Modeling analysis method suitable for high holding power anchor group system

Abstract

The invention discloses a modeling analysis method suitable for a high holding power anchor group system, which comprises the following steps of: S1, establishing a solid model of the high holding power anchor group system and seabed soil in a finite element model, and obtaining a finite element model main program; s2, anchor chain tension is applied to an anchor chain tension application point at the front end of the mooring anchor chain entity model; S3, in the calculation process of the finite element model main program, horizontal displacement and vertical displacement of a front mooring point are monitored, horizontal displacement and vertical displacement of a rear mooring point are monitored, and a movement track curve of the high holding power anchor group system entity model is obtained. According to the method, the predictability of the embedding behavior of the high holding power anchor group system can be improved, the accuracy of numerical simulation can be improved, the real-time changing anchor chain tension borne by the mooring anchor chain and the spatial form and transmission tension of the mooring anchor chain and the connecting anchor chain can be accurately described, the modeling complexity of a finite element model is reduced, and the calculation efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep - sea anchoring simulation, and particularly relates to a modeling and analysis method applicable to a large - holding - power anchor group system. Background Art

[0002] With the utilization of deep - sea resources and the development of deep - sea space, the mooring systems of large - scale offshore floating platforms such as offshore floating wind power platforms, offshore oil and gas exploitation platforms, offshore airports, and artificial floating islands have become key technologies. As the operating water depth continues to increase, catenary mooring systems have been widely used, and higher requirements have been put forward for the bearing capacity and deep - water installation performance of the anchoring structures in catenary mooring systems.

[0003] Currently, the existing typical deep - water anchoring structures include suction anchors, drag - embedded plate anchors, suction - embedded plate anchors, and gravity - penetrated anchors; as a type of drag - embedded plate anchor, the large - holding - power anchor is suitable for the widely used semi - submersible offshore platforms with its bearing characteristics, providing a bottom - layer positioning basis for fields such as offshore wind power, oil and gas, and hydrogen production. When the bearing capacity requirement reaches more than 10000 kN, the bearing efficiency of the large - holding - power anchor exceeds that of the suction anchor, which can reduce the cost of the anchoring structure and is one of the most promising deep - sea mooring anchoring forms at present.

[0004] The large - holding - power anchor is installed by being towed by a mooring anchor chain. Under the reverse catenary action of the mooring anchor chain, it gradually embeds into the seabed and reaches the designed embedment depth position to exert its bearing capacity and provide a positioning function for the upper - layer offshore floating platform. However, in actual production activities, with the increasing scale of offshore floating platforms, the demand for bearing capacity has increased rapidly. The above - mentioned large - holding - power anchor has problems such as insufficient bearing capacity and shallow embedment depth in soft seabed soil, which affect the positioning stability and reliability of offshore floating platforms in soft - soil sea areas; moreover, the above - mentioned large - holding - power anchor has problems such as difficult - to - predict downward embedding trajectories, and the large - holding - power anchor has a large size, resulting in high labor and material costs for on - site tests. In addition, the above - mentioned large - holding - power anchor has problems such as complex numerical simulation modeling and replacing dynamic anchor chain tension with constant anchor chain tension, which interfere with the design and judgment of the downward embedding and bearing capacity of such large - holding - power anchors in engineering practice. Summary of the Invention

[0005] In view of the above - mentioned defects of the prior art, the present invention provides a modeling and analysis method applicable to a large - holding - power anchor group system, which can improve the predictability of the downward embedding behavior of the large - holding - power anchor group system, enhance the accuracy of numerical simulation, and can accurately depict the anchor chain tension received by the mooring anchor chain that changes in real time, as well as the spatial forms of the mooring anchor chain and the connecting anchor chain and the transmitted tension, reduce the complexity of finite - element model modeling, and improve the calculation efficiency.

[0006] The technical solution adopted by the present invention to solve its technical problems is:

[0007] A modeling and analysis method applicable to a large holding power anchor group system. The large holding power anchor group system includes a front large holding power anchor and a rear large holding power anchor. The front end of the front large holding power anchor forms a front mooring point, and the front mooring point is connected to the rear end of the mooring anchor chain. The front end of the rear large holding power anchor forms a rear mooring point, and a connecting anchor chain is provided between the rear end of the front large holding power anchor and the rear mooring point.

[0008] The modeling and analysis method includes the following steps:

[0009] S1. Establish the solid models of the large holding power anchor group system and the seabed soil in the finite element model, and obtain the main program of the finite element model;

[0010] S2. Apply the anchor chain tension to the anchor chain tension application point at the front end of the mooring anchor chain solid model. Specifically, it includes the following sub-steps:

[0011] S2.1. Compile a subroutine for calculating the anchor chain tension and the loading angle, and obtain the anchor chain tension loading angle subroutine;

[0012] S2.2. The anchor chain tension loading angle subroutine reads the vertical depth coordinate of the anchor chain tension application point at the current moment from the main program of the finite element model;

[0013] S2.3. Obtain the loading angle according to the vertical depth coordinate and the initial value of the set anchor chain tension;

[0014] S2.4. Apply the anchor chain tension to the anchor chain tension application point according to the loading angle;

[0015] S2.5. The main program of the finite element model calculates and obtains the structural state of the large holding power anchor group system solid model at the next moment according to the applied anchor chain tension and the loading angle, and updates the vertical depth coordinate of the anchor chain tension application point;

[0016] S2.6. Judge whether the towing speed meets the control speed according to the displacement magnitude of the mooring anchor chain solid model within the corresponding time period, and update the anchor chain tension in the anchor chain tension loading angle subroutine;

[0017] S2.7. Obtain the updated loading angle according to the updated anchor chain tension and the updated vertical depth coordinate;

[0018] S2.8. The main program of the finite element model calculates and judges whether the large holding power anchor group system solid model has completed the towing installation. If not, repeat steps S2.4 - S2.7 until the towing installation analysis is completed;

[0019] S3. Monitor the horizontal displacement and vertical displacement of the front mooring point and monitor the horizontal displacement and vertical displacement of the rear mooring point during the calculation process of the main program of the finite element model to obtain the motion trajectory curve of the large holding power anchor group system solid model.

[0020] Further, in step S1, an entity model of the large-grip anchor group system is established in the finite element model, which specifically includes the following sub-steps:

[0021] S1.1. Establish an entity model of the multi-segment connecting anchor chain body in the finite element model, and set rigid body condition constraints. Set a rigid body reference point at the front end of each entity model of the multi-segment connecting anchor chain body and set a binding constraint point at the rear end. Establish a first discrete line segment between adjacent entity models of the multi-segment connecting anchor chain body. The front end of each first discrete line segment is connected to the binding constraint point at the rear end of the previous entity model of the multi-segment connecting anchor chain body, and the rear end of each first discrete line segment is connected to the rigid body reference point at the front end of the subsequent entity model of the multi-segment connecting anchor chain body. Create connection properties for each first discrete line segment so that the lengths of each first discrete line segment are constant and form a first connection unit. Each entity model of the multi-segment connecting anchor chain body and each first connection unit cooperate to form a connecting anchor chain entity model;

[0022] S1.2. Establish a front large-grip anchor entity model on the front side of the connecting anchor chain entity model and a rear large-grip anchor entity model on the rear side, and set rigid body condition constraints. Set a rigid body reference point at the front mooring point at the front end of the front large-grip anchor entity model and set a binding constraint point at the connecting part at the rear end. Set a rigid body reference point at the rear mooring point at the front end of the rear large-grip anchor entity model;

[0023] S1.3. Establish a second discrete line segment with the rigid body reference point at the front end of the connecting anchor chain entity model as the end point to connect to the binding constraint point at the rear end of the front large-grip anchor entity model, and establish a third discrete line segment with the binding constraint point at the rear end of the connecting anchor chain entity model as the end point to connect to the rigid body reference point at the front end of the rear large-grip anchor entity model. Create connection properties for the second discrete line segment and the third discrete line segment so that the length of the second discrete line segment is constant and forms a second connection unit, and the length of the third discrete line segment is constant and forms a third connection unit;

[0024] S1.4. Establish an entity model of the multi-segment mooring anchor chain body on the front side of the front large-grip anchor entity model, and set rigid body condition constraints. Set a rigid body reference point at the front end of each entity model of the multi-segment mooring anchor chain body and set a binding constraint point at the rear end. Establish a fourth discrete line segment between adjacent entity models of the multi-segment mooring anchor chain body. The front end of each fourth discrete line segment is connected to the binding constraint point at the rear end of the previous entity model of the multi-segment mooring anchor chain body, and the rear end of each fourth discrete line segment is connected to the rigid body reference point at the front end of the subsequent entity model of the multi-segment mooring anchor chain body. Create connection properties for each fourth discrete line segment so that the lengths of each fourth discrete line segment are constant and form a fourth connection unit. Each entity model of the multi-segment mooring anchor chain body and each fourth connection unit cooperate to form a mooring anchor chain entity model, where the rigid body reference point at the front end of the mooring anchor chain entity model forms an anchor chain tension application point;

[0025] S1.5. Establish a fifth discrete line segment with the binding constraint point at the rear end of the mooring chain entity model as the end point to connect the rigid body reference point at the front end of the large drag embedment anchor entity model; create connection properties for the fifth discrete line segment so that the length of the fifth discrete line segment is constant and forms a fifth connection unit.

[0026] Furthermore, step S2.1 is specifically as follows: Set the effective width of the mooring chain, the mooring chain bearing coefficient, the friction coefficient between the mooring chain and the seabed soil, the undrained shear strength of the seabed soil surface, the undrained shear strength gradient of the seabed soil, and the loading angle of the mooring chain on the seabed surface according to the geometric characteristics of the mooring chain entity model, so as to compile a subroutine for calculating the mooring chain tension and the loading angle, and obtain the mooring chain tension loading angle subroutine.

[0027] Furthermore,

[0028] Step S2.2 is specifically as follows: The mooring chain tension loading angle subroutine reads the horizontal coordinate and the vertical depth coordinate of the mooring chain tension application point at the current moment from the main program of the finite element model;

[0029] Step S2.5 is specifically as follows: The main program of the finite element model calculates the structural state of the large drag embedment anchor group system entity model at the next moment according to the initial value of the applied mooring chain tension and the loading angle, and updates the horizontal coordinate and the vertical depth coordinate of the mooring chain tension application point.

[0030] Furthermore, step S2.3 is specifically as follows: Set the initial value T L0 of the mooring chain tension, and substitute the initial value of the mooring chain tension and the vertical depth coordinate of the mooring chain tension application point into the mooring chain equation (1) to obtain the loading angle θ L ;

[0031]

[0032] In formula (1): z L is the vertical depth coordinate of the mooring chain tension application point; z U is the vertical coordinate of the seabed surface; μ l is the friction coefficient between the mooring chain and the seabed soil, and its value range in marine clay is usually 0.1 - 0.6; θ U is the angle between the mooring chain tension and the horizontal plane at the seabed surface; Q l is the normal soil resistance force per unit length of the mooring chain, and is calculated by Q l = N l qb l where b l is the effective width borne by the mooring chain, N l is the bearing capacity coefficient of the mooring chain in the seabed soil, and q is the soil pressure corresponding to the mooring chain embedment depth.

[0033] Further, step S2.6 is specifically as follows: According to the displacement magnitude of the mooring chain entity model within the corresponding time period, determine whether the towing speed meets the controlled speed of mooring chain towing. If the towing speed is less than the controlled speed of mooring chain towing, increase the mooring chain tension in the mooring chain tension loading angle subroutine; if the towing speed is greater than the controlled speed of mooring chain towing, decrease the mooring chain tension in the mooring chain tension loading angle subroutine, so as to maintain the towing speed at the controlled speed of mooring chain towing.

[0034] Further, in step S2.6: The mooring chain tension adjustment value ΔT within the corresponding time period is determined by ΔT = T[v c -(Δu / Δt)] / v c where T is the reference amplitude of the mooring chain tension adjustment value, v c is the controlled speed of mooring chain towing, Δu is the displacement of the mooring chain entity model in the previous time period, and Δt is the length of the previous time period.

[0035] Further, the front large-grip anchor includes a front large-grip anchor plate, a front large-grip anchor shank is fixed on the top surface of the front large-grip anchor plate, the front end of the front large-grip anchor shank forms a front mooring point, the front mooring point is connected to the rear end of the mooring chain; the rear large-grip anchor includes a rear large-grip anchor plate, a rear large-grip anchor shank is fixed on the top surface of the rear large-grip anchor plate, the front end of the rear large-grip anchor shank forms a rear mooring point, and a connecting mooring chain is used to connect between the connecting member at the rear end of the front large-grip anchor plate and the rear mooring point.

[0036] Further, a front first toothed plate is provided at the left part of the front end of the front large-grip anchor plate and a front second toothed plate is provided at the right part of the front end, so that the front large-grip anchor forms a front double-toothed large-grip anchor.

[0037] Further, a rear first outer toothed plate, a rear first inner toothed plate, a rear second inner toothed plate and a rear second outer toothed plate are sequentially provided at the front end of the rear large-grip anchor plate from left to right, so that the rear large-grip anchor forms a rear four-toothed large-grip anchor.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] The modeling and analysis method applicable to the large-grip anchor group system in the present invention realizes the towing installation analysis of the finite element model of the large-grip anchor group system by establishing the solid models of the large-grip anchor group system and the seabed soil, programming the subroutine for the loading angle of the anchor chain tension, and applying the anchor chain tension to the anchor chain tension application point at the front end of the mooring anchor chain solid model in the solid model of the large-grip anchor group system. It can greatly simplify the modeling process of the mooring anchor chain finite element model, accurately depict the spatial forms of the mooring anchor chain and the connecting anchor chain and the transmitted tension during the embedding installation process of the large-grip anchor group system, and is applicable to the finite element analysis of the towing installation process of large-grip anchor group systems with various structural forms.

[0040] In summary, the present invention can improve the predictability of the embedding behavior of the large-grip anchor group system, enhance the accuracy of numerical simulation, accurately depict the anchor chain tension received by the mooring anchor chain that changes in real time, as well as the spatial forms of the mooring anchor chain and the connecting anchor chain and the transmitted tension, reduce the complexity of finite element model modeling, and improve the calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic structural diagram of the large-grip anchor group system in the present invention;

[0042] Figure 2 is a schematic diagram of the rigid body constraint conditions of the connecting anchor chain body solid model;

[0043] Figure 3 is a schematic diagram of the first connecting unit connecting adjacent two sections of the connecting anchor chain body solid model;

[0044] Figure 4 is a schematic diagram of the connecting mechanical properties of the first connecting unit;

[0045] Figure 5 is a schematic diagram of the process flow of the anchor chain tension application;

[0046] Figure 6 is a schematic diagram of the movement trajectory curve of the solid model of the large-grip anchor group system.

[0047] Explanation of the reference numerals in the drawings: 1. Front large-grip anchor, 101. Front large-grip anchor anchor plate, 102. Front large-grip anchor shank, 103. Front mooring point, 104. Connecting piece, 2. Rear large-grip anchor, 201. Rear large-grip anchor anchor plate, 202. Rear large-grip anchor shank, 203. Rear mooring point, 3. Mooring anchor chain, 301. Mooring anchor chain body solid model, 302. Fourth connecting unit, 303. Anchor chain tension application point, 4. Connecting anchor chain, 401. Connecting anchor chain body solid model, 402. First connecting unit, 403. Connecting anchor chain body rigid reference point, 404. Connecting anchor chain body binding constraint point. DETAILED DESCRIPTION OF THE INVENTION

[0048] The following further elaborates on the specific embodiments of the present invention in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0049] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0050] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] In addition, in the description of the present invention, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0052] A modeling and analysis method applicable to a large-grip anchor group system. The large-grip anchor group system includes a front large-grip anchor 1 and a rear large-grip anchor 2. A front mooring point 103 is formed at the front end of the front large-grip anchor. The rear end of the front mooring point 103 is connected to the front end of the mooring anchor chain 3. A rear mooring point 203 is formed at the front end of the rear large-grip anchor 2. A connecting anchor chain 4 is provided between the rear end of the front large-grip anchor 1 and the rear mooring point 203. See Figure 1 ;

[0053] The modeling and analysis method includes the following steps:

[0054] S1. Establish a solid model of the large-grip anchor group system and the seabed soil in the finite element model, and obtain the main program of the finite element model;

[0055] S2. As shown in Figure 5 , apply an anchor chain tension to the anchor chain tension application point 303 at the front end of the mooring anchor chain solid model, which specifically includes the following sub-steps:

[0056] S2.1. Compile a subprogram for calculating the anchor chain tension and the loading angle, and obtain the anchor chain tension loading angle subprogram;

[0057] S2.2. The anchor chain tension loading angle subroutine reads the horizontal coordinate and vertical depth coordinate of the anchor chain tension application point 303 at the current moment from the main program of the finite element model;

[0058] S2.3. According to the vertical depth coordinate and the initial value of the set anchor chain tension, the loading angle is obtained;

[0059] S2.4. Apply the anchor chain tension to the anchor chain tension application point 303 at the loading angle;

[0060] S2.5. The main program of the finite element model calculates the structural state of the large drag force anchor group system entity model at the next moment according to the applied anchor chain tension and the loading angle, and updates the horizontal coordinate and vertical depth coordinate of the anchor chain tension application point 303;

[0061] S2.6. According to the displacement magnitude of the mooring anchor chain entity model within the corresponding time period, judge whether the towing speed meets the control speed, and update the anchor chain tension in the anchor chain tension loading angle subroutine;

[0062] S2.7. According to the updated anchor chain tension and the updated vertical depth coordinate, the updated loading angle is obtained;

[0063] S2.8. The main program of the finite element model calculates and judges whether the large drag force anchor group system entity model has completed the towing installation. If not, repeat steps S2.4 - S2.7 until the towing installation analysis is completed;

[0064] S3. During the calculation process of the main program of the finite element model, monitor the horizontal displacement and vertical displacement of the front mooring point 103, and monitor the horizontal displacement and vertical displacement of the rear mooring point 203 to obtain the motion trajectory curve of the large drag force anchor group system entity model, as shown in Figure 6 .

[0065] Among them, in step S1, establishing the entity model of the large drag force anchor group system in the finite element model specifically includes the following sub - steps:

[0066] S1.1. Establish the entity model 401 of multiple - segment connected anchor chain bodies in the finite element model, and set the rigid body condition constraints. Set the rigid body reference point, that is, the connected anchor chain body rigid body reference point 403, at the front end of each entity model 401 of the connected anchor chain body, and set the bound constraint point, that is, the connected anchor chain body bound constraint point 404, at the rear end, as shown in Figure 2; Establish a first discrete line segment between adjacent two segments of the connecting anchor chain body entity model 401. The front end of each first discrete line segment is connected to the binding constraint point at the rear end of the previous segment of the connecting anchor chain body entity model 401, and the rear end of each first discrete line segment is connected to the rigid body reference point at the front end of the subsequent segment of the connecting anchor chain body entity model 401; Create connection properties for each first discrete line segment so that the lengths of each first discrete line segment are constant and form a first connection unit 402, see Figure 3 and Figure 4 ; Each segment of the connecting anchor chain body entity model 401 and each segment of the first connection unit 402 cooperate to form a connecting anchor chain entity model;

[0067] Among them, assign material properties to each segment of the connecting anchor chain body entity model 401, including the density, stiffness, and Poisson's ratio of the material;

[0068] Preferably, each segment of the connecting anchor chain body entity model 401 is a simplified cylinder model. Set a rigid body reference point at the center point of the right end of each segment of the connecting anchor chain body entity model 401 and set a binding constraint point at the center point of the left end;

[0069] S1.2. Establish a front large holding power anchor entity model on the front side of the connecting anchor chain entity model and a rear large holding power anchor entity model on the rear side, and set rigid body condition constraints. Set a rigid body reference point at the front mooring point 103 at the front end of the front large holding power anchor entity model and set a binding constraint point at the connecting part at the rear end. Set a rigid body reference point at the rear mooring point 203 at the front end of the rear large holding power anchor entity model;

[0070] Among them, assign material properties to the front large holding power anchor entity model and the rear large holding power anchor entity model, including the density, stiffness, and Poisson's ratio of the material;

[0071] S1.3. Establish a second discrete line segment with the rigid body reference point at the front end of the connecting anchor chain entity model as the end point to connect to the binding constraint point at the rear end of the front large holding power anchor entity model, and establish a third discrete line segment with the rigid body reference point at the rear end of the connecting anchor chain entity model as the end point to connect to the rigid body reference point at the front end of the rear large holding power anchor entity model; Create connection properties for the second discrete line segment and the third discrete line segment so that the length of the second discrete line segment is constant and forms a second connection unit, and the length of the third discrete line segment is constant and forms a third connection unit;

[0072] S1.4. Establish a multi-segment mooring chain body entity model 301 in front of the front large-grip anchor entity model, and set rigid body condition constraints. Set a rigid body reference point at the front end of each mooring chain body entity model 301 and a binding constraint point at the rear end; establish a section of the fourth discrete line segment between adjacent mooring chain body entity models 301. The front end of each section of the fourth discrete line segment is connected to the binding constraint point at the rear end of the previous mooring chain body entity model 301, and the rear end of each section of the fourth discrete line segment is connected to the rigid body reference point at the front end of the subsequent mooring chain body entity model 301; create connection properties for each section of the fourth discrete line segment so that the lengths of each section of the fourth discrete line segment are constant and form the fourth connection unit 302; each mooring chain body entity model 301 and each section of the fourth connection unit 302 cooperate to form a mooring chain entity model, where the rigid body reference point at the front end of the mooring chain entity model forms the anchor chain tension application point 303;

[0073] Among them, assign material properties to each mooring chain body entity model 301, including the density, stiffness, and Poisson's ratio of the material;

[0074] S1.5. Establish a section of the fifth discrete line segment with the binding constraint point at the rear end of the mooring chain entity model as the end point to connect the rigid body reference point at the front end of the front large-grip anchor entity model; create connection properties for the fifth discrete line segment so that the length of the fifth discrete line segment is constant and forms the fifth connection unit.

[0075] Among them, step S2.1 is specifically: set the effective width borne by the mooring chain, the bearing coefficient of the mooring chain in the seabed soil, the friction coefficient between the mooring chain and the seabed soil, the undrained shear strength of the seabed surface soil of the seabed soil, the undrained shear strength gradient of the seabed soil, and the angle between the anchor chain tension and the horizontal plane at the seabed surface according to the geometric characteristics of the mooring chain entity model, so as to compile a subroutine for calculating the anchor chain tension and the loading angle, and obtain the anchor chain tension loading angle subroutine.

[0076] Preferably, the effective width borne by the mooring chain is 0.2 m, the bearing coefficient of the mooring chain in the seabed soil is 10, the friction coefficient between the mooring chain and the seabed soil is 0.2, the undrained shear strength of the seabed surface soil of the seabed soil is 6 kPa, the undrained shear strength gradient of the seabed soil is 1.5 kPa / m, and the angle between the anchor chain tension and the horizontal plane at the seabed surface is 0°.

[0077] Among them, step S2.3 is specifically: set the initial value T L0 of the anchor chain tension, and substitute the initial value T L0 of the anchor chain tension and the vertical depth coordinate of the anchor chain tension application point 303 into the mooring chain equation 1 for iterative calculation to obtain the loading angle θ L ;

[0078]

[0079] In Equation (1): z L is the vertical depth coordinate of the mooring chain tension application point 303; z U is the vertical coordinate of the seabed surface; μ l is the friction coefficient between the mooring chain and the seabed soil, and its value range in marine clay is usually 0.1 - 0.6 under normal circumstances; θ U is the angle between the mooring chain tension and the horizontal plane at the seabed surface; Q l is the normal soil resistance per unit length of the mooring chain, and Q l = N l qb l is calculated, where b l is the effective width borne by the mooring chain, N l is the bearing coefficient of the mooring chain in the seabed soil, and q is the soil pressure corresponding to the buried depth of the mooring chain.

[0080] Preferably, T L0 = 5000 kN.

[0081] Among them, step S2.6 is specifically: according to the displacement magnitude of the mooring chain physical model within the corresponding time period, determine whether the towing speed meets the control speed of the towing of mooring chain 3. If the towing speed is less than the control speed of the towing of mooring chain 3, increase the mooring chain tension in the mooring chain tension loading angle subroutine; if the towing speed is greater than the control speed of the towing of mooring chain 3, decrease the mooring chain tension in the mooring chain tension loading angle subroutine, so as to maintain the towing speed at the control speed of the towing of mooring chain 3.

[0082] Preferably, in step S2.6: the mooring chain tension adjustment value ΔT within the corresponding time period is determined by ΔT = T[v c -(Δu / Δt)] / v c , where T is the reference amplitude of the mooring chain tension adjustment value, v c is the control speed of the towing of mooring chain 3, Δu is the displacement of the mooring chain physical model in the previous time period, and Δt is the length of the previous time period. Preferably, v c is taken as 1 times the anchor plate length of the front large holding power anchor 1 per second, and T is taken as 1 kN.

[0083] Among them, the front large-grip anchor 1 includes a front large-grip anchor plate 101. A front large-grip anchor shank 102 is fixed on the top surface of the front large-grip anchor plate 101. The front mooring point 103 is formed at the front end of the front large-grip anchor shank 102. The front mooring point 103 is connected to the rear end of the mooring anchor chain 3. The rear large-grip anchor 2 includes a rear large-grip anchor plate 201. A rear large-grip anchor shank 202 is fixed on the top surface of the rear large-grip anchor plate 201. The rear mooring point 203 is formed at the front end of the rear large-grip anchor shank 202. A connecting anchor chain 4 is used to connect between the connecting member 104 at the rear end of the front large-grip anchor plate 101 and the rear mooring point 203.

[0084] Preferably, a front first toothed plate is provided at the left part of the front end of the front large-grip anchor plate 101 and a front second toothed plate is provided at the right part of the front end, so that the front large-grip anchor 1 forms a front double-toothed large-grip anchor.

[0085] Preferably, a rear first outer toothed plate, a rear first inner toothed plate, a rear second inner toothed plate and a rear second outer toothed plate are sequentially provided at the front end of the rear large-grip anchor plate 201 from left to right, so that the rear large-grip anchor 2 forms a rear four-toothed large-grip anchor.

[0086] In the present invention, by establishing a physical model 301 of several sections of the mooring anchor chain body, the loading angle at the anchor chain tension application point 303 at the front end of the mooring anchor chain physical model is calculated by using the mooring anchor chain equation. The anchor chain tension is applied to the anchor chain tension application point 303, replacing the finite element modeling of the complete mooring anchor chain 3, greatly reducing the modeling length of the finite element model of the mooring anchor chain 3 and greatly reducing the overall model calculation cost. The anchor chain tension is transmitted by the connecting anchor chain physical model to realize the application of the towing force to the physical model of the large-grip anchor group system. On the premise of retaining the spatial form, force transmission characteristics and calculation accuracy during the towing process of the mooring anchor chain 3 and the connecting anchor chain 4, the modeling and calculation efficiency of the finite element model is improved, and the motion trajectory curve of the physical model of the large-grip anchor group system is obtained accurately.

[0087] In summary, the present invention not only simplifies the complexity of the finite element modeling process of the mooring anchor chain 3 in the large-grip anchor group system and improves the modeling efficiency, but also retains the spatial form and force transmission characteristics of the connecting anchor chain 4 and the mooring anchor chain 3 during the towing process, realizes the dynamic application of the anchor chain tension during the towing installation process of the physical model of the large-grip anchor group system, avoids using a constant anchor chain tension to replace the dynamic anchor chain tension, and provides an effective numerical simulation prediction method for predicting the complex embedding behavior and motion trajectory of the large-grip anchor group system in the seabed.

[0088] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and replacements can still be made, and these improvements and replacements should also be regarded as the protection scope of the present invention.

Claims

1. A modeling and analysis method suitable for a large holding force anchor system, characterized in that: The large holding power anchor group system comprises a front large holding power anchor (1) and a rear large holding power anchor (2), wherein the front end of the front large holding power anchor forms a front mooring point (103), the front mooring point (103) is connected to the rear end of a mooring anchor chain (3), the front end of the rear large holding power anchor (2) forms a rear mooring point (203), and a connecting anchor chain (4) is provided between the rear end of the front large holding power anchor (1) and the rear mooring point (203); The modeling analysis method includes the following steps: S1. Establishing a solid model of a large holding force anchor system and seabed soil in a finite element model, and obtaining a main program of the finite element model; S2, applying anchor chain tension to the anchor chain tension application point (303) at the front end of the mooring anchor chain physical model, specifically comprising the following sub-steps: S2.

1. Prepare a subroutine for calculating the anchor chain tension and loading angle, and obtain the anchor chain tension loading angle subroutine; S2.2, the anchor chain tension loading angle subroutine reads the vertical depth coordinate of the anchor chain tension application point (303) at the current moment from the finite element model main program; S2.3, obtaining the loading angle according to the vertical depth coordinate and the set initial value of the anchor chain tension; S2.4, applying anchor chain tension to the anchor chain tension application point (303) according to the loading angle; S2.5, the finite element model main program calculates the structural state of the entity model of the large holding force anchor group system at the next moment according to the applied anchor chain tension and loading angle, and updates the vertical depth coordinate of the anchor chain tension application point (303); S2.

6. According to the displacement of the mooring anchor chain entity model in the corresponding time period, determine whether the towing speed meets the control speed, and update the anchor chain tension in the anchor chain tension loading angle subroutine; S2.7, obtaining an updated loading angle according to the updated anchor chain tension and the updated vertical depth coordinate; S2.8, the finite element model main program calculates and determines whether the dragging installation of the large holding force anchor group system entity model is completed. If not, repeat steps S2.4-S2.7 until the dragging installation analysis is completed; S3. During the calculation process of the finite element model main program, the horizontal displacement and vertical displacement of the front mooring point (103) are monitored, and the horizontal displacement and vertical displacement of the rear mooring point (203) are monitored to obtain a motion trajectory curve of the large holding force anchor group system entity model.

2. A modeling and analysis method for a large holding force anchor system according to claim 1, characterized in that: In step S1, a solid model of the large holding force anchor group system is established in the finite element model, which specifically includes the following sub-steps: S1.

1. Establishing a multi-segment anchor chain entity model (401) in a finite element model, and setting rigid body condition constraints, setting a rigid body reference point at the front end of each anchor chain entity model (401) and setting a binding constraint point at the rear end; establishing a first discrete line segment between two adjacent anchor chain entity models (401), the front end of each first discrete line segment being connected to the binding constraint point at the rear end of the front anchor chain entity model (401), and the rear end of each first discrete line segment being connected to the rigid body reference point at the front end of the rear anchor chain entity model (401); creating connection attributes for each first discrete line segment, so that the length of each first discrete line segment is constant and constitutes a first connection unit (402); each anchor chain entity model (401) and each first connection unit (402) cooperate to form the anchor chain entity model; S1.2, establishing a front high-holding power anchor entity model at the front side of the connecting anchor chain entity model and establishing a rear high-holding power anchor entity model at the rear side, and setting rigid body condition constraints, setting a rigid body reference point at the front mooring point (103) at the front end of the front high-holding power anchor entity model and setting a binding constraint point at the connection part at the rear end, and setting a rigid body reference point at the rear mooring point (203) at the front end of the rear high-holding power anchor entity model; S1.

3. Establish a second discrete line segment with the rigid reference point at the front end of the anchor chain entity model as an endpoint to connect the binding constraint point at the rear end of the front large holding power anchor entity model, and establish a third discrete line segment with the binding constraint point at the rear end of the anchor chain entity model as an endpoint to connect the rigid reference point at the front end of the rear large holding power anchor entity model; create connection attributes for the second discrete line segment and the third discrete line segment, so that the length of the second discrete line segment is constant and constitutes a second connection unit, and the length of the third discrete line segment is constant and constitutes a third connection unit; S1.

4. Establishing a multi-section mooring anchor chain entity model (301) at the front side of the front large holding power anchor entity model, and setting rigid body condition constraints, setting a rigid body reference point at the front end of each section of the mooring anchor chain entity model (301) and setting a binding constraint point at the rear end; establishing a fourth discrete line segment between two adjacent sections of the mooring anchor chain entity model (301), the front end of each section of the fourth discrete line segment is connected to the binding constraint point at the rear end of the front section of the mooring anchor chain entity model (301), and the rear end of each section of the fourth discrete line segment is connected to the rigid body reference point at the front end of the rear section of the mooring anchor chain entity model (301); creating connection attributes for each section of the fourth discrete line segment, so that the length of each section of the fourth discrete line segment is constant and constitutes a fourth connection unit (302); each section of the mooring anchor chain entity model (301) and each section of the fourth connection unit (302) cooperate to form a mooring anchor chain entity model, wherein the rigid body reference point at the front end of the mooring anchor chain entity model forms an anchor chain tension application point (303); S1.

5. Establish a fifth discrete line segment with the binding constraint point at the rear end of the mooring anchor chain entity model as the endpoint to connect the rigid reference point at the front end of the front large holding force anchor entity model; create connection attributes for the fifth discrete line segment so that the length of the fifth discrete line segment is constant and constitutes a fifth connection unit.

3. A modeling and analysis method for a large holding force anchor system according to claim 1, characterized in that: Step S2.1 is specifically as follows: according to the geometric characteristics of the mooring anchor chain entity model, the effective width of the mooring anchor chain bearing, the bearing coefficient of the mooring anchor chain in the seabed soil, the friction coefficient between the mooring anchor chain and the seabed soil, the undrained shear strength of the seabed soil surface, the undrained shear strength gradient of the seabed soil, and the angle between the anchor chain tension on the seabed surface and the horizontal plane are set to compile a subroutine for calculating the anchor chain tension and loading angle, and obtain the anchor chain tension loading angle subroutine.

4. A modeling and analysis method for a large holding force anchor system according to claim 1, characterized in that: Step S2.2 is specifically as follows: the anchor chain tension loading angle subroutine reads the horizontal coordinates and vertical depth coordinates of the anchor chain tension application point (303) at the current moment from the finite element model main program; Step S2.5 is specifically as follows: the finite element model main program calculates the structural state of the large holding force anchor group system entity model at the next moment according to the applied anchor chain tension initial value and loading angle, and updates the horizontal coordinate and vertical depth coordinate of the anchor chain tension application point (303).

5. A modeling and analysis method for a large holding force anchor system according to claim 1, characterized in that: Step S2.3 is as follows: Set the initial value of the anchor chain tension T L0 , and substitute the initial value of the anchor chain tension and the vertical depth coordinate of the anchor chain tension application point (303) into the mooring anchor chain equation 1) to obtain the loading angle θ L ; In formula 1), z L z is the vertical depth coordinate of the anchor chain tension application point (303); U is the vertical coordinate of the seabed surface; μ l is the friction coefficient between the mooring chain and the seabed soil, which is usually in the range of 0.1 to 0.6 in marine clay; θ U Q is the angle between the anchor chain tension on the seabed and the horizontal plane; l is the normal soil resistance per unit length of the mooring chain, and is expressed by Q l =N l qb l Calculated, where b l is the effective width of the mooring chain, N l is the bearing coefficient of the mooring chain in the seabed soil, and q is the soil pressure corresponding to the buried depth of the mooring chain.

6. A modeling and analysis method for a large holding force anchor system according to claim 1, characterized in that: Step S2.6 specifically comprises: judging whether the towing speed satisfies the control speed of the towing of the mooring anchor chain (3) according to the displacement of the mooring anchor chain entity model in the corresponding time period; if the towing speed is less than the control speed of the towing of the mooring anchor chain (3), increasing the anchor chain tension in the anchor chain tension loading angle subroutine; if the towing speed is greater than the control speed of the towing of the mooring anchor chain (3), reducing the anchor chain tension in the anchor chain tension loading angle subroutine to maintain the towing speed at the control speed of the towing of the mooring anchor chain (3).

7. A modeling and analysis method for a large holding force anchor system according to claim 6, characterized in that: In step S2.6: the anchor chain tension adjustment value ΔT in the corresponding time period is ΔT = T[v c -(Δu / Δt)] / v c Determine, where T is the reference amplitude of the anchor chain tension adjustment value, v c is the controlled speed of the mooring anchor chain (3) dragging, Δu is the displacement of the mooring anchor chain entity model in the previous time period, and Δt is the length of the previous time period.

8. A modeling and analysis method for a large holding force anchor system according to claim 1, characterized in that: The front high-grip anchor (1) comprises a front high-grip anchor plate (101), a front high-grip anchor shank (102) is fixed on the top surface of the front high-grip anchor plate (101), the front end of the front high-grip anchor shank (102) forms a front mooring point (103), and the front mooring point (103) is connected to the rear end of a mooring anchor chain (3); the rear high-grip anchor (2) comprises a rear high-grip anchor plate (201), a rear high-grip anchor shank (202) is fixed on the top surface of the rear high-grip anchor plate (201), the front end of the rear high-grip anchor shank (202) forms a rear mooring point (203), and a connecting piece (104) at the rear end of the front high-grip anchor plate (101) is connected to the rear mooring point (203) via a connecting anchor chain (4).

9. A modeling and analysis method for a large holding force anchor system according to claim 8, characterized in that: The front high-holding power anchor plate (101) is provided with a front first tooth plate at the left front end and a front second tooth plate at the right front end, so that the front high-holding power anchor (1) forms a front double-tooth high-holding power anchor.

10. A modeling and analysis method for a large holding force anchor system according to claim 8, characterized in that: The front end of the rear high-holding power anchor plate (201) is provided with a rear first outer tooth plate, a rear first inner tooth plate, a rear second inner tooth plate and a rear second outer tooth plate in sequence from left to right, so that the rear high-holding power anchor (2) forms a rear four-tooth high-holding power anchor.

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