JP4759325B2 - Movable breakwater and moving speed adjustment method of movable breakwater - Google Patents

Description

The present invention relates to a movable breakwater that can be moved up and down and a method for adjusting the lifting speed of the movable breakwater.

  Conventionally, for example, in Patent Document 1, the outer diameter of a plurality of steel pipe sheet piles continuously embedded in the seabed ground at a port entrance is slightly smaller than the inner diameter of the steel pipe sheet pile, and the upper portion is closed. An emergency response type breakwater is disclosed in which the inner steel pipe of the steel pipe pile is inserted into each outer steel pipe so as to be movable up and down, and the top end of each inner steel pipe is provided with a compressed air inlet / outlet capable of injecting and discharging compressed air. ing. In this structure, during dredging, the columns of internal steel pipes are buried in the bottom of the sea to completely open the outside of the port and the inside of the port, and in stormy weather, air is sent into each internal steel pipe by a drive mechanism such as a compressor. It is lifted from the bottom of the sea, and the port entrance is closed with the column of internal steel pipes protruding above the sea surface, preventing the incidence of waves and keeping the port calm.

Further, in Patent Document 2, an outer steel pipe of a plurality of sheath pipes extending in the vertical direction on the seabed ground at the port entrance and embedded at intervals, and a hollow portion formed inside the sheath pipe in the vertical direction. An internal steel pipe inserted into an external steel pipe so as to be movable, a film body provided between adjacent internal steel pipes and folded on the seabed, and air supplied from an air supply device is supplied to each internal steel pipe There is disclosed a flexible breakwater composed of a pipe that feeds air inside and an anchor that fixes an end of the membrane on the seabed side to the seabed. In this structure, the columns and membranes of the inner steel pipes are buried on the sea bottom during dredging to completely open the outside of the port and the inside of the port, and in stormy weather, air is sent into each internal steel pipe by the drive mechanism, It is raised from the bottom of the sea, and the port entrance is closed in a state where the film body stretched between the column of inner steel pipes and between the pillars protrudes above the sea surface, thereby preventing the incidence of waves.
Japanese Patent Laid-Open No. 10-37153 JP 2004-116131 A

  However, in the breakwaters described in Patent Documents 1 and 2, in consideration of the diameter error that occurs in the manufacturing process of the outer steel pipe and the inner steel pipe, the deformation of the steel pipe body that occurs when the outer steel pipe is driven on the sea floor, It is necessary to ensure a slightly large gap between the outer steel pipe and the inner steel pipe at the design stage. However, when this gap is increased, the frictional resistance between the outer steel pipe and the inner steel pipe generated when the inner steel pipe is raised and lowered is small, and the raising and lowering speed of the inner steel pipe is increased. Therefore, there is a problem in that parts such as a stopper have to be enlarged and cost is increased. Moreover, in order to ensure the wide space for installing this stopper, there existed a problem that the diameter or length of a steel pipe became long and installation took time.

  Further, in the breakwater described in Patent Documents 1 and 2, a mechanism for lowering the internal steel pipe by releasing compressed air and a valve at the upper end of the internal steel pipe, respectively, and releasing the air in the internal steel pipe to the outside However, since these compressed air inlets and outlets and valves are laid in the sea, there is a problem in that maintenance and management such as inspection takes time and cost.

  Therefore, the present invention has been made in view of the above-mentioned problems, and its purpose is from being buried on a calm seabed such as a dredge to the sea at the time of abnormalities such as during stormy weather or when a tsunami warning is issued. The ascending / descending speed of the levee body can be adjusted at the time of ascent to the projecting state and from the state of projecting to the sea at the time of abnormality to the state where it was buried on the seabed at the time of calm, and easy to maintain A movable breakwater is provided.

In order to achieve the above-mentioned object, the movable breakwater of the present invention penetrates through the foundation concrete provided on the bottom of the sea at a position separating the inside and outside of the port and is vertically inserted into the seabed ground, and the top surface of the foundation concrete is covered. A plurality of external steel pipes that are opened and linearly arranged, an internal steel pipe that is inserted into each external steel pipe so as to be movable up and down, and whose bottom is open and whose upper part is closed, and air supply that is connected to the bottom of each of the external steel pipes A supply pipe and an air supply device for supplying air to each internal steel pipe through the supply pipe, and buoyancy is generated in the internal steel pipe by the supply of air into the internal steel pipe to project it onto the sea surface. In the movable breakwater that partitions the inside and outside of the port,
A plate-like opening ratio adjusting material for adjusting the opening ratio of the gap formed between the outer periphery of the inner steel pipe and the inner periphery of the outer steel pipe is provided detachably on the inner peripheral upper end of the outer steel pipe (First invention).

In the present invention, the inner steel pipe is provided with a detachable adjusting plate on an outer periphery of a lower end portion for suppressing rattling with respect to the outer steel pipe.

The present invention relates to a lifting speed adjustment method of the movable breakwater, is vertically inserted into the seabed through the foundation concrete provided on seafloor position for partitioning the inside and outside of the harbor, the upper surface on the surface of the concrete foundation A plurality of external steel pipes arranged in a straight line with the openings, an internal steel pipe that is inserted into each external steel pipe so as to be movable up and down, and whose bottom is open and whose top is closed, and air supply that is connected to the bottom of each of the external steel pipes A supply pipe and an air supply device for supplying air to each internal steel pipe through the supply pipe, and buoyancy is generated in the internal steel pipe by the supply of air into the internal steel pipe to project it onto the sea surface. In the method of adjusting the lifting speed of the movable breakwater that partitions the inside and outside of the port,
By attaching a plate-like opening ratio adjusting material to the inner periphery of the outer steel pipe, and changing the thickness and width of the opening ratio adjusting material , between the outer periphery of the inner steel pipe and the inner periphery of the outer steel pipe The raising / lowering speed of the internal steel pipe is adjusted by adjusting the opening ratio of the gap formed in the inner steel pipe.

  According to the movable breakwater according to the present invention, it is possible to adjust the lifting speed of the inner steel pipe by adjusting the opening ratio of the gap formed between the outer periphery of the inner steel pipe and the inner periphery of the outer steel pipe. . Therefore, for example, in an emergency where a warning such as a tsunami warning is issued or in a stormy weather where a warning such as a wave warning is issued, the internal steel pipe is quickly raised within a predetermined time determined for each port and the port entrance is closed. This makes it possible to prevent the incidence of waves.

  In addition, since the opening ratio adjusting material is detachably installed at the inner peripheral upper end of the outer steel pipe, the outer steel pipe is deformed by the placement, and the opening ratio adjusting material cannot be installed at a predetermined position or has a predetermined thickness. Even if a problem such as the inability to install the aperture ratio adjusting material occurs, it is necessary to change the installation position or thickness of the aperture ratio adjusting material as appropriate to ensure a predetermined aperture ratio, so that it can be moved up and down at a predetermined lifting speed Is possible. Furthermore, when the aperture ratio adjusting material is worn due to friction or the like, the predetermined aperture ratio can be secured by replacing with a new aperture ratio adjusting material. . Further, by changing the plate thickness and the plate width of the aperture ratio adjusting material, the set value of the aperture ratio can be finely changed, and various ascending / descending speeds can be set.

  By attaching the aperture ratio adjusting material to the outer steel pipe and the adjusting material to the inner steel pipe, the inner steel pipe completely rises, and the rattling caused by the waves generated when standing on the sea surface is suppressed, and the inner steel pipe breaks. It becomes possible to prevent damage such as breakage of the upper end of the external steel pipe.

  Hereinafter, preferred embodiments of the movable breakwater according to the present invention will be described in detail with reference to the drawings. 1 to 3 show a plan view and a front sectional side view, respectively, of the movable breakwater according to the first embodiment of the present invention. As shown in FIGS. 1 to 3, a foundation concrete 2 having a predetermined thickness with the sea bottom GL as the top end is placed in the seabed ground E of the movable breakwater 1 that partitions the inside and outside of the port, and the surrounding area is solidified. Stone 3 is laid. The outer steel pipes 4 penetrating vertically through the foundation concrete 2 and reaching the deep portion of the seabed ground E are densely embedded in a straight line. The bottom of each outer steel pipe 4 is closed by underwater concrete 5 and the upper side is opened to the surface side of the foundation concrete 2, and the inner steel pipe 6 is inserted into each outer steel pipe 4 so as to be movable up and down. Moreover, the bottom face of each internal steel pipe 6 is opened, and the top is closed. Opening ratio adjustment for adjusting the opening / closing speed of the inner steel pipe 6 by adjusting the opening ratio of the gap formed between the outer periphery of the inner steel pipe 6 and the inner periphery of the outer steel pipe 4 at the inner peripheral upper end of the outer steel pipe 4 The material 7 is detachably provided.

  A stopper 8 for determining the lower limit of the braking range at the time of lowering is provided at the lower part of each outer steel pipe 4 while serving as a cradle for storing the inner steel pipe 6. Further, an air supply / exhaust port 14 is provided on the lower end side of the stopper 8, and one end of a steel pipe supply / exhaust pipe 15 for supplying / exhausting the air in the internal steel pipe 6 and an embedding buried in the seabed ground. One end of the air supply / exhaust pipe 16 is connected so as to communicate via the air supply / exhaust port 14. The steel pipe supply / exhaust pipe 15 extends from the supply / exhaust port 14 to the vicinity of the top end face inside the internal steel pipe 6, and the end thereof is fixed by a fixing jig 17. The steel pipe supply / exhaust pipe 15 has a bellows-like mechanism so that it can follow up and down of the internal steel pipe 6 and can be folded. The other end of the buried supply / exhaust pipe 16 is connected to a compressor 9 that is installed on the ground and supplies compressed air and a suction device 11 that sucks compressed air through a switching valve 10. The drive control of the machine 11 and the switching control of the switching valve 10 are performed by the control unit 12. The supply pressure of the compressor 9 is sequentially controlled by the control unit 12 according to the detected pressure of the pressure gauge 13 provided in the buried supply / exhaust pipe 16.

  FIG. 4 is a schematic cross-sectional view of the outer steel pipe 4 according to the present embodiment, and FIG. 5 is a schematic cross-sectional view of the inner steel pipe 6 according to the present embodiment. In this embodiment, for example, a steel pipe having an outer diameter of 1100 mm and an inner diameter of 1076 mm is used for the outer steel pipe 4, and a steel pipe having an outer diameter of 1000 mm and an inner diameter of 976 mm is used for the inner steel pipe 6. However, the dimensions of the outer steel pipe 4 and the inner steel pipe 6 are not limited to this, and the outer diameter and inner diameter of the outer steel pipe 4 and the inner steel pipe 6 may be appropriately designed according to the field conditions.

  As shown in FIG. 5, the inner steel pipe 6 is provided with a detachable adjusting plate 21 at the lower end of the outer periphery for suppressing the shakiness caused by waves that are generated when the steel pipe 6 is completely raised and standing at a certain height on the sea surface. In the present embodiment, a plurality of adjustment plates 21 are attached at intervals along the outer periphery of the internal steel pipe 6.

  FIG. 6 is a plan view of the external steel pipe to which the aperture ratio adjusting material 7 according to this embodiment is attached, and FIG. 7 is a cross-sectional view of the external steel pipe to which the aperture ratio adjusting material 7 according to this embodiment is attached. As shown in FIGS. 6 and 7, the opening ratio adjusting member 7 is detachably installed at the upper end portion of the inner periphery of the outer steel pipe 4 with a fixture 18. Further, on the upper portion of the fixture 18 of the aperture ratio adjusting material 7, a sealing material 19 that prevents intrusion of foreign matter such as sand and stone into the gap and whose tip is in contact with the outer peripheral surface of the internal steel pipe 6, and this sealing material 19 and the protective material 20 that protects the aperture ratio adjusting material 7 are detachably installed.

The ascending / descending speed of the internal steel pipe when the aperture ratio adjusting member 7 is attached can be calculated by the equations (1) and (2) using the parameters shown in FIG. 8 as parameters. That is, as shown in FIG. 8, the weight of the internal steel pipe is m _G , the top end depth of the internal steel pipe 6 is Z _G , the difference between the water pressure Pout acting on the top end position of the internal steel pipe 6 and the air pressure Pin is P, and the internal steel pipe 6 when the weight W at the top end position of the steel tube 6 is A _Gi , the cross-sectional area of the internal steel pipe 6 is A _Gi , the water level in the internal steel pipe 6 is Z _WG , and the opening ratio adjusting material 7 is attached between the external steel pipe 4 and the internal steel pipe 6. If the cross-sectional area of the gap is A _P , and the flow rate of water passing through the gap when the opening ratio adjusting material 7 is attached between the outer steel pipe 4 and the inner steel pipe 6 is v _P , the equation of motion of the inner steel pipe 6, the inner The water level fluctuation formulas in the steel pipe 6 are the formulas (1) and (2), respectively.

In FIG. 8, in order to illustrate the parameters used in the equations (1) and (2), the illustration of the steel pipe supply / exhaust pipe 15, the fixing jig 17, and the like is omitted.
m _G · (d ² Z _G / dt ² ) = P−W (1)
A _Gi · (d ² Z _WG / dt) = A _P v _P (2)

The top height of the inner steel pipe 6 and the water level in the inner steel pipe 6 at each time are calculated by the expressions (1) and (2). Here, the cross-sectional area A _P of the gap when fitted with a numerical aperture adjusting material 7 between the outer steel pipe 4 and the inner steel tube 6, the aperture ratio adjustment from the cross-sectional area of the gap portion between the outer steel pipe 4 and an inner steel pipe 6 It is calculated in advance by reducing the cross-sectional area of the material. Further, the flow velocity v _P of water passing through the gap when the opening ratio adjusting member 7 is attached between the outer steel pipe 4 and the inner steel pipe 6 flows from the sea into the inner steel pipe 6 using Bernoulli's theorem. In this case, when flowing from the internal steel pipe 6 into the sea, the values are calculated in advance from the equations (3) and (4), respectively.
Here, E ₀ : Reference specific energy, z _e : Entrance loss coefficient of the water passage (z _e = 0.5), z _o : Exit loss coefficient of the water passage (z _o = 1.0), f: It is a friction loss coefficient. And the friction coefficient f of a water flow part is computed from Formula (5) using the roughness coefficient n of Manning.
Here, n is the Manning roughness coefficient, R _{p is} the diameter of the water passage (R _p = A _p / P _p ), and P _p is the wet side of the water passage.

Further, water communicating portion total length L _p is calculated from the equation (6).
_{L p = Z b - (Z} G -H G) (6)
Here, z _b: sea bottom (outer tube crest elevation), k _m: permeability of sediment penetration preventing film, L _m: is the thickness of the sediment penetration preventing film.

  FIG. 9 shows a change in the top height of the internal steel pipe 6 and a change in the water level in the internal steel pipe 6 at each time calculated by the expressions (1) and (2). As shown in FIG. 9, from the top end height of the inner steel pipe 6 at each time calculated by the formula (1) and the formula (2), the sea level after the top end of the inner steel pipe 6 starts to rise (T1). The elapsed time (T2-T1) until it completely protrudes (T2) is set within a predetermined time set for each port. Here, when the elapsed time (T2-T1) calculated from the equations (1) and (2) is longer than the predetermined time set for each port, the plate thickness of the aperture ratio adjusting material 7 The width of the plate is changed, and the flow rate of water passing through the gap between the inner steel pipe 6 and the outer steel pipe 4 is changed so that the inner steel pipe 6 can completely protrude above the sea surface within a predetermined time. ) And formula (2) to calculate again.

  In the present embodiment, the aperture ratio adjusting material 7 is, for example, a sector shape in which the arc length is 28 ° from the center of the outer steel pipe 4, the thickness is 28 mm, and the six aperture ratio adjusting materials 7 are included in the outer steel pipe 4. The opening ratio of the gap formed between the outer steel pipe 4 and the inner steel pipe 6 is set to 67% by being affixed radially around the circumference.

10-16 is a figure which shows the raising / lowering state of the breakwater which concerns on this embodiment.
As shown in FIG. 10, in the case of dredging, the inner steel pipe 6 is lowered and stored in the outer steel pipe 4 so as to be at the same level as the sea bottom GL and completely open to the outside of the port and the inside of the port. Vessels sailing on and off can freely enter and leave the port.

  As shown in FIG. 11, when the state of dredging shifts to a stormy season and the sea swell becomes strong, various kinds of transmission means such as an electric bulletin board, ship radio, and harbor broadcasting are used for ships navigating in the vicinity. The warning that the inside of the port is closed is performed, and after confirming the safety of the ship, the compressor 9 is driven by the control unit 12 (not shown), and the air from the compressor 9 can be supplied to the inner steel pipe 6 When the switching valve 10 is switched to inject compressed air into the inner steel pipe 6, the seawater in the inner steel pipe 6 is discharged into the sea through the gap between the inner steel pipe 6 and the outer steel pipe 4. When discharged into the sea, sediments such as sand and stone deposited between the bottom of the sea and the top surface of the inner steel pipe 6 are ejected together with the sea water. In the present embodiment, for example, the flow velocity at which seawater flows toward the sea through the gap between the inner steel pipe 6 and the outer steel pipe 4 is calculated as 0.2 m / sec from the expressions (1) and (2). .

  When the air injection is continued, as shown in FIG. 12, when the internal steel pipe 6 gains buoyancy and rises, seawater flows into the gap between the internal steel pipe 6 and the external steel pipe 4 from the sea, The water level also rises. As the internal steel pipe 6 rises and the steel pipe supply / exhaust pipe 15 also expands, one end of the steel pipe supply / exhaust pipe 15 is always kept in the vicinity of the top end surface of the internal steel pipe 6. In the present embodiment, for example, the flow rate at which seawater flows through the gap between the inner steel pipe 6 and the outer steel pipe 4 toward the lower side of the outer steel pipe 4 is 0.2 to 2 from the expressions (1) and (2). Calculated as 0.0 m / sec.

  As shown in FIG. 13, when the internal steel pipe 6 is completely raised, the internal steel pipe 6 stands up on the sea and receives the incoming waves to keep the harbor in a calm state. In this state, there is no flow of water between the sea and the inside steel pipe 6.

  When it is determined that the stormy weather condition has subsided and the sea is crawling, an alarm to open the harbor is issued, and the suction unit 11 is driven by the controller 12 as shown in FIG. When the switching valve 10 is switched so that the air in the steel pipe 6 can be sucked and the compressed air in the inner steel pipe 6 is sucked, the column of the inner steel pipe 6 loses buoyancy and begins to descend into the outer steel pipe 4. In this state, only the air pressure in the internal steel pipe 6 is reduced, and there is no flow of seawater between the sea and the internal steel pipe 6.

  When the air suction is continued, as shown in FIG. 15, when the internal steel pipe 6 loses buoyancy and descends, the seawater in the internal steel pipe 6 is discharged into the sea through the gap between the internal steel pipe 6 and the external steel pipe 4. The In this embodiment, for example, the flow velocity at which seawater flows toward the sea through the gap between the inner steel pipe 6 and the outer steel pipe 4 is calculated as 0 to 1.5 m / sec from the expressions (1) and (2). Is done.

  As shown in FIG. 16, the inner steel pipe 6 is completely lowered and stored in the outer steel pipe 4, an open water area is formed, and the ship can freely enter and leave. In this state, there is no flow of water between the sea and the inside steel pipe 6.

  According to the above embodiment, by adjusting the opening ratio of the gap formed between the outer periphery of the inner steel pipe 6 and the inner periphery of the outer steel pipe 4, it is possible to adjust the lifting speed of the inner steel pipe 6. . For example, during a stormy weather when a warning such as a wave warning is issued, it is possible to quickly raise the internal steel pipe 6 within a predetermined time determined for each port and close the port entrance to prevent the incidence of waves. .

  Further, the opening ratio adjusting material 7 is detachably installed on the inner peripheral upper end portion of the outer steel pipe 4, so that the outer steel pipe 4 is deformed by placing and the opening ratio adjusting material 7 cannot be installed at a predetermined position, or Even if a problem such as the inability to install the aperture ratio adjusting material 7 having a predetermined thickness occurs, the installation position or thickness of the aperture ratio adjusting material 7 can be appropriately changed to ensure the predetermined aperture ratio. It is possible to move up and down at a speed. Further, when the aperture ratio adjusting material 7 is worn due to friction or the like, it is possible to ascend and descend at a predetermined ascending / descending speed because a predetermined aperture ratio can be secured by replacing with a new aperture ratio adjusting material 7. It becomes.

  Further, by changing the plate thickness and the plate width of the aperture ratio adjusting material 7, the set value of the aperture ratio can be finely changed, and various ascending / descending speeds can be set.

Further, by attaching the aperture ratio adjusting material 7 to the outer steel pipe 4 and the adjusting material 21 to the inner steel pipe 6, the inner steel pipe 6 is completely raised and caused by waves generated when standing at a certain height on the sea surface. Sticking is suppressed, and damage such as breakage of the inner steel pipe 6 and breakage of the upper end portion of the outer steel pipe 4 can be prevented.
In addition, by installing the steel pipe supply / exhaust pipe 15 from the bottom of the outer steel pipe 4 to the vicinity of the upper end surface in the inner steel pipe 6, maintenance work such as a compressed air inlet / outlet and a valve in the sea is not required. Management becomes easy.

  In the present embodiment, the thickness of the aperture ratio adjusting material 7 is 28 mm, but is not limited to this. For example, as shown in FIGS. 17 and 18, the thicknesses are 9 mm and 19 mm, respectively. In short, in order to obtain an opening ratio that allows the internal steel pipe 6 to be lifted and lowered during a predetermined lifting time determined for each port, the plate thickness is appropriately changed.

  In the present embodiment, in order to set the aperture ratio to 67%, the width of the arc length of the aperture ratio adjusting member 7 is 28 ° and the thickness is 28 mm. However, the present invention is not limited to this. 19, the width of the arc length of the aperture ratio adjusting member 7 is 41 °, the thickness is 19 mm, and the width of the arc length of the aperture ratio adjusting member 7 is appropriately set so that the aperture ratio becomes a predetermined value. The thickness may be changed.

  Furthermore, in this embodiment, the width of the arc length of the aperture ratio adjusting material 7 is 28 °, and the six aperture ratio adjusting materials 7 are attached to the inner circumference of the outer steel pipe 4 so as to be radially spaced. However, the present invention is not limited to this, and a method of sticking one ring-shaped aperture ratio adjusting material 7 to the inner periphery of the outer steel pipe 4 may be used.

It is a top view of the movable breakwater which concerns on 1st embodiment of this invention. It is a front view of the movable breakwater which concerns on 1st embodiment of this invention. It is a sectional side view of the movable breakwater which concerns on 1st embodiment of this invention. It is a schematic sectional drawing of the external steel pipe concerning this embodiment. It is a schematic sectional drawing of the internal steel pipe which concerns on this embodiment. It is a top view of the external steel pipe which attached the aperture ratio adjustment material which concerns on this embodiment. It is sectional drawing of the external steel pipe which attached the aperture ratio adjustment material which concerns on this embodiment. It is a schematic sectional drawing of the breakwater which described the parameter for calculating the raising / lowering speed of the internal steel pipe concerning this embodiment. It is a figure which shows the change of the top end height of the internal steel pipe in each time calculated by Formula (1) and Formula (2) which concern on this embodiment, and the water level in an internal steel pipe. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is explanatory drawing which shows the raising / lowering state of the breakwater which concerns on this embodiment. It is a figure which shows an example of the aperture ratio adjustment material from which board thickness differs which concerns on this embodiment. It is a figure which shows an example of the aperture ratio adjustment material from which board thickness differs which concerns on this embodiment. It is a figure which shows an example of the aperture ratio adjustment material from which the board thickness and board width which concern on this embodiment differ.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Movable breakwater 2 Foundation concrete 3 Root-hardening stone 4 External steel pipe 5 Underwater concrete 6 Internal steel pipe 7 Opening ratio adjustment material 8 Stopper 9 Air compressor 10 Switching valve 11 Suction machine 12 Control part 13 Pressure gauge 14 Supply / exhaust port 15 Supply in steel pipe Exhaust pipe 16 Buried air supply / exhaust pipe 17 Fixing jig 18 Mounting tool 19 Sealing material 20 Protective material 21 Adjustment material E Submarine ground WL Sea surface GL Sea bottom

Claims (3)

A plurality of external steel pipes that pass through the foundation concrete provided on the bottom of the sea at a location that divides the inside and outside of the port, are vertically inserted into the seabed ground, and are arranged in a straight line with the top surface opened to the surface of the foundation concrete. An internal steel pipe that is inserted into the steel pipe so as to be movable up and down, and whose bottom is open and whose top is closed, an air supply pipe connected to the bottom of each external steel pipe, and each internal steel pipe is supplied through the air supply pipe. A movable breakwater that divides the inside and outside of the harbor by generating buoyancy in the internal steel pipe and projecting it on the sea surface by supplying air into the internal steel pipe,
A plate-like opening ratio adjusting material for adjusting the opening ratio of the gap formed between the outer periphery of the inner steel pipe and the inner periphery of the outer steel pipe is provided detachably on the inner peripheral upper end of the outer steel pipe This is a movable breakwater. 2. The movable breakwater according to claim 1, wherein the inner steel pipe includes a detachable adjusting plate on an outer periphery of a lower end portion for suppressing rattling with respect to the outer steel pipe. A plurality of external steel pipes that pass through the foundation concrete provided on the bottom of the sea at a location that divides the inside and outside of the port, are vertically inserted into the seabed ground, and are arranged in a straight line with the top surface opened to the surface of the foundation concrete. An internal steel pipe that is inserted into the steel pipe so as to be movable up and down, and whose bottom is open and whose top is closed, an air supply pipe connected to the bottom of each of the external steel pipes, and an air supply to each internal steel pipe through the air supply pipe In the method for adjusting the ascending / descending speed of the movable breakwater that partitions the inside and outside of the port by generating buoyancy in the internal steel pipe and projecting it on the sea surface by supplying air into the internal steel pipe,
By attaching a plate-like opening ratio adjusting material to the inner periphery of the outer steel pipe, and changing the thickness and width of the opening ratio adjusting material , between the outer periphery of the inner steel pipe and the inner periphery of the outer steel pipe A method for adjusting the lifting speed of the movable breakwater, wherein the lifting speed of the inner steel pipe is adjusted by adjusting the opening ratio of the gap formed in the inner wall.