anchor

Abstract

To provide an anchor with improved pull-out resistance. [Solution] The anchor (10) comprises a main steel pipe (1A) and secondary steel pipes (1B, 1C) that are shorter in length than the main steel pipe (1A), and each steel pipe is fixed in place.

Description

Technical Field

[0001] The present invention relates to an anchor installed on the seabed.

Background Art

[0002] There are two types of structural forms of offshore wind power generation facilities: "fixed-bottom type" and "floating type". Since the floating type is less affected by water depth compared to the fixed-bottom type, in the future, as the installation target area of offshore wind power generation facilities is expected to expand to deeper offshore areas with greater water depth, the need for the floating type is increasing.

[0003] In the floating type, a mechanism is generally known in which a floating structure carrying a power generation facility is floated on the sea, and the floating structure is moored by connecting it to an anchor installed on the seabed using a mooring cable. In such a mooring mechanism, since a pulling force acts on the anchor through the mooring cable, a corresponding pulling resistance is required.

[0004] It is known that there are various types of anchors. For example, in Patent Document 1, a mooring foundation disposed in a soft layer is disclosed. As another type, there is a type that exhibits a pulling resistance due to friction with the ground, such as a pile type. In a conventional pile-type anchor, a single columnar structure is inserted into the ground, and a mooring cable is connected to the upper end portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In conventional anchors, which involve inserting a single columnar structure into the ground, improving pull-out resistance can be achieved by increasing the diameter or length of the columnar structure to increase the contact area with the ground. However, this requires specialized manufacturing and is costly, as well as the use of special crane vessels for transportation, further increasing costs.

[0007] Another way to improve pull-out resistance is to increase the coefficient of friction between a single columnar structure and the ground by increasing the cohesion of the surrounding ground. However, this would not only lead to a significant increase in costs, but the ground improvement methods would also be limited in the case of deep water.

[0008] Therefore, one aspect of the present invention aims to realize an anchor with improved pull-out resistance while keeping costs down. [Means for solving the problem]

[0009] To solve the above problems, an anchor according to one aspect of the present invention comprises a main column having a mooring point at its upper end and a group of sub-columns consisting of one or more sub-columns, wherein the length of the sub-columns is shorter than that of the main column, and the main column and the group of sub-columns are integrated.

[0010] According to the above configuration, by providing a group of secondary columns in addition to the main column, a greater pull-out resistance can be achieved compared to the pull-out resistance that can be achieved with the main column alone.

[0011] Specifically, the presence of a group of secondary columns in addition to the main column increases the contact area between the circumferential surface of the main column and the ground, thereby improving the pull-out resistance. For example, if the same contact area as the anchor of the present invention were to be achieved with a single main column, the diameter and length of the column would increase, making manufacturing special and costly, and a special crane ship would be required for transportation, further increasing costs. On the other hand, according to the above configuration of the present invention, since it is a combination of a main column and a group of secondary columns, the diameter and length of the main column can be the same as that of a conventional anchor column. In addition, the group of secondary columns is shorter than the main column, making transportation easier.

[0012] Furthermore, the presence of not only main columns but also a group of secondary columns increases the total weight of the anchor compared to an anchor composed of a single main column, thereby improving its pull-out resistance.

[0013] Furthermore, since the secondary columns integrated with the main column are shorter in length than the main column, by inserting the entire secondary column group below the seabed surface, in-situ ground material is deposited above the upper ends of the secondary column group, and this ground material imparts passive earth pressure to the anchor. As a result, in addition to the circumferential friction between the circumferential surfaces of each column constituting the main column and secondary column group and the ground, the passive earth pressure can be included in the pull-out resistance force. Therefore, an anchor with improved pull-out resistance can be realized.

[0014] An anchor according to one aspect of the present invention may be configured such that, in the above configuration, the group of sub-columns includes a plurality of sub-columns, and the columns constituting the main column and the group of sub-columns are arranged such that the length of the sub-columns decreases as they move away from the main column, and the upper ends of the sub-columns are lower in the vertical direction as they move away from the main column.

[0015] According to the above configuration, by inserting the entire group of sub-pillars into the seabed, a virtual inclined surface is created above the upper end of each sub-pillar in the seabed, and the ground located above this virtual inclined surface can apply passive earth pressure to the anchor.

[0016] In one aspect of the present invention, the anchor may be configured such that each of the columns is arranged such that its respective axis is contained within the same plane.

[0017] According to the above configuration, by inserting the entire group of sub-pillars into the seabed, a virtual inclined surface is created above the upper end of each sub-pillar in the seabed, and the ground located above this virtual inclined surface can effectively impart passive earth pressure to the anchor.

[0018] An anchor according to one aspect of the present invention may further include a mooring rope for securing a floating body to a predetermined position, wherein at least a portion of the main column and all of the sub-column group are inserted into the seabed, and when the anchor is viewed from a vertical direction, the direction in which the sub-column group protrudes from the main column coincides with or substantially coincides with the direction of the mooring rope from the mooring point to the predetermined position.

[0019] According to the above configuration, the ground located above the virtual inclined surface realized above the upper end of the group of secondary pillars located underground on the seabed can exert passive earth pressure on the anchor, in opposition to the tensile force extending in the direction of the mooring rope from the mooring point to the predetermined position.

[0020] In one aspect of the present invention, the anchor, in the above configuration, may have multiple sub-column groups.

[0021] According to the above configuration, it is possible to increase the weight of the anchor. Furthermore, if the installation positions of each sub-column group are different from each other, it is possible to achieve pull-out resistance against tensile forces in multiple different directions.

[0022] The anchor according to one aspect of the present invention further includes a plurality of mooring cables for mooring each of the plurality of floating bodies at respective predetermined positions in the above-described configuration, at least a part of the main column and all of the plurality of sub-column groups are inserted into the seabed, and when the anchor is viewed from the vertical direction, each direction in which each sub-column group protrudes from the main column coincides or substantially coincides with the direction of each mooring cable from the mooring point to the respective predetermined positions.

[0023] According to the above-described configuration, the sedimentary ground located above the virtual inclined plane realized above the upper end of the sub-column group in the seabed soil can apply passive earth pressure to the anchor against the tensile force acting in the direction of each mooring cable.

Effect of the Invention

[0024] According to one aspect of the present invention, it is possible to realize an anchor with improved pull-out resistance while suppressing cost increase.

Brief Description of the Drawings

[0025] [Figure 1] It is a schematic view showing one aspect in which an anchor according to an embodiment of the present invention is applied. [Figure 2] It is a cross-sectional view of the portion surrounded by the broken line shown in FIG. 1. [Figure 3] It is a plan view of the portion surrounded by the broken line shown in FIG. 1. [Figure 4] It is a plan view of an anchor according to another embodiment of the present invention. [Figure 5] It is a side view of the anchor shown in FIG. 4. [Figure 6] It is a plan view of an anchor according to another embodiment of the present invention. [Figure 7] It is a view of an anchor of a comparative configuration. [[ID=_{38}]]

Mode for Carrying Out the Invention

[0026] 〔Embodiment 1〕 One embodiment of the present invention will be described in detail below. Figure 1 is a schematic diagram showing one embodiment in which the anchor of this embodiment is applied. Figure 2 is a cross-sectional view of the area enclosed by the dashed line in Figure 1. Figure 3 is a plan view of the area enclosed by the dashed line in Figure 1.

[0027] As shown in Figure 1, the anchor 10 of this embodiment is installed on the seabed 800 to moor, for example, a floating structure 100 (floating body) to be installed on the sea. The anchor 10 generally comprises a plurality of columnar structures extending along the axial direction and a mooring rope 700. The floating structure 100 is connected to the end of the mooring rope 700. The mooring rope 700 can be a well-known mooring rope such as a chain.

[0028] Note that the structure of the floating structure 100 shown in Figure 1 is just one example. The floating structure 100 could be an offshore wind power generation facility, etc. The number of anchors 10 installed on a single floating structure 100 or the form of the mooring ropes 700 shown in Figure 1 is also just one example and is not limited to these. Furthermore, although Figure 1 is intended for application in the ocean 802, it is not limited to lakes or other seas. The anchor 10 is an anchor installed on the seabed to moor a floating structure installed on the water. As an example, the anchor 10 of this embodiment is intended to be placed on the seabed at a depth of 200m or more, but it can also be placed at greater depths, for example, on the seabed at a depth of 1000m or 2000m. There are no particular restrictions on the geology of the seabed, and it may be sandy, clayey, or a mixture of these.

[0029] Each drawing also shows the three-dimensional coordinate system (XYZ). In this three-dimensional coordinate system, the vertical direction is defined as the Z-axis, and the horizontal plane is defined as the XY plane.

[0030] The anchor 10 generally comprises a plurality of columnar structures extending along the axial direction. Here, each columnar structure may be a hollow structure with a cavity formed inside (also called a tubular structure or cylindrical structure), or a solid structure with material filled inside, or, when viewed along the axial direction, part of it may be a hollow structure and the other part may be a solid structure. Furthermore, it is preferable that the columnar structure satisfies the predetermined strength required for an anchor (e.g., strength against bending). In addition, it is preferable that the cross-sectional area of ​​the cross-section (a section perpendicular to the axial direction) of the columnar structure is small. The smaller the cross-sectional area of ​​the cross-section of the columnar structure, the less resistance can be generated when inserting the structure into the seabed. Examples of preferred cross-sectional shapes include closed rings such as circles and polygons, and H-shapes (also called I-shapes). In this embodiment, a group of cylindrical steel pipes with a circular cross-sectional shape (more specifically, a hollow ring) is used. When using a hollow columnar structure, the anchor 10 is inserted into the seabed from the open lower end, and sand or soil may fill the internal cavity.

[0031] The anchor 10 comprises a group of steel pipes with open lower ends, forming a plurality of columnar structures. Specifically, it comprises a main steel pipe 1A (main column) as shown in Figures 2 and 3, and a group of secondary steel pipes (secondary column group) consisting of a first secondary steel pipe 1B (secondary column) and a second secondary steel pipe 1C (secondary column). Each steel pipe (each column) may be inserted into the ground on the seabed from its open lower end, allowing sand and soil to fill the cavity inside the pipe.

[0032] The main steel pipe 1A has a lower end portion 2Aa and an upper end portion 2Ab. The lower end portion 2Aa may be open as described above. In this embodiment, the upper end portion 2Ab is also open. Having both ends of the anchor 10 open makes it easier to insert the anchor 10 into the seabed. However, even if the lower end portion 2Aa is open, the upper end portion 2Ab may be closed. Here, the "end portion" of the lower end portion 2Aa and the upper end portion 2Ab refers to the end portion when viewed along the central axis 1AC (Figure 3) of the main steel pipe 1A. In this embodiment, as described above, the main steel pipe 1A is cylindrical and cut so that both ends are perpendicular to the central axis 1AC. In this case, the end faces formed at both ends constitute the lower end portion 2Aa and the upper end portion 2Ab. However, at least one of the ends of the main steel pipe 1A may be cut so that it intersects the central axis 1AC at an angle other than 90 degrees. In this case, the diagonally cut tip of the main steel pipe 1A constitutes at least one of the lower end portion 2Aa and the upper end portion 2Ab.

[0033] The main steel pipe 1A has a mooring point 1a near its upper end 2Ab. When the main steel pipe 1A is installed in the ground at the seabed 800, the upper end 2Ab side, specifically the part where the mooring point 1a is located, protrudes into the sea from the surface of the seabed 800. The location where the mooring point 1a is provided on the main steel pipe 1A may be at the upper end 2Ab (the upper end face in this embodiment) or in the vicinity of the upper end 2Ab. Here, the vicinity of the upper end 2Ab is defined as the section of the main steel pipe 1A that includes the upper end 2Ab and has a length equivalent to the diameter from the radius of the main steel pipe 1A.

[0034] A mooring rope 700 is connected to mooring point 1a. The shape and configuration of mooring point 1a are not particularly limited. A tensile force acts on mooring point 1a from the mooring rope 700. This tensile force is the force exerted on the mooring rope 700 in order to moor the floating structure 100 (Figure 1) connected to the mooring rope 700 in a predetermined position.

[0035] The first auxiliary steel pipe 1B has a lower end 2Ba and an upper end 2Bb. The upper end 2Bb is located vertically below the upper end 2Ab of the main steel pipe 1A. For example, the vertical length of the first auxiliary steel pipe 1B, i.e., the length of the pipe between the lower end 2Ba and the upper end 2Bb, is shorter than the vertical length of the main steel pipe 1A.

[0036] When the first auxiliary steel pipe 1B is installed in the ground at sea level 800, its upper end 2Bb is below the surface of the sea level 800. In other words, when the first auxiliary steel pipe 1B is installed in the ground at sea level 800, the entirety of the first auxiliary steel pipe 1B is buried in the ground at sea level 800. For example, the upper end 2Bb is buried below the surface of the sea level 800 by an amount equivalent to the diameter of the first auxiliary steel pipe 1B.

[0037] The first auxiliary steel pipe 1B only needs to have its upper end 2Bb in the position described above, and there are no particular restrictions on the position of its lower end 2Ba. However, as an example, the lower end 2Ba is located in approximately the same position as the lower end 2Aa of the main steel pipe 1A in the vertical direction, more specifically, in the same horizontal plane, as shown in Figure 2.

[0038] The diameter of the first auxiliary steel pipe 1B is, for example, less than or equal to the diameter (pipe diameter) of the main steel pipe 1A.

[0039] The first auxiliary steel pipe 1B may be a hollow columnar structure with its lower end 2Ba and upper end 2Bb open in the same way as the lower end 2Aa and upper end 2Ab of the main steel pipe 1A. In Figure 2, the upper end 2Bb has a pipe end face (annular surface) perpendicular to the central axis of the first auxiliary steel pipe 1B, but is not limited to this. The pipe end face may also be along a hypothetical inclined surface K, which will be described in detail later.

[0040] The second auxiliary steel pipe 1C has a lower end portion 2Ca and an upper end portion 2Cb. For example, the length of the second auxiliary steel pipe 1C along the vertical direction, i.e., the length between the lower end portion 2Ca and the upper end portion 2Cb, is shorter than the length of the first auxiliary steel pipe 1B along the vertical direction.

[0041] When the second auxiliary steel pipe 1C is installed in the ground at sea level 800, its upper end 2Cb is below the surface of the sea level 800, and its upper end 2Cb is located vertically lower than the upper end 2Bb of the first auxiliary steel pipe 1B. In other words, when the second auxiliary steel pipe 1C is installed in the ground at sea level 800, the entirety of the second auxiliary steel pipe 1C is buried in the ground at sea level 800, and as an example, its upper end 2Cb is buried underground to a depth equivalent to twice the diameter of the second auxiliary steel pipe 1C below the surface of the sea level 800.

[0042] The second auxiliary steel pipe 1C only needs to have its upper end 2Cb in the position described above, and there are no particular restrictions on the position of its lower end 2Ca. However, as an example, as shown in Figure 2, the lower end 2Ca is located in approximately the same position in the vertical direction as the lower end 2Aa of the main steel pipe 1A and the lower end 2Ba of the first auxiliary steel pipe 1B, more specifically, in the same horizontal plane.

[0043] The diameter of the second auxiliary steel pipe 1C may, for example, be the same as the diameter of the first auxiliary steel pipe 1B.

[0044] The second auxiliary steel pipe 1C may be a hollow columnar structure with its lower end 2Ca and upper end 2Cb open, similar to the lower end 2Ba and upper end 2Bb of the first auxiliary steel pipe 1B. In Figure 2, the upper end 2Cb has an end face (annular surface) perpendicular to the central axis of the second auxiliary steel pipe 1C, but is not limited to this. The end face may also be along a hypothetical inclined surface K, which will be described in detail later.

[0045] Furthermore, the main steel pipe 1A, the first auxiliary steel pipe 1B, and the second auxiliary steel pipe 1C are integrated. Specifically, they are connected to each other. For example, adjacent lower ends 2Aa, 2Ba, and 2Ca may be connected by connecting members, but there are no particular restrictions. Instead of the lower ends 2Aa, 2Ba, and 2Ca being connected to each other, for example, the outer surfaces of the main steel pipe 1A, the first auxiliary steel pipe 1B, and the second auxiliary steel pipe 1C may be fixed to each other.

[0046] The main steel pipe 1A, the first secondary steel pipe 1B, and the second secondary steel pipe 1C are located almost in a straight line in the plan view shown in Figure 3 (when viewed from the vertical direction). As shown in Figure 3, in this example, the main steel pipe 1A, the first secondary steel pipe 1B, and the second secondary steel pipe 1C are arranged in this order in the negative direction of the X axis. The central axis of each steel pipe is aligned with the vertical direction. In other words, each steel pipe is arranged such that its respective central axis is contained in the same plane, and the length of the secondary steel pipes 1B and 1C decreases as they move away from the main steel pipe 1A. This can be rephrased as follows: when the anchor 10 is viewed from the vertical direction, the direction in which the group of secondary steel pipes protrudes from the main steel pipe 1A coincides with the direction of the mooring rope 700 that goes from the mooring point 1a to the predetermined position. Note that this configuration is not limited to this example, and as shown in Figure 3, when viewed from the plan, the line connecting the mooring rope 700 and the central axis of each steel pipe may coincide. In this case, when viewed in a plan view as shown in Figure 3, an angle of, for example, ±45 degrees may be provided between the mooring rope 700 and the line connecting the central axes of each steel pipe, with mooring point 1a as the center.

[0047] As shown in Figure 2, the secondary steel pipes 1B and 1C are arranged such that their lengths decrease as they move away from the main steel pipe 1A, and the upper ends of the secondary steel pipes 1B and 1C are arranged so that they become lower in the vertical direction as they move away from the main steel pipe 1A. As a result, the upper end groups of the secondary steel pipes (upper ends 2Bb and 2Cb) are configured in a downward step-like manner as they move away from the main steel pipe 1A relative to the surface of the seabed 800. Approximating this, it can be considered that a virtual inclined surface K is formed that slopes away from the surface of the seabed 800 as it moves away from the main steel pipe 1A.

[0048] The method for installing (driving) such an anchor 10 to the seabed 800 is as follows: Before driving, for example, the main steel pipe 1A, the first auxiliary steel pipe 1B, and the second auxiliary steel pipe 1C are connected on a workboat at sea, then lowered into the sea, descended to the seabed 800, and driven into the seabed 800. The driving method can utilize the conventional method of driving a single columnar structure into the seabed. Although connecting the steel pipes before driving results in a relatively large anchor, the penetration resistance is not very large because each steel pipe has an open end.

[0049] Connecting the steel pipes before driving them into the ground offers the advantage of easily arranging them in the positional relationship shown in Figure 3. However, the installation (driving) method is not limited to this. After each steel pipe is driven to a predetermined depth of 800 mm below the seabed, if necessary, the top of each auxiliary steel pipe is covered with in-situ material from the seabed (such as sand or clay). This makes it possible to create a ground surface at the same height as the surrounding 800 mm seabed surface in the original location. This is also true when solid columnar structures are used instead of steel pipes.

[0050] Incidentally, the anchor 10 is installed on the seabed (seabed) away from the seabed (seabed) directly below the floating structure 100 in order to moor the floating structure 100 in a predetermined position. For this reason, the mooring ropes 700 are extended at a predetermined angle of inclination with respect to the vertical direction, and as shown in Figure 1, the mooring ropes 700 connected to each anchor 10 are extended in a direction away from each other toward the seabed. In this case, a force acts on each mooring rope 700 in an oblique upward direction toward the floating structure 100, and this force is applied as a "tensile force" to the mooring point 1a of the anchor 10.

[0051] Here, a comparative configuration that falls outside the scope of the present invention is shown in Figure 7. Figure 7 is a replacement for Figure 2. The comparative configuration anchor 1000 shown in Figure 7 is a single columnar structure, and its central axis 1000C is inserted into the ground at seabed 800 along the vertical direction. The comparative configuration anchor 1000 inserted vertically in this way is subjected to circumferential friction T that resists the tensile force P received from the mooring rope 700. The circumferential friction T is the frictional resistance between the circumferential surface of the steel pipe of the comparative configuration anchor 1000 and the ground in contact with that circumferential surface.

[0052] In the comparative anchor configuration 1000, the force resisting the tensile force P, i.e., the pull-out resistance, can be rephrased as being solely due to circumferential friction T. In contrast, the anchor 10 of this embodiment can include passive earth pressure in addition to circumferential friction T, thus increasing the pull-out resistance compared to the comparative anchor configuration 1000. This will be explained below.

[0053] When anchor 10 receives a tensile force P from the mooring rope 700 and attempts to pull up so that the mooring point 1a approaches the predetermined position (the mooring position of the floating structure 100), a passive earth pressure S, as shown in Figure 2, is exerted on the upper end groups (upper end 2Ab, 2Bb, 2Cb) of each steel pipe that constitute the virtual inclined surface K. This passive earth pressure S is generated by the ground in the area between the passive collapse line B, which virtually extends toward the sea surface from the position of the lower end 2Ca of the second auxiliary steel pipe 1C, and the virtual inclined surface K.

[0054] In other words, the anchor 10 shown in Figure 2 can include passive earth pressure S in addition to circumferential friction T as part of its pull-out resistance. This makes it possible to achieve an anchor with higher pull-out resistance compared to the comparative anchor configuration 1000.

[0055] Here, the inclination angle θ1 (shown in Figure 2) of the virtual inclined surface K with respect to an axis along the vertical direction (for example, the central axis of the second auxiliary steel pipe 1C) can be in the range of 5 to 45 degrees, for example. Within this range, it is preferable to have an inclination angle of 15 to 35 degrees.

[0056] Furthermore, the angle θ2 (shown in Figure 2) between the straight line (or its extension) connecting the predetermined position and the mooring point 1a and the axis along the vertical direction (for example, the central axis 1AC of the main steel pipe 1A) may be between 5 degrees and 45 degrees. When subjected to a tensile force from the predetermined position, the passive collapse line virtually extending from the lower end of the anchor toward the seabed surface and the seabed ground in the area enclosed by the circumferential surface of the anchor exert a passive earth pressure on the circumferential surface of the anchor, thereby realizing an anchor with high pull-out resistance.

[0057] The inclination angles θ1 and θ2 described above can both be predetermined before the anchor 10 is installed on the seabed 800. Specifically, the inclination angles θ1 and θ2 described above can be predetermined based on at least the position where the floating structure 100 will be moored (a predetermined position), the planned installation location of the anchor 10, the length and diameter of each steel pipe of the anchor 10, and the total weight.

[0058] Furthermore, the inclination angle θ1 of the virtual inclined surface K can be freely adjusted by changing the length and number of auxiliary steel pipes.

[0059] For example, anchor 10 may consist of a main steel pipe 1A with a diameter of 1000 mm, a length of 5000 mm, and a weight of 1500 kg, a first secondary steel pipe 1B with a diameter of 900 mm, a length of 3000 mm, and a weight of 800 kg, and a second secondary steel pipe 1C with a diameter of 900 mm, a length of 2000 mm, and a weight of 530 kg, with the inclination angle θ1 of the hypothetical inclined surface K being 45 degrees and the angle θ2 being 45 degrees, but is not limited to this.

[0060] As described above, the anchor 10 of this embodiment provides an anchor 10 with increased pull-out resistance. In short, it is possible to create an anchor 10 that is less likely to come loose compared to an anchor of the same size that is driven in vertically (comparative configuration anchor 1000 in Figure 7).

[0061] Furthermore, within the limits of cost permissible, the anchor 10 can be expected to provide greater passive earth pressure resistance by increasing the length of each steel pipe. In addition, by making the cross-sectional shape of each steel pipe more conducive to obtaining passive earth pressure resistance, an increase in pull-out resistance can be expected.

[0062] Here, we will explain the advantages of the anchor 10 of this embodiment compared to the case where a single steel pipe is driven diagonally into the seabed 800 with respect to the vertical direction, and the circumferential surface of that steel pipe becomes the inclined surface K.

[0063] When constructing a single columnar structure driven at an angle (hereinafter referred to as an inclined pile), in typical port construction (up to a water depth of about 50m), the steel pipe is driven while maintaining the specified angle of inclination using leaders or pile keepers mounted on a crane ship, or guide frames (guide members) constructed separately as temporary structures. While it is possible to physically maintain the specified angle of inclination with leaders or pile keepers, this would require pliers capable of handling water depths of 1000m, which is impractical. Furthermore, holding the end of the steel material, including the pliers, which would exceed 1000m in length, raises concerns about deflection of the steel pipe. In addition, the weight of the steel, including the pliers, would increase, requiring a larger lifting capacity.

[0064] Furthermore, the aforementioned guide material also presents similar challenges to those for leaders and pile keepers, as it involves handling steel materials exceeding 1000m in length. In fact, installing a structure, even a temporary one, at a depth of 1000m is inherently impractical.

[0065] In this embodiment, the floating structure 100 moored by the anchor according to one aspect of the present invention is intended for use in the Exclusive Economic Zone (EEZ), and is designed to handle water depths exceeding 1000m. Therefore, the anchor 10 of this embodiment avoids the aforementioned problems that arise when constructing inclined piles, and by realizing the inclined surface of the inclined pile as a virtual inclined surface K using a secondary steel pipe, it makes it possible to include passive earth pressure in the pull-out resistance.

[0066] Furthermore, the addition of auxiliary steel pipes 1B and 1C to the main steel pipe 1A increases the total weight and circumferential area of ​​the anchor 10. Therefore, it is more advantageous against tensile forces than a single inclined pile.

[0067] In this embodiment, the auxiliary steel pipes consist of two pipes, a first auxiliary steel pipe 1B and a second auxiliary steel pipe 1C. However, the present invention is not limited to this, and one or more auxiliary steel pipes are sufficient, but two or more are preferable when considering passive earth pressure.

[0068] The cross-sectional shape of each steel pipe 1 of the anchor 10 is not limited to a circle. A cross-section refers to a section perpendicular to the central axis of the steel pipe. The cross-sectional shape of each steel pipe may be a shape that is more likely to provide passive earth pressure resistance. This is expected to increase the pull-out resistance. Possible cross-sectional shapes of steel pipes other than a circle include a square (square, rectangle) or an H-shape (I-shape), etc.

[0069] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0070] In the anchor of Embodiment 1 described above, the auxiliary steel pipes 1B and 1C are arranged along the negative X-axis direction of the main steel pipe 1A. In this case, the direction in which the tensile force acts is unidirectional. In contrast, the anchor of this embodiment differs in that the auxiliary steel pipe group is also arranged in the positive X-axis direction of the main steel pipe 1A. In other words, the anchor of this embodiment has multiple auxiliary steel pipe groups (auxiliary column groups). This will be explained using Figures 4 and 5.

[0071] Figure 4 is a plan view of the anchor 10A of this embodiment, and corresponds to Figure 3 of Embodiment 1. Figure 5 is a side view of the anchor 10A of this embodiment.

[0072] As shown in Figures 4 and 5, the anchor 10A has auxiliary steel pipes 1B and 1C arranged along the negative X-axis direction of the main steel pipe 1A, as well as a third auxiliary steel pipe 1D and a fourth auxiliary steel pipe 1E arranged along the positive X-axis direction of the main steel pipe 1A.

[0073] The third auxiliary steel pipe 1D may have the same configuration as the first auxiliary steel pipe 1B, and the fourth auxiliary steel pipe 1E may have the same configuration as the second auxiliary steel pipe 1C. However, they do not have to be the same. The main steel pipe 1A, the third auxiliary steel pipe 1D, and the fourth auxiliary steel pipe 1E are arranged such that their respective central axes are contained in the same plane, and the lengths of the third auxiliary steel pipe 1D and the fourth auxiliary steel pipe 1E decrease as they move away from the main steel pipe 1A. Furthermore, as shown in Figure 5, the upper ends 2Db and 2Eb of the third auxiliary steel pipe 1D and the fourth auxiliary steel pipe 1E are arranged such that they become lower along the vertical direction as they move away from the main steel pipe 1A. In addition, the lower ends 2Aa, 2Da, and 2Ea of the main steel pipe 1A, the third auxiliary steel pipe 1D, and the fourth auxiliary steel pipe 1E are located in the same position in the vertical direction, more specifically, within the same plane.

[0074] As shown in Figure 5, the arrangement of the auxiliary steel pipes 1D and 1E results in the upper end groups (upper end 2Db, 2Eb) being configured in a downward step-like manner, moving away from the main steel pipe 1A and away from the seabed 800 surface. Approximating this, it can be considered that a virtual inclined surface K is formed that slopes away from the seabed 800 surface as it moves away from the main steel pipe 1A.

[0075] In other words, since the anchor 10A of this embodiment is equipped with a group of auxiliary steel pipes at symmetrical positions with respect to the main steel pipe 1A, it can withstand tensile forces from a floating structure in two directions. In this case, the floating structures in each direction may be separate floating structures. The two tensile forces from the floating structure are indicated by the two mooring ropes 700 shown in Figure 5. When the anchor 10A is viewed from the vertical, the directions in which each group of auxiliary steel pipes protrudes from the main steel pipe 1A coincide with or approximately coincide with the direction of each mooring rope 700 that goes from the mooring point 1a to the respective predetermined position. Here, approximately coincidence means that when the anchor 10A is viewed from the vertical, there may be an angle, for example, within the range of ±45 degrees, between the mooring rope 700 and the line connecting the central axis of each auxiliary steel pipe in the group of auxiliary steel pipes corresponding to the mooring rope 700, with respect to the mooring point 1a.

[0076] By configuring it in this way, the anchor 10A of this embodiment can include not only the passive earth pressure S on the negative X-axis side of the main steel pipe 1A, but also the passive earth pressure S on the positive X-axis side of the main steel pipe 1A in its pull-out resistance.

[0077] The ability to withstand tensile forces in multiple directions is an advantage over anchors constructed from a single columnar structure or columnar structures inclined in one direction.

[0078] Furthermore, if multiple mooring points 1a are pre-arranged on the main steel pipe 1A, it is possible to realize either the anchor 10 of Embodiment 1 or the anchor 10A of this embodiment, and it is also possible to switch between them easily. Therefore, even if the number or direction of the mooring ropes 700 is different, an anchor with high pull-out resistance can be realized, for example, at a construction site for a floating structure, by changing the number or arrangement direction of the auxiliary steel pipes.

[0079] In this embodiment, anchor 10A was an anchor that could withstand tensile forces in two directions, but it is also possible to realize anchor 10B, for example, as shown in Figure 6.

[0080] Figure 6 corresponds to Figure 4. The anchor 10B shown in Figure 6 includes, in addition to the auxiliary steel pipes 1B, 1C, 1D, and 1E of anchor 10A, the 5th and 6th auxiliary steel pipes 1F and 1G, and the 7th and 8th auxiliary steel pipes 1H and 1I. The 5th auxiliary steel pipe 1F and the 6th auxiliary steel pipe 1G are arranged in this order in the positive Y-axis direction. The 7th auxiliary steel pipe 1H and the 8th auxiliary steel pipe 1I are arranged in this order in the negative Y-axis direction.

[0081] The fifth auxiliary steel pipe 1F and the sixth auxiliary steel pipe 1G are arranged such that their respective central axes are contained within the same plane, and that the lengths of the fifth auxiliary steel pipe 1F and the sixth auxiliary steel pipe 1G decrease as they move away from the main steel pipe 1A. Because the lengths of the auxiliary steel pipes 1F and 1G decrease as they move away from the main steel pipe 1A, the upper end groups of the auxiliary steel pipes 1F and 1G form a virtual inclined surface K that slopes away from the surface of the seabed 800 as it moves away from the main steel pipe 1A.

[0082] Similarly, the seventh auxiliary steel pipe 1H and the eighth auxiliary steel pipe 1I are arranged such that their respective central axes are contained within the same plane, and that the lengths of the seventh auxiliary steel pipe 1H and the eighth auxiliary steel pipe 1I decrease as they move away from the main steel pipe 1A. Because the auxiliary steel pipes 1H and 1I are arranged in such a way that their lengths decrease as they move away from the main steel pipe 1A, the upper end groups of the auxiliary steel pipes 1H and 1I form a virtual inclined surface K that slopes away from the surface of the seabed 800 as it moves away from the main steel pipe 1A.

[0083] Anchor 10B can withstand tensile forces from floating structures in four directions. Furthermore, the configuration of anchor 10B allows for the inclusion of the passive earth pressure S on the negative X-axis side of the main steel pipe 1A, the passive earth pressure S on the positive X-axis side of the main steel pipe 1A, and the passive earth pressure on the positive Y-axis side of the main steel pipe 1A, in the pull-out resistance.

[0084] The configurations of each of the above embodiments provide anchors with improved pull-out resistance. Such effects contribute, for example, to achieving United Nations Sustainable Development Goals (SDGs) Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation," and Goal 14, "Conserve and sustainably use the oceans, seas and marine resources for sustainable development."

[0085] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0086] 1A main steel pipe (main pillar) 1a Mooring point 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I Secondary steel pipe (secondary column) 2Aa, 2Ba, 2Ca, 2Da, 2Ea Lower end 2Ab, 2Bb, 2Cb, 2Db, 2Eb Upper end 10, 10A, 10B anchors 100 Floating structures (floating bodies) 700 Mooring line 800 Undersea

Claims

1. An anchor comprising a main column having a mooring point at its upper end, and a group of sub-columns consisting of one or more sub-columns, The length of the aforementioned secondary column is shorter than that of the aforementioned main column. The main column and the group of secondary columns are integrated into an anchor.

2. The group of sub-columns includes a plurality of sub-columns, The anchor according to claim 1, wherein each column constituting the main column and the group of sub-columns is arranged such that the length of the sub-columns decreases as they move away from the main column, and the upper ends of the sub-columns are lower in the vertical direction as they move away from the main column.

3. The anchor according to claim 2, wherein each of the columns is arranged such that their respective axes are contained within the same plane.

4. The floating body is further equipped with a mooring rope to secure it in place. At least a portion of the main pillar and all of the secondary pillars are driven into the seabed. The anchor according to claim 1 or 2, wherein, when the anchor is viewed from the vertical, the direction in which the group of sub-pillars protrudes from the main pillar coincides with or substantially coincides with the direction of the mooring rope moving from the mooring point to the predetermined position.

5. The anchor according to claim 1 or 2, wherein the number of the sub-column groups is multiple.

6. Each of the multiple floating bodies is further equipped with multiple mooring lines for securing it to its respective predetermined position, At least a portion of the main pillar and all of the group of secondary pillars are driven into the seabed. The anchor according to claim 5, wherein, when the anchor is viewed from the vertical, the direction in which each group of sub-posts protrudes from the main post coincides with or substantially coincides with the direction of each mooring rope moving from the mooring point to the respective predetermined position.

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