JP3333431B2 - Construction body for sand drift control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction for preventing sand erosion and improving a beach environment by guiding sand drift in the sea in a predetermined direction such as a shore direction or an erosion area.

[0002]

BACKGROUND OF THE INVENTION The problem of coastal erosion is exacerbated by the recent rapid decline in sediment discharge from rivers, which has been a major source of sediment transport. In addition, coastal erosion due to land reclamation and the construction of artificial islands in large cities, which are part of port development projects, is unavoidable, and urgent measures are needed to address the shortage of sand resources and future coastal development. Have been.

[0003] As one means for eliminating such coastal erosion, the use of waves of seawater as a driving force prevents sand drift in seawater from flowing offshore and draws it to the coast, In some cases, sand movement is controlled, for example, by transporting sand deposited in the sea to the shore. This is based on the phenomenon that the wavy sand generated on the sandy bottom of the sea by the subsurface flow of waves restrains the flow of sediment, that is, the flow of subsurface flow including drifting sand. Sand drift is included in the flow toward the coast by the action of strained sand bricks that are distorted to the side.

[0004] One of the applicants of the present invention has proposed and made an application as Japanese Patent Application No. 3-28965 and an application as Japanese Unexamined Patent Application Publication No. 4-269207 as a device capable of controlling the drifting sand flow due to such strained sand. Some have been published.
In this method, blocks having a shape approximating the waveform of a distorted sand brick are prepared, and these blocks are installed on the seabed with the position where the deflection side of the distortion faces offshore.

[0005] By disposing a block having a shape similar to the shape of the distorted sand brick on the sea floor, the bottom layer current along the surface of the block from offshore to the coast during one cycle in which the peaks and valleys of the seawater pass is reduced. Can be generated. Therefore, for example, if the sand deposited offshore moves by waves or currents and reaches the block installation area, it will be carried to the shore side by the flow of bottom flow, thereby preventing erosion and offshore It is possible to collect the sand deposited on the coast to the coast.

[0006]

In the case of using the distorted sand-brick-shaped blocks according to the prior application, the blocks themselves are restrained by overlapping the ends facing the shore and the offshore with each other. Thus, a construction body having a so-called distorted sand-brick waveform obtained by distorting a sine wave in an offshore direction by a continuous profile of a block surface is obtained.

However, even if each block has a large weight of about 10 tons, if a typhoon or the like repeatedly receives large waves or high waves, it is inevitable that the blocks will be displaced. Therefore, if one block is misaligned,
Under the influence, the position of the next block also shifted,
This misalignment spreads over the whole, and eventually the pattern shape of the distorted sand brick is broken.

In order to prevent such a displacement, the block may be anchored to the seabed, for example, and fixed. However, it is important that the alignment of the entire block be properly maintained, as the blocks can be constrained and transported to the shore side by the shape of the distorted sand bricks rather than on its own, rather than on its own. Depending on whether anchoring is good or bad for each block, it is unavoidable that the rows are disturbed by waves and the pattern of the distorted sand bricks is unavoidable. In order to anchor the block to the seabed, the installation area is once dredged, the foundation is built in the seabed, and then fixed by anchors, which is inconsistent with the current situation in terms of construction cost and construction period.

[0009] Further, in the earlier application, the shape of the block for promoting the movement of the sand on the shore side only discloses the basic shape of distorting the sinusoidal waveform to the offshore side. For example, the wavelength and amplitude of seawater waves are affected by wind and pressure, and some of them have large swells, and cannot be identified within a certain range. Since the purpose is to recover from offshore, etc., it is possible to design the system to correspond to typical values throughout the year. The term "representative" here means, for example, the magnitude of a high wave that strikes several times a year or a wave selected for the purpose of coastal conservation. In other words, in the earlier application, there is no idea of trying to optimize the pitch and size of the distortion deviation part by grasping the wavelength of the wave of such a typical value, and when actually installing it on the seabed. There is still some uncertainty about how effective the sand transfer is.

As described above, in the conventional arrangement of blocks to which the distorted sand brick is applied, misalignment between the blocks occurs, the pattern of the distorted sand brick collapses, and the function of transporting the sand is deteriorated. At present, it cannot be said that optimum efficiency suitable for such conditions has been obtained.

The problem to be solved in the present invention is that, when installed along the shore, each of the blocks can maintain the function of transporting sand without distorting the pattern of the sand erosion and high sand transport efficiency. It is to provide a construction body for use.

[0012]

According to a first aspect of the present invention, there is provided a construction for controlling drifting sand, comprising: a deformable sheet following the seabed; and a plurality of blocks joined to the sheet and arranged uniformly. Blocks when you arrange these sandy
And the sine wave being displaced in one of the wavelength direction so as to approximate the sand Ren formed on the shore of the seabed sand a shape to draw a continuous surface profile, yet one strain sand goodwill surface profile as the profile of the said block Is the wavelength of λ, and the total amplitude of the water particle orbital motion along the surface profile of the block is d ₀
, The value of d ₀ / λ is set to approximately 1.7.

In such a configuration, the block includes a seating portion formed on the lower surface side and joined to the seat, and an inclined surface formed on the upper surface side and inclined upward toward one end in the arrangement direction. In addition, the arrangement direction of the blocks is the same as the inclination direction of the inclined surface, and the ends of the blocks in the arrangement direction of the adjacent arrangement are vertically overlapped with each other, and the adjacently arranged blocks can be bent with the overlapped portion as a fulcrum. It can be a relationship. In this case, a hinge portion having a substantially semicircular vertical cross-sectional shape is provided on the upper surface on the base end side of the inclined surface, and the lower surface on the distal end side of the inclined surface covers the hinge portion and rotates between the sliding surfaces. May be provided, and these hinge portions and the hinge receiving portions may be overlapped portions of the adjacent arrangement blocks.

[0014] block, in conditions where the angle between the traveling direction of the wave is included in a certain range, the bottom layer flow seawater regardless traveling direction of the wave in the direction perpendicular to the peaks of distortions sand Ren It can have a controllable surface profile and size.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of blocks used in a construction for controlling sand drift according to the present invention and an arrangement thereof and connection by sheets. FIG. 1 (a) shows the block alone and FIG. ) Indicates the positional relationship between the arranged blocks and the sheet.

In the figure, a concrete block 1 is shown.
A seating portion 1a having a uniform flat surface except for one end side,
Inclined surface 1 having a constant inclination angle with respect to seating portion 1a
b are formed on the upper and lower surfaces. A hinge portion 1c having a substantially upper half having a circular cross section is formed at one end in the direction in which the seating portion 1a and the inclined surface 1b intersect, and the adjacently arranged block is formed at one end in the opposite direction. A curved hinge receiving portion 1d that covers the hinge portion 1c is formed by denting. The head 1e, which is closer to the tip end than the hinge receiving portion 1d, has a thickness such that the head 1e covers the inclined surface 1b when joined to the adjacent block 1 and rises sharply from the inclined surface 1b.

Each block 1 is a unit in which both ends in the width direction are arranged adjacent to each other in a posture shown in FIG. 2B and integrally joined by a sheet 2, and the unit is carried to the site and constructed. I do. The seat 2 is a non-vulcanized rubber sheet having a strength enough to withstand the load of the plurality of blocks 1 and elastically deformable, and has an adhesive layer for firmly adhering to the seating portion 1 a of the block 1. It shall be formed on the surface.

FIG. 2 is a schematic view showing the arrangement of the units of the block 1 in which the sheets 2 are integrally joined. The blocks 1 in each row held on each sheet 2 have the hinge receiving portions 1d having the hinge portions 1c. It is arranged to cover on. The hinge 1c and the hinge receiver 1
Due to the curved surface shape of d, the adjacent blocks 1 are connected to each other so that they can be bent. Therefore, the block 1 bonded to the sheet 2 which is elastically deformed freely can be arranged according to the seabed topography of the beach to be installed.

As shown in FIG. 2, the block 1 is restrained by the overlap of the hinge portion 1c and the hinge receiving portion 1d and their engagement, so that the hinge portion 1c faces the shore and the head 1e faces the offshore. They are arranged as postures. That is, when the blocks 1 are arranged, the head 1e of the shore-side block 1 covers the inclined surface 1b of the adjacent offshore-side block 1, and these heads 1e and the inclined surface 1b
A trough 3 is formed at the boundary between the two and has a sharp V-shape. Therefore, when the blocks 1 are arranged from the shore to the offshore in a posture as shown in FIG. 2, the peaks at the tip of the inclined surface 1b and the valleys due to the trough 3 between the head 1e and the inclined surface 1b are repeated. Is formed.

The wave profile obtained by the arrangement of the blocks 1 approximates the shape of the sand brick formed on the seabed sand on the sandy beach. The effect on the behavior will be described with reference to FIG.

FIG. 3A shows a waveform of a strained sand brick.
The term “distorted sand brick” is defined in this specification as a surface shape of sand that draws a waveform profile obtained by distorting a sine wave having a wavelength λ and a wave height η shown in the figure in an offshore direction. Then, the arrangement of the blocks 1 shown in FIG. 2 is similarly arranged in the direction orthogonal to the drawing (see FIG. 1B).
It shall be called a strained sand mat.

FIG. 3B shows the behavior of sand drift when waves pass from the offshore side to the shore side, that is, from right to left in the figure, on the strained sand brick mat.

On the sea bottom, the water particles reciprocate within the range of the full amplitude d _o of the orbital motion of the water particles according to the scale and depth of the water, and when the trough of the wave passes, as shown by the thick line in the figure. Offshore phase flow occurs. And, in the part where the sand brick faces the offshore and is steep (corresponding to the trough 3 in FIG. 2), it becomes a flow field in the steep dent facing the top of the sand brick. The steep surface at the top acts like a small weir, which generates a strong swirl in the swirling direction indicated by the arrow.

In the process in which the eddy current in the sand turbulence is excited and evolves, the seawater flowing along the sand porcelain going from the shore to the offshore is resisted by the eddy current at the stagnation point. At the same time, the eddy current is absorbed by the eddy current, so that it tends to stay near the eddy current and hinder the flow of the flow to the offshore. Then, the interaction between the vortex and the steep profile (corresponding from the bottom of the trough 3 to the head 1e in FIG. 2) from the bottom of the portion corresponding to the trough of the strained sand and the vortex causes the water containing the vortex to flow. A flow force is generated in the lump in the direction indicated by the arrow f in the figure. As described above, in the recessed portion in the strained sand, the flow from the coast side to the offshore side stagnates, and at the same time, the flow force in the direction of the arrow f pointing toward the coast side is caused.
A strong flow toward the shore along the surface of the strained sand, that is, a bottom flow, will be promoted.

On the other hand, when the peak of the wave passes, the slope from the top to the shore of the strained sand has a gentle slope, so that flow separation along the surface of the strained sand and generation and growth of a vortex flow. Ends in a minute.

As described above, during one cycle of the wave, a bottom layer flow along the surface of the strained sand is generated as a forced flow toward the shore. Therefore, if the distorted sand mat is installed on the sea floor, for example, if the sand deposited offshore moves by waves or currents and reaches the distorted sand mat,
This sand can be transported to the shore by forced flow to the shore.

As described above, with the profile of the corrugated strained sand brick shown in FIG. 3, the sand drifting or the sand flowing from the offshore can be transferred to the shore by the wave of the seawater. Therefore, block 1 as shown in FIG.
With this arrangement, a profile approximating a distorted sand brick can be made on the seabed, and it is possible to transport drifting sand and the like to the shore by the same principle.

FIG. 4 is a schematic diagram showing, in order, the arrangement of the blocks 1 and the movement of the sand drift due to the flow of the bottom flow along each block 1 due to the movement of the waves. The behavior of the bottom flow and the movement of the sand drift are described in FIG. According to the same principle as the ones. Here, as the wave proceeds to a place where the water depth is shallower, the influence of the bottom surface becomes stronger, and the waveform is distorted, so that the effect of the distorted sand brick is reduced. On the other hand, the present inventors have learned from the knowledge that the condition of H / h <0.5 is suitable as the application water depth of the strained sand brick. Here, H is the wave height and h represents the water depth.

FIG. 5 is a schematic view of an example of installation on a sandy beach, in which the heads 1e of each block 1 are arranged in a posture facing offshore. By arranging such a group of Block 1 arrangements at appropriate locations on the coast,
Since drifting sand and suspended sediment of offshore sediment can be carried to the shore side, even if shore sand is eroded, this can be compensated for and erosion can be effectively prevented.

As shown in FIG. 1B, a plurality of blocks 1 are prepared by adhering them to the sheet 2 in advance as a unit.
It only needs to be lifted with a crane and thrown into the seabed. Therefore, the block described in the conventional example is replaced by 1
Compared with the case where the individual units are installed, it is not necessary to perform the alignment or the like in block units, and the workability is significantly improved.

Furthermore, since the row of each block 1 is held by the sheet 2, even if the seabed has irregularities, the sheet 2
Is deformed in accordance with this, and separation and floating from the seabed are prevented. On the other hand, since the arrangement of the blocks 1 from the shore toward the offshore direction is a connected form in which the hinge portion 1c and the hinge receiving portion 1d are overlapped, the front and rear blocks 1 are bent at this connected portion. Can take. Therefore, if the beach 1 is stably held against the sea bottom by changing the posture following the deformation of the sheet 2 and there is no large dent, a mountain, a rock or a reef, as shown in FIG. It can be arranged neatly to form a pattern of strained sand bricks.

The fact that the shape between the troughs 3 of the adjacent blocks 1 as shown in FIG. 2 corresponds to the waveform of one wavelength of the distorted sand brick shown in FIG. 3 from the above description. it is obvious. That is, block 1 in FIG.
In this arrangement, the range indicated by λ is the shape corresponding to one wavelength of the strained sand brick, and it is extremely effective to optimize the shape and size of the strain to promote the transport of sand drift to the shore.

In order to optimize the shape and size of the block 1, the present inventors measure the average velocity of the bottom laminar flow and observe the movement of sediment by model tests, We analyzed the flow and eddy current around the brick by numerical calculation. As a result, between the wavelength lambda of the total amplitude d _o and sand Ren described in (b) of FIG. 3, d _o / λ
We found that if there is a relationship of 1.7, sand drift can be controlled most efficiently.

The total amplitude d _o various changes by distribution such as a reef of the situation and the wind and the surrounding coast. On the other hand, for the site to be constructed, the situation of the wave can be statistically grasped in advance and calculated as a representative value,
With this typical value, there is no problem even if it is specified as a value that can control sand drift well throughout the year. Therefore, the value of the width d _o can be narrowed down to a range of certain values as corresponding to each of the construction site, thereby the block 1 having dimensions of λ which satisfies d _o /λ≒1.7 Size and shape can be obtained.

The block 1 shown in the above example has a total length of 140c from the hinge 1c to the head 1e.
m, the total height from the seat 1a to the head 1e is 50cm,
Width 102cm, total weight 900kg, total capacity 0.3
9 m ³ . In the specification of such a block 1, λ = 1
It is about 00cm, thus the width d _o which corresponds to the moving total amplitude of the water particles can be suitably used for beach waves values of d _o ≒ 1700 cm is considered as a typical wave.

Further, when the blocks 1 are arranged to transport drifting sand or offshore deposited sand to the shore, if the traveling direction of the waves is within a certain angle range with respect to the blocks 1, the traveling direction of the waves with respect to the blocks 1 It was found from the knowledge that no matter how the shape was changed, sand drift and the like could be transferred in a direction perpendicular to the arrangement direction of the blocks 1. FIG. 6 is a schematic diagram for explaining this.

With respect to the strained sand brick shown in FIG.
When a wave travels from above (wave direction positive) that forms an angle of α with the direction perpendicular to the peak line, sand drift is controlled as an average flow in the direction of the arrow shown as the direction of sand drift control in the figure. . Experiments have also revealed that the flow of sand drift is similarly controlled in the same direction of sand drift control when a wave travels from the bottom of the figure (reverse wave direction). According to the experiment, the conditions under which the strained sand can control the direction of drifting sand are specified in the range of α <50 ° for both forward and reverse wave directions as described below with reference to FIG. Therefore, depending on the posture when the strained sand is applied, it is possible to control sand drift in a range of 50 ° × 4 = 200 °.

FIG. 6B schematically shows a planar shape of a portion corresponding to the range of λ shown in FIG. 2, and a line indicated by a chain line extends from the inclined surface 1b of the block 1 to the head 1e. Is the highest ridgeline, and the two upper and lower solid lines sandwiching this ridgeline correspond to the deepest position of the trough. Here, when a wave with a flow velocity U proceeds at an angle of α as shown in the figure with respect to the strained sand, the water particles flow at a flow velocity U in the direction of the wave. When the streamlines of the range of the length of the full amplitude d _o progresses by the flow, generates a pressure difference before and after the flowing direction of the distortion sand Ren peak line as a boundary. Then, when the vector of the velocity U is decomposed into components Un and Up perpendicular and parallel to the strained sand, the parallel component Up may be considered to be infinitely long in the direction of the strained sand peak due to the strained sand. It is almost independent of the gradient. On the other hand, Un which is a vertical component greatly contributes to the pressure gradient, and generates a vortex as a wake behind the strained sand as shown in the figure.

That is, the direction of vortex generation is a flow field included in the following flow orthogonal to the strained sand, and a bottom layer flow is generated in the direction orthogonal to the strained sand regardless of the angle of incidence of the wave on the strained sand. Let it. Such a phenomenon,
It is apparent that the above-mentioned phenomenon occurs steadily when Up does not substantially contribute to the pressure gradient, and when a line segment orthogonal to the peak line of the block 1 is used as an axis, ± 50 ° on the left and right sides, that is, a total of 50 ° × 4 = 200 °.

As described above, since the bottom layer flow can be induced in a direction perpendicular to the strained sand brick regardless of the traveling angle of the wave, the direction of the drift sand to be transported on the bottom layer flow is set in advance.
If the blocks 1 are arranged in a direction perpendicular to this direction, the transport direction of the drifting sand can be controlled.

FIG. 7 is a schematic view showing an example of construction in which the movement of sand drift can be controlled by setting the direction of such a bottom layer flow.

In this example, a rocky diving point is constructed on the beach near the shore, and sand drift can be transferred from the rocky shore to the offshore side and the shore side.

The blocks 1 surrounding the four sides of the rock R are arranged such that the head 1e side faces the rock. Therefore, one row of blocks facing offshore is shown in FIG.
The arrangement of the blocks 1 for preventing erosion of the seashore is opposite to that, and when a wave from offshore hits, the floating of the sand that has entered the rocky side R is taken as drifting sand and transferred to the offshore side. And, for the block row 1 facing the coast, FIG.
And the sand drift contained in the waves passing through the rocky area R can be transported to the shore side.

As described above, by setting the posture of each row of blocks surrounding the rocky area R to be opposite to each other on the offshore side and the shore side, the rocky area R is prevented by preventing the accumulation of sand on the rocky area R and transferred to the outside. Can be maintained as a diving spot. In addition, in the figure, as for the row of four sets of blocks which are arranged in an oblique posture with respect to the shoreline, if the offshore side and the shoreside are each set to the above-described posture, the discharge of the sand from the rocky area R is also the same. It is possible.

FIG. 8 shows an example in which the blocks 1 are arranged around a jetty P in a fishing port to transfer sand from a portion where sand tends to accumulate to a portion where erosion is likely to occur.

In this example, a wave rushes from the left to the jetty P protruding from the shore. If such a wave is traveling, sand is deposited on the left side of the jetty P when viewed from the offshore side. And erosion on the right. On the other hand, by arranging the rows of the blocks 1 so as to surround the left side of the jetty P to the front and right sides thereof, the sand deposited on the left side is transferred to the eroded portion on the right side.

That is, the blocks 1 arranged around the jetty P from the left side to the right side have the head 1e directed to the shore in the arrangement portion on the left side of the jetty P, and the head 1e directed to the left side in the arrangement portion along the front of the jetty P. Further, in the arrangement portion along the right side of the jetty P, the head 1e is directed to the offshore side.

Thus, in the arrangement of the blocks 1 on the left side of the pier P, the sand deposited near the shore is taken as drifting sand by the waves drawn from the shore and transported in the offshore direction. In the arrangement section 1, sand drifting from a row of blocks arranged on the left side is transported along the jetty P to the right side thereof by a wave lapping obliquely. In addition, jetty P
In the arrangement part of block 1 located on the right side of
Transport the sand transported along the front of the coast to the coast. Therefore, the drifting sand can be carried to the eroded portion of the shore on the right side of the jetty P by using the waves of seawater, and erosion can be prevented without any operation such as dredging.

Further, as shown in the figure, a row of blocks projecting obliquely in the offshore direction may be provided at the left and right corners of the row of blocks. In this case, each block 1 can take the sand from offshore as drifting sand and transfer it to the shore side, as in the example shown in FIG. Therefore, sand from the offshore can also be supplied to the eroded portion of the shore on the right side of the jetty P, so that erosion prevention is more effectively performed.

FIG. 9 shows an example in which the arrangement of the blocks 1 shown in the example of FIG. 5 is constructed at an angle with respect to the shoreline, and the head 1e of each block 1 is oriented in the offshore direction. . When waves strike the coast diagonally, coastal sedimentation occurs due to the coastal component of its momentum. Coastal sediment spreads and spreads offshore in the course of its movement. Therefore, if the movement of the sand was controlled in the shore direction in the direction of pulling back by the strained sand, the movement of the sand in the coastal direction and in the offshore direction was controlled, and a jetty was installed on the coast as if it were erosion prevention. The same effect can be expected.

[0051]

EXAMPLE A concrete strained sand brick having a sectional shape shown in FIG. 10 (b) spread over a total length of 6 m was prepared for an experiment. FIG. 10A shows a sine wave waveform as a prototype of the strained sand brick, which is shown for comparison of the profile with the strained sand brick.

The distorted sand brick is set in the two-dimensional wave making channel,
Water depth 29cm, wave height 5-9cm and period 0.8-2.
A wave of 0 seconds was applied, and the horizontal flow velocity u was measured from the top of the strained sand brick by a laser velocimeter. Then, based on the measurement result, the horizontal flow rate u was integrated in the vertical direction to calculate the horizontal flow rate Q. The result is shown in FIG.

[0053] (b) in FIG. 11 is a moving speed Vg when placed in the horizontal direction of the flow Q and various sediments calculated on distortion sand Ren the longitudinal axis, the water particles moving full amplitude d _o and distortion sand It is a plot of the experimental value of the shore-facing flow rate and the sediment movement velocity on the strained sand with the ratio (d _o / λ) to the wavelength λ of the brick on the horizontal axis.

In this experiment, the wavelength of the strained sand was λ =
5.5 cm (sand brick A in the figure) and geometrically 2
The measurement was performed for the doubled λ = 11 cm (sand brick B in the figure). Further, as can be seen from the figure, in both cases of λ = 5.5 cm and λ = 11 cm, the distribution in which the flow rate Q takes the maximum value is obtained when d _o / λ is approximately around 1.7. It can also be seen that Vg when various sediments are placed has a maximum value corresponding to the value of d _o / λ near this value of 1.7. Therefore, experimentally, it can be said that the condition for maximizing the effect of controlling the drift sand by the strained sand is that d _o / λ is a value of approximately 1.7.

Further, the condition for maximizing the flow rate Q in the horizontal direction along the bottom surface can be obtained by numerical simulation. The condition is obtained as a solution by solving the Poisson equation and the transient transport equation relating to the flow function as eddy diffusion coefficients, and the results are shown in FIG.

[0056] As can be seen from FIG. 12, although the result is uneven, when taking into consideration the distribution characteristics of the experimental results shown in FIG. 11, the maximum value is seen as near d _o = 8 cm, the strain on the calculations to this Considering that the wavelength of the sand goodwill is λ = 5cm, the value of d _o / λ is approximately 1.6. Therefore, from the results of experiments and numerical simulations on the flow rate Q and sediment movement, it was confirmed that a value of d _o / λ of 1.7 maximized the drift control effect of the strained sand.

[0057]

According to the present invention , in accordance with the orientation of the blocks forming the surface profile approximated to the distorted sand brick, the outflow of sand from the shore is suppressed and the drifting sand is transported to the shore, and the sand is transferred from a certain place on the shore. It is possible to control sand drift such as transporting sediment and sediment sand to another place, thereby preventing coastal erosion. And since the blocks are joined to the sheet and their positions are restrained and the disturbance of the positional relationship of the blocks is suppressed even after the blocks are installed on the seabed, the collapse of the pattern of the distorted sand brick is prevented, and the sand is maintained for a long time. Transfer function can be maintained.

[0058] Also, if possible bent is connected portion of the block each other, when placed on the sea floor with the sheet, it is possible to maintain the posture of the modeled after allowed to block the unevenness of the seabed, from the coast of the block offshore direction The array is not shredded. Therefore, even if a part of the block is sharply bent, the function of transporting sand drift by the entire arrangement is not impaired, and it is possible to cope with a site where the seabed topography is complicated.

[0059] Further, when formed by the hinge and the hinge receiving portion which forms a sliding surface of the arcuate surface of the connecting portion of the block each other, the operation of the bending becomes quickly, the sheet also block when installed in seabed Since the sheet is deformed so as to be adapted to the movement, it is possible to perform a good construction without causing the sheet to be torn.

In the present invention, the flow rate of the bottom layer flow contributing to the transport of sediment transport can be set to the maximum by specifying the wavelength of the surface profile with respect to the total amplitude of the water particle orbital motion along the surface profile of the block. As a result, it is possible to transport sand drift efficiently without making the block unnecessarily large. Therefore, the design of the block is optimized, and the workability can be improved by achieving the miniaturization and measurement of the block.

[0061] Since it controls the average flow direction of the sand drift with respect to the traveling direction of the wave by the array orientation of the block in a direction perpendicular to the block, if appropriate sequence in accordance with the coast of terrain and jetties arrangement such In addition to more effectively preventing erosion of the coast, sand can be guided on the coast freely, and construction of shore facilities such as rocks for diving is simplified.

[Brief description of the drawings]

1A and 1B are details of a block in an embodiment of the present invention, in which FIG. 1A is a perspective view of a single block, and FIG. 1B is a perspective view showing a unit in which a plurality of blocks are bonded and arranged on a sheet. .

FIG. 2 is a schematic side view of blocks arranged on a sheet.

FIGS. 3A and 3B are diagrams for explaining strained sand and control of drifting sand caused by the sand, wherein FIG. 3A shows a waveform of the strained sand, and FIG. FIG.

FIG. 4 is a schematic diagram showing the behavior of drifting sand on a block surface approximated to a strained sand brick together with waves.

FIG. 5 is a diagram showing an example in which a block row is constructed on a sandy beach.

FIG. 6 is a diagram illustrating that a bottom layer flow is generated in a direction orthogonal to a block even when a traveling direction of a wave with respect to the block changes within a certain angle range.

FIG. 7 is a diagram showing a construction example in which blocks are arranged around a rocky area for diving spots.

FIG. 8 is a diagram showing a construction example in which blocks are arranged around a jetty in a fishing port.

FIG. 9 is a diagram showing an example in which the blocks are arranged in an oblique posture with respect to the shoreline.

FIGS. 10A and 10B are diagrams showing a strained sand brick used in the model experiment in comparison with the original sine wave, wherein FIG. 10A shows a sine wave waveform, and FIG. The waveform is shown.

FIG. 11 (a) is a diagram plotting a calculated value of a shore-facing flow rate on a strained sand brick, and FIG. 11 (b) is a diagram plotting a measurement result of a sediment movement speed.

FIG. 12 is a diagram showing a calculation result of a shore-facing flow rate Q.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 1a Seating part 1b Inclined surface 1c Hinge part 1d Hinge receiving part 1e Head 2 Seat 3 Trough

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Takewaka 4-10-3, Azuma, Tsukuba-shi, Ibaraki Bldg.No.206 Room 206 Joint Referee Yutaka Kihara Judge Makoto Nakada Judge Noriko Suzuki (56) References 4-269207 (JP, A) JP 6-40659 (JP, B2)

Claims (1)

(57) [Claims] The present invention comprises a deformable sheet that follows the seabed, and a plurality of blocks that are respectively bonded and uniformly arranged on the sheet, and the blocks are arranged such that when they are arranged , the seabed sand on a sandy beach shore. It is similar to the sand brick formed in
Uni sine wave is offset to one wavelength direction and shape to draw a continuous surface profile, the as yet a wavelength of one strain sand goodwill surface profile as the profile of the blocks lambda,
A construction for controlling sand drift, wherein the value of d ₀ / λ is approximately 1.7 when the total amplitude of the water particle orbital motion along the surface profile of the block is d ₀ .