JP2000273838A - Beach nourishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To break up waves on a beach and produce the beach by utilizing its natural force. SOLUTION: Latticelike frame wave breaking spreading materials (a) forming latticelike squares having required size by a material having resistance against shearing force and tensile resistance force such as a steel material or reinforced concrete are continuously spread along the vicinity of a beach line of a beach to be nourished. Next, a wave breaking material 7 such as a stone or a block is put on the front and rear wave breaking spreading materials to engage a lower part of the stone or the block with the latticelike squares of the wave breaking spreading material (a) tightly by waves, and a wave breaking structure B consisting of the wave breaking spreading materials (a) and the stone or block engaged therewith is automatically sunk due to washing and digging actions by means of waves to constitute the rigid wave breaking structure B. Sands carried by waves are deposited on a land side on a rear surface of the wave breaking structure B to produce a beach.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shore nourishment method for preventing erosion of a shore and creating a sandy beach by utilizing natural force.

[0002]

2. Description of the Related Art Conventionally, various concrete blocks are laid along a shoreline to prevent wave erosion on a coast.
Or a concrete retaining wall is being constructed. The applicant also
Previously, a wave-dissipating structure was proposed in which a stone or concrete block was engaged with a strong grid-like laying material made of steel or the like (Japanese Patent Laid-Open No. 7-3739).

[0003] Next, as an artificial sandy beach, there are a large number of piles which are driven into the sea so as to become gradually lower from the land side to the sea side, and have a plurality of ridges of sand stoppers bent toward the sea side. There has been proposed a device in which a plate is fixed stepwise, and an appropriate amount of sand is sprayed on the front surface of the plate (Japanese Utility Model Publication No. 56-21).
850).

[0004]

The above-mentioned various types of conventional concrete blocks, concrete retaining walls and wave-breaking structures are all places where the waves are rough and are intended to prevent the shore from being eroded every year. If the waves continue for many years, concrete blocks or concrete retaining walls may eventually be destroyed. At least not for the purpose of creating a sandy beach, but for the purpose of wave extinction and erosion prevention.

[0005] The above-mentioned invention is an artificial sand beach, which is entirely man-made and far from a beach nourishment work.

[0006] Breakwaters and the like can slide or even fall, even with thousands of tons of concrete caisson. For example, the breakwater disaster at Senboshi Fishing Port is a good example.

[0007] Therefore, it is extremely difficult to make a stable structure on the sandy ground of the beach. There are no examples in the world where stable structures were built on beaches by omitting foundation work. Each of the existing coastal structures is spending enormous amounts of money on foundation work (because it is underground and invisible to the public). It is still broken. It has been common knowledge that sea structures cost money on the foundation, and in order to solve this technically, a pile is driven into a stable ground layer on sandy ground, and There is no solution other than making a structure or digging sand to that depth, assuming a depth that will not be scoured by the waves, and then putting in crushed stones and the like. Therefore, except for specific important structures, such foundation works are not performed.

Until now, many coastal breakwaters have been directly rubbed or piled up blocks on sandy ground. As a result, the blocks are scattered apart, the wave-breaking effect is completely lost, harming the landscape, and the blocks washed offshore cause secondary pollution such as catching fish nets,
It even caused fisheries compensation problems across the country.

Conventionally, there has been no clear theory regarding the amount of settlement of a structure installed near the shoreline, and there has been no construction method of installing a wave-dissipating structure near the shoreline and naturally accumulating sand. And it has never been implemented.

[0010] An object of the present invention is to provide a beach nourishment method using a wave-dissipating structure using a lattice-shaped frame a in order to improve the current method for such beach erosion.

[0011]

According to the present invention, a wave-breaking structure is laid along a shoreline to absorb wave energy, and the wave-breaking structure is used as a sand stop. They succeeded in creating a sandy beach on the land side of the object. The above method is to absorb the energy of the waves to reduce the wave power of the waves, reduce the thrust acting on the sand, and leave the sand when the waves return, making good use of the natural power As a result, large sandy beaches are automatically created every year without fear of erosion.

In addition, as the wave breaking structure, a stone or concrete block is placed on the wave breaking laying material, and the two are integrated, and the water breaking structure is naturally settled by scouring and is firmly installed. In response to the waves, it is built stably as the forefront.

That is, the present invention relates to a shoreline of a shore where a grid-shaped frame wave-breaking laying material having a grid of a required size formed of a material having shear resistance and tensile resistance such as steel or reinforced concrete is to be nourished. After continuously laying along the vicinity, place a wave-damping material such as a stone or a block on the front and rear wave-damping laying material, and place the lower part of the stone or the block or the like due to waves, and a grid-like structure of the wave-damping laying material. In addition to tightly engaging the eyes, the wave-breaking laying material and the wave-breaking structure consisting of the stones or blocks engaged with the wave-breaking material are automatically lowered by the scouring action of the waves, so A beach nourishment method characterized by forming a structure, and depositing the sand carried by the waves on the land side behind the wave-dissipating structure to form a sandy beach,
The wave-damping structures are installed in parallel at a predetermined interval, and sand is deposited on the land side of the wave-damping structures to form a sandy beach.

The present invention is more effective when provided on a shore where a large amount of sand is mixed in the waves. In addition, the beach with a relatively gentle slope is good, and the sandy beach can be expanded infinitely.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to provide a wave-breaking laying material continuously along a shoreline of a beach, thereby using both a wave-breaking and a sand stop, and using a natural force to form a sandy beach. It is a method of creating. Therefore, a plurality of rows of the lattice-shaped frame wave-breaking laying materials can be installed, and the beach can be gradually increased.

[0016]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a lattice-shaped frame a, where 1 is a vertical inner partitioning material and 2 is a horizontal inner partitioning material. The peripheral parts 1 and 2 may have a larger cross section of the member than the inner parts 1 and 2. FIG. 2 shows a grid-like frame a arranged near the shoreline 3 of the coast in a manner substantially parallel to the shoreline 3, where S is the sea and L is the land.

FIG. 3 shows that in the conventional wave-dissipating structure, the blocks are fragmented or the blocks are too large so that the energy of the waves is not diminished. It shows the situation.

FIG. 4 shows a state in which a lattice-shaped frame a is installed near the shoreline of the shore, and a wave-absorbing material such as a block large enough not to come off from the mesh of the lattice-shaped frame a is installed and laminated thereon. This is the wave-breaking structure A of the present invention, which was constructed by the above-described method. B ₁ represents the width of the bottom surface of the digestion wave structure A. h ₁ is the overall height, B ₃ is crest width, alpha is the angle which the vertical surface makes with the horizontal, G denotes the sand ground.

FIG. 5 shows a state where the wave-absorbing structure A of the present invention installed near the shoreline of the coast is eroded from the sand around the wave-absorbing structure, and sinks by that much. When submerged in this way, most of the structure is buried in the sand ground saturated with seawater, and receives a buoyancy U corresponding to the weight of the removed sand. B ₂ is the wave-breaking structure A on the upper end surface a at that time
Is the width of the embankment. Thus the difference between the total weight W of the wave dissipating structure A becomes the acting on the bottom surface B ₁ of the dam,

[0020]

(Equation 1)

Here, F may be designed so as to satisfy the safety factor, equation (1). Generally, the buoyancy U is very large and p
Is much smaller than the normal bearing capacity of sandy ground. therefore,
It can be considered that the subsidence of the wave-dissipating structure A is almost solely due to the scouring of the waves, and therefore, if the influence of the waves on the bottom is no longer present, the soil bearing capacity is much larger than the weight minus the buoyancy of the embankment, The subsidence of the wave-dissipating structure A stops. What is important is that the wave-breaking material is not disintegrated by scouring, and the reason for using the lattice-shaped frame a for the wave-breaking structure A of the present invention is here. However, in the event of shrinkage, the sand in front of the wave-dissipating structure A is shaved again, and the waves are strongly affected by the wave-dissipating structure A.
However, the waves break and their energy is greatly reduced, and they run up. Therefore, sand is deposited at the time of the wake, and the former sand ground surface 8 rises to 9. FIG. 6 shows a state of the beach newly constructed in this manner.

A calculation example is as follows. Figure 5 trapezoidal BCED area A _1: wave absorbing structure is part Δ area of DEH A 2 who died buried in sand soil saturated with sea _water: the part in the air wave dissipating structure, sand voids dry in filled by that portion delta DHF area a _3: the wave dissipating structure at the portion in the air, part of the wave dissipating only those blocks [rho: the porosity of the wave dissipating blocks 0.52 1-ρ: the wave dissipating blocks Actual volume ratio 1-0.52 = 0.48 γ ₁ : Unit volume weight of wave-dissipating block 2.3 t / m ³ γ ₂ : Unit volume weight of sand in air 2.3 t / m ³ = Specific gravity of sand × Porosity = 2.6 × 0.5 = 1.3 t / m ³ γ ₃ : Unit volume weight of sand saturated with sea water = Specific gravity of sand × Porosity + Unit volume weight of sea water × (1−Void of sand rate) = 2.6 × 0.5 + 1.03 ( 1-0.5) = 1.815 ≒ 1.8t / m 3 γ 4: unit seawater volume weight 1.0 _{^{t / m 3 cotα = 2/}} 3 h 1 = 3m, h 2 = 2m, h 3 = 1m, if _{B 1 = 6m, B 2 =} 4.66m, B 3 = 4m, the weight of the A ₁ = A ₁ [(1-ρ) γ ₁ + ρ · γ ₃ ] = A ₁ [(0.48 × 2.3 + 0.52 × 1.8) = 2.04 A ₁ t / m ³ A ₂ weight = A ₂ [ (1-ρ) γ ₁ + ρ · γ ₂ ] = A ₂ [(0.48 × 2.3 + 0.52 × 1.3) = 1.78 A ₂ t / m ³ A ₃ weight = A ₃ (1- ρ) γ ₁ = A ₃ × 0.48 × 2.3 = 1.104 A ₃ t / m ³ The weight W of the wave-absorbing structure is W = (A ₁ + A ₂ + A ₃ ) weight = 2.04A ₁ +1 .78A ₂ + 1.104A ₃ The buoyancy U of the sand ground saturated with seawater is U = A ₁ × γ ₃ = 1.8A ₁ t / m ³ The load on the bottom BC of the wave-dissipating structure is W−U = 2. 04A ₁ + 1.78A ₂ + _{.104A 3 -1.8A 1 = 0.24A 1 +} 1.78A 2 + 1.104A 3 (2) A 1 = (B 1 + B 2) / 2 × h 2 = {(8 + 4.66) / 2} × 2 _{= 12.66 (3-1) A 2 =} (1/2) × B 2 × h 3 = (1/2) × 4.66 × 1 = 2.33 (3-2) A 3 = (1/2) × B 3 × h ₃ = (1/2) × 4 × 1 = 2.0 (3-3) Substituting equations (3-1), (3-2), and (3-3) into equation (2), W−U = 0.24 × 12.66 + 1.78 × 2.33 + 1.104 × 2.0 = 9.3938 ≒ 9.394t (4) (W−U) / B ₁ = 9.394 / 8 = 1.174 t / m ² (5) Unless disturbed by waves, the sand ground corresponds to a well-tightened sand ground. In this case, the bearing capacity is generally several tens t / m ² or more, so even if the safety factor F is 2.5, It is safe enough. Therefore, as described in the previous section, if the wave does not affect the bottom, the wave-dissipating structure of the present invention does not dissipate the laminated wave-dissipating blocks, so that the subsidence stops and the structure as a structure is stopped. It is stable.

FIG. 7 shows that the wave-absorbing structure A of the present invention does not collapse even in the event of shrinkage, and thus stabilizes by accumulating sand on the land side on the back side. In some seasons on the front, sand may come. At that time, the wave-dissipating structure B of the present invention is installed near the new shoreline in front of the wave-dissipating structure A in the same manner as before. Thus, there is sand between A and B, and the new beach 9 '
Shows how is created.

[0024]

As is apparent from the above description,
Coastal wave-dissipating structures using the lattice-shaped frame wave-dissipating laying material of the present invention, even if the periphery and the bottom surface of the wave-dissipating structure are scoured, the blocks are not scattered and scattered, and the whole is integrally formed. It sinks by the amount scoured and finally stabilizes.

If the influence of the waves does not reach the periphery or the bottom surface of the wave-dissipating structure even after the shrinkage arrives, the waves are broken by the wave-dissipating structure, and the energy is greatly reduced, so that the wave goes up. It does not have enough power to cut down the shore, but instead leaves a large amount of sand during the wake.

In this manner, the wave-dissipating structure of the present invention crushes the waves which come intensely at every shrinkage, and deposits sand on the land side behind the wave-dissipating structure by natural force. Since the head of the wave-dissipating structure is almost completely buried, a very natural sandy beach is restored.

Therefore, by installing one or more rows of the wave-dissipating structure of the present invention in the vicinity of the shoreline in parallel with the shoreline, it is possible to catch the sand coming along with the shore and prevent the sand from escaping. Therefore, the shore can be regained near the shoreline of the sandy beach where it used to be.

Since the position where the wave-breaking structure is installed is near the shoreline, it is easy to carry out the work during calm, and the waves always hit the wave-breaking structure, and the wave-breaking structure is necessary and sufficient with the force of the wave. Down to a suitable position.

The reason why the sand is accumulated on the back of the wave-dissipating structure is that natural waves broken by the wave-dissipating structure carry the sand. In this way, all of the most difficult parts of civil engineering are done with the power of nature.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of a lattice-like frame wave-breaking laying material.

FIG. 2 is a plan view in which the lattice-shaped frames are arranged near a coastal shoreline.

FIG. 3 shows a state in which a conventional wave-dissipating structure is scoured by a wave, broken apart, and loses its wave-dissipating effect, so that the seashore is shaved by the waves that have run up.

FIG. 4 is a cross-sectional view showing a state in which a wave-breaking structure of the present invention using a lattice-like frame wave-breaking laying material is installed near a shoreline.

FIG. 5 is a cross-sectional view showing a state where sand has been scraped off by sinking and settled after the wave-breaking structure of the present invention has been installed.

FIG. 6 is a cross-sectional view showing a state in which sand naturally accumulates on the back surface of the wave breaking structure of the present invention.

FIG. 7 is a cross-sectional view showing a state in which sand accumulates between the wave-dissipating structure of the present invention and the shoreline when the wave-damping structure is installed in parallel with the shoreline.

[Explanation of symbols]

a Laminate frame wave breaking laying material A, B Wave breaking structure S Sea L Land 1 Vertical inner partitioning material 2 Horizontal inner partitioning material 3 Shoreline 4 Breaking wave 5,5 ', 5 " 6, 6 ', 6''Shaved sand ground surface 7 Wave-absorbing material 8, 8' Original sand ground surface 9, 9 'Ground surface after sand has accumulated B ₁ Width of bottom surface of wave-absorbing structure B ₂ wave absorbing structures, the total height h ₂ wave absorbing structures crest width h ₁ wave absorbing structures embankment width B ₃ wave absorbing structure sand upper surface that is saturated with sea water, saturated with sea water The height of the part buried in the sandy ground to the top surface h ₃ The height of the land part of the wave-absorbing structure α The angle between the vertical surface of the wave-absorbing structure and the horizontal plane W Do not consider the buoyancy of the wave-absorbing structure Total weight U Buoyancy of the water-absorbing structure due to sandy ground saturated with seawater

Claims (2)

[Claims] 1. A method of forming a grid-shaped wave-breaking laying material having a grid of a required size using a material having a shearing resistance and a tensile resistance, such as steel or reinforced concrete, along a shoreline of a beach to be nourished. After laying continuously, put wave-damping material such as stone or block on the front and rear wave-damping laying material,
The lower part of the stone or block is closely engaged with the lattice of the wave-breaking laying material due to the waves, and the wave-breaking wave is formed by the wave-breaking laying material and the stone or block engaged with the wave-breaking laying material. The structure is automatically submerged by the scouring action of waves to make it a solid wave-dissipating structure, and on the land side behind this wave-dissipating structure, the sand carried by the waves is deposited to form a beach. Beach nourishment method. 2. A method of forming a grid-shaped wave-dissipating laying material having a grid of a required size by using a material having a shearing resistance and a tensile resistance, such as steel or reinforced concrete, along a shoreline of a coast to be nourished. The beach nourishment method according to claim 1, wherein the beach is provided in parallel at predetermined intervals, and sand is deposited on the land side of the wave-dissipating structure to form a sandy beach.