JP4951726B2 - 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 breakwaters, coasts, etc., are provided with wave-dissipating blocks stacked on the front (sea side) of the structure (see, for example, Patent Document 1) 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. 15 and 16 has been developed as means for reducing this long-period wave (Patent Document 3).

The structure shown in FIG. 15 is provided with a so-called double-sided slit caisson 3 having barrier walls 1 and 2 each having slit-shaped water-permeable holes formed on the sea side and the land side. 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. 16 includes a water permeable portion 5 having a slit-like opening 5a on the sea side, a water retentive portion 7 disposed on the back side (land side) with a side partition wall 6 therebetween, and water permeable A water-absorbing material layer 8 made of crushed stone and the like stacked in the portion 5, and the water-permeable portion 5 and the water retentive portion through the water-permeable holes 6 a formed in the side partition wall 6 as the water level in the water-permeable portion 5 varies 7, water enters and exits, and water level fluctuations at the sea side of the permeable portion 5 are suppressed.
JP 2000-204528 A JP 2002-146746 A Japanese Patent Laid-Open No. 2005-42528

  15 and FIG. 16 are effective for reducing the long-period wave of the offshore structure. However, in order to obtain a sufficient effect of reducing the quenching, a depth of about 50 m is required. There is a problem that it is difficult to make a smaller structure. In addition, it is conceivable that conventional structures subjected to long-period wave reduction measures are mainly constructed by using a precast concrete structure or the like and sinking it to a construction site. For this reason, the process of manufacturing a structure and the process of installing this in the field are required, and there are problems such as a yard for manufacturing the structure, and time and cost for manufacturing.

  The present invention solves the above-mentioned problems seen in the conventional countermeasures for reducing the long-period wave, and can sufficiently reduce the influence of the long-period wave even on a small scale, and at the construction site. An object is to provide a structure having a long-period wave reduction effect that can be directly constructed.

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. The front wall has a vertical water passage opening in the front wall, and the front wall has a recessed portion that recedes toward the ridge side for each of the water passage ports. the through Mizuguchi is opened in a position, by providing a retarding portion communicating with this behind the vent Mizuguchi, a reduction measure structure period to reduce the height of a few tens of seconds to several minutes long periodic wave The front wall is constructed with a steel sheet pile, steel pipe sheet pile or concrete sheet pile.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the water retentive part on the back surface of the front wall is continuous across the plurality of water inlet positions and does not have a partition wall inside. There is to be.

  According to a third aspect of the present invention, in addition to the configuration of the first aspect, the side partition wall and the peripheral wall are configured such that one water reserving part is formed in the water reserving part corresponding to one water passage. It is in having.

  The feature of the invention described in claim 4 is that the long-period wave reduction countermeasure structure according to any one of claims 1 to 3 is used as a pier, a quay, a seawall or a breakwater. is there.

  In addition, when constructing the long-period wave reduction countermeasure structure according to the present invention under the pier where the ship berths, a floor slab that covers the upper surface of the water retentive part is installed, and a pile for supporting the floor slab A pier, etc., may be installed in the water reserving part, and the berthing wall part for the ship to berth is in front of the front wall, a long period between the lower end and the bottom surface of the water. You may install in the state which gave the space | interval which a wave can move.

  Since the structure according to the present invention is an offshore structure having a water recirculation part connected to the rear of the water inlet, a vortex is generated when a wave rushing to the front wall is led to the water inlet and flows into the water reserving part. Is generated, wave energy loss occurs, and an effective wave reduction effect is obtained.

  Furthermore, since this structure is constructed with steel sheet piles, steel pipe sheet piles, or concrete sheet piles, the front wall and the peripheral wall of the water retentive part are constructed. However, for example, piers, revetments, revetments or breakwaters can be made into long-period wave reduction countermeasure structures without step-by-step processes such as the precast method, and the structure of existing piers and revetments can be used. It can be installed additionally to existing structures. Moreover, this structure can provide a slit from the bottom of the water to the water surface, and can increase the effective length of the slit unlike the caisson structure that requires an upright foundation near the bottom of the water.

  In the present invention, the front wall facing the sea side is formed for each water inlet to form a recessed part that recedes toward the reed, and the water is pushed toward the front wall by providing the water flow opening at a position on the reef side. The energy loss of the wave guided to the front wall and collected at the water inlet and flowing into the water retentive section increases, and an effective wave-dissipating effect is obtained for long-period waves.

  Furthermore, in the present invention, by using as a pier, quay, revetment, or breakwater, long-period waves can be effectively reduced or wave-dissipated even at a small scale, and the oscillation of a ship that touches the offshore structure can be prevented. It is possible to appropriately suppress the cargo handling work to the ship and the like.

  In addition, since the structure is simple and the scale can be reduced, it can be adapted to existing ports. Therefore, it can be suitably applied as a pier, quay, revetment or breakwater.

  In the present invention, the water reserving part on the back of the front wall is continuous across a plurality of the water outlet positions, and has a structure in which no side partition wall is provided, and the water reserving part corresponds to one water inlet. In any case where the side partition wall and the peripheral wall are provided so as to constitute one water reserving part, a substantially equivalent 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.

  A first embodiment of an offshore structure according to the present invention will be described with reference to FIGS. The offshore structure 10 shown in FIG. 1 has a front wall 11 facing the sea side that receives long-period waves, side partition walls 12 and 12 on both sides thereof, and a rear wall 13 on the land side. The front wall 11 is provided with a vertically elongated slit-shaped water passage 14, and a water reserving portion 15 communicating with the water passage 14 is formed at the back of the water passage 14.

  The water reserving part 15 forms a closed space surrounded by a peripheral wall composed of the side partition walls 12, 12 and the rear wall 13, and the front wall 11 serves as a side partition wall that separates the sea side and the water reclaiming part 13. ing. A plurality of water retentive parts 13, 13... Are continuously formed laterally across the side partition wall 12.

  The water inlet 14 is formed to have a length from the sea bottom to a position higher than the highest wave height of a normal long-period wave, and when the long-period wave enters and exits the water-reserving part 15 from the water inlet 14, The air is opened so as to reach a height at which the air in 15 can sufficiently enter and exit. 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 partition wall 12.

  In the structure of FIG. 1, the front wall 11, the side partition wall 12, and the rear wall 13 are constructed by continuously placing sheet piles 41, 41... On the water bottom ground. . The illustrated sheet pile 41 uses a steel pipe sheet pile, and by placing the steel pipe sheet piles in close contact with each other in a row, the vertical surfaces corresponding to the outer diameter dimensions of the steel pipes are formed on the outer surfaces of the walls 11, 12 and 13. Although it has a shape with irregularities in the direction, various sheet piles such as steel sheet piles and concrete sheet piles can also be used, and irregularities may be provided on the outer wall surface by these sheet piles, flat sheet piles It can be used without unevenness.

  When the peripheral wall including the front wall 11 is constructed by the steel pipe sheet pile 41 etc., as shown in FIG. 2, a beam material 42 made of, for example, shaded concrete is provided for connecting the heads of the continuous steel pipe sheet pile 41 etc. And good. By providing such a beam member 42, the heads of the individual sheet piles 41 are connected and integrated with each other, and the stability of the entire peripheral wall including the front wall 11 formed by the sheet piles 41 can be enhanced.

  Since the structure 10 has a wave energy loss when a wave rushing to the front wall 11 is guided to the water inlet 14 and flows into the water retentive part 15, an effective wave-reducing effect can be obtained. Furthermore, since this structure 10 constructs the front wall 11 and the peripheral wall with steel sheet piles, steel pipe sheet piles, or concrete sheet piles, it does not go through the process of pre-constructing a box-shaped concrete structure like the precast method. It is a structure that can construct a long-period wave reduction countermeasure structure directly on site.

  The structure 10 shown in FIG. 1 is formed with a recess 11a in which the central portion of the front wall 11 recedes toward the ridge between the side partition walls 12, 12, that is, corresponding to one water passage hole 14. The water inlet 14 is provided at the most extreme position. 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.

  Further, as shown in FIG. 3, the structure 10 according to the present invention is used for a pier on which a ship can berth, and the upper open portion of the water reserving unit 15 is closed with a top plate 17, and the upper part is used effectively. In such a case, the top plate 17 may be supported by providing a plurality of piles 16, 16.

  Moreover, when using it for the pier which a ship can berth, as shown by a virtual line in FIG. 3, you may install the berthing wall part 18 in the front drooping shape in the further front side of the front wall 11. FIG. In this case, the berthing wall portion 18 is installed in a state where a long-period wave can move between the lower end and the bottom surface of the water.

  The piles 16, 16... Can be ordinary piles such as concrete sheet piles and steel pipe concrete sheet piles. Moreover, what has the height which supports the top plate 17 and the superstructure (illustration omitted) of the said structure 10 should just be used.

  The offshore structure 10 is constructed with a single water reserving section 15 corresponding to a single water inlet 14 as a unit, and a large number of water structures are continuously constructed on both sides according to the length of a quay or a breakwater where a ship is berthed. Anyway.

  Further, the offshore structure 10 to which the present invention is applied is not limited to a pier, a quay, and a breakwater where a ship handling work is performed, and any offshore structure may be used. There is no need for a top plate or superstructure.

Next, performance experiments of the long-period wave reduction countermeasure structure according to the present invention shown in FIGS. 1 to 4 will be described.
1. Experimental device

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

  Tests are conducted for the four cases shown in Table 1 as incident waves.

(2) Experimental model Tests are conducted for the six experimental model cases shown in Table 2. In the experimental model case, in the structure shown in FIG. 1, a structure whose front wall and peripheral wall are made of concrete is a basic shape for comparison, and as an example of the present invention, as shown in FIG. 6 having piles in the part (abbreviated as 6 piles), as shown in FIG. 4 (B), having 8 piles in the water retentive part (abbreviated as 8 piles), the front wall is steel pipe An experiment is performed on a steel pipe sheet pile having an outer diameter of 1 m and an outer surface of the front wall having an uneven shape (abbreviated as a steel pipe sheet pile).

  In FIG. 4 (A), a pile with a diameter of 1 m is used, and a total of six piles of three front rows and three rear rows are provided in two rows at a depth of 6 m and a width of 7.5 m. In B), a total of eight piles of four front rows and four rear rows are provided in two rows at intervals of a depth and a width of 6 m using the same piles.

（３）実験方法

(3) Experimental method

The incident wave shown in Table 1 is given to the above structure model, and the water level in front of the structure is measured using the wave height meters 20d to 20f shown in FIG. taking measurement.
3. Experimental result

  The experimental results are shown in the graphs of FIGS. 6 (A), (B), (C), and (D). 6A is a wave height of 0.5 m and a period of 30 s, FIG. 6B is a wave height of 0.25 m and a period of 30 s, FIG. 6C is 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, it is a small structure with a depth of about 20 m, and the reflectivity is about 0.7 to 0.8 in all cases, and it has effective performance for long-period waves that are multiply reflected. I was able to confirm. If there is a margin in the construction area, increasing the depth further reduces the reflectivity, resulting in an effective structure. Although the reflectivity slightly fluctuated depending on the period and wave height, there was no problem in performance and the effect could be confirmed sufficiently.

  Next, a second embodiment of the long-period wave reduction countermeasure structure according to the present invention will be described with reference to FIGS. The same parts as those in FIG.

  In this embodiment, the water reserving section 15 is continuous over a plurality of water inlets 14, 14... And has a structure in which no partition wall is provided therein. The embodiment shown in FIG. The front wall 11 is constructed with an interval sufficient to form the water retentive part 15 on the front side of the rear wall 13 without providing the side partition wall 12 in FIG. The front wall 11 is provided with water passages 14 similar to those shown in FIG. 1 at intervals, and for each of the water passages 14, a recess 11 a is formed in which the front wall 11 recedes toward the back side, and the center of the recess 11 a is formed. The water inlet 14 is opened in the innermost part.

  Also in this embodiment, the front wall 11 is constructed by a sheet pile 41, and the sheet pile is constructed by placing steel pipe sheet piles in close contact with each other in the same manner as described above, as well as a steel sheet pile, concrete sheet pile, etc. Various kinds of sheet piles can be used, and unevenness may be provided on the outer surface of the wall by these sheet piles, or flat sheet piles may be used and there may be no unevenness.

  Further, similarly to the example shown in FIG. 2, a beam member made of, for example, captive concrete for integrally connecting the heads of the continuous steel pipe sheet piles 41 or the like may be provided. In the case where the structure 10 according to the invention is used for a pier where a ship can berth, the upper open part of the water reserving part 15 is closed with a top plate, and the upper part is used for effective use. A plurality of piles may be provided on 15 to support the top plate. Further, as in the example shown by the phantom line in FIG. 3, the berthing wall portion may be installed in a front hanging shape further forward of the front wall 11.

  In each of the above-described embodiments, the rear wall 13 is constituted by a sheet pile such as a steel pipe sheet pile. However, the rear wall may be a quay wall or a concrete wall for revetment.

Next, a comparative experiment between the embodiment shown in FIG. 1 and the embodiment shown in FIG. 7 of the long-period wave reduction countermeasure structure according to the present invention will be described.
Experimental device

A plane wave water tank having a shape as shown in FIGS. 9A and 9B was used. This water tank was 20 m long, 30 m wide and 1.5 m high.
Table 3 shows the experimental conditions.

  However, the water depth, wave height, and cycle are local scales.

  A regular wave having a depth of 10 m, a period of 30 s, and a wave height of 0.25 m was used on a local scale. The scale was set to 1/100 in consideration of the wavelength of the long period wave. The wave direction to be waved is only perpendicular to the wave plate, and the wave direction with respect to the model is set to 0 ° and 30 ° by changing the installation angle with respect to the wave direction to be waved as shown in FIGS. It was.

Moreover, in order to reduce the influence of a diffraction scattering wave, the side wall was installed beside the 20 m wide wave-making apparatus. Measurement was performed for 60 s from the start of wave making at a sampling frequency of 20 Hz.
Experimental model

As shown in FIG. 10A, a model A-1 with a partition wall (countermeasure) corresponding to the embodiment shown in FIG. 1 and a model A-2 without partition shown in FIG. 7 as shown in FIG. Measures) and an upright wall model B whose front wall is an upright wall with no irrigation part at the back, and the model A-1 with a partition has a space between the side partition walls of 30 m, and the side partition wall part The depth (space between the front wall and the rear wall) was 25 m, the slit opening width was 0.75 m, and the non-partitioned model A-2 was shaped and sized without the side partition walls of the model with partitions.
Wave height meter installation status

As shown in FIG. 11, the wave height meter is installed in the center of the model in the vertical direction with a distance of 30 cm, 20 cm, 50 cm, 50 cm in the order of 30 cm, 30 cm from the front of the model, Parallel to the model, they were placed side by side on a straight line from the center of the model to both ends at an interval of 37.5 cm.
Experimental result

  a. 30m (local scale) wave height distribution from the model

  The wave height distribution of 30 m from the model is as shown in FIG. 12 for the wave direction of 0 °, and as shown in FIG. 13 at the wave direction of 30 °.

For any wave direction, both the models A-1 and A-2 according to the present invention have a higher wave-dissipation effect than the upright wall model B, and the models A-1 and A-2 The same wave-dissipating effect was observed.
b. Reflectance at the center of the model

  The reflectivity at the center of the model was as shown in FIG. 14A for the wave direction 0 ° and as shown in FIG. 14B 5 for the wave direction 30 °.

  In any wave direction, the models A-1 and A-2 according to the present invention have a lower reflectance than the upright wall model B, and the models A-1 and A-2 are both substantially the same. The effect of reducing reflectivity was observed.

It is a long-period wave reduction countermeasure structure which concerns on this invention, Comprising: It is a fragmentary perspective view which shows the example constructed | assembled with the steel pipe sheet pile. It is a long-period wave reduction countermeasure structure which concerns on this invention, Comprising: It is a fragmentary perspective view which shows the example which connected the steel pipe sheet pile head with the beam material. It is a long-period wave reduction countermeasure structure which concerns on this invention, Comprising: It is a fragmentary perspective view which shows the example which has a pile in a water retentive part. In the structure shown in FIG. 3, it is a top view which shows arrangement | positioning of the pile of a water retentive part. It is sectional drawing of a test water tank. It is a graph which shows an experimental result. FIG. 2 is a plan view showing an example of a long-period wave reduction countermeasure structure according to the present invention, in which a side partition wall is not provided in a water retentive part. FIG. 8 is a partially enlarged perspective view of the long-period wave reduction countermeasure structure shown in FIG. 7. It is a top view which shows the display plane wave water tank which is an experimental apparatus, (a) has shown the case where the wave direction is 0 degree, (b) shows the case where the wave direction is 30 degrees. It is a top view which shows the model used for the experimental apparatus shown in FIG. 9, (a) shows model A-1 with a partition wall, (b) has shown model A-2 without a partition. It is a top view which shows the installation condition of the wave height meter in the experimental apparatus shown in FIG. 10 is a graph showing a wave height distribution when the wave direction is 0 ° at a position of 30 m (local scale) from the model obtained by the experimental apparatus shown in FIG. 9. It is a graph which similarly shows the wave height distribution in case of 30 degrees of wave directions. 9 shows the reflectance at the center of the model obtained by the experimental apparatus shown in FIG. 9, where (a) is a graph showing a case where the wave direction is 0 °, and (b) is a graph showing a case where the wave direction is 30 °. It is a longitudinal section which shows the conventional example of a long period wave reduction measure structure. It is a longitudinal cross-sectional view which shows the other conventional example of a long-period wave reduction countermeasure structure.

DESCRIPTION OF SYMBOLS 10 Long-period wave reduction countermeasure structure 11 Front wall 12 Side partition wall 13 Rear wall 14 Water inlet 15 Reservoir part 16 Pile 17 Top plate 18 Quay wall part 20a-20h Wave height meter 21 Current meter 41 Steel pipe sheet pile etc. 42 Beam material

Claims (4)

There is a front wall on the inner surface of the harbor of marine structures such as ship berths, breakwaters, revetments, etc. in the harbor, and a vertical water passage opening is opened in the front wall, and the front wall is provided for each of the water passages. A recess that recedes toward the dredging side is formed, and the water flow port is opened at a position on the dredging side of the recess , and a water reserving unit that communicates with this is provided behind the water flow port, so that the period is several tens. a reduction measure structure to reduce the height of the second to a few minutes long period waves,
A long-period wave reduction countermeasure structure characterized in that the front wall is constructed of steel sheet piles, steel pipe sheet piles or concrete sheet piles.   2. The long-period wave reduction countermeasure structure according to claim 1, wherein the water reserving portion on the back surface of the front wall is a structure that is continuous across a plurality of the water inlet positions and does not have a partition wall inside.   The long-period wave reduction countermeasure structure according to claim 1, wherein the water-reserving part includes a side partition wall and a peripheral wall so that one water-reserving part is configured corresponding to one water passage.   The long-period wave reduction countermeasure structure according to any one of claims 1 to 4, which is used as a pier, a quay, a revetment or a breakwater.

Images