JP6045196B2 - Offshore structure - Google Patents

Description

  The present invention relates to an offshore structure installed in a port, coast, fishery facility, or the like.

  In general, for example, breakwaters, which are offshore structures, are mostly composed of hybrid dike composed of a plurality of concrete caissons arranged on a foundation mound from an economical viewpoint. The role of the foundation mound is to provide a load distribution effect that reduces the installation pressure on the soft submarine ground, and to provide a foundation on which the caisson can be installed as planned by leveling the top surface. The stability of the rubble of the foundation mound is usually determined by the required weight so that the wave resistance stability can be ensured according to the wave conditions of the installation sea area. Further, when the required weight of the stone material is insufficient, a concrete block such as a covering block or a rooting block is used.

  The tsunami cycle is a long-period water level fluctuation ranging from several minutes to several hours, and has a characteristic of having large wave energy even if the wave height is small because the duration is an order of magnitude. However, the design wave height of a wave (wind wave or swell) of several seconds to 20 seconds has been large conventionally, and the section of the levee body has been determined by the wave resistance stability against this. However, it has become clear that the fundamental mound collapses due to the action of a huge tsunami that has never been experienced before, and the stability of the caisson is significantly reduced. For example, because the tsunami cycle is long, a permeable structure such as a foundation mound made of laminated rubble easily penetrates the inside of the dam body, and the plan layout and water depth of the structure change to change the tsunami. Phenomenon in which the foundation mound collapses due to the influence of the wave height of the water and the flow velocity increasing accordingly (according to Green's law, proportional to the 1/2 power of the channel width and the 1/4 power of the water depth). Has become clear. Therefore, when estimating the flow velocity considering the deformation of the tsunami and calculating the stable mass for it, it may become necessary to have a mass of several hundred tons, which is not practical with the weight structure. It was.

  As described above, the factors that cause the foundation mound to become unstable can be assumed to be the lifting pressure accompanying the surface flow velocity, the flow that propagates through the permeation layer (inside the foundation mound), and to suppress these It is considered effective to cover the foundation mound.

  For example, in Patent Document 1, when constructing a structure such as an artificial mound, a large-size mat member is used, and a lump of a certain size such as rubble or concrete is stacked as a filling material. It is described that it is constructed to cover and integrate.

JP 2005-23635 A

  However, in the invention of Patent Document 1, an artificial mound is covered and integrated with a mat member, but a normal mat member has poor tensile strength and elasticity, and can be damaged or broken when an offset load is applied to the mat member. There is a nature and cannot be adopted.

  This invention is made | formed in view of this point, and it aims at providing the offshore structure which ensures stability of a foundation mound.

As a means for solving the above-mentioned problems, the present invention is characterized in that the foundation mound of an offshore structure is impervious to block the flow of seawater into the foundation mound. The covering sheet is covered with a coating sheet having a hardly water-permeable property, and the covering sheet contains an organic fiber having a high strength of a tensile strength of 15 cN / dtex or more and a high elasticity property of a tensile elastic modulus of 400 cN / dtex or more. The organic fibers are made of a polyolefin resin .
The invention described in claim 2 is the invention described in claim 1, wherein the organic fiber has a tensile strength of 15 cN / dtex to 60 cN / dtex and a tensile strength of 400 cN / dtex or more. It has a characteristic of high elasticity of 2400 cN / dtex or less.
In the first aspect of the invention, since the covering sheet has a water-impermeable or hardly water-permeable characteristic, the flow passing through the basic mound can be blocked, and the flow propagates through the permeable layer (inside the basic mound). In contrast, stability can be improved.
In the inventions of claims 1 and 2, since the covering sheet contains organic fibers having particularly high elasticity and high strength, it is possible to follow fine irregularities on the surface of the foundation mound, and an uneven load acts. Even in this case, breakage and breakage can be suppressed, and as a result, the stability of the foundation mound can be ensured for a long time.
Furthermore, the invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2 , the covering sheet is arranged so as to cover the whole of the basic mound.

The invention described in claim 4 is characterized in that, in the invention described in any of claims 1 to 3 , the covering sheet is stretched by a plurality of earth anchors.
In the invention of claim 4 , the covering sheet can be firmly fixed to the foundation mound.

The invention described in claim 5 is characterized in that, in the invention described in any of claims 1 to 4 , a plurality of the covering sheets are overlapped.
In the invention of claim 5 , since a plurality of covering sheets are overlapped, the stability of the basic mound can be further improved.

  According to the marine structure of the present invention, the entire foundation mound of the marine structure is covered with the coating sheet having impermeable or hardly permeable characteristics, so that the surface layer portion of the foundation mound is not exposed to the outside. The propagation of water to the inside of the foundation mound can be blocked, and the stability of the foundation mound can be ensured even when a tsunami or the like occurs. Furthermore, since the coated sheet contains organic fibers having a high strength with a tensile strength of 15 cN / dtex or more and a high elasticity with a tensile modulus of 400 cN / dtex or more, the coated sheet is damaged or broken by an unbalanced load on the coated sheet. Can be suppressed, and the basic mound can be stabilized for a long period of time.

FIG. 1 is a cross-sectional view of an offshore structure according to an embodiment of the present invention. 2 is a cross-sectional view of FIG. 1 with the caisson removed.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS. 1 and 2.
As shown in FIG. 1, an offshore structure 1 according to an embodiment of the present invention includes a foundation mound 2 extending in a direction perpendicular to the wave direction, a plurality of caissons 3 arranged on the foundation mound 2, and a foundation mound 2. It is comprised from the coating sheet 4 arrange | positioned so that the whole may be covered. Each caisson 3 is filled with a filling material such as stone.

  As shown in FIGS. 1 and 2, the foundation mound 2 is configured by stacking rubble and the like in a trapezoidal cross section. The entire base mound 2 is covered with a covering sheet 4. The covering sheet 4 has a width longer than the entire width in the width direction (wave direction) of the foundation mound 2, and covers the sea bottom surface at a predetermined distance from the lower ends of the slopes on both sides of the foundation mound 2 in the width direction.

  Further, as shown in FIG. 2, the covering sheet 4 is fixed on the foundation mound 2 by a plurality of earth anchors 5. Specifically, the covering sheet 4 has two cross-sections with a distance from the lower end of the offshore slope of the foundation mound 2 to the offshore seabed, and a distance of 2 offshore slope of the foundation mound 2. Two places are fixed at a distance from the bottom of the land side slope of the foundation mound 2 and two places are fixed from the bottom of the land side slope of the foundation mound 2 to the bottom of the sea surface at the land side. The earth anchors 5 arranged on the slopes on the offshore side and on the land side of the foundation mound 2 pass through the foundation mound 2 and have their lower ends reaching the inside of the seabed. The covering sheet 4 is stretched so as to stick to the surface of the foundation mound 2 by each earth anchor 5. In addition, the fixed location by the earth anchor 5 of the covering sheet 4 is not limited to the above-described fixed location, and the fixed location and the number thereof may be set as needed.

  In the above-described embodiment, the covering sheet 4 is disposed so as to cover the entire foundation mound 2. However, depending on the case, the covering sheet is in the vicinity of the center in the width direction in the contact range of the foundation mound 2 with the caisson 3. It is not necessary to cover with 4. Further, in the present embodiment, the basic mound 2 is covered with a single covering sheet 4, but a plurality of covering sheets 4 may be overlapped to cover the basic mound 2.

  The covering sheet 4 uses organic fibers having high strength and high elastic modulus as main constituent materials. This organic fiber has a high tensile strength (tensile strength) of 15 cN / dtex or more and 60 cN / dtex or less, and a high tensile elastic modulus of 400 cN / dtex or more and 2400 cN / dtex or less as measured by the method defined in JIS L1013. Has elastic properties. This organic fiber is excellent in wear resistance, fatigue resistance, and durability. The organic fiber can be used in the form of a woven fabric, a knitted fabric, a net or the like. The organic fiber can be obtained by, for example, melt spinning or gel spinning of high molecular weight polyolefin (preferably polyethylene or polypropylene).

Moreover, the coating sheet 4 has a water-impermeable or hardly water-permeable characteristic. By the way, the water impermeability means a water permeability coefficient measured by a method prescribed in JIS A1218 of 1 × 10 ⁻⁹ or less, and the poor water permeability means a water permeability coefficient of 1 × 10 ⁻² or less. Since the effect of the present invention is ensured by reducing the hydraulic conductivity of the stone layer used for the foundation mound 2 by about two orders of magnitude, the covering sheet 4 of the present embodiment has a hydraulic conductivity of 1 ×. It is preferably 10 ⁻² or less, particularly preferably 1 × 10 ⁻³ or less.

Therefore, as a means for the covering sheet 4 to have water-impermeable or hardly water-permeable characteristics, for example, it can be achieved by combining a sheet-like body with the organic fiber.
For example, when a non-woven fabric is employed as the composite sheet-like body, the non-woven fabric preferably has a constituent fiber of 5.5 dTex or less in order to reduce water permeability, and particularly preferably 1.5 dTex to 3.3 dTex. It is as follows. The basis weight of the nonwoven fabric is at least 80 g / m ² or more, preferably 150 g / m ² or more and 1000 g / m ² or less. The material of the nonwoven fabric is not particularly limited, but is particularly preferably polyolefin or polyester. The method for joining the organic fiber and the nonwoven fabric is not particularly limited, but it is possible to join by a method using a heat-bonding fiber or sewing.

  For example, when a film-like sheet is employed as the composite sheet-like body, a polyolefin film having a thickness of about 50 to 3000 microns can be employed. The material of the film is particularly preferably a material similar to organic fiber from the viewpoint of adhesion and durability from the viewpoint of adhesion and durability. When the film is thin, some voids may be generated when heat lamination is performed. However, if the thickness is 50 microns or more, it is possible to ensure the poor water permeability required in the present invention. On the other hand, if the thickness is greater than 3000 microns, the followability of the foundation mound 2 to the unevenness is lowered and a large heavy machine is required for laying work, which is not preferable.

  In addition, as a means in which the coating sheet 4 has water-impermeable or hardly water-permeable characteristics, for example, the organic fiber is coated with a weather-resistant resin, for example, an acrylic resin or a polyolefin resin. Means may be employed.

First, by covering the entire foundation mound 2 with the covering sheet 4, the surface stone or concrete block is not directly subjected to the flow on the surface layer. That is, in the conventional method for calculating the stable mass of stone with respect to the flow, the inner stone is more stable than the surface stone, and the effect is exerted on the action of the lifting pressure due to the surface flow velocity by the same mechanism. . Furthermore, since the covering sheet 4 has water-impermeable or hardly water-permeable characteristics, the flow passing through the foundation mound 2 can be blocked, and the flow that propagates through the permeable layer (inside the foundation mound 2). Can also increase stability.
In addition, the covering sheet 4 includes organic fibers having a high strength with a tensile strength of 15 cN / dtex or more and 60 cN / dtex or less, and a high modulus of elasticity of 400 cN / dtex or more and 2400 cN / dtex or less. It is possible to follow the fine irregularities on the surface of the mound 2 and to suppress breakage and breakage even when a load (uneven load) is applied locally.

  As described above, in the offshore structure 1 according to the embodiment of the present invention, the entire base mound 2 is covered with the covering sheet 4, and the covering sheet 4 has a high strength of 15 cN / dtex or more, In addition, since the covering sheet 4 includes an organic fiber having a high elasticity characteristic of an elastic modulus of 400 cN / dtex or more, and the covering sheet 4 has a water-impermeable or hardly water-permeable characteristic, fine irregularities on the surface of the basic mound 2 Even if a load (uneven load) acts locally, breakage and breakage can be suppressed. As a result, the foundation mound 2 can be controlled with respect to the foundation mound 2 over a long period of time, and the flow propagating through the permeation layer (inside the foundation mound 2) can be blocked. 2 stability can be improved. And even if a huge tsunami etc. act, the effect mentioned above can be produced and the foundation mound 2 can be stabilized.

  1 offshore structure, 2 foundation mound, 3 caisson, 4 covering sheet, 5 earth anchor

Claims (5)

The foundation mound of the offshore structure is covered with a covering sheet having impermeable or hardly permeable characteristics to block the flow of seawater into the foundation mound,
The cover sheet is viewed contains tensile strength strength of more than 15 cN / dtex, and elongation modulus organic fibers having the characteristics of more high elastic 400 cN / dtex,
The said organic fiber consists of polyolefin resin, The marine structure characterized by the above-mentioned .   2. The organic fiber according to claim 1, wherein the organic fiber has a high strength with a tensile strength of 15 cN / dtex or more and 60 cN / dtex or less, and a high elasticity with a tensile modulus of 400 cN / dtex or more and 2400 cN / dtex or less. The offshore structure described. Marine structure according to claim 1 or 2, characterized in that placing the cover sheet so as to cover the entirety of the foundation mound. The offshore structure according to any one of claims 1 to 3 , wherein the covering sheet is stretched by a plurality of earth anchors. The marine structure according to any one of claims 1 to 4 , wherein a plurality of the covering sheets are overlapped.

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