Multi-physical field collaborative generation experiment method for floating tunnel truncation model

Abstract

The invention provides a multi-physical-field collaborative generation experiment method for a floating tunnel truncation model, and belongs to the technical field of floating tunnel tests, and the method can efficiently and accurately simulate the multi-field coupling effect of waves, ocean currents and earthquakes. And a reliable experiment means is provided for researching the dynamic response and the safety performance of the floating tunnel structure under the complex environmental load. The experimental method comprises the steps of truncation design of a full-scale ultra-long floating tunnel prototype, design of a reduced scale floating tunnel truncation model, construction of a wave-flow-earthquake multi-field input system and collection of dynamic response of the reduced scale floating tunnel truncation model. According to the invention, stable lateral earthquake input can be realized based on the existing wave-flow water channel, the influence of the earthquake effect transmitted from the cable to the tension leg type suspension tunnel pipe body on the dynamic response can be simulated, and the coupling effect of wave, flow and earthquake can be reproduced; and a wave-flow-earthquake multi-field collaborative generation experiment scheme is provided for the ultra-long tension leg type floating tunnel truncation model.

Description

Technical Field

[0001] The invention belongs to the technical field of suspended tunnel experiments, and in particular relates to a multi-physical field collaborative generation experimental method for a suspended tunnel truncation model. Background Art

[0002] With the rapid growth of the demand for cross-sea channel construction in deep-sea areas, floating tunnels have gradually become an innovative solution for the construction of transportation infrastructure in deep-sea areas due to their advantages of small impact on the environment, strong crossing capacity and relatively low long-distance construction cost. However, the complex environmental conditions in the deep sea, such as multiple environmental loads such as waves, ocean currents and earthquakes, have greatly increased the difficulty of the design and construction of floating tunnels, and posed a severe challenge to their long-term service safety.

[0003] At present, most of the research on ultra-long suspended tunnels focuses on the influence of single environmental loads (such as waves, ocean currents or earthquakes) on their dynamic response and fatigue performance. The research content is relatively independent and lacks a comprehensive multi-hazard coupling research framework. Especially in the context of multi-hazard coupling, the experimental study of the truncated model of ultra-long tension-leg suspended tunnels needs to solve the simulation problem of the synergistic effect of multiple physical fields, including the coupling effect between multiple fields, the rationality of the test scale and the accuracy of data acquisition. At present, the experimental method system for this problem is still imperfect, and it is urgent to develop a systematic experimental method that can simulate the synergistic effect of multiple physical fields to provide reliable technical support for actual engineering design. Summary of the invention

[0004] In view of the shortcomings of the existing technology, the present invention proposes a multi-physical field collaborative generation experimental method for a suspended tunnel truncation model. This method can efficiently and accurately simulate the multi-field coupling of waves, ocean currents and earthquakes, and provides a reliable experimental means for studying the dynamic response and safety performance of suspended tunnel structures under complex environmental loads.

[0005] The technical solution adopted by the present invention is as follows: a multi-physical field collaborative generation experimental method for a suspended tunnel truncation model, comprising the following steps:

[0006] S1: Truncated design of full-scale ultra-long suspended tunnel prototype:

[0007] S11: Truncation design: A full-scale finite element model of the reference suspended tunnel was established in the Mechanical module of the finite element analysis software ANSYS, as follows:

[0008] S111: Construction of full-scale numerical model: The tunnel body is simulated using "SOLID185" units, the cables are simulated using "LINK180" units, the fluid domain width is set to 50 times the diameter of the tunnel body, and the water body is simulated using "FLUID30" units;

[0009] S112: Boundary conditions and load settings: Set global gravity in the vertical direction, select the outer surface of the floating tunnel tube as the fluid-solid coupling interface, add static water pressure based on the free liquid surface condition, and set the boundary conditions on both sides to fully constrained fixed boundary conditions;

[0010] S113: Construct analysis process: First, static analysis is performed to determine the stress distribution and deformation state of the suspended tunnel structure under static load. Based on the static analysis results, wet modal analysis is performed to extract the modal parameters of the suspended tunnel structure. The ultra-long tension leg suspended tunnel consists of n suspended tunnel segments, and its wet modal calculation is achieved through formulas (1)-(4):

[0011] Mu″+Ku=0 (1)

[0012] (K-λM)Φ=0 (2)

[0013] M=M T +M W (3)

[0014] K=K T +K C (4)

[0015] Where: M is the overall mass matrix of the full-scale suspended tunnel model; M T is the mass matrix of the suspended tunnel body; M W is the additional mass matrix of the water body around the suspended tunnel; K is the overall stiffness matrix of the suspended tunnel, which is obtained by the cable stiffness matrix K C and the stiffness matrix K of the suspended tunnel body T Composition; u and u″ are the displacement matrix and acceleration matrix of the suspended tunnel respectively; λ is the system eigenvalue vector, which represents the square of the modal frequency; Φ is the modal vibration matrix, which describes the vibration form of the system in the modal state;

[0016] For the i-th suspended tunnel segment, its single segment stiffness K i The bending stiffness of the suspended tunnel body The axial stiffness of the cable part K i C The two parts of stiffness are superimposed in the form of a series system and a parallel system, as shown in formulas (5)-(8):

[0017]

[0018] Where: is the bending stiffness of the pipe body of a single segment suspended tunnel; E T I is the elastic modulus of the material of the suspended tunnel body; Tis the section modulus of the cross section of the suspended tunnel body; L T K is the length of the suspended tunnel body of a single segment; i C is the axial stiffness of the cable section of a single segment suspended tunnel; E C A is the elastic modulus of the cable material of the suspended tunnel; C L is the equivalent area of ​​the cable part of a single segment suspended tunnel; C Length of suspended tunnel cables;

[0019] For the single-segment unconstrained suspended tunnel truncation model, its wet modal calculation is expressed by formula (9):

[0020] (K i -ω 2 M i )Φ=0 (9)

[0021] For an ultra-long tension-leg suspension tunnel, when the number of segments n exceeds 20, its overall stiffness characteristics tend to satisfy K C >>K T Under this condition, the bending stiffness of the suspended tunnel body is ignored in the truncation design process, that is, Therefore, only the axial stiffness of the cable is considered. The first few modal frequencies calculated based on formula (1) and formula (9) are highly consistent; S2: The design of the scaled suspended tunnel truncation model satisfies the following similarity criteria:

[0022] (1) Froude similarity: the similarity in fluid dynamics between the scaled suspended tunnel truncation model and the full-scale ultra-long suspended tunnel prototype;

[0023] (2) Gravity similarity: ensuring that the mechanical responses of the scaled suspended tunnel truncation model and the full-scale ultra-long suspended tunnel prototype under gravity are similar;

[0024] (3) Geometric similarity: The size of the scaled suspended tunnel truncation model is proportional to the full-scale super-long suspended tunnel prototype to maintain consistent geometric features;

[0025] (4) Elastic similarity: The cable stiffness characteristics of the scaled suspended tunnel truncation model are scaled proportionally with the full-scale ultra-long suspended tunnel prototype to ensure the similarity of mechanical behavior;

[0026] The scaled suspended tunnel truncation model includes the suspended tunnel body and cables, and its design steps are as follows:

[0027] S21: Floating tunnel body:

[0028] (1) Similarity criteria: satisfying Froude similarity, gravity similarity and geometric similarity;

[0029] (2) Structure and material: The main body is a central hollow cylinder made of plexiglass with a cylindrical shape. Its length and diameter are reduced in spatial scale according to the same geometric similarity ratio to meet the design requirements;

[0030] (3) Adjustment device: symmetrical fan-shaped grids are set on both sides of the tube model, and counterweight blocks are filled in the grids. The center of gravity and buoyancy weight ratio parameters of the model are accurately controlled by adjusting the position of the counterweight blocks;

[0031] S22: Cable:

[0032] (1) Similarity criteria: satisfying geometric similarity and elastic similarity;

[0033] (2) Material selection: The main body is made of steel strands, and the ends are connected with equivalent springs to adjust the overall stiffness to ensure that the design requirements are met; S23: Connection method: The suspended tunnel tube and the cable are reliably connected through anchor points set on the side of the tube to ensure the integrity of the structure and the rationality of force transmission;

[0034] S3: Construct a wave-flow-earthquake multi-field input system: including wave action input system, flow input system and earthquake action input system. The specific design is as follows:

[0035] S31: Wave action input system: A mechanical wave maker is installed at one end of the wave tank to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves, by adjusting the hydrodynamic input parameters; a wave absorbing device is installed at the other end of the wave tank to effectively absorb reflected waves and ensure the accuracy of wave conditions;

[0036] S32: Flow input system: diversion channels are set at both ends of the water tank, and the bottom of the diversion channel is connected to the turbine motor through a circular pipe; by adjusting the power parameters of the turbine motor, accurate input of different flow rates can be achieved, forming a multi-level flow rate environment to simulate the water flow characteristics of the deep sea area;

[0037] S33: Earthquake input system: An electric actuator is installed above the model placement area to transmit power to the scaled suspended tunnel truncation model through a directional conduction bracket; anchor points for connecting model cables are designed on the conduction bracket to ensure the accuracy of earthquake force transmission; by adjusting the power parameters of the electric actuator, high-precision simulation of ground motion is achieved to reproduce the real earthquake action environment;

[0038] S4: Collection of dynamic response of scaled suspended tunnel truncation model:

[0039] S41: Liquid level measurement: Use a wave height meter to monitor the liquid level around the scaled floating tunnel cutoff model in real time to accurately capture the changing characteristics of wave loads;

[0040] S42: Flow velocity measurement: Use a Doppler velocimeter to measure the flow velocity at the height of the scaled floating tunnel cutoff model to obtain the key parameters of the fluid dynamics;

[0041] S43: Acceleration measurement: Cable anchor point location: Use a three-way waterproof acceleration sensor to monitor the real-time acceleration of the cable anchor point to ensure the consistency of the seismic input of multiple cable anchor points; Electric actuator output: Use a unidirectional acceleration sensor to test the real-time acceleration of the electric actuator to accurately evaluate the characteristics of the seismic power input;

[0042] S44: Cable tension measurement: A waterproof unidirectional tension pressure sensor is used to measure the cable tension changes in real time, providing key data on the cable stress state;

[0043] S45: Displacement response measurement: Based on the binocular camera test system, high-contrast fluorescent marking points are arranged on the side of the scaled suspended tunnel truncation model. Through the image recognition program, the displacement response of the scaled suspended tunnel truncation model is captured in real time to obtain three-dimensional motion characteristic data.

[0044] The advantages and beneficial effects of the present invention are as follows: the present invention can realize stable lateral earthquake input based on the existing wave-flow flume, simulate the influence of earthquake action transmitted by the cable to the tension-leg suspension tunnel pipe body on its dynamic response, and reproduce the coupling effect of wave, flow and earthquake, and provide an experimental scheme for the coordinated generation of wave-flow-earthquake multi-fields for the tension-leg suspension tunnel truncation model. In addition, the present invention also provides a measurement method for the dynamic response of the structure, which is particularly suitable for the multi-load coupling test process, helps to deeply explore the dynamic characteristics of the super-long suspension tunnel under the action of multiple disasters, and provides support for the characteristic evaluation of related projects. Through the present invention, high-precision measurement can be achieved, and the engineering characteristics of the super-long tension-leg suspension tunnel under the wave-flow-earthquake coupling can be effectively evaluated, which has a wide range of engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the front view of the super-long tension-leg suspension tunnel;

[0046] Figure 2 It is a schematic diagram of the side view of the cut-off area of ​​the ultra-long tension-leg suspension tunnel;

[0047] Figure 3 It is a schematic side view of the truncated pipe body of the suspended tunnel model;

[0048] Figure 4 A schematic front view of a suspended tunnel truncation model test system for collaboratively generating a multi-physics field simulating wave-flow-earthquake provided in an embodiment of the present application;

[0049] Figure 5A schematic top view of a suspended tunnel truncation model test system for collaboratively generating a simulated wave-flow-earthquake multi-physics field provided in an embodiment of the present application;

[0050] Figure numerals: 1-suspended tunnel cut-off model tube body; 2-cable steel strand; 3-equivalent spring; 4-fluorescent marking point; 5-tube body-cable connection anchor point; 6-three-way waterproof acceleration sensor; 7-unidirectional acceleration sensor; 8-tension and pressure sensor; 9-wave height meter; 10-Doppler velocimeter; 11-electric actuator; 12-translational wave-making plate; 13-wave breaking device; 14-wave flow tank; 15-free liquid surface; 16-flow guide pipe; 17-turbine motor; 18-directional pulley; 19-directional guide rail; 20-transmission bracket; 21-binocular camera system; 22-waterproof cavity; 23-counterweight area; 24-cable constraint section. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] Example 1

[0053] A multi-physics field collaborative generation experimental method for a suspended tunnel truncation model includes the following steps:

[0054] S1: Truncated design of full-scale ultra-long suspended tunnel prototype:

[0055] S11: Truncation design: A full-scale finite element model of the reference suspended tunnel was established in the Mechanical module of the finite element analysis software ANSYS, as follows:

[0056] S111: Construction of full-scale numerical model: The tunnel body is simulated using "SOLID185" units, the cables are simulated using "LINK180" units, the fluid domain width is set to 50 times the diameter of the tunnel body, and the water body is simulated using "FLUID30" units;

[0057] S112: Boundary conditions and load settings: Set global gravity in the vertical direction, select the outer surface of the floating tunnel tube as the fluid-solid coupling interface, add static water pressure based on the free liquid surface condition, and set the boundary conditions on both sides to fully constrained fixed boundary conditions;

[0058] S113: Construct analysis process: First, static analysis is performed to determine the stress distribution and deformation state of the suspended tunnel structure under static load. Based on the static analysis results, wet modal analysis is performed to extract the modal parameters of the suspended tunnel structure. The ultra-long tension leg suspended tunnel consists of n suspended tunnel segments, and its wet modal calculation is achieved through formulas (1)-(4):

[0059] Mu″+Ku=0 (1)

[0060] (K-λM)Φ=0 (2)

[0061] M=M T +M W (3)

[0062] K=K T +K C (4)

[0063] Where: M is the overall mass matrix of the full-scale suspended tunnel model; M T is the mass matrix of the suspended tunnel body; M W is the additional mass matrix of the water body around the suspended tunnel; K is the overall stiffness matrix of the suspended tunnel, which is obtained by the cable stiffness matrix K C and the stiffness matrix K of the suspended tunnel body T Composition; u and u″ are the displacement matrix and acceleration matrix of the suspended tunnel respectively; λ is the system eigenvalue vector, which represents the square of the modal frequency; Φ is the modal vibration matrix, which describes the vibration form of the system in the modal state;

[0064] For the i-th suspended tunnel segment, its single segment stiffness K i The bending stiffness of the suspended tunnel body The axial stiffness of the cable part K i C The two parts of stiffness are superimposed in the form of a series system and a parallel system, as shown in formulas (5)-(8):

[0065]

[0066]

[0067] Where: is the bending stiffness of the pipe body of a single segment suspended tunnel; E T I is the elastic modulus of the material of the suspended tunnel body; T is the section modulus of the cross section of the suspended tunnel body; L T is the length of the suspended tunnel body of a single segment; is the axial stiffness of the cable section of a single segment suspended tunnel; E CA is the elastic modulus of the cable material of the suspended tunnel; C L is the equivalent area of ​​the cable part of a single segment suspended tunnel; C Length of suspended tunnel cables;

[0068] For the single-segment unconstrained suspended tunnel truncation model, its wet modal calculation is expressed by formula (9):

[0069] (K i -ω 2 M i )Φ=0 (9)

[0070] For an ultra-long tension-leg suspension tunnel, when the number of segments n exceeds 20, its overall stiffness characteristics tend to satisfy K C >>K T Under this condition, the bending stiffness of the suspended tunnel body is ignored in the truncation design process, that is, Therefore, only the axial stiffness of the cable is considered. The first few modal frequencies calculated based on formula (1) and formula (9) are highly consistent; S2: The design of the scaled suspended tunnel truncation model satisfies the following similarity criteria:

[0071] (1) Froude similarity: the similarity in fluid dynamics between the scaled suspended tunnel truncation model and the full-scale ultra-long suspended tunnel prototype;

[0072] (2) Gravity similarity: ensuring that the mechanical responses of the scaled suspended tunnel truncation model and the full-scale ultra-long suspended tunnel prototype under gravity are similar;

[0073] (3) Geometric similarity: The size of the scaled suspended tunnel truncation model is proportional to the full-scale super-long suspended tunnel prototype to maintain consistent geometric features;

[0074] (4) Elastic similarity: The cable stiffness characteristics of the scaled suspended tunnel truncation model are scaled proportionally with the full-scale ultra-long suspended tunnel prototype to ensure the similarity of mechanical behavior;

[0075] The scaled suspended tunnel truncation model includes the suspended tunnel body and cables, and its design steps are as follows:

[0076] S21: Floating tunnel body:

[0077] (1) Similarity criteria: satisfying Froude similarity, gravity similarity and geometric similarity;

[0078] (2) Structure and material: The main body is a central hollow cylinder made of plexiglass with a cylindrical shape. Its length and diameter are reduced in spatial scale according to the same geometric similarity ratio to meet the design requirements;

[0079] (3) Adjustment device: symmetrical fan-shaped grids are set on both sides of the tube model, and counterweight blocks are filled in the grids. The center of gravity and buoyancy weight ratio parameters of the model are accurately controlled by adjusting the position of the counterweight blocks;

[0080] S22: Cable:

[0081] (1) Similarity criteria: satisfying geometric similarity and elastic similarity;

[0082] (2) Material selection: The main body is made of steel strands, and the ends are connected with equivalent springs to adjust the overall stiffness to ensure that the design requirements are met; S23: Connection method: The suspended tunnel tube and the cable are reliably connected through anchor points set on the side of the tube to ensure the integrity of the structure and the rationality of force transmission;

[0083] S3: Construct a wave-flow-earthquake multi-field input system: including wave action input system, flow input system and earthquake action input system. The specific design is as follows:

[0084] S31: Wave action input system: A mechanical wave maker is installed at one end of the wave tank to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves, by adjusting the hydrodynamic input parameters; a wave absorbing device is installed at the other end of the wave tank to effectively absorb reflected waves and ensure the accuracy of wave conditions;

[0085] S32: Flow input system: diversion channels are set at both ends of the water tank, and the bottom of the diversion channel is connected to the turbine motor through a circular pipe; by adjusting the power parameters of the turbine motor, accurate input of different flow rates can be achieved, forming a multi-level flow rate environment to simulate the water flow characteristics of the deep sea area;

[0086] S33: Earthquake input system: An electric actuator is installed above the model placement area to transmit power to the scaled suspended tunnel truncation model through a directional conduction bracket; anchor points for connecting model cables are designed on the conduction bracket to ensure the accuracy of earthquake force transmission; by adjusting the power parameters of the electric actuator, high-precision simulation of ground motion is achieved to reproduce the real earthquake action environment;

[0087] S4: Collection of dynamic response of scaled suspended tunnel truncation model:

[0088] S41: Liquid level measurement: Use a wave height meter to monitor the liquid level around the scaled floating tunnel cutoff model in real time to accurately capture the changing characteristics of wave loads;

[0089] S42: Flow velocity measurement: Use a Doppler velocimeter to measure the flow velocity at the height of the scaled floating tunnel cutoff model to obtain the key parameters of the fluid dynamics;

[0090] S43: Acceleration measurement: Cable anchor point location: Use a three-way waterproof acceleration sensor to monitor the real-time acceleration of the cable anchor point to ensure the consistency of the seismic input of multiple cable anchor points; Electric actuator output: Use a unidirectional acceleration sensor to test the real-time acceleration of the electric actuator to accurately evaluate the characteristics of the seismic power input.

[0091] S44: Cable tension measurement: A waterproof unidirectional tension pressure sensor is used to measure the cable tension changes in real time, providing key data on the cable stress state;

[0092] S45: Displacement response measurement: Based on the binocular camera test system, high-contrast fluorescent marking points are arranged on the side of the scaled suspended tunnel truncation model. Through the image recognition program, the displacement response of the scaled suspended tunnel truncation model is captured in real time to obtain three-dimensional motion characteristic data.

[0093] Example 2

[0094] (1) An ultra-long tension-leg suspension tunnel across the Qiongzhou Strait in the design plan is selected as an example. First, a numerical full-scale finite element model of the full-scale ultra-long suspension tunnel prototype is established. The cross-section of the pipe segment of the design example is circular, the length of each pipe segment is 100m, and the total length is 3000m. Based on these parameters, a full-scale finite element model of the suspension tunnel is established, and the ratio of the cable tensile stiffness and the bending stiffness of the pipe body of a single pipe segment is calculated to be K i C / K T i = 0.85, the ratio of the tensile stiffness of the overall cable and the bending stiffness of the tube of the super-long suspended tunnel is K C / K T =383, which meets the requirement of using unconstrained boundary conditions as the boundary of the scaled suspended tunnel truncation model. The modal analysis of the full-scale ultra-long suspended tunnel prototype shows that the lateral first-order wet modal period of this embodiment is about 10s.

[0095] (2) Design the suspended tunnel truncation model according to the actual size of the wave flow flume 14. In this embodiment, the geometric scale ratio of the model design is set to 1:100, and a pipe section prototype with a truncation length of 80m is selected for scale design. Figure 2 and Figure 3As shown, the tube body 1 of the scaled suspended tunnel truncation model is a hollow cylinder with an overall length of 80 cm, an outer diameter of 12 cm, and an inner diameter of 10 cm. A water-proof cavity is arranged in the middle, and two cable constraint sections 24 are arranged 5 cm near both sides of the model. In addition, counterweight areas 23 are arranged on both sides of the model, and the buoyancy ratio of the model is adjusted to 1.35 by adjusting the weight of the composite counterweight block, so as to keep the buoyancy ratio consistent with the prototype design. The cable stiffness of the full-scale suspended tunnel truncation prototype is proportionally reduced according to the truncation length of the pipe section prototype, and the adjusted cable stiffness is reduced according to the stiffness scale and then divided into four equal parts. According to the spring design specification "GB / T 2088-2009 Dimensions and Parameters of Ordinary Cylindrical Helical Tension Springs", springs of appropriate specifications are selected. The overall assembly of the scaled suspended tunnel truncation model is as follows. Figure 4 As shown, the lower end of the cable strand 2 is connected to the equivalent spring 3, and the upper end is connected to the pipe body-cable connection anchor point 5. The spatial positioning of the pipe body of the scaled suspended tunnel truncation model is achieved by adjusting the relative length of the strand. After the free oscillation test, the first lateral vibration wet mode of the scaled suspended tunnel truncation model is 1.05s, which meets the scale ratio requirements of the natural vibration period of the full-scale ultra-long suspended tunnel prototype.

[0096] (3) Figure 4-5 As shown, the wave-flow-seismic multi-physics input system includes a wave action input system, a flow action input system and a seismic action input system. The wave action input system is a mechanical wave maker installed at one end of the wave tank. By adjusting the hydrodynamic input parameters, it is used to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves, and a wave-breaking device 13 is set at the other end of the water tank; the flow input system is provided with a diversion pipe 16 at both ends of the water tank, and the bottom of the diversion pipe 16 is connected by a round pipe equipped with a turbine motor 17, and multi-level flow rate input is achieved by adjusting the power parameters of the turbine motor 17. The seismic action input system is realized by an electric actuator 11 and a conductive bracket installed on the upper part of the model placement area, wherein the conductive bracket is provided with an anchor point connected to the model cable, and the original ground motion is simulated by adjusting the seismic action dynamic parameters of the electric actuator 11.

[0097] (4) Figure 4-5 As shown, in this embodiment, a variety of instruments are used to collect the load input and the dynamic response of the scaled floating tunnel truncation model. Specifically, a wave height meter 9 is used to measure the height of the waves, a Doppler velocimeter 10 is used to test the flow velocity of the water flow, a three-way waterproof acceleration sensor 6 is installed to test the acceleration input of the anchor point under the cable, a unidirectional acceleration sensor is used to test the acceleration output of the electric actuator 11, a tension and pressure sensor 8 is used to test the cable force change, and a binocular camera system 21 is used to identify the displacement, velocity and acceleration of the scaled floating tunnel truncation model tube body movement. The specific method is as follows:

[0098] ● Water surface elevation: Two wave height meters 9 are installed directly above the test model to measure the change of water surface elevation. They are arranged at the test section positions on both sides.

[0099] Water flow velocity: A Doppler velocimeter 10 is installed 1.0 m in front of the test model, at a height consistent with the centroid height of the scaled suspended tunnel truncation model, for testing the water flow velocity.

[0100] Acceleration: Four three-way waterproof acceleration sensors 6 are installed at the restraint point of each cable, and a unidirectional acceleration sensor 7 is installed at the output end of the electric actuator 11 to test the acceleration output of the actuator in real time.

[0101] Cable tension: Four waterproof tension and pressure sensors 8 are installed between the lower anchor point of each cable and the spring to test the cable tension changes.

[0102] Motion state: Three high-contrast fluorescent markers 4 are arranged on the side of the scaled suspended tunnel truncation model, with a center spacing of 5 cm. The motion time history of these three markers is recognized in real time based on the binocular camera system 21 and the marker recognition program written in Python. Then, the displacement, velocity and acceleration of the scaled suspended tunnel truncation model are obtained in real time through motion synthesis and data derivation.

[0103] In addition, the data of all sensors are synchronously collected through the NIPXI real-time data acquisition system. The specific sampling frequencies are: the sampling frequency of water surface elevation, acceleration response and cable force response is 1000Hz; the sampling frequency of flow velocity is 200Hz; and the motion state extraction frequency of the test model is 20Hz.

[0104] (5) Finally, through the above-mentioned testing and data acquisition methods, the dynamic response of the scaled suspended tunnel truncation model under wave action, flow action, earthquake action and wave-flow-earthquake coupling action can be obtained, including response data such as displacement, velocity, acceleration and cable force.

Claims

1. A multi-physics field collaborative generation experimental method for a suspended tunnel truncation model, characterized in that: The following steps are involved: S1: Truncated design of full-scale ultra-long suspended tunnel prototype: S11: Truncation design: A full-scale finite element model of the reference suspended tunnel was established in the Mechanical module of the finite element analysis software ANSYS, as follows: S111: Construction of full-scale numerical model: The tunnel body is simulated using "SOLID185" units, the cables are simulated using "LINK180" units, the fluid domain width is set to 50 times the diameter of the tunnel body, and the water body is simulated using "FLUID30" units; S112: Boundary conditions and load settings: Set global gravity in the vertical direction, select the outer surface of the floating tunnel tube as the fluid-solid coupling interface, add static water pressure based on the free liquid surface condition, and set the boundary conditions on both sides to fully constrained fixed boundary conditions; S113: Construct analysis process: First, static analysis is performed to determine the stress distribution and deformation state of the suspended tunnel structure under static load. Based on the static analysis results, wet modal analysis is performed to extract the modal parameters of the suspended tunnel structure. The ultra-long tension leg suspended tunnel consists of n suspended tunnel segments, and its wet modal calculation is achieved through formulas (1)-(4): Mu″+Ku=0 (1) (K-λM)Φ=0 (2) M=M T +M W (3) K=K T +K C (4) Where: M is the overall mass matrix of the full-scale suspended tunnel model; M T is the mass matrix of the suspended tunnel body; M W is the additional mass matrix of the water body around the suspended tunnel; K is the overall stiffness matrix of the suspended tunnel, which is obtained by the cable stiffness matrix K C and the stiffness matrix K of the suspended tunnel body T Composition; u and u″ are the displacement matrix and acceleration matrix of the suspended tunnel respectively; λ is the system eigenvalue vector, which represents the square of the modal frequency; Φ is the modal vibration matrix, which describes the vibration form of the system in the modal state; For the i-th suspended tunnel segment, its single segment stiffness K i The bending stiffness of the suspended tunnel body and the axial stiffness of the cable part The two parts of stiffness are superimposed in the form of a series system and a parallel system, as shown in formulas (5)-(8): Where: is the bending stiffness of the pipe body of a single segment suspended tunnel; E T I is the elastic modulus of the material of the suspended tunnel body; T is the section modulus of the cross section of the suspended tunnel body; L T is the length of the suspended tunnel body of a single segment; is the axial stiffness of the cable section of a single segment suspended tunnel; E C A is the elastic modulus of the cable material of the suspended tunnel; C is the equivalent area of ​​the cable part of a single segment suspended tunnel; L C Length of suspended tunnel cables; For the single-segment unconstrained suspended tunnel truncation model, its wet modal calculation is expressed by formula (9): (K i -oh 2 M i )Φ=0 (9) For an ultra-long tension-leg suspension tunnel, when the number of segments n exceeds 20, its overall stiffness characteristics tend to satisfy K C >>K T Under this condition, the bending stiffness of the suspended tunnel body is ignored in the truncation design process, that is, Therefore, only the axial stiffness of the cable is considered. This makes the first few modal frequencies calculated based on formula (1) and formula (9) highly consistent; S2: The design of the scaled floating tunnel truncation model meets the following similarity criteria: (1) Froude similarity: the similarity in fluid dynamics between the scaled suspended tunnel truncation model and the full-scale ultra-long suspended tunnel prototype; (2) Gravity similarity: ensuring that the mechanical responses of the scaled suspended tunnel truncation model and the full-scale ultra-long suspended tunnel prototype under gravity are similar; (3) Geometric similarity: The size of the scaled suspended tunnel truncation model is proportional to the full-scale super-long suspended tunnel prototype to maintain consistent geometric features; (4) Elastic similarity: The cable stiffness characteristics of the scaled suspended tunnel truncation model are scaled proportionally with the full-scale ultra-long suspended tunnel prototype to ensure the similarity of mechanical behavior; The scaled suspended tunnel truncation model includes the suspended tunnel body and cables, and its design steps are as follows: S21: Floating tunnel body: (1) Similarity criteria: satisfying Froude similarity, gravity similarity and geometric similarity; (2) Structure and material: The main body is a central hollow cylinder made of plexiglass with a cylindrical shape. Its length and diameter are reduced in spatial scale according to the same geometric similarity ratio to meet the design requirements; (3) Adjustment device: symmetrical fan-shaped grids are set on both sides of the tube model, and counterweight blocks are filled in the grids. The center of gravity and buoyancy weight ratio parameters of the model are accurately controlled by adjusting the position of the counterweight blocks; S22: Cable: (1) Similarity criteria: satisfying geometric similarity and elastic similarity; (2) Material selection: The main body is made of steel strands, and equivalent springs are connected at the ends to adjust the overall stiffness to ensure that the design requirements are met; S23: Connection method: The suspended tunnel tube and cables are reliably connected through anchor points set on the side of the tube to ensure the integrity of the structure and the rationality of force transmission; S3: Construct a wave-flow-earthquake multi-field input system: including wave action input system, flow input system and earthquake action input system. The specific design is as follows: S31: Wave action input system: A mechanical wave maker is installed at one end of the wave tank to reproduce the complex wave loads in the deep sea area, including regular waves and irregular waves, by adjusting the hydrodynamic input parameters; a wave absorbing device is installed at the other end of the wave tank to effectively absorb reflected waves and ensure the accuracy of wave conditions; S32: Flow input system: diversion channels are set at both ends of the water tank, and the bottom of the diversion channel is connected to the turbine motor through a circular pipe; by adjusting the power parameters of the turbine motor, accurate input of different flow rates can be achieved, forming a multi-level flow rate environment to simulate the water flow characteristics of the deep sea area; S33: Earthquake input system: An electric actuator is installed above the model placement area to transmit power to the scaled suspended tunnel truncation model through a directional conduction bracket; anchor points for connecting model cables are designed on the conduction bracket to ensure the accuracy of earthquake force transmission; by adjusting the power parameters of the electric actuator, high-precision simulation of ground motion is achieved to reproduce the real earthquake action environment; S4: Collection of dynamic response of scaled suspended tunnel truncation model: S41: Liquid level measurement: Use a wave height meter to monitor the liquid level around the scaled floating tunnel cutoff model in real time to accurately capture the changing characteristics of wave loads; S42: Flow velocity measurement: Use a Doppler velocimeter to measure the flow velocity at the height of the scaled floating tunnel cutoff model to obtain the key parameters of the fluid dynamics; S43: Acceleration measurement: Cable anchor point location: Use a three-way waterproof acceleration sensor to monitor the real-time acceleration of the cable anchor point to ensure the consistency of the seismic input of multiple cable anchor points; Electric actuator output: Use a unidirectional acceleration sensor to test the real-time acceleration of the electric actuator to accurately evaluate the characteristics of the seismic power input; S44: Cable tension measurement: A waterproof unidirectional tension pressure sensor is used to measure the cable tension changes in real time, providing key data on the cable stress state; S45: Displacement response measurement: Based on the binocular camera test system, high-contrast fluorescent marking points are arranged on the side of the scaled suspended tunnel truncation model. Through the image recognition program, the displacement response of the scaled suspended tunnel truncation model is captured in real time to obtain three-dimensional motion characteristic data.

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