Anchor installation method, anchors, and anchor groups

Abstract

To provide an anchor with improved pull-out resistance. [Solution] The anchor (10) comprises a steel pipe (1) having a lower end (2a) and an upper end (2b), and a mooring point (1a) for connecting a mooring rope (700) is provided at the upper end (2b). Compared to the case in which the steel pipe is inserted into the seabed with its central axis parallel to the vertical, the steel pipe (1) is inserted into the seabed (800) with its central axis (1C) tilted from the vertical so that the mooring point (1a) is further away from the predetermined position for mooring the floating structure.

Description

Technical Field

[0001] The present invention relates to an installation method of an anchor installed on the seabed, an anchor, and an anchor group.

Background Art

[0002] There are two types of structural forms of offshore wind power generation facilities: "fixed type" and "floating type". Since the floating type is less affected by water depth compared to the fixed 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 via 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, a type that exhibits a pulling resistance due to friction with the ground, such as a pile type, is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the case of pile-type anchors, controlling (improving) pull-out resistance can be easily achieved by increasing the pile diameter or length to increase the contact area with the ground, or by increasing the coefficient of friction between the pile and the ground. However, increasing the pile diameter or length to increase the contact area leads to increased material costs. Also, the pile weight increases, requiring a more powerful crane vessel, which also increases costs.

[0007] Another approach is to increase the coefficient of friction by increasing the cohesion of the ground. Specifically, this involves improving the ground around the piles with cement or other materials. 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 installation method, an anchor, and an anchor group that improve pull-out resistance while keeping costs down. [Means for solving the problem]

[0009] To solve the above problems, an anchor installation method according to one aspect of the present invention is a columnar anchor having a mooring point at or near its upper end, and is an anchor installation method for mooring a floating body to a predetermined position, comprising an insertion step of inserting the anchor into the seabed from its lower end, wherein, compared to the case in which the anchor is inserted into the seabed with the first axis being parallel to the vertical direction, the first axis is tilted from the vertical direction and the anchor is inserted into the seabed with at least one of the following conditions is met: (1) the distance from the predetermined position to the lower end is shortened, and (2) the distance from the predetermined position to the upper end is lengthened.

[0010] An anchor having the above configuration can include not only the friction on the surface of the anchor but also the passive earth pressure acting on the anchor as pull-out resistance against the tensile force from the predetermined position. Therefore, compared to anchors of the same size, it is possible to create an anchor that is less likely to come out than an anchor inserted into the seabed so that the first axis of the anchor is parallel to the vertical direction. Thus, it is possible to provide an anchor with improved pull-out resistance while suppressing the cost increase that would be associated with increasing the length or diameter.

[0011] A method for installing an anchor according to one aspect of the present invention further includes a placement step of placing a guide at the anchor installation position, the guide being provided on the base and having open ends at both ends, wherein the guide has a second axis which is the axis of the guide and the bottom surface at a predetermined angle, compared to the case where the guide is inserted into the seabed so that the second axis is parallel to the vertical, the guide is placed on the seabed surface with the second axis tilted from the vertical, and the method is configured such that at least one of the following conditions is met: (3) the distance from the predetermined position to the lower end of the guide is shortened, and (4) the distance from the predetermined position to the upper end of the guide is lengthened. In the insertion step, the anchor is inserted into the guide from the upper end of the guide and the anchor is inserted into the seabed.

[0012] According to the above configuration, the anchor can be easily inserted into the seabed with the first axis tilted from the vertical using the guide.

[0013] In one aspect of the present invention, the method for installing an anchor may be configured such that the plane stretched by the predetermined position and the first axis is parallel to the vertical direction.

[0014] According to the above configuration, passive earth pressure is applied to the region along the first axial direction on the circumferential surface of the anchor.

[0015] In one aspect of the present invention, the method for installing an anchor, in the above configuration, may have an angle between the straight line connecting the predetermined position and the anchor's mooring point and the first axis that is 45 degrees or more and 135 degrees or less.

[0016] According to the above configuration, 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.

[0017] To solve the above problems, an anchor according to one aspect of the present invention has a lower end inserted into the seabed, and a mooring point is provided at or near the upper end protruding from the seabed, and the floating body is moored in a predetermined position, wherein the first axis, which is the axis of the anchor, is inclined from the vertical direction to satisfy at least one of the following conditions: (1) the distance from the predetermined position to the lower end is shortened, and (2) the distance from the predetermined position to the upper end is lengthened, compared to the case in which the anchor is inserted into the seabed so that the first axis is parallel to the vertical direction.

[0018] An anchor having the above configuration can include not only the friction on the surface of the anchor but also the passive earth pressure acting on the anchor as pull-out resistance against the tensile force from the predetermined position. Therefore, compared to anchors of the same size, it is possible to create an anchor that is less likely to come out than an anchor inserted into the seabed so that the first axis of the anchor is parallel to the vertical direction. Thus, it is possible to provide an anchor with improved pull-out resistance while suppressing the cost increase that would be associated with increasing the length or diameter.

[0019] In one aspect of the present invention, the anchor may be configured such that the plane stretched by the predetermined position and the first axis is parallel to the vertical direction.

[0020] According to the above configuration, the passive earth pressure acts on the area along the first axial direction on the peripheral surface of the anchor.

[0021] In the anchor according to one aspect of the present invention, in the above configuration, the angle formed by the straight line connecting the predetermined position and the mooring point and the first axis may be 45 degrees or more and 135 degrees or less.

[0022] According to the above configuration, the passive failure line that extends virtually from the lower end of the anchor toward the seabed surface in response to the tensile force from the predetermined position, and the seabed ground within the range surrounded by the peripheral surface of the anchor act on the peripheral surface of the anchor as passive earth pressure, and an anchor with high pull-out resistance can be realized.

[0023] The anchor group according to one aspect of the present invention includes a plurality of anchors in the above configuration.

[0024] According to the above configuration, when installing a plurality of anchors on one floating body, it is possible to further prevent the floating body from inconveniently moving from the predetermined position, and a highly reliable anchor can be provided. Also, if a plurality of anchors are provided, one anchor group can be applied to a plurality of floating bodies, and the anchors can be driven in an inclined manner as described above at positions suitable for each floating body so that each floating body is moored at a predetermined position.

Effects of the Invention

[0025] According to one aspect of the present invention, it is possible to realize an installation method of an anchor, an anchor, and an anchor group that improve the pull-out resistance while suppressing cost increase.

Brief Description of the Drawings

[0026] [Figure 1] It is a schematic diagram showing one aspect of applying the anchor according to one embodiment of the present invention. [Figure 2] It is a cross-sectional view of the portion surrounded by the broken line shown in FIG. 1. [Figure 3] This is a plan view of the area enclosed by the dashed line shown in Figure 1. [Figure 4] This diagram illustrates the flow chart for the anchor installation method in this embodiment. [Figure 5] This diagram illustrates the method for installing the anchor in this embodiment. [Figure 6] This diagram illustrates another method for installing the anchor in this embodiment. [Figure 7] This is a diagram of the anchors in the comparative configuration. [Modes for carrying out the invention]

[0027] [Embodiment 1] The following describes in detail one embodiment of the present invention. Figure 1 is a schematic diagram showing one application of the anchor of this embodiment. 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. Figure 4 is a flowchart showing each step included in the anchor installation method. Figure 5 is a diagram illustrating the flow of the anchor installation method.

[0028] As shown in Figure 1, the anchor 10 of this embodiment is installed on the seabed 800 to moor a floating structure 100 (float) installed on the sea surface, for example. The anchor 10 and the floating structure 100 are connected by a mooring rope 700 such as a chain. 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 for one floating structure 100 or the form of the mooring rope 700 shown in Figure 1 is also just one example and is not limited to these. Also, although Figure 1 is intended for application in the ocean 802, it is not limited to the sea such as a lake. The anchor 10 is an anchor installed on the seabed to moor a floating structure installed on the water surface.

[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 is placed in the seabed at a depth of 800m. As an example, in this embodiment, it is assumed that the anchor 10 will be placed in the seabed at a depth of 200m or more, but it is also possible to place it in the seabed at greater depths, for example, 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.

[0031] The anchor 10 is generally a columnar structure that extends along the axial direction. Here, the 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 part of it may be a hollow structure and part of it may be a solid structure when viewed along the axial direction. Furthermore, it is preferable that this columnar structure satisfies the required strength for an anchor (e.g., strength against bending). In addition, it is preferable that the cross-sectional area of ​​the cross-section (cross-section perpendicular to the axial direction) of this 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 circular or polygonal closed rings, and H-shaped (also called I-shaped) shapes. In this embodiment, a cylindrical steel pipe 1 (Figure 2) with a circular cross-sectional shape (more specifically, a hollow ring) is used. When a hollow columnar structure is used as the anchor 10, the anchor 10 is inserted into the seabed from its open lower end, and sand or soil may fill the internal cavity.

[0032] As shown in Figure 2, the anchor 10 (steel pipe 1) has a lower end 2a and an upper end 2b. The lower end 2a may be open as described above. In this embodiment, the upper end 2b 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 2a is open, the upper end 2b may be closed. Here, the "end" of the lower end 2a and the upper end 2b refers to the end when viewed along the central axis 1C of the anchor 10 (the central axis 1C will be described later with reference to Figure 2). In this embodiment, as described above, a cylindrical steel pipe 1 is used as the anchor 10, and the steel pipe 1 is cut so that both ends are perpendicular to the central axis 1C. In this case, the end faces formed at both ends constitute the lower end 2a and the upper end 2b. However, at least one of the ends of the steel pipe 1 may be cut so that it intersects the central axis 1C at an angle other than 90 degrees. In this case, the diagonally cut tip of the steel pipe 1 constitutes at least one of the lower end portion 2a and the upper end portion 2b.

[0033] In this embodiment, a mooring point 1a is provided near the upper end 2b of the steel pipe 1, and the upper end 2b protrudes from the seabed 800. The position where the mooring point 1a is provided on the steel pipe 1 may be at the upper end 2b (the upper end face in this embodiment) or near the upper end 2b. Here, the section of the steel pipe 1 that includes the upper end 2b and has a length equivalent to the diameter from the radius of the steel pipe 1 is defined as the vicinity of the upper end 2b. A mooring rope 700 is connected to the mooring point 1a. The shape and configuration of the mooring point 1a are not particularly limited. A tensile force from the mooring rope 700 acts on the mooring point 1a. 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.

[0034] Anchor 10 is installed on the seabed (seabed) away from the seabed (seabed) directly beneath 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 is exerted on each mooring rope 700 in an oblique upward direction toward the floating structure 100, and this force is exerted as a "tensile force" on the mooring point 1a of the anchor 10 (steel pipe 1).

[0035] 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 and the anchor 10 of this embodiment shown in Figure 2 differ in the orientation of the (steel pipe 1) inserted into the ground on the seabed. The comparative configuration anchor 1000 is inserted into the ground on the seabed 800 such that its central axis 1000C is aligned vertically. The comparative configuration anchor 1000 inserted vertically in this manner 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, and can be rephrased as pull-out resistance.

[0036] In the comparative anchor configuration 1000, increasing the pull-out resistance requires increasing the circumferential friction T, which necessitates increasing the length and diameter to enlarge the circumferential area, leading to increased costs. In contrast, the anchor 10 of this embodiment, shown in Figure 2, can achieve significantly greater pull-out resistance when compared to the comparative anchor configuration 1000 with the same length and diameter (and weight).

[0037] Specifically, in the anchor 10 shown in Figure 2, the steel pipe 1 is inserted into the seabed with its central axis 1C (first axis) tilted from the vertical direction, so that the mooring point 1a is further away from the predetermined position, compared to the comparative anchor 1000 (i.e., when the steel pipe is inserted into the seabed so that its central axis is parallel to the vertical direction).

[0038] When the anchor 10, which has been inserted in this tilted position, 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, a passive earth pressure S, as shown in Figure 2, is exerted on the circumferential surface 2c of the steel pipe 1. This passive earth pressure S is generated by the ground in the area between the passive collapse line B, which virtually extends from the position of the lower end 2a toward the sea surface, and the circumferential surface 2c facing the sea surface.

[0039] 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.

[0040] Here, the inclination angle θ1 of the central axis 1C from the vertical direction, as shown in Figure 2, 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.

[0041] Furthermore, the angle θ2 between the straight line (or its extension) connecting the predetermined position and the mooring point 1a and the central axis 1C may be between 45 degrees and 135 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.

[0042] The inclination angles θ1 and θ2 described above can both be predetermined before the anchor 10 is installed on the seabed 800. Specifically, they can be predetermined based on at least the mooring location (predetermined location) of the floating structure 100, the planned installation location of the anchor 10, and the length, diameter, and weight of the anchor 10 (steel pipe 1).

[0043] Figure 2 shows a cross-sectional view in the XZ plane including the central axis 1C and the extension line of the mooring cable 700. This represents a state where the mooring cable 700 and the central axis 1C overlap when viewed from above the anchor 10 and the mooring cable 700, as shown in Figure 3. In other words, the plane stretched by the central axis 1C and the extension line of the mooring cable 700 is parallel to the vertical direction. Alternatively, this can be rephrased as the plane stretched by the predetermined position and the central axis 1C being parallel to the vertical direction. This configuration allows passive earth pressure to be exerted on the region along the first axis direction on the circumferential surface of the anchor. However, the configuration is not limited to this example; for example, when viewed in a plan view as shown in Figure 3, an angle of, for example, 0 to ±15 degrees may be provided between the mooring cable 700 and the central axis 1C with the mooring point 1a as the center.

[0044] The method for inserting the anchor 10 (steel pipe 1) at an inclination angle θ1 (for example, in the range of 5 to 45 degrees) as shown in Figure 2 will be described later. Whether or not the anchor 10 (steel pipe 1) is inclined at the inclination angle θ1 shown in Figure 2 can be determined by measuring (confirming) the inclination angle of the portion of the steel pipe 1 that includes the upper end 2b protruding above the seabed 800.

[0045] Next, the installation method (setup method) for anchor 10 will be explained using Figures 4 and 5. As shown in Figure 4, the anchor installation method S10 includes a position determination step S11 and an insertion step S12.

[0046] In position determination step S11, the installation position for the steel pipe 1 as an anchor is determined based on the mooring position (predetermined position) of the floating structure 100. The installation position can be determined considering the seabed topography, etc.

[0047] In insertion step S12, the steel pipe is inserted into the seabed from the lower end 2a (Figure 2) at the installation position determined in position determination step S11. In insertion step S12, the steel pipe 1 is inserted into the seabed 800 with its central axis 1C tilted from the vertical direction, compared to the case where the steel pipe is inserted into the seabed 800 with its central axis parallel to the vertical direction, so that the mooring point 1a is further away from the predetermined position. In other words, in insertion step S12, the anchor 10 is inserted into the seabed 800 with its central axis 1C tilted from the vertical direction, satisfying at least one of the following conditions: (1) the distance from the predetermined position to the lower end 2a (Figure 2) is shorter, and (2) the distance from the predetermined position to the upper end 2b (Figure 2) is longer, compared to the case where the steel pipe is inserted into the seabed 800 with its central axis parallel to the vertical direction.

[0048] One method of insertion is to use a guide 200 as shown in Figure 5. This guide 200 comprises a base 205 which is placed on the surface of the seabed 800 with its bottom surface 205a in contact with it, and a guide tube 207 provided on the base 205 and having open ends, wherein the angle of inclination between the axis 207C (second axis) of the guide tube 207 and the bottom surface 205a is a predetermined angle. This guide 200 is placed on the installation position of the seabed 800 determined in the position determination process S11. This state is shown in 11s of Figure 5. In short, the installation process of placing the guide 200 on the aforementioned installation position of the seabed 800 is also included in the position determination process S11.

[0049] The guide 200 in the state shown in 11s of Figure 5 is placed on the surface of the seabed 800 with the axis 207C of the guide tube 207 tilted from the vertical, so as to satisfy at least one of the following conditions: (3) the distance from the predetermined position to the lower end of the guide tube is shorter, and (4) the distance from the predetermined position to the upper end of the guide tube is longer, compared to the case where the guide tube is inserted into the seabed so that the axis of the guide tube is parallel to the vertical.

[0050] Following the position determination process S11, the steel pipe 1 of the anchor 10 is inserted into the guide 200, and the well-known steel pipe insertion operation is performed while it is inserted (insertion process S12). This allows the steel pipe 1 to be inserted into the seabed 800 with the central axis 1C tilted from the vertical direction so that the mooring point 1a moves away from the predetermined position. This state is shown in 12s of Figure 5. The insertion operation can be performed, for example, using a vibro-hammer or hydraulic hammer 201 that can be operated from the work vessel 900.

[0051] Furthermore, the guide 200 may be designed to be removable from its installation position after the anchor 10 has been inserted. This allows the guide 200 to be reused, which can contribute to reducing construction costs.

[0052] As described above, according to the anchor installation method S10 of this embodiment, the central axis 1C of the anchor 10 is tilted from the vertical direction to satisfy at least one of the following conditions: (1) the distance from the predetermined position to the lower end 2a is shortened, and (2) the distance from the predetermined position to the upper end 2b is lengthened, compared to the case where the anchor is driven into the seabed so that the central axis of the anchor is parallel to the vertical direction (comparative configuration anchor 1000 in Figure 7). As a result, an anchor 10 that is less likely to come loose can be realized without changing the length or diameter, compared to an anchor of the same size driven in vertically (comparative configuration anchor 1000 in Figure 7). Therefore, an anchor 10 with improved pull-out resistance can be provided while suppressing the cost increase associated with increasing the length or diameter.

[0053] For example, anchor 10 may have a diameter of 1000 mm, a length of 5000 mm, a weight of 1500 kg, an inclination angle θ1 of 15 degrees, and an angle θ2 of 90 degrees in the portion of steel pipe 1, but is not limited to these.

[0054] Furthermore, within the limits of cost permissible, the length of the steel pipe of the anchor 10 can be increased to provide greater passive earth pressure resistance. Also, the cross-sectional shape of the anchor 10 (steel pipe 1) is not limited to a circle. A cross-section refers to a cross-section perpendicular to the central axis 1C. The cross-sectional shape of the anchor 10 (steel pipe 1) 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 the anchor 10 (steel pipe 1) other than a circle include square, rectangular, H-shaped (I-shaped), etc.

[0055] Furthermore, according to this embodiment, the steel pipe 1 of the anchor 10 is inserted using the guide 200. This can also be applied to the seabed at great depths.

[0056] Furthermore, as shown in Figure 1, an anchor group comprising multiple anchors 10 is also within the scope of the present invention. When installed on a single floating structure 100 as shown in Figure 1, it is possible to further prevent the floating structure 100 from moving undesirably from its predetermined position, thereby providing a highly reliable anchor.

[0057] [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.

[0058] In the above-described Embodiment 1, the steel pipe 1 of the anchor 10 was inserted using the guide 200. In contrast, in this embodiment, the steel pipe of the anchor 10 is inserted at an angle, similar to Embodiment 1, using a construction method that does not utilize the guide. Figure 6 is a diagram illustrating the construction method (installation method) of the anchor 10 in this embodiment.

[0059] As shown in Figure 6, the method of constructing (installing) the anchor 10 in this embodiment involves inserting the reaction pile 600 near the installation position (planned installation position of the anchor) determined in the position determination step S11 in Figure 4 of Embodiment 1. The insertion is performed by free-falling the reaction pile 600 into the sea, but a vibro-hammer or hydraulic hammer may also be used. A suspension ring 601 is provided on the head of the reaction pile 600, and a suspension wire 605 is connected to the steel pipe 1 (anchor 10) through the suspension ring 601. This state is shown in 21s of Figure 6.

[0060] From the state at 21s in Figure 6, the suspension wire 605 is lifted so that the steel pipe 1 (anchor 10) is at a predetermined inclination angle, and while lifting, the insertion work is performed using a vibro-hammer or hydraulic hammer 201. As a result, the steel pipe 1 (anchor 10) is inserted into the seabed 800 at an inclination angle θ1 (Figure 2). This state is shown at 22s in Figure 6.

[0061] Furthermore, by providing multiple reaction piles 600, the steel pipe 1 (anchor 10) can be controlled more precisely so that its inclination angle θ1 is achieved. Additionally, the reaction piles 600 can be reused, contributing to a reduction in construction costs.

[0062] 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."

[0063] 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]

[0064] 1 Steel pipe 1a Mooring point 1C center axis 2a Bottom end 2b Upper end 2c circumferential surface 10 Anchors 100 Floating structures 200 Guides 700 Mooring line 800 Undersea

Claims

1. A columnar anchor having a mooring point at or near its upper end, and a method for installing the anchor to moor a floating body in a predetermined position, The anchor is inserted into the seabed from its lower end, An anchor installation method, wherein in the insertion step, the anchor is inserted into the seabed with the first axis tilted from the vertical direction, so as to satisfy at least one of the following conditions: (1) the distance from the predetermined position to the lower end is shortened, and (2) the distance from the predetermined position to the upper end is lengthened, compared to the case in which the anchor is inserted into the seabed with the first axis parallel to the vertical direction.

2. The method further includes a placement step of placing a guide, which comprises a base that is placed on the seabed surface with its bottom surface in contact with it, and a guide tube provided on the base and having open ends, wherein the angle of inclination between the second axis, which is the axis of the guide tube, and the bottom surface is a predetermined angle, at the anchor installation position. In the above-mentioned installation step, compared to the case in which the guide tube is inserted into the seabed with the second axis parallel to the vertical direction, the guide is placed on the seabed surface with the second axis tilted from the vertical direction such that at least one of the following conditions is met: (3) the distance from the predetermined position to the lower end of the guide tube is shortened, and (4) the distance from the predetermined position to the upper end of the guide tube is lengthened. The method for installing an anchor according to claim 1, wherein in the insertion step, the anchor is inserted into the guide tube from the upper end of the guide tube, and the anchor is inserted into the seabed.

3. The method for installing an anchor according to claim 1 or 2, wherein the plane stretched by the predetermined position and the first axis is parallel to the vertical direction.

4. The method for installing an anchor according to claim 3, wherein the angle between the straight line connecting the predetermined position and the mooring point of the anchor and the first axis is 45 degrees or more and 135 degrees or less.

5. An anchor having its lower end inserted into the seabed, with a mooring point provided at or near the upper end protruding from the seabed, and which moors a floating body to a predetermined position, An anchor in which the first axis is inclined from the vertical direction, compared to the case in which the anchor is driven into the seabed so that the first axis is parallel to the vertical direction, satisfies at least one of the following conditions: (1) the distance from the predetermined position to the lower end is shortened, and (2) the distance from the predetermined position to the upper end is lengthened.

6. The anchor according to claim 5, wherein the plane stretched by the predetermined position and the first axis is parallel to the vertical direction.

7. The anchor according to claim 6, wherein the angle between the straight line connecting the predetermined position and the mooring point and the first axis is 45 degrees or more and 135 degrees or less.

8. A group of anchors comprising a plurality of anchors as described in any one of claims 5 to 7.

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