Compound anchor system for depth-keeping mooring of underwater platform

Abstract

The invention discloses a compound anchor system for depth-keeping mooring of an underwater platform, and belongs to the technical field of underwater equipment. A bowl-shaped rotating body hydrodynamic appearance scheme is adopted, the design contradiction between resistance reduction and stability in theory is solved through the design that size parameters are combined with the evenly-distributed water permeable holes, the resistance coefficient is optimal under the condition of the large incident flow area, and on the premise that it is guaranteed that the resistance of the compound anchor meets the depth-keeping speed requirement of an underwater platform, the effect that the underwater platform depth-keeping speed requirement is met is achieved. And the damage of a large incident flow area to the attitude stability in water is avoided. Besides, by adopting the scheme of integrating an adjustable buoyancy structure and a counterweight structure and through the mass-buoyancy center design facing the dynamic stability, the large mass-buoyancy center distance of the compound anchor system on the axis of a rotating body is achieved, it is ensured that the compound anchor system keeps good underwater descending posture stability, cable tension vibration sudden change in the depth setting process is reduced, and the cable tension vibration sudden change in the depth setting process is reduced. And stable and accurate depth setting of the underwater platform is ensured.

Description

Technical Field

[0001] The invention relates to a composite anchor system for fixed-depth mooring of an underwater platform, belonging to the technical field of underwater equipment. Background Art

[0002] The deep-deep fixed-depth mooring technology is a technology that realizes the relative motion control of the positive buoyancy platform and the negative buoyancy anchor through cable tension control, thereby realizing the fixed-depth mooring of the underwater platform. It is widely used in fields such as marine exploration. A typical fixed-depth mooring system generally consists of three parts: a platform, a depth-fixing device (including cables), and an anchor. Among them, the anchor is the core component for achieving accurate depth determination and reliable anchoring. On the one hand, it must have sufficient bearing capacity to overcome the upward pull and horizontal forces to ensure that the platform is reliably moored for a long time; on the other hand, it must have good fluid dynamic characteristics, maintain good stability of the descent posture in the water while meeting the requirements of the resistance coefficient, reduce the sudden changes in cable tension during the depth determination process, and ensure that the platform is stable and accurate in depth determination.

[0003] At present, the anchor systems used for underwater platforms, submerged buoys, buoys and other depth-fixed moorings only achieve the requirements of horizontal and vertical bearing capacity through technical means such as stringing anchors, penetration, and suction, but they generally have problems such as complex structure, difficult assembly, and high cost. At the same time, the requirements for the hydrodynamic characteristics of the anchor system during the depth-fixed mooring process are ignored, and the stability of the anchor system's descent posture in the water cannot be guaranteed. There is no special design for the descent speed in the water, which makes it difficult to control the cable tension during the depth-fixed mooring process. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a duplex anchor system for fixed-depth mooring of underwater platforms, to achieve the requirements of horizontal bearing capacity and vertical bearing capacity, and to solve the difficult problem of the duplex anchor system maintaining stable underwater posture under complex ocean loads while meeting the requirements of long-term anchoring reliability.

[0005] The technical solution of the present invention is: a composite anchor system for fixed-depth mooring of an underwater platform, comprising:

[0006] A three-legged steel cable connection assembly is used to connect the cable to the composite anchor system of the present invention, with a shackle and an eye bolt respectively provided at both ends, one end of the shackle is connected to the cable, and one end of the eye bolt is connected to the bowl-shaped counterweight structure;

[0007] The buoyancy structure is a multi-layer circular plate structure, and through holes are evenly distributed on the surface of each layer of circular plate for connecting the annular adapter plate;

[0008] The annular adapter plate is a circular ring structure. Countersunk holes are evenly arranged on the upper end surface of the circular ring, corresponding to the through holes evenly arranged on the surface of the circular ring plate of the buoyancy structure, and is used to connect the buoyancy structure; threaded holes are evenly arranged on the side of the circular ring, and are used to connect the cylindrical counterweight structure;

[0009] The cylindrical counterweight structure is a thin-walled cylindrical structure. Two rows of radial countersunk holes are evenly arranged on the side wall of the cylinder. The upper row of radial countersunk holes corresponds to the threaded holes evenly arranged on the side of the annular adapter plate, and is used to connect the annular adapter plate; the lower row of radial countersunk holes corresponds to the threaded holes evenly arranged on the upper side wall of the bowl-shaped counterweight structure, and is used to connect the bowl-shaped counterweight structure; water-permeable holes are evenly arranged in the middle of the cylinder side wall;

[0010] The bowl-shaped counterweight structure is a bowl-shaped structure including two circular cavities, the upper and lower ones. The bottom surface of the upper circular cavity is evenly provided with three threaded through holes for installing the three-legged steel cable connection assembly; the top surface of the lower circular cavity is provided with a number of threaded holes for fixing the unlocking release assembly and the grip anchor assembly; the bottom surface of the bowl-shaped structure is evenly provided with a number of threaded holes for installing the transparent fragile cover; the outer side wall of the upper cavity is evenly provided with threaded holes for connecting the cylindrical counterweight structure; the middle part of the side wall of the straight cylinder section of the bowl-shaped structure is evenly provided with water-permeable holes;

[0011] A transparent fragile cover is fixed to the bottom surface of the bowl-shaped counterweight structure and is provided with an end surface static seal, which is used to protect the unlocking release assembly and the gripping anchor assembly in the ground state, and is automatically broken under the impact of the compound anchor touching the bottom or under a certain water pressure, thereby completing the release of the gripping anchor assembly;

[0012] An unlocking and releasing assembly is fixedly connected to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure and is used to release the grip anchor assembly;

[0013] The grip anchor assembly is fixed to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure to provide horizontal anchoring force.

[0014] Further, the three-legged steel cable connection assembly includes a shackle, three steel cables, and three eyebolts;

[0015] The shackle is a D-shaped shackle or a bow-shaped shackle;

[0016] The upper end of the steel cable is a pressed ring hole joint, and the lower end is crimped with the ring of the eye bolt. The length of the steel cable is 0.75 to 0.85 times the inner diameter of the ring of the annular adapter plate;

[0017] The ring hole joints at the upper ends of the three steel cables are connected by a shackle, and the three eye bolts crimped at the lower ends are connected to the threaded holes on the upper end surface of the bowl-shaped counterweight structure.

[0018] Furthermore, the buoyancy structure includes several layers of buoyancy circular plates; the material of the buoyancy circular plates is pure glass beads material with a pressure resistance level corresponding to the working depth of the compound anchor, and the surface is sprayed with polyurea to increase the surface hardness to prevent bumps, and the density is not more than 500kg / m 3 .

[0019] Furthermore, the inner diameter of the buoyancy circular ring plate is consistent with the inner diameter of the annular adapter plate ring, and the outer diameter is 0.8 times the inner diameter of the circular cavity at the upper end of the bowl-shaped counterweight structure; during actual installation, according to the mass buoyancy center design requirements, a corresponding number of buoyancy circular ring plates are stacked and installed to form a buoyancy structure.

[0020] Furthermore, the annular adapter plate is a circular ring structure, and the material is carbon structural steel; the inner diameter of the ring is 1.25 times the diameter of the pitch circle of the three threaded holes evenly distributed on the upper end surface of the bowl-shaped counterweight structure, and the outer diameter of the ring is consistent with the inner diameter of the cylindrical counterweight structure, and is set to a clearance fit.

[0021] Furthermore, the material of the cylindrical counterweight structure is carbon structural steel; the inner diameter of the cylinder is consistent with the outer diameter of the annular adapter plate ring, and is set to be a clearance fit; the diameter of the water-permeable hole is 0.25 times the height of the thin-walled cylinder.

[0022] Furthermore, the material of the bowl-shaped counterweight structure is carbon structural steel; the inner diameter of the upper circular cavity is 0.95 times the outer diameter of the circular ring of the annular adapter plate, and the depth is 0.3 times the overall height of the bowl-shaped counterweight structure; the inner diameter of the lower circular cavity is 0.6 times the outer diameter of the circular ring of the annular adapter plate, and the depth is 0.45 times the overall height of the bowl-shaped counterweight structure; the diameter of the bottom surface of the bowl-shaped structure is 0.625 times the diameter of the upper end, and the height of the frustum section is 0.4 times the overall height; the diameter of the water-permeable hole is 0.35 times the height of the straight cylinder section.

[0023] Furthermore, the transparent fragile cover is made of thin-walled non-metallic material, and the wall thickness is designed according to the pressure resistance level corresponding to the working depth of the compound anchor.

[0024] Furthermore, the unlocking and releasing assembly 7 locks the position of the restraining grip anchor rod.

[0025] Further, the grip anchor assembly includes a grip anchor, a shackle, a steel chain, and an eye bolt;

[0026] The gripping anchor is an AC-14 anchor, and the gripping force design is determined according to the ocean load and seabed geology combined with the working requirements;

[0027] The end of the anchor rod is connected to the steel chain via a shackle;

[0028] The length of the steel chain is 1.6 times the diameter of the bottom surface of the bowl-shaped counterweight structure; the other end of the steel chain is connected to the eye bolt;

[0029] The eye bolts are fixed to corresponding threaded holes on the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure.

[0030] The advantages of the present invention compared with the prior art are:

[0031] (1) The present invention adopts a bowl-shaped rotating body hydrodynamic shape scheme, and solves the design contradiction between drag reduction and stability in theory by combining size parameters with evenly distributed water-permeable holes, and achieves the optimal drag coefficient under the condition of a large frontal area. On the premise of ensuring that the resistance of the compound anchor meets the requirements of the underwater platform's constant depth speed, the damage to the stability of the underwater posture caused by the large frontal area is avoided.

[0032] (2) The present invention adopts an integrated solution of an adjustable buoyancy structure and a counterweight structure. Through the mass-buoyancy center design for dynamic stability, a larger mass-buoyancy center distance of the duplex anchor system on the axis of the rotating body is achieved, ensuring that it maintains good stability of its descent posture in the water, reducing the sudden change of cable tension during the depth setting process, and ensuring that the underwater platform sets the depth stably and accurately.

[0033] (3) The gripping anchor assembly of the present invention cooperates with the transparent fragile cover and the unlocking release assembly to provide sufficient horizontal gripping force; it can provide sufficient vertical bearing capacity by relying on its own weight; the horizontal bearing capacity and vertical bearing capacity requirements of the duplex anchor system are achieved through the combined effects of the anchor body's own weight, seabed friction, and detachable gripping anchor, and the structure is simpler and more convenient to use.

[0034] (4) The annular adapter plate, cylindrical counterweight structure, and bowl-shaped counterweight structure of the present invention are all made of carbon structural steel or other metal materials and are connected by bolts and nuts, with low processing costs and low assembly difficulty. The outer contours are simple and regular, which is convenient for integration and installation with underwater platforms and other equipment, which is conducive to the overall deployment of the underwater platform and can effectively reduce the deployment difficulty and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0036] Figure 1 , 2 It is a schematic diagram of the overall structure of the composite anchor system of the present invention;

[0037] Figure 3 This is a schematic diagram of a three-legged steel cable connection assembly of the present invention;

[0038] Figure 4 This is a schematic diagram of the installation of the three-legged steel cable connection assembly of the present invention;

[0039] Figure 5 It is a cross-sectional view of the composite anchor system of the present invention;

[0040] Figure 6 It is a schematic diagram of the grip anchor assembly of the present invention;

[0041] Figure 7 It is a schematic diagram of the center of mass and center of buoyancy of the duplex anchor system of the present invention;

[0042] Figure 8 It is a schematic diagram of the mooring state of the composite anchor system of the present invention. DETAILED DESCRIPTION

[0043] In order to better understand the above technical scheme, the technical scheme of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical scheme of the present invention, rather than limitations on the technical scheme of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0044] The following is a further detailed description of a composite anchor system for fixed depth mooring of an underwater platform provided by an embodiment of the present invention in conjunction with the accompanying drawings of the specification. The specific implementation method may include:

[0045] A three-legged steel cable connection assembly 1, used to connect the cable to the composite anchor system of the present invention, with a shackle and an eye bolt at both ends, one end of the shackle is connected to the cable, and one end of the eye bolt is connected to the bowl-shaped counterweight structure 5;

[0046] The buoyancy structure 2 is a multi-layer circular plate structure, and through holes are evenly distributed on the surface of each layer of circular plate for connecting the annular adapter plate 3;

[0047] The annular adapter plate 3 is a circular ring structure, and countersunk holes are evenly arranged on the upper end surface of the circular ring, corresponding to the through holes evenly arranged on the surface of the circular ring plate of the buoyancy structure 2, for connecting the buoyancy structure 2; threaded holes are evenly arranged on the side of the circular ring for connecting the cylindrical counterweight structure 4;

[0048] The cylindrical counterweight structure 4 is a thin-walled cylindrical structure, and two rows of radial countersunk holes are evenly arranged on the side wall of the cylinder. The upper row of radial countersunk holes corresponds to the threaded holes evenly arranged on the side of the ring of the annular adapter plate 3, and is used to connect the annular adapter plate 3; the lower row of radial countersunk holes corresponds to the threaded holes evenly arranged on the upper side wall of the bowl-shaped counterweight structure 5, and is used to connect the bowl-shaped counterweight structure 5; water-permeable holes are evenly arranged in the middle of the side wall of the cylinder;

[0049] The bowl-shaped counterweight structure 5 is a bowl-shaped structure including two circular cavities, an upper one and a lower one. Three threaded through holes are evenly arranged on the bottom surface of the upper circular cavity for installing the three-legged steel cable connection assembly 1; a plurality of threaded holes are arranged on the top surface of the lower circular cavity for fixing the unlocking release assembly 7 and the gripping anchor assembly 8; a plurality of threaded holes are evenly arranged on the bottom surface of the bowl-shaped structure for installing the transparent fragile cover 6; threaded holes are evenly arranged on the outer side wall of the upper cavity for connecting the cylindrical counterweight structure 4; water-permeable holes are evenly arranged in the middle of the side wall of the straight cylinder section of the bowl-shaped structure;

[0050] The transparent fragile cover 6 is fixed to the bottom surface of the bowl-shaped counterweight structure 5 and is provided with an end surface static seal, which is used to protect the unlocking release assembly 7 and the gripping anchor assembly 8 in the ground state, and is automatically broken under the impact of the compound anchor touching the bottom or under a certain water pressure, thereby completing the release of the gripping anchor assembly 8;

[0051] The unlocking release assembly 7 is fixedly connected to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure 5, and is used to release the grip anchor assembly 8;

[0052] The gripping anchor assembly 8 is fixed to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure 5 to provide horizontal anchoring force.

[0053] like Figure 1 , 2 As shown, a duplex anchor system for fixed-depth mooring of an underwater platform of the present invention comprises a three-legged steel cable connection assembly 1, a buoyancy structure 2, an annular adapter plate 3, a cylindrical counterweight structure 4, a bowl-shaped counterweight structure 5, a transparent fragile cover 6, an unlocking and releasing assembly 7, and a gripping anchor assembly 8.

[0054] like Figure 3 , 4 As shown, the three-legged steel cable connection assembly 1 includes a shackle 101, three steel cables 102, and three eyebolts 103; the shackle 101 is a D-type shackle or a bow-shaped shackle; the upper end of the steel cable 102 is a pressed ring hole joint, and the lower end is crimped with the ring of the eyebolt 103, and the length of the steel cable is 0.75 to 0.85 times the inner diameter of the ring of the annular adapter plate 3; the pressed ring hole joints at the upper ends of the three steel cables 102 are connected by a shackle 101, and the shackle 101 is connected to the cable; the three eyebolts 103 crimped at the lower end are connected to the threaded holes on the upper end surface of the bowl-shaped counterweight structure 5; the three-legged steel cable connection can ensure that the duplex anchor system maintains a horizontal posture in a force balance state, and also ensures the underwater posture stability to a certain extent.

[0055] like Figure 5 As shown, the buoyancy structure 2 is composed of several layers of buoyancy circular plates. The main material of the buoyancy circular plates is pure glass beads with a pressure resistance level corresponding to the working depth of the compound anchor. The surface is sprayed with polyurea to increase the surface hardness to prevent bumps. The density is not more than 500kg / m 3 ; The inner diameter of the buoyancy circular ring plate is consistent with the inner diameter of the circular ring of the annular adapter plate 3, and the outer diameter is 0.8 times the inner diameter of the circular cavity at the upper end of the bowl-shaped counterweight structure 5; the surface of the buoyancy circular ring plate is provided with through holes corresponding to the countersunk holes uniformly distributed on the upper end surface of the circular ring of the annular adapter plate 3, which are used to connect the annular adapter plate 3; during actual installation, the corresponding number of buoyancy circular ring plates can be assembled to form the buoyancy structure 2 according to the requirements of mass buoyancy center adjustment, Figure 4 The diagram shows that three layers of buoyancy circular ring plates form a buoyancy structure 2, and the multiple layers of buoyancy circular ring plates are stacked and fixedly connected to the annular adapter plate 3 by bolts and nuts.

[0056] The annular adapter plate 3 is a circular ring structure, and its main material is carbon structural steel; the inner diameter of the ring is 1.25 times the diameter of the dividing circle of the three threaded holes evenly distributed on the upper end surface of the bowl-shaped counterweight structure 5, and the outer diameter of the ring is consistent with the inner diameter of the cylindrical counterweight structure 4, and is set as a clearance fit; countersunk holes are evenly distributed on the upper end surface of the ring for connecting the buoyancy structure 2; threaded holes are evenly distributed on the side of the ring for connecting the cylindrical counterweight structure 4.

[0057] The cylindrical counterweight structure 4 is a thin-walled cylindrical structure, and its main material is carbon structural steel; the inner diameter of the cylinder is consistent with the outer diameter of the circular ring of the annular adapter plate 3, and is set to a clearance fit; two rows of radial countersunk holes are evenly distributed on the side wall of the cylinder, and the upper row of radial countersunk holes corresponds to the threaded holes evenly distributed on the side surface of the circular ring of the annular adapter plate 3, and is used to connect the annular adapter plate 3; the lower row of radial countersunk holes corresponds to the threaded holes evenly distributed on the upper end side wall of the bowl-shaped counterweight structure 5, and is used to connect the bowl-shaped counterweight structure 5; water-permeable holes are evenly distributed in the middle of the side wall of the cylinder, and the diameter of the water-permeable holes is 0.25 times the height of the thin-walled cylinder.

[0058] The bowl-shaped counterweight structure 5 is a bowl-shaped structure including two circular cavities, the main material of which is carbon structural steel; the inner diameter of the upper circular cavity is 0.95 times the outer diameter of the circular ring of the annular adapter plate 3, and the depth is 0.3 times the overall height of the bowl-shaped counterweight structure 5. Three threaded through holes are evenly distributed on the bottom surface of the cavity for installing three eyebolts 103; the inner diameter of the lower circular cavity is 0.6 times the outer diameter of the circular ring of the annular adapter plate 3, and the depth is 0.45 times the overall height of the bowl-shaped counterweight structure 5. A number of threaded holes are arranged on the top surface of the cavity for fixing the unlocking and releasing assembly 7 and the grabbing anchor assembly 8; the diameter of the bottom surface of the bowl-shaped structure is 0.625 times the diameter of the upper end, the height of the frustum section is 0.4 times the overall height, and a number of threaded holes are evenly arranged on the bottom surface for installing the transparent fragile cover 6; threaded holes are evenly arranged on the outer side wall of the upper end cavity for connecting the cylindrical counterweight structure 4; water-permeable holes are evenly arranged in the middle of the side wall of the straight cylinder section of the bowl-shaped structure, and the diameter of the water-permeable holes is 0.35 times the height of the straight cylinder section.

[0059] like Figure 6 As shown, the transparent fragile cover 6 is made of thin-walled non-metallic material, the wall thickness of which is designed according to the pressure resistance grade corresponding to the working depth of the compound anchor, and is fixed to the bottom surface of the bowl-shaped counterweight structure 5 by bolt connection, and an end face static seal is set; the transparent fragile cover 6 is used to protect the unlocking release component 7 and the gripping anchor component 8 in the ground state, and is automatically broken under the impact of the compound anchor touching the bottom or under a certain water pressure, thereby completing the release of the gripping anchor component 8.

[0060] The unlocking and releasing component 7 is used to release the gripping anchor component 8, and is fixed to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure 5 by bolt connection; the unlocking and releasing component 7 can be in the form of an electromagnet mechanism, a water pressure mechanism, a delay mechanism, etc.; the unlocking and releasing component 7 locks the anchor rod position of the restraining gripping anchor 801.

[0061] The grab anchor assembly 8 includes a grab anchor 801, a shackle 802, a steel chain 803, and an eye bolt 804; the grab anchor 801 is an AC-14 type anchor, and the grab force design is determined according to the ocean load and seabed geology combined with the working requirements; the end of the anchor rod is connected to the steel chain 803 through the shackle 802; the length of the steel chain 803 is 1.6 times the diameter of the bottom surface of the bowl-shaped counterweight structure 5; the other end of the steel chain 803 is connected to the eye bolt 804; the eye bolt 804 is fixed to the corresponding threaded hole on the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure 5.

[0062] like Figure 7 As shown, a compound anchor system for depth-fixed mooring of an underwater platform of the present invention has a center of mass G and a center of buoyancy B on the central axis of the rotating body. Thanks to the layout of the buoyancy structure and the counterweight structure, the center of mass and the center of buoyancy do not coincide. By increasing the distance between the center of mass and the center of buoyancy, the stability of its descent posture in the water can be effectively improved, and the sudden change of cable tension during the depth-fixed process can be reduced, thereby ensuring that the platform's depth is fixed stably and accurately.

[0063] like Figure 8 As shown, when the duplex anchor system touches the bottom during the depth setting process, the transparent fragile cover 6 breaks by itself under the impact of touching the bottom or a certain water pressure; the unlocking release component 7 is passively unlocked to release the gripping anchor component 8; under the action of flow load, the gripping anchor 801 drives the shackle 802 and the steel chain 803 to disengage, and the gripping anchor 801 is anchored to the bottom of the water through the anchor claw, and grips tighter and tighter under the action of horizontal force, thereby being able to provide sufficient horizontal gripping force; at the same time, the duplex anchor can overcome the upward pulling force by relying on its own weight, and the contact friction between the duplex anchor and the bottom of the water can also overcome a certain degree of horizontal force; the two comprehensively realize the requirements of horizontal bearing capacity and vertical bearing capacity.

[0064] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0065] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A composite anchor system for underwater platform fixed depth mooring, characterized in that: include: A three-legged steel cable connection assembly (1) is used to connect the cable to the composite anchor system of the present invention, and has a shackle and an eye bolt at both ends, one end of the shackle is connected to the cable, and one end of the eye bolt is connected to the bowl-shaped counterweight structure (5); The buoyancy structure (2) is a multi-layer circular ring plate structure, and through holes are evenly distributed on the surface of each layer of the circular ring plate for connecting the annular adapter plate (3); The annular adapter plate (3) is a circular ring structure, and countersunk holes are evenly arranged on the upper end surface of the circular ring, corresponding to the through holes evenly arranged on the surface of the circular ring plate of the buoyancy structure (2), and is used to connect the buoyancy structure (2); threaded holes are evenly arranged on the side surface of the circular ring, and are used to connect the cylindrical counterweight structure (4); The cylindrical counterweight structure (4) is a thin-walled cylindrical structure, and two rows of radial countersunk holes are evenly arranged on the side wall of the cylinder. The upper row of radial countersunk holes corresponds to the threaded holes evenly arranged on the side of the ring of the annular adapter plate (3), and is used to connect the annular adapter plate (3); the lower row of radial countersunk holes corresponds to the threaded holes evenly arranged on the upper side wall of the bowl-shaped counterweight structure (5), and is used to connect the bowl-shaped counterweight structure (5); and water-permeable holes are evenly arranged in the middle of the cylindrical side wall; The bowl-shaped counterweight structure (5) is a bowl-shaped structure comprising an upper and lower circular cavity, wherein three threaded through holes are evenly arranged on the bottom surface of the upper circular cavity for installing a three-legged steel cable connection assembly (1); a plurality of threaded holes are evenly arranged on the top surface of the lower circular cavity for fixing an unlocking release assembly (7) and a grip anchor assembly (8); a plurality of threaded holes are evenly arranged on the bottom surface of the bowl-shaped structure for installing a transparent fragile cover (6); threaded holes are evenly arranged on the outer side wall of the upper cavity for connecting to the cylindrical counterweight structure (4); and water-permeable holes are evenly arranged in the middle of the side wall of the straight cylindrical section of the bowl-shaped structure; A transparent fragile cover (6) is fixed to the bottom surface of the bowl-shaped counterweight structure (5) and is provided with an end surface static seal, which is used to protect the unlocking and releasing assembly (7) and the gripping anchor assembly (8) in the ground state, and is automatically broken under the impact of the compound anchor touching the bottom or under a certain water pressure, thereby completing the release of the gripping anchor assembly (8); An unlocking and releasing assembly (7) is fixedly connected to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure (5) and is used to release the gripping anchor assembly (8); The gripping anchor assembly (8) is fixed to the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure (5) and is used to provide horizontal anchoring force.

2. A composite anchor system for underwater platform fixed depth mooring according to claim 1, characterized in that: The three-legged steel cable connection assembly (1) comprises a shackle (101), three steel cables (102), and three eye bolts (103); The shackle (101) is a D-shaped shackle or a bow-shaped shackle; The upper end of the steel cable (102) is a pressed ring hole joint, and the lower end is crimped to the ring of the eye bolt (103), and the length of the steel cable is 0.75 to 0.85 times the inner diameter of the ring of the annular adapter plate (3); The ring hole joints at the upper ends of the three steel cables (102) are connected via a shackle (101), and the three eye bolts (103) crimped at the lower ends are connected to the threaded holes on the upper end surface of the bowl-shaped counterweight structure (5).

3. A composite anchor system for underwater platform fixed depth mooring according to claim 1, characterized in that: The buoyancy structure (2) comprises several layers of buoyancy circular ring plates; the material of the buoyancy circular ring plates is pure glass microbead material with a pressure resistance level corresponding to the working depth of the compound anchor, the surface is sprayed with polyurea to increase the surface hardness to prevent bumping, and the density is not more than 500kg / m 3 .

4. A composite anchor system for underwater platform fixed depth mooring according to claim 3, characterized in that: The inner diameter of the buoyancy circular ring plate is consistent with the inner diameter of the circular ring of the annular adapter plate (3), and the outer diameter is 0.8 times the inner diameter of the circular cavity at the upper end of the bowl-shaped counterweight structure (5); during actual installation, according to the design requirements of the mass buoyancy center, a corresponding number of buoyancy circular ring plates are stacked and installed to form the buoyancy structure (2).

5. The composite anchor system for fixed depth mooring of an underwater platform according to claim 1, characterized in that: The annular adapter plate (3) is a circular ring structure made of carbon structural steel; the inner diameter of the circular ring is 1.25 times the diameter of the pitch circle of three threaded holes evenly distributed on the upper end surface of the bowl-shaped counterweight structure (5); the outer diameter of the circular ring is consistent with the inner diameter of the cylindrical counterweight structure (4), and is set to be a clearance fit.

6. A composite anchor system for underwater platform fixed depth mooring according to claim 1, characterized in that: The material of the cylindrical counterweight structure (4) is carbon structural steel; the inner diameter of the cylinder is consistent with the outer diameter of the annular ring of the annular adapter plate (3), and is arranged to be clearance-fitted; the diameter of the water-permeable hole is 0.25 times the height of the thin-walled cylinder.

7. A composite anchor system for underwater platform fixed depth mooring according to claim 2, characterized in that: The material of the bowl-shaped counterweight structure (5) is carbon structural steel; the inner diameter of the circular cavity at the upper end is 0.95 times the outer diameter of the circular ring of the annular adapter plate (3), and the depth is 0.3 times the overall height of the bowl-shaped counterweight structure (5); the inner diameter of the circular cavity at the lower end is 0.6 times the outer diameter of the circular ring of the annular adapter plate (3), and the depth is 0.45 times the overall height of the bowl-shaped counterweight structure (5); the diameter of the bottom surface of the bowl-shaped structure is 0.625 times the diameter of the upper end, and the height of the frustum section is 0.4 times the overall height; the diameter of the water-permeable hole is 0.35 times the height of the straight cylinder section.

8. A composite anchor system for underwater platform fixed depth mooring according to claim 1, characterized in that: The transparent fragile cover (6) is made of a thin-walled non-metallic material, and the wall thickness is designed according to the pressure resistance level corresponding to the working depth of the composite anchor.

9. A composite anchor system for underwater platform fixed depth mooring according to claim 1, characterized in that: The unlocking and releasing assembly 7 locks the anchor rod position of the restraining grip anchor (801).

10. A composite anchor system for underwater platform fixed depth mooring according to claim 1, characterized in that: The gripping anchor assembly (8) comprises a gripping anchor (801), a shackle (802), a steel chain (803), and an eyebolt (804); The gripping anchor (801) is an AC-14 anchor, and the gripping force design is determined according to the ocean load and seabed geology combined with the working requirements; The end of the anchor rod is connected to the steel chain (803) via a shackle (802); The length of the steel chain (803) is 1.6 times the diameter of the bottom surface of the bowl-shaped counterweight structure (5); the other end of the steel chain (803) is connected to the eye bolt (804); The eye bolt (804) is fixed to a corresponding threaded hole on the top surface of the circular cavity at the lower end of the bowl-shaped counterweight structure (5).

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