WO2003016639A1

WO2003016639A1 - Sand shift preventing sea bottom dam and method of constructing the dam

Info

Publication number: WO2003016639A1
Application number: PCT/JP2002/008067
Authority: WO
Inventors: Kenji Ishikura
Original assignee: Soken Kogyo Co Ltd; Kenji Ishikura
Priority date: 2001-08-10
Filing date: 2002-08-07
Publication date: 2003-02-27
Also published as: JPWO2003016639A1

Abstract

A sand shift preventing sea bottom dam and a method of constructing the dam capable of suppressing the erosion of coast and building a sandy beach, the method characterized by comprising the steps of allowing a depth of breaking to artificially shallow so as to weaken wave energy, building a debris foundation ground on a sea bottom ground near a breaking point or on the coast side of the breaking point to prevent sand from shifting to an offing, installing a water breaking structural body on the debris foundation ground, and constructing a sand shift preventing bank on the coast side rear part of the water breaking structural body.

Description

Description Submarine dam for preventing sediment transport and its construction method

The present invention relates to a sediment-prevention submarine dam for preventing coastal sedimentation and a method of constructing the same. Background art

Conventionally, artificial reefs, submerged embankments, breakwaters, headlands, jetties, etc. are known as measures to prevent erosion of the coast and maintain the sandy beach. Other than the artificial reefs and submerged embankments, there are some opinions that the structure of the structure looks large on the water surface, which is not preferable in terms of use or landscape. Disclosure of the invention

The artificial reef and submerged submergence were below the water surface and did not impair the landscape. However, there was a problem that the tip of the basic rubble was easily scoured and the main purpose was to extinguish the waves, so it was not possible to directly prevent the sand from being washed away.

In other words, the artificial reefs, submerged levee, etc. weaken the power of the waves, so that sand can be stored behind them (shore side), but these levee bodies have high seawater permeability and can directly store sand. Because it is not structured, it may be re-driven by the direction of the waves, coastal currents, etc. In other words, the artificial reefs and submerged embankments can indirectly accumulate sand, but do not have a structure that actively and directly accumulates sand. Therefore, there was a problem that the sand near the beach line, which was wound up by the waves, penetrated the embankment and was carried offshore.

On the other hand, there is a structure for directly storing sand, but such a conventional structure is built at a point where the wave power after breaking the wave is weakened, and the structure itself resists a strong wave force. I couldn't.

As mentioned above, conventional structures have not been able to prevent sand from flowing out, Breaking is a major problem. This problem is occurring all over the world, not to mention Japan.

However, there is no fundamental and effective countermeasure against this problem, and at present, the symptomatic treatment has been started, such as collecting seabed sand from offshore or importing sand from abroad and putting it on the broken coast. is there. In this situation, it is hopeless that the problem will be sufficiently improved, and despite enormous maintenance costs being invested every year, it is getting worse year by year.

Preventing coastal erosion and maintaining sandy beaches can be achieved by reducing the speed of the waves that hit the coast due to wave extinction, and by lowering the coastal sand to the shore side of the submarine dam, reducing the amount of sand carried offshore. The effect is expected.

Therefore, the present invention not only minimizes the sedimentation caused by natural energy, but also uses it to convert the power of nature not to destructive force but to the creation force, and to assist the artificial. The above problem was solved by retaining quicksand on the shore. Specifically, an artificial submarine dam was used to reduce the strength of the waves breaking and breaking the shore, and the sand that was carried offshore was settled on the shore of the submarine dam, successfully preventing the coast from collapsing. Not only that, sandy beach development was successful. In other words, the invention of the submarine dam is to create a rubble foundation on the seabed near the breaking point or on the shore side of the breaking point, install a wave-breaking structure on the rubble foundation, A sand runoff dike was constructed behind the side.

Here, the rubble foundation ground is composed of a breaking wave laying material in which a grid frame formed by joining high-strength members is installed on the seabed ground, and a wave breaking laying material fitted and locked in the grid frame of the breaking wave laying material. It can be constituted by a corrugated material.

In addition, the wave-absorbing structure can be a wave breaking block array in which prefabricated wave-breaking blocks are three-dimensionally combined in the direction of the waves, the horizontal direction of the coast, and the depth direction so that there is a gap inside. . The reason for having a void inside is to keep only the shore sand on the shore side of the submarine dam and allow ebb to pass offshore from the submarine dam.

The sand runoff prevention levee can be formed by appropriately combining a quarry stone, a wave breaking material, and a buried soil. Next, the invention of the method of constructing a submarine dam is to lay a grid frame made of high-strength members horizontally on the seabed near the breaking point or on the shore side of the breaking point, To form a rubble foundation ground, install a wave-damping structure on the rubble foundation ground in a three-dimensional combination, and place a wave-damping material offshore of the wave-damping structure. In this method, they are juxtaposed to form a submarine dam.

Moreover, after juxtaposing the wave-breaking material to the offshore side of the wave-absorbing structure, stacking the quarry stone with the sediment-prevention material behind the shore side of the wave-breaking structure, burying the shore side of the quarry stone It can be turned into a submarine dam.

Here, using Fig. 8 and Fig. 9, the mechanism of stone movement on the coast will be explained. Much research has been conducted on the movement of sand on the coast, but the actual situation has not yet been fully elucidated. However, in this situation, it is generally considered as follows.

In Fig. 8, the symbol i indicates the seabed gradient. H is the equivalent deep water wave and L is the equivalent. Indicates a wavelength. Here, is calculated from the offshore wave height H ₀ , but the description of the calculation method and the like is omitted. Waves break at seabed gradient i and waveform gradient H. / L. Although it varies greatly depending on the condition of, it generally breaks at a position where the water depth h _b is 1.5 to 2.5 times H (.

Therefore, a large offshore deep wave goes to the shore without breaking, and the wave breaks when approaching a shallow water where the value of h _{b /} wave height H (is approximately 1.5 to 2.5 or less. This is called breaking waves.

Fig. 9 conceptually shows how the breaking waves travel toward the shore, reach the run-up area, cut the sandy beach and erode the shore.

The breaking wave 33 is generated at the breaking point 30 where the water depth wave height 1 ^ is approximately 1.5 to 2.5, and the wave height 1 ^ proceeds while breaking further. The breaking wave 3 3 which reached the run-up area 3 1 cuts the sandy beach 3 2 and erodes the coast.

The shaved sand is transported offshore and settles and deposits near the breaking point 30, forming sand bars 34. When the moss is settled, even the smaller waves break at the sand bar 34, and the sand in the sand bar 34 is transported again to the upstream area 31. If this balance is maintained, no erosion will occur, but the sand will float and move not only when it is shrimp, but also when it is a small wave. This is related to the offshore waves and the particle size of the sand, the water temperature, etc. In general, the longer the offshore wave cycle, the more the sand moves offshore. However, the amount is a problem, and the amount of movement in the case of moss is overwhelmingly large. The mechanism of movement of sand on the coast is generally considered as described above.

Therefore, the submarine dam of the present invention aims at artificially reducing the breaking water depth. Submarine dam 2 5 of the present invention as FIG. 7, lever to construction near碎波band of conventional, since breaking the water depth h ₂ becomes shallow, large waves conventionally that did not crumble even depth h _{2 /} 1 the value of the wave height H ₂ is a condition of breaking. 5-2. will be satisfied 5 is broken at this location. The wave power is greatly weakened, and the ascending area 35 in FIG. 7 is much narrower than the conventional ascending area 31 in FIG. Very low. In addition, the new reef stops just before the submarine dam 25, so that the shaved sand does not fall offshore.

In addition, when the waves that scour the shore make the ebb tide, the submarine dam acts as a resistance, weakens the flow velocity, and promotes the sedimentation of the sand. As described above, the submarine dam of the present invention is located near the breaking point, breaks waves, and has the effect of weakening its power.Therefore, the foundation is built firmly on the submarine ground, and scattering of blocks due to scouring, etc. The structure must be durable. Therefore, the material constituting the rubble foundation ground on which the submarine dam of the present invention is based is a high-strength member such as steel.

In addition, the offshore part of the upper part of the submarine dam must be able to withstand large waves and provide characteristics to steadily extinguish waves. Therefore, the height of the submarine dam needs to be set up near the area where the sudden change of the wave below the water surface occurs.

The submarine dam is a structure whose purpose is to receive the breaking of a large wave and further dissipate the energy of the wave. Therefore, on the shore side of the submarine dam, a wave-dissipating structure is constructed by packing the wave-dissipating blocks and others, and its width is at least 7π! It is desirable that the length be 10 m or more. In this way, the energy of the waves is By contrast, the destructive forces applied to the shore are rapidly weakened, and the destruction of the shore is thus minimized.

The shore side of the wave-dissipating structure shall have a structure that can withstand the flow of the wave-dissipating current by reinforcing the strength with quarry stone and the like. In addition, the shore side shall be gently sloped to promote sedimentation of quicksand.

Since the submarine dam is located at the forefront of the sandy beach to be maintained and constructed, it is conceivable to build a sand stop structure separate from the seabed dam between the coast and the submarine dam.

The submarine dam of the present invention can create a sandy beach by utilizing natural force by minimizing the destruction and erosion of the shore, especially the sandy beach, and by sedimenting a large amount of sand carried offshore. In other words, the present invention fulfills the auxiliary role of sand development (helping natural power). Therefore, the destruction of the coast by natural forces is not only prevented beforehand, but also the beach area can be increased year by year. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an enlarged conceptual view in which a part of a side surface of a triangular structure in which a prefabricated breakwater block of a submarine dam according to an embodiment of the present invention is assembled is omitted.

Fig. 2 (a) is an enlarged conceptual diagram of the submarine dam shown in Fig. 1 with a part of the surface where the triangle structure adjacent to the triangle structure shown in Fig. 1 appears, omitted. Fig. 2 (b) shows the triangular structure shown in Fig. 1 and the triangular shape shown in Fig. 2 (a) in the wave-dissipating structure of the submarine dam shown in Fig. 1 and Fig. 2 (a). FIG. 4 is an enlarged conceptual diagram in which a part of a state in which the structure is alternately connected in the left-right direction is omitted.

FIG. 3 is an enlarged cross-sectional view of a trapezoidal structure in which a prefabricated breakwater block of a submarine dam according to another embodiment is partially omitted, showing a side surface thereof.

FIG. 4 (a) is an enlarged conceptual view of the submarine dam shown in FIG. 3, in which a part of a surface where a trapezoidal structure adjacent to the trapezoidal structure shown in FIG. 3 appears is omitted.

Fig. 4 (b) shows the trapezoidal structure shown in Fig. 3 and the trapezoidal structure shown in Fig. 4 (a) in the wave-damping structure of the submarine dam shown in Figs. 3 and 4 (a). FIG. 3 is an enlarged conceptual diagram in which a part of a state in which are alternately connected in the left-right direction is omitted. FIG. 5 is a conceptual diagram omitting a part of an embodiment in which a different assembly type wave canceling block is assembled.

FIG. 6 (a) is a conceptual diagram of an embodiment in which a submarine dam is installed in a plane U shape. FIG. 6 (b) is a conceptual diagram of an embodiment in which the submarine dam is installed in a plane arch shape. FIG. 7 is an explanatory view in which a part of the beach on which the submarine dam of the present invention is installed is omitted. FIG. 8 is an explanatory view of conditions for generating a breaking wave.

FIG. 9 is an explanatory view in which a part of a conventional beach is omitted. BEST MODE FOR CARRYING OUT THE INVENTION

Example 1

A submarine dam 25 embodiment of the present invention will be described with reference to FIGS.

First, near the conventional breaking point, a wave-breaking laying material 1 having a grid-like mesh is installed horizontally on the submarine ground G, and a wave-breaking material 2 such as a stone or concrete block is closely fitted into the grid. Make a horizontal rubble foundation 3. The position where the wave-breaking laying material 1 is installed may be on the shore or offshore from the breaking point as long as it is near the breaking point.

'· A suitable horizontal section 41 is provided at the tip of the rubble foundation ground 3 on the offshore side. On the shore side of the horizontal part 41, a wave-dissipating structure 42 constructed by assembling the assembly-type wave-dissipating blocks 4 so as to have a porosity of several tens of percent is installed. This wave-absorbing structure 42 is constructed on land, and is installed on the horizontal portion 41 of the submarine rubble foundation 3. In addition, as the prefabricated type wave-eliminating block 4, a block according to Japanese Patent No. 2037152 can be used.

This prefabricated breaker block 4 has a short block and a long block. The short work has a shape in which convex portions are provided on both sides of both ends in the longitudinal direction. The long block has a shape in which convex portions are further provided on both sides at the center in the longitudinal direction. The prefabricated wave-dissipating block 4 can form a wave-dissipating structure 42 of various shapes by locking the other prefabricated wave-dissipating block 4 to the projection.

When viewed from the side as shown in Fig. 1, the wave-absorbing structure 42 has a long block 4a forming the bottom, a long block 4b forming the hypotenuse on the shore, and a long block 4 forming the hypotenuse on the offshore. c combine to form a triangular structure 43.

In this triangular structure 43, the long block 4a is placed horizontally on the rubble foundation 3, the long block 4b is placed diagonally on top of it, and the long block 4c is connected to the lower end by the horizontal section. It is formed so that it is locked to the step part 41a on the shore side of the minute 41 and leans against the offshore end of the long block 4a. At this time, the long blocks 4a, 4b, and 4c are locked to each other's projections, and form a strong triangle.

The prefabricated breaker block 4 has almost the same shape as the triangular structure 43 using long blocks 4d, 4e, and 4f, but differs in the manner of assembling as shown in Fig. 2 (a). A triangular structure 4 4 is formed.

As shown in FIG. 2 (b), the wave-absorbing structure 42 is composed of triangular structures 43 and 44 alternately arranged in a plurality of rows in the left and right directions, and is provided via spacer protrusions 15 and 15. It is connected by steel materials 16 and 16.

By arranging and connecting a plurality of triangular structures 43, 44 in different ways in the left-right direction in this manner, the wave-absorbing structure 42 is constructed as an integrated structure.

FIG. 2 (b) is a conceptual diagram when the wave-dissipating structure 42 is viewed from the sea side. A backing stone 5 is inserted into the back of the shore side of the wave-dissipating structure 42 configured as described above. : At this time, the side of the shore where the backing stone 5 was inserted is a slope corresponding to the slope of the long block 4b. On the slope of the backing stone 5, a sand-prevention sheet 6 as a sand-prevention material is attached. This is to prevent the sand on the beach from flowing through the backing stone 5 and into the wave-dissipating structure 42 and the rubble foundation ground 3.

The top of the sand protection sheet 6 is covered with chestnut stone 7, and then a split stone 8 is put on the back side of the shore. On the upper surface of the backing stone 5 and the chestnut stone 7, large stones 14 with a mass of about 200 kg are laid. By constructing the submarine dam 25 in this way, the sand 8a naturally accumulates behind the shore of the crushed stone 8.

Here, if the portion where the sand 8a has accumulated can be dug locally deep, a stone stone 9 may be laid behind the shore of the split stone 8 as shown in FIG. A grid net 10 is laid below and locked to this 9 and so on to prevent scattering. If Kuriishi 9 etc. are not scattered, seaweed such as kelp will grow, which will have the effect of improving the coastal environment. JP02 / 08067 In the figures, reference numerals 10 and 11 indicate a steel mesh grid, and reference numeral 12 indicates a water surface.

In the above-described embodiment, when a wave comes in from the sea side as indicated by arrow 13, first, the wave is roughly broken by the wave-dissipating structure 42, and then the crushed stone 14 (for example, mass

The wave is further broken by the above (200 kg or more), and the 5 large waves are eliminated during the passage of about 10 m width. As a result, the large waves break and then break, and the sand generally settles on the shore of the sea bottom dam 25.

Then, at the time of towing, the sand is clogged between the broken stones or the like, and the sand is prevented from flowing out by the sandproof sheet 6, so that the amount of sand carried to the sea side by the waves is significantly reduced.

L0 On the other hand, since the waves are broken by the action of the prefabricated breaker block 4 and the breaker 2, the power of the waves hitting the shore is remarkably reduced, and the great power of shore destruction is greatly reduced. Example 2

L5 Another embodiment of the present invention will be described with reference to FIGS. '' The difference between the submarine dam 45 of this embodiment and the submarine dam 25 of the first embodiment is that the method of assembling the assembled wave-dissipating block 4, that is, the shape of the wave-dissipating structures 42 and 46 The only difference is.

The wave-absorbing structure 46 of this embodiment is different from the wave-absorbing structure 42 of Embodiment 1 when viewed from the side as shown in FIG. The short block 4 g and the short block 4 h forming the hypotenuse are combined to form a trapezoidal structure 47.

In this trapezoidal structure 47, the long work 4a is placed horizontally on the rubble foundation 3 and the short work 4g is placed thereon in parallel, and the short work 4h is placed on the shore end of the long work 4a. It is formed so as to lean against 5 parts.

The assembled wave-breaking block 4 has the same shape as the trapezoidal structure 47, with the short block 4h further leaning against the offshore end of the long block 4a, but is assembled differently. (A) Form a trapezoidal structure 48 as shown.

As shown in Fig. 4 (b), the wave-absorbing structure 46 is formed by connecting the trapezoidal structures 47 and 48 to the left and right sides. A plurality of rows are alternately arranged in parallel in the direction, and connected by steel materials 16 and 16 via spacer projections 15 and 15.

A plurality of the trapezoidal structures 47 and 48 in such a different manner are arranged in parallel in the left and right direction and connected to each other, whereby the wave-absorbing structure 46 is constructed as an integrated structure.

FIG. 4 (b) is a conceptual diagram when the wave-dissipating structure 46 is viewed from the sea side. The second embodiment is the same as the first embodiment in the structure, operation, and effects except that the shapes of the wave-dissipating structures 42 and 46 are different. About the same configuration as the submarine dam of the first embodiment, The same reference numerals are given in the drawings, and the description thereof will be omitted. Example 3

Another embodiment of the present invention will be described with reference to FIG.

The difference between the submarine dam 49 of this embodiment and the submarine dam 25 described in Embodiment 1 is that the method of assembling the prefabricated wave-dissipating block 4, that is, the shape of the wave-dissipating structures 42 and 50 The only difference is.

When viewed from the side as shown in FIG. 5, the wave-breaking structure 50 of this embodiment has a triangular structure 4 3 (44) in the wave-breaking structure 42 of Embodiment 1 in the direction in which waves hit. In a triangular space formed between the two triangular structures 4 3 (4 4) and 4 3 (4 4), an inverted triangular structure 4 3 (4 4) is formed. Further combined, they form a large trapezoid. That is, three triangular structures 4 3 (44) in Example 1 are arranged in a trapezoid, and these are arranged in a plurality of rows in the left-right direction via the spacer projections 15, 15, and the steel material 16, It is composed by connecting by 16.

The third embodiment has the same structure, operation, and effect as the first embodiment except that the shape of the wave-dissipating structures 42 and 50 is different. The same reference numerals are given in the drawings, and the description thereof will be omitted.

The submarine dams 25, 45, and 49 of the present invention may be arranged in a flat U shape as shown in FIG. 6 (a) to prevent sand from flowing out.

In addition, as shown in Fig. 6 (b), there are cases where the land is arranged in a flat arch between capes in a terrain such as a pocket beach. In the figure, reference numeral 24 denotes a shoreline, and 23 denotes a breakwater. Is a cape). The submarine dams 25, 45, and 49 of the present invention are provided near the wave breaking position 36 as shown in FIG. Therefore, even if the sand naturally accumulates or the sand is poured into the submarine dam and the recess on the shore side, the sand does not flow out as in the past, so the sandy beach is secured.

The effects of the present invention include the following.

That is, according to the present invention, a submarine dam is constructed near the breaking wave point, and the power of the waves is reduced by breaking waves, breaking waves, etc., so that sand is precipitated and erosion and destruction of the coast is minimized. effective.

In addition, the sand carried offshore by the submarine dam settles on the shore of the submarine dam and prevents outflow, so that it has the effect of automatically creating a sandy beach.

According to the present invention, since the natural force is used to the utmost, there is an effect that, after the construction of the seabed dam, the erosion of the coast is prevented and the sand beach is automatically created without applying any artificial force.

In addition, the wave-damping laying material 1 is installed horizontally on the seabed ground G, and the wave-damping structure consisting of the wave-damping material and wave-damping block is installed on top of it. There is no risk of the materials and wave-breaking structures tilting or collapsing.

Claims

The scope of the claims

1. Build a rubble foundation on the seabed near the breaking point or on the shore side of the breaking point, install a wave-absorbing structure on the rubble foundation, and run off the sand behind the shore of the wave-breaking structure. A sediment-prevention submarine dam characterized by the construction of a breakwater.

2. The rubble foundation ground is composed of a breaking wave laying material in which a grid frame formed by joining high-strength members is installed on the seabed ground, and a wave breaking material fitted and locked in the grid frame of the breaking wave laying material. The submarine dam for preventing sediment transport according to claim 1, characterized by comprising:

3. The wave-absorbing structure is characterized by a wave breaking block array in which a prefabricated wave-breaking block is three-dimensionally combined in the direction of the waves, the horizontal direction of the coast, and the depth direction so that there is a gap inside. The submarine dam for preventing sediment transport according to claim 1.

4. The sediment-prevention submarine dam according to claim 1, wherein the sand runoff prevention embankment is made of split stone, wave-breaking material and buried soil.

5. A grid frame made of high-strength material is laid horizontally on the seabed near the wave breaking point or on the shore side of the wave breaking point. And a wave-absorbing structure in which wave-absorbing blocks are three-dimensionally combined is installed on the rubble foundation ground, and a wave-absorbing material is juxtaposed offshore of the wave-absorbing structure. How to build a bottom dam.

6. A grid frame consisting of high-strength members is laid horizontally on the seabed near the wave breaking point or on the shore side of the wave breaking point. Constructing the ground, installing a wave-damping structure three-dimensionally combining wave-damping blocks on the rubble foundation ground, and juxtaposing wave-damping materials offshore of the wave-damping structure; A method of building a sediment-prevention submarine dam characterized by stacking quarry stones with a sediment-prevention material behind the shore and burying the shore of the quarry stone.