A device and method for simulating the backfilling process of a trench for a submarine pipeline under different complex natural conditions

Abstract

The application discloses a device and method for simulating a backfilling process of a submarine pipeline ditch under different complex natural conditions, and belongs to the technical field of marine engineering experiments.The device comprises an experimental water tank, a simulated seabed is laid in the experimental water tank, a pipeline model is arranged in the simulated seabed, a monitoring mechanism is arranged in the pipeline model, a leveling mechanism is arranged on the experimental water tank, the leveling mechanism comprises a laying assembly which is in sliding connection with the experimental water tank and a leveling assembly which is arranged at the bottom of the experimental water tank, a wave simulation module and an ocean current simulation module are arranged in the experimental water tank respectively, a tide simulation module is arranged at the bottom of the experimental water tank, and a drainage system and a vibrating mechanism are arranged at the bottom of the experimental water tank.The device can simultaneously simulate the coupling of various complex sea condition factors such as waves, ocean currents, tides and seabed soil vibration, can truly restore the actual service environment of the backfilling of the submarine pipeline ditch, and the experimental result is closer to the engineering practice, thereby providing a reliable basis for design and construction.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering experimental technology, and in particular relates to a device and method for simulating the backfilling process of submarine pipeline trenches under different complex natural conditions. Background Technology

[0002] As a critical infrastructure for transporting marine oil and gas resources, the safe and stable operation of subsea pipelines is of paramount importance. Trench backfilling is a crucial step in ensuring the stability of subsea pipelines and preventing damage from the external environment. However, the marine environment is complex and variable. Sea conditions such as waves, ocean currents, and tides, as well as different seabed geological conditions such as soil type and excavation shape, all significantly affect the backfilling process and its effectiveness. Different soil types, such as sand, clay, and silt, possess different physical and mechanical properties, exhibiting varying deformation characteristics, compaction characteristics, and interaction mechanisms with the pipeline during backfilling.

[0003] Currently, research on backfilling of subsea pipeline trenches primarily employs methods such as on-site observation and numerical simulation. While on-site observation can obtain realistic data, it is limited by factors such as the complex and variable marine environment, high construction costs, and construction schedules, making it difficult to comprehensively and systematically acquire experimental data under different sea conditions and the backfilling process under different soil conditions. Numerical simulation, while flexible and efficient, lacks precision in simulating the multi-physics coupling effects during backfilling under complex soil characteristics and sea conditions, leading to significant deviations between simulation results and actual conditions. Furthermore, existing experimental devices and methods mostly only simulate single or a few sea condition factors, failing to realistically reproduce backfilling scenarios under complex sea conditions, and are unable to effectively simulate various soil conditions or accurately reproduce complex physical phenomena during the backfilling process, such as soil compaction, pore water pressure changes, and particle migration. This results in a lack of sufficiently reliable experimental data to address complex sea conditions during the design and construction of subsea pipelines, increasing engineering risks and uncertainties. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for simulating the backfilling process of submarine pipeline trenches under different complex natural conditions, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention provides a simulation device for the backfilling process of submarine pipeline trenches under different complex natural conditions, including an experimental water tank, a simulated seabed laid in the experimental water tank, a pipeline model placed in the simulated seabed, a monitoring mechanism installed in the pipeline model, the monitoring mechanism being electrically connected to a data acquisition system, a leveling mechanism on the experimental water tank, the leveling mechanism including an arrangement component slidably connected to the experimental water tank and a leveling component disposed at the bottom of the experimental water tank, the arrangement component being electrically connected to the data acquisition system, a wave simulation module and an ocean current simulation module respectively placed in the experimental water tank, a tide simulation module placed at the bottom of the experimental water tank, and a drainage system and a vibration mechanism respectively placed at the bottom of the experimental water tank.

[0006] Preferably, the monitoring mechanism includes guideable scour probes evenly spaced on the pipe model, a plurality of pressure sensors evenly spaced on one side of the top of the pipe model, and a plurality of displacement sensors evenly spaced on the other side of the top of the pipe model. The pressure sensors and the displacement sensors are electrically connected to the data acquisition system through a second transmitter.

[0007] Preferably, the monitoring mechanism further includes a pore water pressure sensor, a soil pressure sensor, and a strain sensor that are equally spaced at the bottom of the pipe model. The pore water pressure sensor is electrically connected to the data acquisition system via a third transmitter, the soil pressure sensor is electrically connected to the data acquisition system via a fourth transmitter, and the strain sensor is electrically connected to the data acquisition system via a fifth transmitter.

[0008] Preferably, the arrangement component includes longitudinal slide rails symmetrically arranged on the top surface of the experimental water tank, a plurality of transverse lead screws between the two longitudinal slide rails, a lead screw slider slidably connected to the transverse lead screw, a vertical rod fixed to the bottom of the lead screw slider, a stepper motor provided on one side of the top of the experimental water tank, the longitudinal slide rails being drivenly connected to the stepper motor through a coupling, and the stepper motor being electrically connected to the data acquisition system through a frequency converter.

[0009] Preferably, the leveling component includes a first partition plate and a second partition plate respectively disposed in the experimental water tank, and the pipe model is disposed between the first partition plate and the second partition plate.

[0010] Preferably, the data acquisition system includes a display, a control host, an ultrasonic velocimeter and a capacitive wave height meter disposed at the bottom of the vertical pole, the ultrasonic velocimeter and the capacitive wave height meter being electrically connected to the display via a first transmitter, the display being electrically connected to the control host, and the second transmitter, the third transmitter, the fourth transmitter, the fifth transmitter and the frequency converter being electrically connected to the display.

[0011] Preferably, one of the lead screw sliders is provided with a scraper at its bottom, and one of the transverse lead screws is provided with a leveler.

[0012] Preferably, the experimental water tank is connected to a soil simulation system, which includes multiple soil storage tanks connected to the experimental water tank.

[0013] Preferably, the ocean current simulation module includes multiple axial flow pumps disposed on the inner wall of the experimental water tank, and the ocean current simulation module also includes a guide plate and a flow stabilizer fixed in the experimental water tank.

[0014] A simulation method for the backfilling process of submarine pipeline trenches under different complex natural conditions includes the following steps:

[0015] S1. Experimental preparation: Select the simulated soil type and mix ratio according to the experimental purpose, and put the prepared soil into the soil storage box; check the working status of each component of the experimental device and calibrate the sensors; install the pipe model in the experimental water tank, and adjust the pipe burial depth and tilt angle to the design parameters through the support; arrange various sensors in the pipe model and soil and ensure that the connection is normal.

[0016] S2. Sea State Simulation Loading: The wave simulation module, ocean current simulation module, and tide simulation module are sequentially activated by the computer control system. After setting wave parameters to generate stable waves, the speed and number of axial flow pumps are adjusted to control the direction of water flow velocity to form ocean currents. After the ocean currents stabilize, the tide simulation module is activated to set rise and fall parameters. The parameters of each module are adjusted in real time to simulate complex sea state combinations such as storm surges.

[0017] S3. Soil laying and trench excavation: Soil is sprayed into the experimental water tank according to the set ratio to form a simulated seabed; a trench that meets the engineering requirements is excavated in the simulated seabed using the backfill arm excavator bucket, and the stress on the excavator bucket and soil deformation are monitored simultaneously.

[0018] S4. Simulation of backfilling process: Move the excavator bucket to the side of the experimental water tank and obtain soil backfill trench from the soil storage box through the conveying mechanism; adjust the backfilling speed and compaction pressure according to the characteristics of sand / clay, and simultaneously start the vibration mechanism at the bottom of the experimental water tank; combine the waves, ocean currents, tides and vibrations generated by the sea state simulation system to observe the changes in soil under the combined action of complex sea conditions and backfilling.

[0019] S5. Data Acquisition and Analysis: The data acquisition system collects real-time data on pipeline stress and deformation, soil pore water pressure, soil pressure distribution, strain, and sea state parameters; the control host processes the data in real time and generates time-varying curves, comparing and analyzing the influence of the backfilling process on pipeline stress, soil deformation, and backfilling effect under different soil conditions; and checks the soil condition and pipeline stability after the experiment.

[0020] This invention discloses the following technical effects: It can simultaneously simulate the coupled effects of multiple complex sea conditions, such as waves, ocean currents, tides, and seabed soil vibration, realistically recreating the actual service environment of submarine pipeline trench backfilling. The experimental results are closer to engineering practice, providing a reliable basis for design and construction. It can accurately simulate various soil conditions, including single and mixed soil types, allowing for the study of the impact of different soil properties on the submarine pipeline trench backfilling process, providing more comprehensive experimental evidence for pipeline engineering under complex seabed geological conditions. Simultaneously, it can measure various physical quantities during the backfilling process in real time and accurately, and conduct in-depth analysis, helping to reveal the interaction mechanism between the pipeline and the soil during backfilling under different sea conditions, providing scientific guidance for optimizing backfilling processes. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 This is a schematic diagram of the overall structure of the simulation device of the present invention;

[0023] Figure 2 for Figure 1 A magnified view of part A in the image;

[0024] Figure 3 This is a schematic diagram of the pipeline model and sensor arrangement of the present invention;

[0025] Figure 4 This is a schematic diagram of the longitudinal slide rail of the present invention;

[0026] Figure 5 This is a structural diagram of the backfilling process.

[0027] In the diagram: 1. Ultrasonic flow meter; 2. Experimental water tank; 3. Simulated seabed; 4. Vertical rod; 5. Pressure sensor; 6. Stepper motor; 7. Horizontal lead screw; 8. Lead screw slider; 9. Longitudinal slide rail; 10. Guided probe; 11. Pipe model; 12. Pore water pressure sensor; 13. Earth pressure sensor; 14. Strain sensor; 15. First transmitter; 16. Second transmitter; 17. Capacitive wave height meter; 18. Display screen; 19. Control host; 20. Third transmitter Transmitter; 21. Fourth transmitter; 22. Fifth transmitter; 23. Scraper; 24. Leveler; 25. Force sensor; 26. Displacement sensor; 27. Frequency converter; 28. Wave generator; 29. ​​Axial flow pump; 30. Guide plate; 31. Flow stabilizer; 32. Tidal simulation module; 33. Vibration mechanism; 34. Drainage system; 35. Soil storage tank; 36. First partition plate; 37. Second partition plate; 38. Excavation bucket; 39. Conveying mechanism; 40. Compaction mechanism. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Reference Figures 1 to 5 As shown, this embodiment provides a simulation device for the backfilling process of submarine pipeline trenches under different complex natural conditions. It includes an experimental water tank 2, a simulated seabed 3 laid in the experimental water tank 2, a pipeline model 11 installed in the simulated seabed 3, a monitoring mechanism installed in the pipeline model 11, and the monitoring mechanism electrically connected to a data acquisition system. A leveling mechanism is provided on the experimental water tank 2. The leveling mechanism includes an arrangement component slidably connected to the experimental water tank 2 and a leveling component set at the bottom of the experimental water tank 2. The arrangement component is electrically connected to the data acquisition system. A wave simulation module and an ocean current simulation module are respectively provided in the experimental water tank 2. A tide simulation module 32 is provided at the bottom of the experimental water tank 2. A drainage system 34 and a vibration mechanism 33 are respectively provided at the bottom of the experimental water tank 2.

[0031] Experimental tank 2 is made of high-strength transparent plexiglass, allowing researchers to directly observe the backfilling process and structural changes of subsea pipelines under complex sea conditions. Combined with collected data analysis, this reveals the backfilling mechanism and stability issues, providing a scientific basis for engineering optimization. The tank dimensions are customized according to experimental requirements, and the interior features adjustable partitions to divide experimental tank 2 into different areas to simulate various pipeline trench scenarios. A drainage system 34 is installed at the bottom of experimental tank 2 to control water levels and simulate seawater infiltration. A vibration mechanism 33 is also installed at the bottom of experimental tank 2 to simulate low-frequency vibrations in the marine environment, such as seabed soil vibrations caused by earthquakes.

[0032] This invention can simultaneously simulate the coupled effects of multiple complex sea conditions, such as waves, ocean currents, tides, and seabed soil vibrations, realistically recreating the actual service environment of subsea pipeline trench backfilling. The experimental results are closer to engineering practice, providing a reliable basis for design and construction. It can accurately simulate various soil conditions, including single and mixed soil types, allowing for the study of the impact of different soil properties on the subsea pipeline trench backfilling process, providing more comprehensive experimental evidence for pipeline engineering under complex seabed geological conditions. Simultaneously, it can measure various physical quantities during the backfilling process in real time and accurately, and conduct in-depth analysis, helping to reveal the interaction mechanism between the pipeline and the soil during backfilling under different sea conditions, providing scientific guidance for optimizing backfilling processes.

[0033] The wave simulation module employs an advanced wave generator 28, installed at one end of the experimental water tank 2. Driven by a high-precision servo motor, the wave generator 28 precisely controls the movement of the pusher plate via computer, generating regular and irregular waves with varying wave heights (range 0.05-3m, accuracy ±0.01m), wave periods (range 0.5-15s, accuracy ±0.05s), and wave spectra (such as JONSWAP and PM spectra) to simulate waves in various marine environments. The wave generator 28 is equipped with a high-sensitivity displacement sensor 26 and a force sensor, providing real-time feedback on the pusher plate's motion and force conditions to ensure precise control of wave parameters.

[0034] The tidal simulation module 32 drives the lead screw and nut mechanism via a motor to slowly raise and lower the bottom platform of the experimental water tank 2 (raising and lowering speed range 0.01-0.3m / h, accuracy ±0.001m / h, raising and lowering height range 0-1.5m, accuracy ±0.01m), simulating the tidal rise and fall process, realizing the periodic change of water level, and working in conjunction with wave and ocean current simulation to construct a real marine dynamic environment.

[0035] The scheme is further optimized. The monitoring mechanism includes guideable scour probes evenly spaced on the pipe model 11. Multiple pressure sensors 5 are evenly spaced on one side of the top of the pipe model 11, and multiple displacement sensors 26 are evenly spaced on the other side of the top of the pipe model 11. The pressure sensors 5 and displacement sensors 26 are electrically connected to the data acquisition system through the second transmitter 16. The force sensor 25 is electrically connected to the data acquisition system.

[0036] To further optimize the scheme, the monitoring mechanism also includes pore water pressure sensors 12, soil pressure sensors 13 and strain sensors 14, which are equally spaced at the bottom of the pipe model 11. The pore water pressure sensors 12 are electrically connected to the data acquisition system through the third transmitter 20, the soil pressure sensors 13 are electrically connected to the data acquisition system through the fourth transmitter 21, and the strain sensors 14 are electrically connected to the data acquisition system through the fifth transmitter 22.

[0037] A scaled-down model of the subsea pipeline was constructed based on similarity theory, with the model material's mechanical properties similar to those of the actual subsea pipeline. The pipeline model 11 was installed in the experimental water tank 2 using an adjustable support. The support allowed for precise adjustment of the pipeline's burial depth (adjustment range 0-1.5m, accuracy ±0.01m) and tilt angle (range 0-45°, accuracy ±0.5°) to simulate different laying conditions. High-precision pressure sensors 5 (accuracy ±0.01kPa) and displacement sensors 26 (accuracy ±0.01mm) were installed on the surface of the pipeline model 11 to monitor changes in soil pressure and displacement during backfilling.

[0038] A pore water pressure sensor 12 (accuracy ±0.01 kPa), an earth pressure sensor 13 (accuracy ±0.01 kPa), and a strain sensor 14 (accuracy ±0.001 με) are installed in the soil within the experimental water tank 2 to monitor changes in pore water pressure, earth pressure distribution, and strain during the backfilling process. The data acquisition system collects all sensor data in real time at a high sampling frequency (up to 1000 Hz) and transmits it to the computer control system, i.e., the control host 19. The computer control system, through independently developed software, precisely controls various parameters of the sea state simulation system, soil storage tank 35, pipeline simulation system, and backfilling operation simulation system. Simultaneously, it processes and analyzes the collected data in real time, displaying the experimental results in the form of charts, curves, and other formats.

[0039] Further optimization of the scheme includes the arrangement of components including longitudinal slide rails 9 symmetrically arranged on the top surface of the experimental water tank 2, multiple transverse lead screws 7 between the two longitudinal slide rails 9, lead screw sliders 8 slidably connected to the transverse lead screws 7, and vertical rods 4 fixed to the bottom of the lead screw sliders 8. A stepper motor 6 is provided on one side of the top of the experimental water tank 2. The longitudinal slide rails 9 are connected to the stepper motor 6 through a coupling. The stepper motor 6 is electrically connected to the data acquisition system through a frequency converter 27.

[0040] The scheme is further optimized. The leveling component includes a first partition plate 36 and a second partition plate 37 respectively set in the experimental water tank 2, and a pipe model 11 is provided between the first partition plate 36 and the second partition plate 37.

[0041] The longitudinal slide rail 9 includes a transition slide rail, an inner slide rail, and an outer slide rail; the transition slide rail is located between the inner slide rail and the outer slide rail; the vertical rod 4 equipped with the sand bed leveling component is arranged on the inner slide rail; the vertical rod 4 equipped with the image processing system is arranged on the outer slide rail; the leveling component includes a first partition plate 36, a second partition plate 37, an excavation bucket 38, a compaction mechanism 40, and a leveler 24.

[0042] Further optimization of the scheme: The data acquisition system includes a display, a control host 19, an ultrasonic velocimeter 1 installed at the bottom of the vertical rod 4, and a capacitive wave height meter 17 installed at the bottom of the vertical rod 4. The ultrasonic velocimeter 1 and the capacitive wave height meter 17 are electrically connected to the display through the first transmitter 15, the display is electrically connected to the control host 19, and the second transmitter 16, the third transmitter 20, the fourth transmitter 21, the fifth transmitter 22 and the frequency converter 27 are electrically connected to the display.

[0043] In a further optimized design, a scraper 23 is provided at the bottom of one of the lead screw sliders 8, and a leveler 24 is provided on one of the transverse lead screws 7.

[0044] Further optimizing the design, the experimental water tank 2 is connected to a soil simulation system, which includes multiple soil storage tanks 35 connected to the experimental water tank 2. These tanks 35 are equipped with various types of simulated soil, such as sand, clay, and silt. Each storage tank 35 is connected to a delivery pipe equipped with a flow control valve and metering device to precisely control the delivery volume and mixing ratio of different soil types, simulating complex seabed soil conditions. A special nozzle (not shown in the figure) is located at the end of the delivery pipe, which can evenly spray soil into the experimental water tank 2 to simulate the original soil distribution after the excavation of the seabed trench.

[0045] To further optimize the design, the ocean current simulation module includes multiple axial flow pumps 29 installed on the inner wall of the experimental tank 2. By adjusting the rotational speed (range 0-6000 rpm, accuracy ±10 rpm) and the number of pumps 29 in operation, the water flow velocity (range 0-3 m / s, accuracy ±0.01 m / s) and direction (360° adjustable, accuracy ±1°) can be precisely controlled to simulate ocean currents with different velocities and directions. The ocean current simulation module also includes a guide plate 30 and a flow stabilizer 31 fixed in the experimental tank 2, which can optimize the water flow pattern, reduce turbulence and eddies, and ensure the accuracy of experimental data.

[0046] A simulation method for the backfilling process of submarine pipeline trenches under different complex natural conditions includes the following steps:

[0047] S1. Experimental preparation: Select the simulated soil type and mix ratio according to the experimental purpose, and put the prepared soil into the soil storage box 35; check the working status of each component of the experimental device and calibrate the sensors; install the pipe model 11 in the experimental water tank 2, and adjust the pipe burial depth and tilt angle to the design parameters through the bracket; arrange various sensors in the pipe model 11 and the soil and ensure that the connection is normal.

[0048] S2. Sea State Simulation Loading: The wave simulation module, ocean current simulation module, and tide simulation module 32 are sequentially activated by the computer control system. After the wave parameters are set to generate stable waves, the speed and quantity of the axial flow pump 29 are adjusted to control the direction of the water flow velocity to form ocean currents. After the waves and ocean currents have been running stably for a period of time, the tide simulation module 32 is activated, and the tide rise and fall speed and height are set to simulate the rise and fall of tides. During the experiment, the computer control system monitors and adjusts the operating parameters of each sea state simulation module in real time to simulate different complex sea state combinations, such as the synergistic effect of strong waves, rapid ocean currents, and large tidal changes during storm surges.

[0049] S3. Soil laying and trench excavation: Soil is sprayed into the experimental water tank 2 according to the set ratio to form a simulated seabed 3; trenches that meet the engineering requirements are excavated in the simulated seabed 3 using the backfilling arm excavator bucket 38, and the stress on the excavator bucket 38 and soil deformation are monitored simultaneously to ensure that the excavation process meets the actual working conditions.

[0050] S4. Simulation of backfilling process: The excavation bucket 38 is moved to the side of the experimental water tank 2, and soil backfill trench is obtained from the soil storage tank 35 through the conveying mechanism 39; the backfilling speed and compaction pressure are adjusted according to the characteristics of sand / clay. For sand, the backfilling speed is appropriately increased and a larger compaction pressure is used; for clay, the backfilling speed is controlled and a smaller compaction pressure is used to simulate different operations in actual construction; at the same time, the vibration mechanism 33 at the bottom of the experimental water tank 2 is turned on, and the changes of the soil under the dual effects of complex sea conditions and backfilling are observed in combination with the waves, ocean currents, tides and vibrations generated by the sea state simulation system.

[0051] S5. Data Acquisition and Analysis: The data acquisition system collects real-time data on pipeline stress and deformation, soil pore water pressure, soil pressure distribution, strain, and sea state parameters. The control host 19 processes and analyzes the collected data in real time. By comparing data under different soil conditions, the influence of soil quality on pipeline stress, soil deformation, and backfilling effect during the backfilling process is studied. After the experiment, the soil and pipeline model 11 in the experimental water tank 2 are inspected to further analyze the soil condition and pipeline stability after backfilling.

[0052] The pipeline model 11 installation system in experimental water tank 2 can flexibly adjust parameters such as pipeline burial depth and tilt angle. The sea state simulation system can freely set parameters such as waves, ocean currents, and tides. The soil storage tank 35 can accurately control the soil type and delivery volume to meet different experimental needs and is suitable for research on backfilling of submarine pipeline trenches under various working conditions.

[0053] Example 1

[0054] Using a real subsea pipeline project as a reference, a pipeline model 11 was constructed at a 1:20 scale. The experimental water tank 2 was set to dimensions of 6m × 3m × 2m. Adjustable first partition plate 36 and second partition plate 37 were installed inside the experimental water tank 2 to divide it into two independent pipeline trench simulation areas. Storage tanks for sand, clay, and silt were prepared. Based on previous experiments, the required ratio of sand, clay, and silt for simulating a certain complex subsea soil was determined to be 3:2:1. The sand, clay, and silt were respectively loaded into the corresponding soil storage tanks 35, and the soil delivery pipeline, flow control valve, and metering device were checked to ensure they were functioning properly.

[0055] A pipe model 11 was installed inside experimental water tank 2. The pipe burial depth was set to 0.5m (model dimensions) and the inclination angle to 5° using adjustable supports. Ten pressure sensors 5 and six displacement sensors 26 were evenly distributed on the surface of the pipe model 11. In the soil, a pore water pressure sensor 12, an earth pressure sensor 13, and a strain sensor 14 were placed every 0.3m along the pipe axis, for a total of ten pore water pressure sensors 12, ten earth pressure sensors 13, and ten strain sensors 14. All sensors were connected to the data acquisition system and calibrated. Seawater was injected into experimental water tank 2 to raise the water level to 1.65m.

[0056] First, according to the set proportions and flow rates, sand, clay, and silt were evenly sprayed into the experimental water tank 2 through nozzles to form a simulated seabed 3 with a thickness of 1.35m. The wave simulation module was activated, and wave parameters were set via the computer control system to generate irregular waves with a wave height of 0.3m (model dimensions) and a wave period of 2s. After the waves had stabilized for 8 minutes, the ocean current simulation module was activated, and the rotation speed of the axial flow pump 29 was adjusted to achieve a water flow velocity of 0.4m / s (model dimensions), with the flow direction forming a 45° angle with the wave propagation direction. After the combined action of waves and ocean currents for 15 minutes, the tide simulation module 32 was activated, setting the tidal rise and fall rate to 0.08m / h (model dimensions) and the rise and fall height to 0.5m (model dimensions) to simulate the tidal rise and fall process. Simultaneously, the vibration mechanism 33 at the bottom of the experimental water tank 2 was activated, setting the vibration frequency to 0.8Hz and the amplitude to 8mm to simulate seabed vibration. During the experiment, the sea state parameters were monitored and adjusted in real time via the computer control system to ensure that the coupling effects of various sea states met the experimental design requirements.

[0057] The soil simulation system was activated, and the excavator bucket 38 on the backfill arm was used to excavate a trench in the simulated seabed 3. The trench width was set to 0.8m (model dimensions), and the depth to 0.6m (model dimensions). During excavation, the excavation speed and angle of the excavator bucket 38 were adjusted in real time by monitoring the pressure changes of the hydraulic system to ensure smooth excavation. Simultaneously, soil deformation was observed, and relevant data were recorded. For example, when excavating clay areas, the excavation speed was appropriately reduced, and the cutting angle of the excavator bucket 38 was increased to ensure excavation efficiency and soil stability.

[0058] After excavation, the excavator bucket 38 moves to one side of the experimental water tank 2 and uses the conveying mechanism 39 to retrieve mixed soil from the soil storage tank 35, which is then transported to the trench area for backfilling. For the sandy soil portion, the backfilling speed is set to 0.2 m³ / min, and the compaction mechanism 40 pressure is set to 0.2 MPa; for the clay portion, the backfilling speed is adjusted to 0.1 m³ / min, and the compaction mechanism 40 pressure is set to 0.1 MPa; for the silty soil mixed with other soil types, the parameters are adjusted according to the actual situation. During the backfilling process, the vibration mechanism 33 at the bottom of the experimental water tank 2 is activated, with a vibration frequency of 1 Hz and an amplitude of 5 mm to simulate vibration in a marine environment. The changes in soil density and the displacement of the pipeline model 11 under vibration, water flow impact, and backfilling are observed, and data is collected in real time using sensors. For example, under strong wave action, local scouring is observed on the surface of the backfill soil; the location and extent of the scouring are recorded in a timely manner, and its impact on pipeline stability is analyzed.

[0059] The data acquisition system collects data from all sensors in real time at a sampling frequency of 500Hz. The computer control system processes and analyzes the collected data in real time, plotting pressure-time curves, displacement-time curves, pore water pressure-time curves, earth pressure-time curves, and strain-time curves for the pipeline model 11, and displaying them in real time on the display screen 18. After the experiment, the collected data is analyzed in depth to compare the backfilling effects in different soil regions and study the influence of soil conditions on pipeline stability and soil mechanical properties. For example, the analysis found that the pore water pressure dissipates faster in sandy soil regions after backfilling, but the compaction degree is relatively low; the compaction degree is higher in clay regions, but the pore water pressure dissipates more slowly, thus providing a reference for optimizing backfilling schemes in actual engineering.

[0060] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for simulating the backfilling process of submarine pipeline trenches under different complex natural conditions, based on a simulation device for the backfilling process of submarine pipeline trenches under different complex natural conditions, characterized in that, Includes the following steps: S1. Experimental preparation: Select the simulated soil type and mix ratio according to the experimental purpose, and put the prepared soil into the soil storage box (35); check the working status of each component of the experimental device and calibrate the sensors; install the pipe model (11) in the experimental water tank (2), and adjust the pipe burial depth and tilt angle to the design parameters through the support; arrange various sensors in the pipe model (11) and the soil and ensure that the connection is normal. S2, Sea State Simulation Loading: The wave simulation module, ocean current simulation module and tide simulation module (32) are started sequentially through the computer control system. After setting the wave parameters to generate stable waves, the rotation speed and quantity of the axial flow pump (29) are adjusted to control the direction of the water flow velocity to form ocean currents. After the ocean currents are stabilized, the tide simulation module (32) is started to set the rise and fall parameters. The parameters of each module are adjusted in real time to simulate the complex combination of storm surge sea conditions. S3. Soil laying and trench excavation: Soil is sprayed into the experimental water tank (2) according to the set ratio to form a simulated seabed (3); a trench that meets the engineering requirements is excavated in the simulated seabed (3) using the backfill arm excavation bucket (38), and the stress on the excavation bucket (38) and soil deformation are monitored simultaneously. S4. Simulation of backfilling process: Move the excavation bucket (38) to the side of the experimental water tank (2), and obtain the soil backfill trench from the soil storage box (35) through the conveying mechanism (39); adjust the backfilling speed and compaction pressure according to the characteristics of sand / clay, and simultaneously start the vibration mechanism (33) at the bottom of the experimental water tank (2); combine the waves, ocean currents, tides and vibration generated by the sea state simulation system to observe the soil changes under the combined action of complex sea conditions and backfilling. S5. Data acquisition and analysis: The data acquisition system collects data on pipeline stress and deformation, soil pore water pressure, soil pressure distribution, strain data and sea state parameters in real time; the host computer (19) processes the data in real time and generates time-varying curves, and compares and analyzes the influence of backfilling process on pipeline stress, soil deformation and backfilling effect under different soil conditions; after the experiment, the soil condition and pipeline stability are checked.

2. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 1, characterized in that: The simulation device for backfilling submarine pipeline trenches under different complex natural conditions includes the experimental water tank (2), the simulated seabed (3) is laid in the experimental water tank (2), the pipeline model (11) is provided in the simulated seabed (3), a monitoring mechanism is installed in the pipeline model (11), the monitoring mechanism is electrically connected to the data acquisition system, a leveling mechanism is provided on the experimental water tank (2), the leveling mechanism includes an arrangement component that is slidably connected to the experimental water tank (2) and a leveling component set at the bottom of the experimental water tank (2), the arrangement component is electrically connected to the data acquisition system, a wave simulation module and an ocean current simulation module are respectively provided in the experimental water tank (2), the tide simulation module (32) is provided at the bottom of the experimental water tank (2), and a drainage system (34) and a vibration mechanism (33) are respectively provided at the bottom of the experimental water tank (2).

3. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 2, characterized in that: The monitoring mechanism includes conductive scour probes that are equally spaced on the pipe model (11). Multiple pressure sensors (5) are equally spaced on one side of the top of the pipe model (11), and multiple displacement sensors (26) are equally spaced on the other side of the top of the pipe model (11). The pressure sensors (5) and the displacement sensors (26) are electrically connected to the data acquisition system through a second transmitter (16).

4. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 3, characterized in that: The monitoring mechanism also includes a pore water pressure sensor (12), a soil pressure sensor (13), and a strain sensor (14) that are equally spaced at the bottom of the pipe model (11). The pore water pressure sensor (12) is electrically connected to the data acquisition system through a third transmitter (20), the soil pressure sensor (13) is electrically connected to the data acquisition system through a fourth transmitter (21), and the strain sensor (14) is electrically connected to the data acquisition system through a fifth transmitter (22).

5. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 4, characterized in that: The arrangement components include longitudinal slide rails (9) symmetrically arranged on the top surface of the experimental water tank (2), and multiple transverse lead screws (7) are provided between the two longitudinal slide rails (9). A lead screw slider (8) is slidably connected on the transverse lead screw (7). A vertical rod (4) is fixed to the bottom of the lead screw slider (8). A stepper motor (6) is provided on one side of the top of the experimental water tank (2). The longitudinal slide rails (9) are connected to the stepper motor (6) through a coupling. The stepper motor (6) is electrically connected to the data acquisition system through a frequency converter (27).

6. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 2, characterized in that: The leveling assembly includes a first partition plate (36) and a second partition plate (37) respectively disposed in the experimental water tank (2), and the pipe model (11) is provided between the first partition plate (36) and the second partition plate (37).

7. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 5, characterized in that: The data acquisition system includes a display, a control host (19), an ultrasonic velocimeter (1) installed at the bottom of the vertical rod (4), and a capacitive wave height meter (17) installed at the bottom of the vertical rod (4). The ultrasonic velocimeter (1) and the capacitive wave height meter (17) are electrically connected to the display through a first transmitter (15). The display is electrically connected to the control host (19). The second transmitter (16), the third transmitter (20), the fourth transmitter (21), the fifth transmitter (22), and the frequency converter (27) are electrically connected to the display.

8. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 5, characterized in that: One of the lead screw sliders (8) has a scraper (23) at its bottom, and one of the transverse lead screws (7) has a leveler (24).

9. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 2, characterized in that: The experimental water tank (2) is connected to a soil simulation system, which includes multiple soil storage tanks (35) connected to the experimental water tank (2).

10. The simulation method for backfilling submarine pipeline trenches under different complex natural conditions according to claim 2, characterized in that: The ocean current simulation module includes multiple axial flow pumps (29) installed on the inner wall of the experimental water tank (2), and the ocean current simulation module also includes a guide plate (30) and a flow stabilizer (31) fixed in the experimental water tank (2).

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