Method and system for calculating the mooring force of a submerged pipeline based on water flow conditions and cable form

Abstract

The present application relates to the technical field of immersed tube mooring force calculation, and discloses a kind of immersed tube mooring force calculation method and system based on water flow condition and cable arrangement form.The present application obtains immersed tube structure parameters, hydrological monitoring data and construction cable arrangement scheme, and respectively uses specification semi-experience method and numerical simulation method based on three-dimensional potential flow theory to calculate each cable tension, and then determines the mapping relationship between the maximum cable force difference value and the main cable stress, solves the calculation deviation and the problem that the application boundary is not clear in the prior art under different working conditions;On this basis, according to different water flow and cable arrangement combination, the mooring force response characteristics are output, the synergistic regulation and control effect of water flow velocity, flow direction and cable arrangement form on mooring force can be quantitatively revealed, the most unfavorable stress working condition in the whole construction process is identified, so as to provide quantitative data support for cable selection and construction scheme optimization in immersed tube mooring system design.

Description

Technical Field

[0001] This invention relates to the field of immersed tube mooring force calculation technology, and in particular to a method and system for calculating immersed tube mooring force based on water flow conditions and cable laying method. Background Technology

[0002] With the continuous advancement of urban cross-river and cross-sea passage construction, large-section immersed tunnels have been widely used in cross-waterway passage projects due to their technical advantages such as minimal interference with the navigation environment, excellent structural integrity, and high construction efficiency. Immersed tunnel construction encompasses core processes such as prefabrication of tunnel sections, floating and transporting, mooring and positioning, immersion and installation, and underwater docking. The entire process is characterized by high risks in surface operations and high precision requirements for underwater installation control.

[0003] Floating transport, mooring, positioning, and immersion installation are the core procedures in immersed tunnel construction, and their operational safety directly depends on the stress stability and attitude control capability of the mooring system. Restricted waterways generally exhibit characteristics such as limited width, shallow depth, cyclical currents, and significant spatiotemporal fluctuations in current velocity. The immersed tunnel sections experience complex and variable hydrodynamic loads during the stages of lateral movement after leaving the dock, temporary mooring, positioning and immersion, and docking. Accurate calculation and dynamic control of mooring forces are crucial prerequisites for ensuring construction safety. Domestic and international scholars have conducted a series of fundamental studies on the hydrodynamic response characteristics of immersed tunnel sections, providing an important theoretical foundation for revealing the hydrodynamic mechanisms during the floating and immersion stages.

[0004] In the study of the force characteristics of mooring systems, existing research mainly revolves around two technical paths: model testing and numerical simulation. The methods for calculating the mooring force of immersed tubes are also mainly divided into two categories: one is the semi-empirical formula method based on industry standards or guidelines, which has a simple calculation process, strong engineering applicability, and is widely used in preliminary design and rapid safety verification; the other is the numerical simulation method based on potential flow theory, computational fluid dynamics, or multibody dynamics, which can accurately characterize complex flow field characteristics and multi-cable collaborative force mechanisms, and is suitable for refined analysis of key working conditions. Among them, analysis software based on three-dimensional potential flow theory, such as ANSYS AQWA, has been widely used in the calculation of hydrodynamics and mooring response of floating bodies. Its theoretical system covers core modules such as hydrodynamic diffraction, radiation, hydrostatic restoring force, and mooring constraints. At the engineering specification level, the "Code for Loads on Port Engineering Structures" provides a standard basis for calculating the hydrodynamic forces of port engineering structures. International guidelines such as the World Association for Waterborne Transport Infrastructure (PIANC), the Unified Facilities Criteria (UFC), and the Oil Companies International Marine Forum (OCIMF) provide technical guidance on aspects such as mooring motion control in ports, design of offshore mooring facilities, mooring system layout, cable safety redundancy, and system reliability. The British BS 6349 series of standards also provides relevant regulations on the effects of marine engineering and the assessment of mooring loads. However, existing codes and guidelines are mostly developed for port structures, ships, and marine floating bodies. Their applicability to narrow, confined waterways, reciprocating current environments, large-section immersed tunnels, and complex shore-side anchoring conditions still needs to be systematically verified in conjunction with specific projects.

[0005] In summary, existing research has achieved preliminary results in areas such as the hydrodynamic response mechanism of immersed tunnels, model test methods, immersion motion control, and mooring system analysis. However, there are still three significant shortcomings: First, most studies focus on immersed tunnel installation in open waters or sea areas, and research on the synergistic regulation mechanism of water flow and cable laying methods on mooring forces under conditions of restricted waters, reciprocating flow environments, and complex shoreline cable laying is still relatively scarce. Second, existing results mostly focus on the single immersion or waiting-to-sink stage, lacking systematic comparative analysis of the evolution of mooring forces throughout the entire construction process, including undocking, river mooring, installation preparation, cable untying and conversion, and trench placement. Third, the standard semi-empirical method and three-dimensional numerical simulation method still lack quantitative and systematic evaluation of the maximum cable force differences, main cable force distribution laws, and safety control thresholds under different water flow conditions and cable laying methods. Summary of the Invention

[0006] To overcome the aforementioned shortcomings in existing immersed tube mooring force calculations, this invention provides a method and system for calculating immersed tube mooring force based on water flow conditions and cable laying configuration.

[0007] In a first aspect, the present invention provides a method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying methods, including:

[0008] Acquire the structural parameters of the immersed tunnel, hydrological monitoring data of the target water area, and the construction cable laying plan; Based on the structural parameters and the water flow velocity and direction in the hydrological monitoring data, the tension value of each cable is calculated using the standard semi-empirical method to obtain the first cable force calculation result; A three-dimensional geometric model of the immersed tube is established based on the structural parameters. A mooring constraint model is established based on the construction cable laying scheme. Water flow load is applied based on the water flow velocity and direction in the hydrological monitoring data. The three-dimensional geometric model of the immersed tube and the mooring constraint model are coupled and solved to obtain the second cable force calculation result. Based on the same water flow conditions and the same cable laying method, under different calculation conditions, the first cable force calculation result and the second cable force calculation result are compared to determine the mapping relationship between the maximum cable force difference value and the main cable force. Based on the mapping relationship, output the mooring force response characteristics under different combinations of water flow conditions and different cable laying methods.

[0009] According to a specific implementation method, obtaining the first cable force calculation result in the above calculation method specifically includes: Based on the water flow velocity and the projected area of ​​the submerged pipe in a plane perpendicular to the flow direction, the standard value of the hydrodynamic force is calculated using the following formula: , in, This is the standard value of the water flow force. The coefficient of water flow resistance. For water density, Design the flow velocity for the water flow. The projected area of ​​the immersed tube on a plane perpendicular to the flow direction; The standard value of the water flow force is decomposed along the longitudinal and transverse directions of the immersed tube. Based on the angle between each cable and the axis of the immersed tube, the static equilibrium equation is established by taking moments at the anchor points on both sides of the immersed tube, and the tension value of each cable is solved.

[0010] According to a specific implementation method, the above calculation method, in which a three-dimensional geometric model of the immersed tube is established, specifically includes: Based on the length, width and height of the immersed tube in the structural parameters, a solid model of the immersed tube is established. The solid model is cut along the still water surface, and the underwater part is used as the wet surface for hydrodynamic calculation. The mooring constraint model includes a cable unit, a immersed tube connection point, and a fixed point. One end of the cable unit is connected to the immersed tube connection point, and the other end is connected to the fixed point. The cable unit adopts a linear elastic constitutive model.

[0011] According to a specific implementation method, the above calculation method involves coupling the solution of the three-dimensional geometric model of the immersed tube with the mooring constraint model, specifically including: Define the boundary conditions for the numerical model; The hydrodynamic load on the wetted surface of the immersed tube is solved based on the three-dimensional potential flow theory and the boundary conditions. The hydrodynamic load includes the resistance load generated by the water flow. The resistance load is applied to the three-dimensional geometric model of the immersed tube; Under the constraints of the resistance load, gravity, buoyancy and the cable unit, the displacement and attitude changes of the immersed tube and the elongation of each cable unit are solved iteratively to make the immersed tube reach an overall equilibrium state. The steady-state tension value of each cable unit when the immersed tube reaches an overall equilibrium state is extracted and used as the result of the second cable force calculation.

[0012] According to a specific implementation, in the above calculation method, the boundary conditions include the object surface boundary conditions at the wet surface of the immersed tube, the free liquid surface boundary conditions at the free liquid surface, the bottom boundary conditions at the bottom of the water, and the far-field boundary conditions at the boundary outside the calculation domain. The boundary condition of the object surface is that the velocity of the fluid particles in the normal direction on the wet surface of the immersed tube is consistent with the normal velocity of the immersed tube surface; The bottom boundary condition is that the normal velocity at the bottom of the water is zero. The far-field boundary condition is that the structural disturbance gradually decays at the outer boundary of the computational domain and remains consistent with the incoming flow condition.

[0013] According to one specific implementation method, in the above calculation method, the resistance-type load is calculated using the following formula: , in, Force exerted by water flow, The coefficient of water flow resistance. ρ For water density, The projected area of ​​the immersed tube in the direction perpendicular to the incoming flow is denoted as . To calculate the flow rate; In the case of oblique flow, the force of the water flow is decomposed into a component along the axial direction of the submerged pipe and a component perpendicular to the axial direction of the submerged pipe.

[0014] According to a specific implementation method, in the above calculation method, the hydrological monitoring data includes multiple sets of combined data on water flow velocity and direction, the water flow velocity includes ebb tide velocity and flood tide velocity, the construction cable laying scheme includes multiple cable laying forms corresponding to each construction stage, the construction stage includes river mooring stage, installation preparation stage, undocking and mooring stage, cable untying and sinking preparation stage, and trench placement stage.

[0015] According to one specific implementation, the above calculation method further includes: Based on the combination of water flow velocity and direction data for each group and the combination of cable laying methods for each construction stage, the first cable force calculation results and the second cable force calculation results are compared respectively. Based on the comparison results under different combinations, the most unfavorable stress condition in the entire process is identified. The most unfavorable stress condition is the condition with the largest cable force in each combination.

[0016] According to a specific implementation method, the mooring force response characteristics in the above calculation method include: the tension value of each cable, the maximum cable force value, the distribution of the main load-bearing cable group, and the nonlinear growth law of the cable force with the water flow velocity, wherein the nonlinear growth law is that the cable force is positively correlated with the square of the water flow velocity.

[0017] Secondly, the present invention provides a system for calculating the mooring force of an immersed tunnel based on water flow conditions and cable arrangement, comprising: a processor, a memory, and a network interface; the processor is connected to the memory and the network interface; the network interface is used to provide data communication functions, the memory is used to store computer programs, and the processor is used to call the computer programs to execute a method for calculating the mooring force of an immersed tunnel based on water flow conditions and cable arrangement as described above. Compared with the prior art, the beneficial effects of the present invention are as follows: This invention acquires immersed tunnel structure parameters, hydrological monitoring data, and construction cable laying schemes, and calculates the tension of each cable using both a standard semi-empirical method and a numerical simulation method based on three-dimensional potential flow theory. This allows for a direct comparison of the calculation results of the two methods under the same water flow and cable laying conditions. Furthermore, by determining the mapping relationship between the maximum cable force difference and the main cable stress, it solves the problems of calculation deviation and unclear applicable boundaries of the two calculation methods under different working conditions in the prior art. Based on this, it outputs mooring force response characteristics according to different water flow and cable laying combinations, which can quantitatively reveal the synergistic control effect of water flow velocity, flow direction, and cable laying form on mooring force. This enables the identification of the most unfavorable stress conditions in the entire construction process, thus providing quantitative data support for cable selection and construction scheme optimization in the design of immersed tunnel mooring systems, and improving the comprehensiveness and engineering applicability of mooring stress analysis. Attached Figure Description

[0018] Figure 1 A flowchart illustrating the method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying configuration, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the mesh generation of the immersed tube model provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the arrangement of immersed tube anchor points provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the submerged pipe position and cable arrangement for working condition 1 provided in an embodiment of the present invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0020] Unless otherwise specified, the terms "upper," "lower," "left," "right," "center," "inner," and "outer," etc., used in the description of specific embodiments of the present invention to indicate orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is usually placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, and for enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0021] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," "parallel," and "coaxial" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, parallel, or coaxial. Slight tilt or deviation is permissible, as long as it does not affect the normal function of the relevant component. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," not that the structure must be perfectly horizontal; a slight tilt is acceptable. "Coaxial" means that two components are arranged as coaxially as possible, allowing them to move coaxially or approximately coaxially when their relative positions change. Alternatively, it can be simplified to mean that the corresponding device / component / element, when arranged in "horizontal," "vertical," "suspended," "parallel," or "coaxial" directions, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. For example, the deviation in the "coaxial" direction is controlled within 0.2-1mm, preferably within 0.2-0.5mm. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present invention.

[0022] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0023] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0024] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to connection methods commonly used in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0025] It should be noted that immersed tunnel construction includes core processes such as segment prefabrication, floating and transfer, mooring and positioning, immersion and installation, and underwater docking. During these processes, the immersed tunnel segments need to be floated and moored on the water surface. The mooring system consists of multiple cables, one end of which is connected to a mooring point on the immersed tunnel segment, and the other end to an anchor point on the shore or an underwater anchor block. The water flow acts on the immersed tunnel segment, generating a current force that is transmitted through the segment to each cable, causing corresponding tension in each cable. Accurate calculation of the mooring force is a crucial aspect of safe management during immersed tunnel construction.

[0026] This invention uses the Dongguan Hongfu West Road-Yinlong Road cross-river immersed tunnel project as an example to illustrate its application. In this project, the standard cross-section of the immersed tunnel is a rectangular box-shaped structure, with dimensions of 28.6 meters (width) × 9.7 meters (height), classifying it as a large-section immersed tunnel structure. The entire tunnel consists of three sections, E1 to E3, where E1 is a transition section, and E2 and E3 are standard immersed tunnel sections in the river. The immersed tunnel prefabrication employs the axial expansion dry dock method, with the dry dock located on the north bank. The entire construction process includes in-dock floating, out-of-dock mooring, river channel floating, sinking and positioning, and multi-section coordinated docking.

[0027] To facilitate understanding of the technical solution of this invention, some of the terms involved in this invention will be explained first.

[0028] In the description of this invention embodiment, the normative semi-empirical method refers to the calculation method of cable tension based on the hydrodynamic force calculation formula in the Chinese "Port Engineering Load Code" (JTS144-1-2010) and combined with the planar force system and moment balance equation. The numerical simulation method refers to the calculation method based on three-dimensional potential flow theory, using ANSYS AQWA software to establish a coupled numerical model of the immersed tube-mooring system, and then applying hydrodynamic loads and mooring constraints to perform quasi-static equilibrium solutions to obtain the cable tension.

[0029] Please refer to Figure 1 This document illustrates a flowchart of a method for calculating the mooring force of an immersed tube tunnel based on water flow conditions and cable laying configuration, provided by an embodiment of the present invention. The method includes: S1: Obtain the structural parameters of the immersed tube, hydrological monitoring data of the target water area, and the construction cable laying plan.

[0030] For example, the structural parameters of the immersed tunnel are obtained based on the engineering design scheme. These structural parameters include the length, width, height, mass, center of gravity position, and moment of inertia of the immersed tunnel. In a specific implementation, for tunnel segment E3, the length is 105 meters, the width is 28.6 meters, and the height is 9.7 meters; for the combined E1+E2 tunnel segment, a complete model is created based on the actual construction conditions. The mass of the immersed tunnel is determined based on the buoyancy balance relationship under a 0.1-meter freeboard condition, and the mass is uniformly distributed along the tunnel segment. The mass attributes of the immersed tunnel model include parameters such as mass, volume, surface area, center of gravity coordinates, principal moment of inertia, and product of inertia. These parameters are used in numerical simulation to characterize the inertial characteristics of the immersed tunnel.

[0031] Hydrological monitoring data is acquired by deploying hydrological monitoring points in the target water area. For example, an in-situ monitoring point is deployed near the Quhai Bridge, using a radar tidal velocity meter to monitor hydrological elements. The monitoring instrument is a JYB-SW model, operating at a frequency of 24 GHz, with a velocity measurement range of 0.1 to 20 m / s and a measurement accuracy of ±0.01 m / s. It can simultaneously collect water level and velocity data. The monitoring period covers the complete tidal cycle and seasonal variations. Statistical analysis of the monitoring data yields data on water flow velocity and direction under different tidal conditions. The water flow velocity includes ebb and flow velocities. In one specific implementation, the angle between the water flow direction and the longitudinal axis of the pipe section is 61°.

[0032] The cable laying plan is obtained based on the actual construction organization plan. The plan includes the cable laying methods corresponding to each of the multiple construction stages, including the river mooring stage, installation preparation stage, undocking and mooring stage, undocking and sinking preparation stage, and trench positioning stage. The cable laying method for each construction stage includes the working cable number involved in force balance, the anchor point position corresponding to each cable, the angle between the cable and the immersed tube axis, the initial tension of the cable, and the axial stiffness of the cable. Anchor points are divided into two categories: underwater anchor blocks and shore-side anchor points. For example, underwater anchor blocks include M1, M2, and M3, deployed in the water area to provide lateral restraint and anti-drift capability for the tube section; shore-side anchor points include L1, L2, and L3, deployed on the shore or around the dry dock to cooperate with the underwater anchor blocks in controlling the longitudinal displacement, lateral offset, and planar rotation of the tube section.

[0033] S2: Based on the structural parameters and the water flow velocity and direction in the hydrological monitoring data, the tension value of each cable is calculated using the standard semi-empirical method to obtain the first cable force calculation result.

[0034] For example, the calculation process of the standard semi-empirical method includes two stages: calculating the standard value of the hydrodynamic force and solving for the cable tension.

[0035] In the first stage, the standard value of the hydrodynamic force is calculated based on the water flow velocity and the projected area of ​​the immersed tube in a plane perpendicular to the flow direction. Specifically, according to the Chinese "Port Engineering Load Code" (JTS144-1-2010), the standard value of the hydrodynamic force is calculated using the following formula: , in, This is the standard value of the hydrodynamic force, in kilonewtons (kN). The value is the flow resistance coefficient, which is taken as 1.624 according to the standard. The density of water is expressed in tons per cubic meter (t / m³), with 1.0 t / m³ for freshwater. The design velocity for water flow is expressed in meters per second (m / s). The projected area of ​​the immersed tube on a plane perpendicular to the flow direction is expressed in square meters (m²).

[0036] In the second stage, the standard value of the hydrodynamic force is decomposed along the longitudinal and transverse directions of the immersed tube. Based on the angle between each cable and the axis of the immersed tube, moments are taken at the anchor points on both sides of the immersed tube to establish static equilibrium equations, and the tension values ​​of each cable are solved. The standard semi-empirical method is based on the assumption of planar static equilibrium and ignores the influence of the vertical elevation angle of the cables. Specifically, in the solution, the most unfavorable stress mode is assumed to be borne by only three main cables, including one longitudinal control cable and two transverse control cables. The solution steps are as follows: First, the total hydrodynamic force is decomposed into axial and transverse components of the tube section; then, based on the tidal direction, the control cable with the smallest angle on both sides is selected, and moments are taken at the anchor points on both sides to solve for the transverse cable tension; finally, the longitudinal cable tension is solved by combining the axial component of the hydrodynamic force.

[0037] Using the above method, the tension value of each cable under this working condition can be obtained, and the maximum cable force can be used as the first cable force calculation result for this working condition.

[0038] S3: Establish a three-dimensional geometric model of the immersed tube based on the structural parameters, establish a mooring constraint model based on the construction cable laying scheme, apply water flow load based on the water flow velocity and direction in the hydrological monitoring data, and couple the three-dimensional geometric model of the immersed tube with the mooring constraint model to obtain the second cable force calculation result.

[0039] For example, this step is performed in the AQWA module of the ANSYS Workbench platform. Specifically, it includes the following sub-steps.

[0040] First, a 3D geometric model of the immersed tunnel is established. Based on the tunnel's length, width, and height from the structural parameters, a solid model of the immersed tunnel is created in SolidWorks. The overall shape of the immersed tunnel is a rectangular box; during modeling, the tunnel is treated as a rigid body, and local structural deformation is not considered. After importing the established geometric model of the immersed tunnel into ANSYS Workbench, the model is processed in the Hydrodynamic Diffraction module. The solid model is cut along the XY plane containing the still water surface, dividing the immersed tunnel into an above-water section and an underwater section. The above-water section corresponds to a 0.1-meter freeboard, and the underwater section serves as the wetted surface for hydrodynamic calculations.

[0041] Next, the 3D geometric model of the immersed tube was meshed. A regularized meshing method was used to ensure uniform mesh distribution, stable element morphology, and reduce the impact of local distorted elements on the calculation results. For example, the Defeaturing Tolerance was set to 0.5 meters to filter out detailed geometric features with minimal impact on the overall hydrodynamic response; the Max Element Size was set to 1.0 meter to control the element size on the model surface. After meshing, the model had 30,122 nodes and 30,124 elements. The overall mesh was uniformly distributed on the outer surface of the immersed tube, reflecting the geometric characteristics of the wetted surface. Please refer to [reference needed]. Figure 2 This shows a schematic diagram of the mesh division of the immersed tube model provided in an embodiment of the present invention.

[0042] Next, a mooring constraint model is established based on the construction cable laying scheme. The mooring constraint model includes cable units, immersed tube connection points, and fixed points. One end of each cable unit is connected to the immersed tube connection point, and the other end is connected to the fixed point. The fixed point simulates anchor blocks, anchor piles, or shore-side mooring points in actual construction; its location is determined based on the anchor point coordinates in the construction drawings and remains stationary during the calculation. The cable unit adopts a linear elastic constitutive model, and its axial tension is determined by both the initial tension and the elastic elongation increment. The initial tension of the cable is taken as 20 kN, and the axial stiffness coefficient is taken as 100 kN / m. The cable only bears tension, and its axial tension can be expressed as: , in, Let the tension be the tension in the i-th cable. For initial tension; For the axial stiffness of the cable; This represents the elongation of the cable relative to its initial length. When the cable is slack, its tension is taken as zero.

[0043] Next, the boundary conditions of the numerical model are set. The boundary conditions include the object surface boundary conditions at the wet surface of the immersed tube, the free liquid surface boundary conditions at the free liquid surface, the bottom boundary conditions at the bottom of the water, and the far-field boundary conditions at the boundary outside the computational domain.

[0044] The boundary condition is that the velocity of the fluid particles on the wet surface of the immersed tube is consistent with the normal velocity of the immersed tube surface, thus satisfying the impenetrability condition. This condition is used to ensure the coordination of motion between the fluid and the structure at the wet surface of the immersed tube.

[0045] The free surface boundary condition adopts a linear free surface boundary condition to describe the free surface disturbance caused by the motion of the floating body. Due to the complete closure of the river channel during construction, the effect of steady water flow is mainly considered, and the coupling effect of ship waves and wind waves is not considered. Therefore, the free surface boundary is mainly used to ensure the reasonable relationship between the wetted surface of the floating body and the still water surface in the AQWA hydrodynamic solution.

[0046] The bottom boundary condition treats the waterbed as a rigid, impenetrable boundary with a zero normal velocity. This condition restricts water penetration of the riverbed boundary. The calculated water depth is determined based on the control water depth during the engineering trench and floating installation phases. For example, the computational domain water depth is 24 meters, which covers the control water depth conditions during the engineering trench and floating installation phases.

[0047] The far-field boundary condition is that, at the outer boundary of the computational domain far from the immersed tube, the structural disturbance gradually decays and remains consistent with the given inflow conditions. To reduce the influence of the computational boundary on the hydrodynamic response near the immersed tube, the computational domain is 150m × 150m in size.

[0048] Subsequently, the hydrodynamic loads on the wetted surface of the immersed tube are solved based on the three-dimensional potential flow theory and the aforementioned boundary conditions. AQWA's hydrodynamic calculations are grounded in the three-dimensional potential flow theory. For an incompressible, inviscid, and irrotational ideal fluid, the velocity of any particle in the flow field is represented by a velocity potential function, which satisfies the Laplace equation within the fluid domain. In the hydrodynamic calculations of the wetted surface of the floating body, the pressure distribution on the surface is solved using the velocity potential, and the pressure on the wetted surface is integrated to obtain the resultant hydrodynamic force and torque acting on the floating body.

[0049] For steady water flow, the horizontal water flow load on the immersed pipe is treated as a resistance load. The resistance load is calculated using the following formula: , in, The force exerted by the water flow is expressed in kilonewtons (kN). This is the coefficient of water flow resistance; This refers to the density of water, expressed in tons per cubic meter (t / m³). The projected area of ​​the immersed tube in the direction perpendicular to the incoming flow is expressed in square meters (m²). For calculating flow velocity, the unit is meters per second (m / s). For example, the flow resistance coefficient... We take 1.624 to be consistent with the normative method.

[0050] In the case of oblique flow, the force of the water flow is decomposed into a component along the axial direction of the immersed tube and a component perpendicular to the axial direction of the immersed tube, and these components are respectively applied to the overall force balance equation of the immersed tube. The direction of water flow is determined according to the actual construction conditions; for example, the angle between the water flow and the axis of the tube section is taken as 61°.

[0051] Subsequently, drag-type loads are applied to the three-dimensional geometric model of the immersed tunnel. Under the constraints of drag-type loads, gravity, buoyancy, and cable elements, the displacement and attitude changes of the immersed tunnel and the elongation of each cable element are iteratively solved to achieve an overall equilibrium state. The overall equilibrium state satisfies the conditions that the resultant external force and the resultant external torque are both zero, and its overall equilibrium relationship can be expressed as: , , in, The resultant force of external forces acting on the immersed tube includes gravity, buoyancy, water flow force, and cable tension, etc. This is the resultant torque generated by each external force about the reference point.

[0052] Finally, the steady-state tension values ​​of each cable unit when the immersed tube reaches overall equilibrium are extracted as the second cable force calculation result. Unlike the standard method which selects a few main cables for planar mechanical equilibrium calculation, the AQWA model can consider the influence of different cable spatial arrangements, connection positions, initial tension, axial stiffness, and fixed point coordinates on cable force distribution.

[0053] S4: Based on the same water flow conditions and the same cable laying method, under different calculation conditions, compare the first cable force calculation results with the second cable force calculation results to determine the mapping relationship between the maximum cable force difference value and the main cable force.

[0054] For example, for each calculation case, the first cable force calculation result obtained from the standard semi-empirical method is compared with the second cable force calculation result obtained from the numerical simulation method. The comparison includes the tensile values ​​of each cable and the maximum cable force value.

[0055] Specifically, for the same cable under the same working condition, record the tension value in the first cable force calculation result and the tension value in the second cable force calculation result, and calculate the difference or ratio between the two. For the maximum cable force under this working condition, extract the maximum value from both the first and second cable force calculation results, and calculate the maximum cable force difference value.

[0056] The mapping relationship refers to the correspondence between the first cable force calculation result and the second cable force calculation result under different combinations of water flow conditions (different flow velocities, different flow directions) and different cable laying methods (different construction stages, different number and arrangement of cables).

[0057] For example, the mapping relationship can be expressed as follows: under the condition of high current velocity of 1.5 m / s at low tide and the cable arrangement is multi-cable fully constrained, the maximum cable force calculated by the first cable force is 924 kN, and the maximum cable force calculated by the second cable force is 750 kN. The first cable force calculation result is larger than the second cable force calculation result, with a deviation range of 18.5% to 25.2%; under the condition of low current velocity of 0.7 m / s at high tide and the cable arrangement is few-cable constrained, the second cable force calculation result is larger than the first cable force calculation result, with a deviation range of 19.4% to 28.8%.

[0058] By establishing the above mapping relationship, the calculation deviation characteristics of the two types of calculation methods under different working conditions can be quantitatively described.

[0059] S5: Output the mooring force response characteristics under different combinations of water flow conditions and different cable laying methods based on the mapping relationship.

[0060] For example, based on the mapping relationship determined in S4, the mooring force response characteristics under different combinations of water flow conditions and different cable deployment methods are output. The mooring force response characteristics include the tension values ​​of each cable, the maximum cable force value, the distribution of the main load-bearing cable group, and the nonlinear growth law of cable force with water flow velocity. The nonlinear growth law shows that the cable force is positively correlated with the square of the water flow velocity.

[0061] Specifically, for each calculation case, the system outputs a tension distribution diagram or data table for each cable under that case, marking the maximum cable tension value and its corresponding cable number, and identifying the main load-bearing cable group (i.e., the set of cables bearing the main load). For cases with different water flow velocities under the same cable laying configuration, the system outputs a curve showing the cable tension versus flow velocity, demonstrating the positive correlation between cable tension and the square of the flow velocity. For cases with different cable laying configurations under the same water flow conditions, the system outputs a comparison of cable tension distribution under different cable laying configurations, demonstrating the influence of cable laying configuration on the spatial distribution of cable tension and the degree of stress concentration.

[0062] For example, by combining the output results of all operating conditions, the most unfavorable stress condition in the entire process can be identified. The most unfavorable stress condition is the one with the largest maximum cable force among all combinations. In a specific implementation, the river mooring stage under a low tide of 1.5 m / s is the most unfavorable stress condition in the entire process, with a maximum cable force of 924 kN according to the standard method and 750 kN according to numerical simulation.

[0063] In one possible implementation, the hydrological monitoring data includes a combination of multiple sets of data on water flow velocity and direction. The water flow velocity includes both ebb and flow velocities. For example, during stages of significant floating current intake, such as mooring, installation preparation, and undocking, three representative flow velocities are set: 1.2 m / s ebb, 1.5 m / s ebb, and 0.8 m / s flow velocities during ebb and flow. For the sinking preparation and sinking into the foundation trench stage, considering the low flow velocity requirements during the construction window, four operating conditions are set: 0.5 m / s ebb, 0.7 m / s ebb, 0.5 m / s flow velocities during flow, and 0.7 m / s flow velocities during flow. The angle between the water flow direction and the pipe section axis is uniformly 61° for all operating conditions.

[0064] The construction cable-laying plan includes the cable-laying methods corresponding to each of the multiple construction stages. These stages include the river mooring stage, the installation preparation stage, the undocking and mooring stage, the cable release and sinking preparation stage, and the trench placement stage. The cable-laying methods differ in each stage, mainly in the number of working cables involved in force balance and the spatial arrangement of the cables.

[0065] In one possible implementation, based on the combination of water flow velocity and direction data for each set and the cable laying method for each construction stage, the calculation results of the first cable force and the second cable force are compared respectively. For example, for the combination of 5 types of construction stages and multiple sets of water flow conditions, standard method calculations and numerical simulations are performed one by one to obtain the calculation results of the first cable force and the second cable force under each combination, and then they are compared one by one.

[0066] Based on the comparison results under different combinations, the most unfavorable stress condition throughout the entire process is identified. The most unfavorable stress condition is the one with the largest maximum cable force among all combinations. For example, under condition 3 (E2+E1 pipe sections are completed and moored in the secondary outfitting area) and a low tide of 1.5 m / s, the maximum cable force calculated by the standard method is 924 kN, which is the maximum value of the standard method for all conditions; under condition 1 (E3 pipe section is moored in the river channel) and a low tide of 1.5 m / s, the maximum cable force simulated by numerical simulation is 750 kN, which is the maximum value of the numerical simulation for all conditions. Therefore, a low tide of 1.5 m / s is the most unfavorable flow condition for the entire process.

[0067] Through the above implementation methods, the regulatory effects of water flow parameters and cable layout on mooring force can be systematically quantified, and the applicable boundaries of semi-empirical methods and numerical simulation methods at different construction stages can be clearly defined.

[0068] The technical solution provided by the present invention will be described and explained in detail below with reference to specific implementation methods.

[0069] After completing the geometric modeling and mesh generation of the immersed tunnel section, a mooring constraint system was established in AQWA based on the actual construction cable laying scheme. The mooring system mainly consists of immersed tunnel connection points, shore-side fixed points, and cable elements. The fixed points simulate anchor blocks, anchor piles, or shore-side mooring points in actual construction, and their locations are determined based on the anchor point coordinates in the construction drawings. The fixed points remain stationary during the calculation process, providing external constraint boundaries for the cables. One end of the cable is connected to the designed mooring point on the immersed tunnel section or segment, and the other end is connected to the shore-side or water-based fixed point, thus forming the segment mooring constraint system. According to the construction scheme, this paper analyzes only the segment mooring cables and does not consider the influence of barge mooring cables on the calculation results. Although the actual number of cables laid during construction is large, different cables have different functions, with some cables mainly used for auxiliary positioning, attitude fine-tuning, or safety backup. The numerical analysis is modeled according to the main cable arrangement determined in the construction scheme to reflect the main force paths of the immersed tunnel mooring system under various typical working conditions.

[0070] The cable model uses linear elastic elements with an initial tension of 20 kN and an axial stiffness coefficient of 100 kN / m. The number of cables, their connection positions, and the spatial angles between them and the immersed tube are all determined according to the actual construction layout. This setup allows the numerical model to reflect the initial tension state of the cables, their elongation characteristics under stress, and the collaborative constraint effect of multiple cables, providing a foundation for subsequent analysis of the main cable tension distribution under different working conditions.

[0071] Furthermore, to systematically reveal the regulatory effect of water flow conditions and cable laying methods on mooring force, this embodiment selects five typical stress states in the entire process of immersed tube construction as calculation conditions, covering the entire stages of undocking and mooring, river mooring, installation preparation, cable unloading and sinking, and trench placement. The specific conditions are shown in Table 1.

[0072] Table 1 Example of Calculation Conditions

[0073] To address the stress characteristics and construction window requirements at different construction stages, differentiated combinations of water flow conditions were established: For stages with significant floating current intake, such as river mooring, installation preparation, and undocking, three representative flow velocities were selected: 1.2 m / s ebb tide, 1.5 m / s ebb tide, and 0.8 m / s high tide. For stages of sinking preparation and sinking to the bottom of the foundation trench, four working conditions were set, considering the low flow velocity requirements during the construction window: 0.5 m / s ebb tide, 0.7 m / s ebb tide, 0.5 m / s high tide, and 0.7 m / s high tide. The angle between the water flow direction and the pipe section axis was uniformly 61° for all working conditions to ensure consistency between the numerical simulation and the calculation conditions of the standard method. During the calculation of each working condition, the corresponding water flow load and mooring constraints were applied first, followed by quasi-static equilibrium solutions to obtain the cable tension response under different combinations of water flow and cable laying. The calculation results focus on extracting the steady-state tension value and the maximum cable force under working conditions of each main cable, and systematically comparing them with the results of the standard method. Based on this, the stress safety of the mooring system at different construction stages and the applicability boundary of the standard method are evaluated.

[0074] Based on the above-mentioned standard semi-empirical calculation method, combined with the water flow conditions and immersed tube projection parameters for each working condition, the total flow force under all working conditions was calculated, and the results are shown in Table 2. Since the projected area of ​​the immersed tube facing the flow is the same for working conditions 1 to 3, the total flow force is the same under the same flow velocity; working conditions 4 to 5 correspond to low flow velocity construction windows, and the amplitude of the flow force is significantly reduced.

[0075] Table 2. Examples of hydraulic force calculation results for various working conditions.

[0076] The standard method for calculating cable tension is based on the assumption of planar static equilibrium, neglecting the influence of the cable's vertical elevation angle, and assuming the most unfavorable stress mode, that only three main cables bear the entire load (including one longitudinal control cable and two transverse control cables). The solution steps are as follows: First, decompose the total flow force into axial and transverse components of the pipe sections; select the control cables with the smallest included angle on both sides according to the tidal direction, and take moments about the anchor points of the cables on both sides to solve for the transverse cable tension; finally, combine the axial component of the flow force to solve for the longitudinal cable tension. The core equilibrium relationship is as follows: , , , in, F W The force of the water flow (kN); L c This refers to the length of the immersed tube; L This refers to the length of the immersed tube when it leaves the dock. F R This refers to the tension of the cable on the right side of the immersed tube. F L This refers to the tension of the cable on the left side of the immersed tunnel. θ The angle between the right-side cable and the immersed tube; β The angle between the cable on the left side of the immersed tube and the immersed tube itself; α F is the angle between the immersed tube and the river channel; l The tension in the cable is along the direction of the pipe section.

[0077] Understandably, during the floating and mooring of the immersed tunnel sections, the arrangement of anchor points is a crucial factor affecting the distribution of cable forces and the stability of the tunnel sections. Please refer to [reference needed]. Figure 3 The diagram illustrates the arrangement of anchor points for the immersed tunnel section provided in this embodiment. According to the cable laying plan at the construction site, the anchor points around the immersed tunnel section are mainly divided into two categories: underwater anchor blocks and shore-side anchor points. M1, M2, and M3 are underwater anchor blocks deployed in the water area, primarily used to provide lateral restraint and anti-drift capability for the tunnel sections. L1, L2, and L3 are shore-side anchor points deployed on the shore or around the dry dock, primarily used to coordinate with the underwater anchor blocks to control the longitudinal displacement, lateral offset, and planar rotation of the tunnel sections. Both types of anchor points are connected to the immersed tunnel mooring points via cables, forming a multi-point restraint system to ensure the stability of the immersed tunnel section's planar position and attitude during the undocking, temporary mooring, installation preparation, and sinking positioning stages.

[0078] Considering that some cables in actual construction are mainly used as spare cables or attitude adjustment cables, and are only activated when the pipe section offset is large, the main cable is under abnormal stress, or construction adjustments are made, they do not bear the main stress under normal calculation conditions. To highlight the main stress path of the immersed tunnel mooring system and improve the clarity of the comparison between the standard method and numerical simulation results, this paper only retains the working cables and main stress anchors involved in the stress balance of each working condition in the cable force calculation. Under different working conditions, the working cables are numbered C1, C2, C3, C4, and C5, respectively, where the prefix indicates the corresponding construction working condition, and the suffix indicates the specific cable involved in the calculation under that working condition. Based on the above anchor point and main cable arrangement, the cable tension is calculated under different water flow velocities, flow directions, and construction conditions, and the maximum cable force under each working condition is extracted as the basis for safety evaluation.

[0079] Specifically, for operating condition 1, please refer to... Figure 4The diagram illustrates the location of the immersed tunnel section and the cable arrangement for Case 1 provided in this embodiment. As shown, under this condition, seven working cables, C1-1 to C1-7, are mainly installed around the tunnel section. C1-1, C1-4, C1-5, and C1-7 are connected to anchor points L1, L5, L4, and L2 on the shore side, respectively, while C1-2, C1-3, and C1-6 are connected to underwater anchor blocks M3, M2, and M1, respectively. These cables together form a multi-point constraint system to limit the lateral drift, longitudinal displacement, and rotation of the tunnel section under the influence of water flow. A comparison of the results from the standard method and numerical simulation is performed under three water flow conditions: Case 1-1, Case 1-2, and Case 1-3, corresponding to ebb tides of 1.2 m / s, 1.5 m / s, and 0.8 m / s, respectively. It can be seen that under low tide conditions, the water flow acts on the pipe sections from left to right along the river channel, with the main load-bearing cables concentrated on C1-6, C1-7, C1-5, and C1-4, which are connected to anchor points M1, L2, L4, and L5. Under high tide conditions, the water flow direction is reversed, and the main load-bearing path shifts to C1-1, C1-3, and C1-2, which are connected to anchor points L1, M2, and M3. Comparing the two calculation methods, in Case 1-1, the maximum cable force using the standard method is 589 kN, while the numerical simulation result is 498 kN, a difference of approximately 15.4%. In Case 1-2, the maximum cable force using the standard method is 920 kN, while the numerical simulation result is 750 kN, a difference of approximately 18.5%. In Case 1-3, the maximum cable force using the standard method is 269 kN, while the numerical simulation result is 274 kN, a difference of only approximately 1.9%. Overall, the maximum cable force obtained by the two methods differs by approximately 2% to 19%, with similar numerical magnitudes and trends, both indicating that Case 1-2 represents the most unfavorable stress state under this condition. The standard method simplifies the water flow force as a concentrated load and performs force and moment balance calculations based on the load borne by the main stressed cable, resulting in a relatively conservative outcome. In contrast, the AQWA numerical simulation considers the spatial arrangement of cables, initial tension, stiffness, fixed point location, and the coordinated stress of multiple cables, allowing for load redistribution among the cables. Therefore, the maximum single cable force under low tide conditions is slightly lower than that under the standard method. Under high tide conditions, due to the smaller water flow force and relatively uniform cable stress, the calculation results from both methods show good agreement.

[0080] Following the steps described above, the same analysis and comparison were performed on all working conditions 2 to 5 to obtain the calculation results of the maximum cable force under all working conditions, as shown in Table 3.

[0081] Table 3. Example of maximum cable force calculation results under all working conditions.

[0082] Table 4 shows that the mooring force during the floating and temporary mooring stages is significantly higher than that during the sinking preparation and sinking to the bottom of the trench stages, with conditions 1-3 under a low tide of 1.5 m / s being the main unfavorable conditions. The maximum mooring force calculated by the standard method occurs in Case 3-2, at 924 kN; the maximum mooring force in numerical simulation occurs in Case 1-2, at 750 kN. For the high-velocity floating condition, the results calculated by the standard method are generally greater than those in the numerical simulation, indicating that the standard method has a certain degree of conservatism. However, during the unmooring and sinking to the bottom of the trench stages, the numerical simulation results are slightly higher than those calculated by the standard method, indicating that the spatial constraints, initial tension, and local attitude adjustments of the remaining working mooring lines have a more significant impact on the mooring force distribution. Combining the results of all conditions, the mooring force response characteristics under different combinations of water flow conditions and different mooring arrangements can be derived: First, water flow conditions dominate the mooring force amplitude and stress distribution. The overall cable force is positively correlated with the square of the flow velocity. As the flow velocity increases from 0.8 m / s to 1.5 m / s, the maximum cable force increases approximately 2.4 times. Changes in flow direction cause a complete switch in the main load-bearing cable group, making it a core controlling factor for the spatial distribution of cable force. A low tide of 1.5 m / s represents the most unfavorable flow condition throughout the entire process and is a core control indicator for selecting the construction window. Secondly, the cable deployment method determines the distribution and concentration of cable force. In multi-cable fully constrained floating mooring conditions, the load can be distributed and transferred among multiple cables, effectively mitigating the peak load on a single cable. During the uncoupling and trench placement stages, the number of working cables decreases, and the constraint system weakens, easily leading to localized cable force concentration. This is a critical stage for attitude control and safety management. The applicable boundaries of the two types of calculation methods have clear stage characteristics: under high flow velocity and multi-cable constraint conditions, the standard method results are conservative with sufficient safety redundancy, making it suitable for preliminary design and rapid safety verification of construction schemes; under low flow velocity and few cable constraints construction transition stages, the numerical simulation method is more accurate in identifying local cable force concentrations and is more suitable for refined stress analysis and risk prediction of key processes.

[0083] Based on the above scheme, this embodiment of the invention obtains immersed tube structure parameters, hydrological monitoring data, and construction cable laying schemes, and calculates the tension of each cable using both the standard semi-empirical method and the numerical simulation method based on three-dimensional potential flow theory. This enables a direct comparison of the calculation results of the two methods under the same water flow and cable laying conditions. Furthermore, by determining the mapping relationship between the maximum cable force difference value and the main cable force, the problem of unclear calculation deviations and applicable boundaries of the two calculation methods under different working conditions in the prior art is solved. On this basis, according to the output mooring force response characteristics based on different water flow and cable laying combinations, the synergistic control effect of water flow velocity, flow direction, and cable laying form on mooring force can be quantitatively revealed, enabling the identification of the most unfavorable stress conditions in the entire construction process. This provides quantitative data support for cable selection and construction scheme optimization in the design of immersed tube mooring systems, improving the comprehensiveness and engineering applicability of mooring stress analysis.

[0084] On the other hand, embodiments of the present invention also provide a system for calculating the mooring force of immersed tunnels based on water flow conditions and cable laying methods. This system includes a processor, a memory, and a network interface. The processor is connected to the memory and the network interface. The network interface provides data communication functions, such as receiving hydrological monitoring data from hydrological monitoring equipment or receiving user-input immersed tunnel structure parameters and construction cable laying schemes. The memory stores computer programs. The processor calls the computer program stored in the memory to execute the immersed tunnel mooring force calculation method based on water flow conditions and cable laying methods described in any of the above method embodiments.

[0085] Those skilled in the art will recognize that the components and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0086] In the embodiments provided by this invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of components is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0087] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0088] In addition, the functional components in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0089] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0090] The storage media described in the embodiments of the present invention are intended to include, but are not limited to, these and any other suitable types of memory.

[0091] Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner for ease of understanding.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method, characterized in that, include: Acquire the structural parameters of the immersed tunnel, hydrological monitoring data of the target water area, and the construction cable laying plan; Based on the structural parameters and the water flow velocity and direction in the hydrological monitoring data, the tension value of each cable is calculated using the standard semi-empirical method to obtain the first cable force calculation result; A three-dimensional geometric model of the immersed tube is established based on the structural parameters. A mooring constraint model is established based on the construction cable laying scheme. Water flow load is applied based on the water flow velocity and direction in the hydrological monitoring data. The three-dimensional geometric model of the immersed tube and the mooring constraint model are coupled and solved to obtain the second cable force calculation result. Based on the same water flow conditions and the same cable laying method, under different calculation conditions, the first cable force calculation result and the second cable force calculation result are compared to determine the mapping relationship between the maximum cable force difference value and the main cable force. Based on the mapping relationship, output the mooring force response characteristics under different combinations of water flow conditions and different cable laying methods.

2. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 1, characterized in that, The first cable force calculation results are obtained, specifically including: Based on the water flow velocity and the projected area of ​​the submerged pipe in a plane perpendicular to the flow direction, the standard value of the hydrodynamic force is calculated using the following formula: ， in, This is the standard value of the water flow force. The coefficient of water flow resistance. For water density, Design the flow velocity for the water flow. The projected area of ​​the immersed tube on a plane perpendicular to the flow direction; The standard value of the water flow force is decomposed along the longitudinal and transverse directions of the immersed tube. Based on the angle between each cable and the axis of the immersed tube, the static equilibrium equation is established by taking moments at the anchor points on both sides of the immersed tube, and the tension value of each cable is solved.

3. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 1, characterized in that, Establishing a three-dimensional geometric model of the immersed tube specifically includes: Based on the length, width and height of the immersed tube in the structural parameters, a solid model of the immersed tube is established. The solid model is cut along the still water surface, and the underwater part is used as the wet surface for hydrodynamic calculation. The mooring constraint model includes a cable unit, a immersed tube connection point, and a fixed point. One end of the cable unit is connected to the immersed tube connection point, and the other end is connected to the fixed point. The cable unit adopts a linear elastic constitutive model.

4. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 3, characterized in that, The three-dimensional geometric model of the immersed tube is coupled with the mooring constraint model for solution, specifically including: Define the boundary conditions for the numerical model; The hydrodynamic load on the wetted surface of the immersed tube is solved based on the three-dimensional potential flow theory and the boundary conditions. The hydrodynamic load includes the resistance load generated by the water flow. The resistance load is applied to the three-dimensional geometric model of the immersed tube; Under the constraints of the resistance load, gravity, buoyancy and the cable unit, the displacement and attitude changes of the immersed tube and the elongation of each cable unit are solved iteratively to make the immersed tube reach an overall equilibrium state. The steady-state tension value of each cable unit when the immersed tube reaches an overall equilibrium state is extracted and used as the result of the second cable force calculation.

5. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 4, characterized in that, The boundary conditions include the object surface boundary conditions at the wet surface of the immersed tube, the free liquid surface boundary conditions at the free liquid surface, the bottom boundary conditions at the bottom of the water, and the far-field boundary conditions at the boundary outside the computational domain. The boundary condition of the object surface is that the velocity of the fluid particles in the normal direction on the wet surface of the immersed tube is consistent with the normal velocity of the immersed tube surface; The bottom boundary condition is that the normal velocity at the bottom of the water is zero. The far-field boundary condition is that the structural disturbance gradually decays at the outer boundary of the computational domain and remains consistent with the incoming flow condition.

6. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 4, characterized in that, The resistance-type load is calculated using the following formula: ， in, Force exerted by water flow, The coefficient of water flow resistance. For water density, The projected area of ​​the immersed tube in the direction perpendicular to the incoming flow is denoted as . To calculate the flow rate; In the case of oblique flow, the force of the water flow is decomposed into a component along the axial direction of the submerged pipe and a component perpendicular to the axial direction of the submerged pipe.

7. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 1, characterized in that, The hydrological monitoring data includes multiple sets of combined data on water flow velocity and direction. The water flow velocity includes ebb tide velocity and flood tide velocity. The construction cable laying scheme includes cable laying methods corresponding to multiple construction stages. The construction stages include the river mooring stage, the installation preparation stage, the undocking and mooring stage, the cable untying and sinking preparation stage, and the trench placement stage.

8. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 7, characterized in that, The method further includes: Based on the combination of water flow velocity and direction data for each group and the combination of cable laying methods for each construction stage, the first cable force calculation results and the second cable force calculation results are compared respectively. Based on the comparison results under different combinations, the most unfavorable stress condition in the entire process is identified. The most unfavorable stress condition is the condition with the largest cable force in each combination.

9. The method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying method according to claim 1, characterized in that, The mooring force response characteristics include: the tension value of each cable, the maximum cable force value, the distribution of the main load-bearing cable group, and the nonlinear growth law of cable force with water flow velocity. The nonlinear growth law is that the cable force is positively correlated with the square of the water flow velocity.

10. A system for calculating the mooring force of immersed tunnels based on water flow conditions and cable laying methods, characterized in that, include: Processor, memory, and network interface; The processor is connected to the memory and the network interface; The network interface is used to provide data communication functions, the memory is used to store computer programs, and the processor is used to call the computer programs to execute the method for calculating the mooring force of immersed tubes based on water flow conditions and cable laying methods as described in any one of claims 1 to 9.

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