body is formed so as to recede toward the ridge, and the position on the heel side is the above. The water inlet is open, and the water reserving part is formed further on the heel side of the water inlet.

  According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect, a shielding wall is provided in a state where waves can be transmitted further forward of the front wall of the structure body, and the waves are allowed to flow through the shielding wall. There is to let it be.

  In the present invention, the ship has a front wall on the inner surface of the harbor of a marine structure such as a ship berthing pier, breakwater, revetment, etc. in the harbor, and a vertical water passage is opened in the front wall, behind the water passage. A long-period wave reduction countermeasure structure having a water recirculation part communicating with the structure, wherein the structure is a precast concrete structure in which a front wall, both side walls, a peripheral wall composed of a rear wall and a bottom plate are integrated. An object body is installed on the bottom of the water, and a compartment is provided at the bottom of the water retentive part in the structure body. In doing so, the weight of the entire structure increases and becomes stable, and durability against waves and earthquakes is improved. It is also suitable when the construction site is on the mound or the ground has already been improved.

  Furthermore, in the present invention, a plurality of compartments partitioned by partition walls are provided at the bottom of the water retentive part of the structure body, and the inside of each compartment is provided with the above-mentioned filling, so that the outflow of waves, especially the flow rate with a high flow rate can be achieved. The movement of filling in the vicinity of the water mouth is preferably prevented.

  Furthermore, in the present invention, the height of the compartment at the bottom of the water reclaiming part is less than half of the water depth, so that even if there is a compartment packed in the bottom of the water reserving part, the wave-dissipating effect is not greatly affected.

  Furthermore, in the present invention, the front wall of the structure main body is formed so as to recede toward the ridge, and the water flow port is provided at the position on the heel side so that the wave traveling toward the front wall is As a result, the energy loss of the waves flowing into the water reserving part increases, and an effective wave-dissipating effect can be obtained from the normal wave range to the long-period wave range.

  Furthermore, in the present invention, a wave barrier is provided in a state where the wave can be transmitted further forward of the front wall of the structure body, and the wave is allowed to flow through the barrier wall so that the wave energy loss is stepped. And a high wave-dissipating effect can be obtained.

  Next, an embodiment of a long-period wave reduction countermeasure structure according to the present invention will be described with reference to the drawings.

  The offshore structure shown in FIG. 1 includes a structure body A made of precast concrete, which is submerged on the bottom of the water and installed on the bottom foundation ground. The main body A of the structure closes the peripheral wall composed of the front wall 11 facing the sea side that receives the long-period wave, the side walls 12 and 12 on both sides, and the rear wall 13 on the land side, and the bottom of the portion surrounded by the peripheral wall. The bottom plate 10 is integrally formed in a box shape.

  The front wall 11 of the structure main body A has a vertically elongated slit-shaped water passage 14 formed therein, and a water retentive portion 15 is formed in which the back portion of the water passage 14 is surrounded by the peripheral wall. . In the water reserving part 15, the front wall 11 serves as a partition wall that separates the sea side from the water reserving part 13. Moreover, the upper part of the structure main body A can be covered with a top plate or a superstructure (not shown) as needed.

  The structure main body A is composed of one water reserving section 15 corresponding to one water inlet 14 as a unit, and a large number of structure main bodies A are adjacent to each other according to the length of a quay or breakwater where a ship is berthed. The matching side walls 12 are joined and installed in a continuous arrangement.

  The water inlet 14 is formed in a length from the surface height position of the bottom plate (not shown) to a position higher than the maximum wave height of a normal long period wave. In the illustrated example, the water inlet 14 is provided at the center of the front wall 11, but the water inlet 14 may be provided close to the side wall 12.

  In the illustrated example, the front wall 11 of the structure main body A is formed so as to recede toward the ridge, and the water inlet 14 is provided at a position on the heel side. By forming in this way, waves that have traveled toward the front wall 11 flow along the front wall 11 and are gathered together at the water inlet 14, increasing the energy loss of the waves flowing into the water retentive unit 15, An effective wave-dissipating effect can be obtained from the normal wave region to the long-period wave region.

  1 is formed with a plurality of compartments 18, 18... Partitioned by a partition wall 17 at the bottom of the water reclaiming part 15, and in each compartment 18 with respect to the installation surface of the structure body A. Filling material 16 for increasing the frictional resistance is filled. As the filling material 16, materials such as sand, gravel, crushed stone, and chestnut can be used. By filling the compartment 18 in this way, the structure body A is prevented from sliding to the sea side due to horizontal external force due to earth pressure from the back, and lifting due to external force from the front due to waves. Is done.

  In addition, the wave flowing into the water retentive part is likely to generate turbulence and eddy currents by contacting the filling material 16, so that wave energy loss occurs, and the wave-dissipating effect or wave-reducing effect is improved. It is possible to have a long period wave reduction countermeasure effect.

  Although not shown in the drawing, the upper surface of the compartment 18 may be closed with cast-in concrete, and in this case, an energy reduction effect due to contact with the filling material cannot be expected.

  The size and number of compartments 18 are not limited. It can be determined as appropriate according to the construction site and the wave condition. Further, the height of the partition wall 17 is suitably less than half the depth of water under the experimental conditions described later, and is lower than that provided with the partition wall 17 having a height of about half the depth of water. A structure having a height of the partition wall 17 provides a good result of the wave-dissipating effect.

  As shown in FIG. 3, the wave-dissipating structure of the present invention has a plurality of water recirculation portions 15 arranged side by side through the side walls 12, 12... A structure body B having a configuration partitioned into a plurality of compartments 18 may be used, and a structure in which the plurality of compartments 18 are packed in the inside can be provided.

  As shown in FIG. 4, the structure main body used for the wave-dissipating structure of the present invention is provided with a shielding wall 19 on the front side of the sea side that receives a long-period wave. A large number of openings 30 may be formed, and the front wall 11 may be configured to recede toward the ridge on the rear side of the shielding wall 19. By providing the shielding wall 19 in this way, a water level difference is generated between the shielding wall 19 and the front wall 11 and in the water reserving part 15, and the long-period wave is further reduced by the water level adjusting function.

  The shielding wall 19 has a horizontally long opening, a vertically long one, a short one, and a front hanging shape in which the lower end of the shielding wall is suspended to the intermediate height position of the structure body A. Various things can be adopted in consideration of the place where the ship is berthed and other conditions, such as those of the ship, but the shielding wall 19 is not necessarily required.

Next, a performance experiment of the long-period wave reduction countermeasure structure according to the present invention will be described.
1. Experimental Apparatus As shown in FIG. 5, a two-dimensional hydraulic model experiment was conducted using a water tank having a length of 50 m, a width of 0.6 m, and a height of 1.2 m. The model scale was 1/50 and the water depth was 10 m. In addition, the code | symbols 20a-20h in a figure are a wave height meter, and the code | symbol 21 is an anemometer.
2. Experimental conditions (1) Incident wave The test is conducted on four cases shown in Table 1 as incident waves.

（２）実験モデル
表２に示す６つの実験モデルケースについて試験を行う。尚、該実験モデルケースは、図１に示す構造物において、奥行き２０ｍ、前面水平長さ３０ｍ、前面壁の角度１５度（現地スケール）のものであって、遊水部に隔室が形成されず、中詰めもされていないものを基本形状とし、図１に示すように、遊水部に隔室を有し隔室高さが５ｍと２.５ｍのものをおのおの設け、それぞれの隔室に中詰めし、中詰め上を蓋コンクリートにて閉鎖したものを実施例２，実施例３とした。

(2) Experimental model Tests are conducted for the six experimental model cases shown in Table 2. The experimental model case in the structure shown in FIG. 1 has a depth of 20 m, a front horizontal length of 30 m, and a front wall angle of 15 degrees (local scale), and no compartment is formed in the water reserving part. In addition, as shown in Fig. 1, the non-filled ones have a basic shape, and there are compartments in the reclaimed water section with compartment heights of 5m and 2.5m, respectively. Examples 2 and 3 were prepared by filling and filling the inside with lid concrete.

（３）実験方法
上述構造物モデルに表１に示す入射波を与え、それぞれ場合における図６に示した波高計２０ｄ〜２０ｆを用いて構造物前面の水位を計測するとともに、通水口近傍の流速を流速計２１によって測定する。
３．実験結果
実験結果を図６（Ａ)、(Ｂ)、(Ｃ)、(Ｄ)のグラフに示す。図６（Ａ)は波高０.５ｍで周期３０ｓ、図６（Ｂ)は波高０.２５ｍで周期３０ｓ、図６（Ｃ)は波高０.５ｍで周期６０ｓ、図６（Ｄ)は波高０.２５ｍで周期６０ｓの場合である。

(3) Experimental method The incident wave shown in Table 1 is given to the above structure model, and the water level on the front surface of the structure is measured using the wave height meters 20d to 20f shown in FIG. Is measured by the anemometer 21.
3. Experimental Results The experimental results are shown in the graphs of FIGS. 6 (A), (B), (C), and (D). 6A shows a wave height of 0.5 m and a period of 30 s, FIG. 6B shows a wave height of 0.25 m and a period of 30 s, FIG. 6C shows a wave height of 0.5 m and a period of 60 s, and FIG. This is a case of .25 m and a period of 60 s.

  As shown in FIG. 6, the structures of the present invention have a reflectance of about 0.7 to 0.8 and a depth of 20 m, except in the case of a bulky model case shown in FIG. It is a small structure and shows a sufficient wave reduction effect. In addition, the basic shape having no compartment has the highest wave-dissipating performance, so that the compartment should be as small as possible, and by further increasing the depth to more than 20 m, higher wave-dissipating performance can be obtained.

It is a partial perspective view which is an example of the long-period wave reduction countermeasure structure which concerns on this invention, Comprising: The example which has several compartments in a water retentive part. It is a longitudinal cross-sectional view which shows the installation state in water about the structure of FIG. It is a top view which shows the other example of the structure main body which concerns on this invention. The example which provided the shielding wall in the front surface of the structure main body used for the structure which concerns on this invention is shown, (A) is a top view, (B) is a front view. It is sectional drawing of a test water tank. It is a graph which shows an experimental result. It is a longitudinal cross-sectional view which shows an example of the conventional long-period wave reduction countermeasure structure. It is a longitudinal cross-sectional view which shows the other example of the conventional long-period wave reduction countermeasure structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Long-period wave reduction countermeasure structure 11 Front wall 12 Side wall 13 Rear wall 14 Water inlet 15 Reservoir part 17 Partition 18 Partition 19 Shielding wall 20a-20h Wave height meter 21 Current meter 30 Opening

Claims (5)

A ship berthed quay and breakwaters in port, a front wall in harbor side of marine structures such as revetments, and openings through water outlet on said front wall, provided with a retarding portion communicating with this behind the vent Mizuguchi period 30 seconds or more of a long period wave reduction measures structures intended for long-period waves,
The structure is made of a precast concrete in which a front wall surrounding both the water retentive part, a side wall, a peripheral wall composed of a rear wall, and a bottom plate are integrated, and the front wall is formed with a water passage opening in the form of one vertical slit . The structure body is installed on the bottom of the water, a compartment is provided at the bottom of the water retentive part in the structure body, and a long-period wave is provided in the compartment to increase sliding friction. Reduction measures structure.   2. The long-period wave reduction countermeasure structure according to claim 1, comprising a plurality of compartments partitioned by a partition wall at a bottom of the water retentive part of the structure main body, and filling the inside of each compartment.   The long-period wave reduction countermeasure structure according to claim 1 or 2, wherein the height of the compartment of the water reserving part is not more than half of the water depth.   The front wall of the structure main body is formed so as to recede toward the ridge, the water passage opening is opened at a position on the heel side, and the water retentive part is formed further on the heel side of the water passage opening. The long-period wave reduction countermeasure structure according to claim 1, 2, or 3.   The long-period wave reduction countermeasure structure according to claim 4, wherein a shielding wall is provided in a state where waves can pass further in front of the front wall of the structure body, and the waves are allowed to flow through the shielding wall.

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