A test device and a test method for offshore wind suction caisson foundation simulation

Abstract

The application relates to the technical field of offshore wind power, and discloses a test device and a test method for simulating a suction cylinder foundation of offshore wind power. The test device comprises a suction cylinder provided with a first through hole and a second through hole; a simulation box containing soil and water and used for simulating an installation environment; a vertical loading device installed at the top of the simulation box and connected with the suction cylinder and used for lowering the suction cylinder to a preset position of the soil; a grouting device communicated with the first through hole and used for grouting the suction cylinder; a sinking device communicated with the second through hole and used for pumping water from the suction cylinder or injecting water into the suction cylinder; and a monitoring device arranged in the simulation box and used for monitoring the strength of the soil and the water film height in the suction cylinder. Thus, the simulation of the whole life cycle of the suction cylinder from installation, service and recovery can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of offshore wind power, for example to a test device and a test method for simulating a suction caisson foundation of offshore wind power. BACKGROUND

[0002] The suction caisson foundation has the advantages of low manufacturing cost, high bearing capacity, and recyclability. The sinking process of the suction caisson foundation is divided into two stages, namely, a self-weight sinking stage and a subsequent negative pressure sinking stage. In the self-weight sinking stage, the suction caisson foundation gradually penetrates into the seabed at a constant speed under the floating weight of the suction caisson foundation and the load of the crane, and ends when the floating weight of the suction caisson foundation is equal to the sum of the end resistance and side friction resistance of the suction caisson foundation penetrating into the seabed. The water in the suction caisson is pumped out to the outside of the suction caisson, a pressure difference is generated, and the suction caisson further penetrates into the seabed to a certain depth. Subsequently, grouting is performed in the suction caisson to make the top cover of the suction caisson fully adhere to the soil body of the seabed. After the end of the service period, the suction caisson is recycled by positive pressure.

[0003] At present, there are many related test studies on the installation and cyclic loading of the suction caisson under negative pressure, but there is still a blank in the simulation study on the whole life cycle of the suction caisson from installation, service, and recycling.

[0004] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0005] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. The summary is not an overall description of the application, nor is it intended to determine key / important elements or delineate the scope of protection of these embodiments, but as a prelude to the detailed description below.

[0006] The embodiments of the present disclosure provide a test device and a test method for simulating a suction caisson foundation of offshore wind power to simulate the whole life cycle of the suction caisson.

[0007] In some embodiments, the test device for simulating a suction caisson foundation of offshore wind power includes a suction caisson provided with a first through hole and a second through hole; a simulation box containing soil and water for simulating an installation environment; a vertical loading device installed at the top of the simulation box and connected with the suction caisson for lowering the suction caisson to a preset position of the soil; a grouting device connected with the first through hole for grouting into the suction caisson; a sinking device connected with the second through hole for pumping water from the suction caisson or injecting water into the suction caisson; and a monitoring device arranged in the simulation box for monitoring the strength of the soil and the water film height in the suction caisson.

[0008] In some embodiments, the grouting device comprises: a grouting pump comprising a first motor and being controllable to adjust frequency; a grouting pipe having a first end connected to an outlet of the grouting pump and a second end connected to the first through hole; a pressure sensor arranged in the first through hole to monitor pressure in the suction cylinder in real time; and a flow sensor arranged in the grouting pipe to measure grout flow in real time.

[0009] In some embodiments, the monitoring device comprises: a ball-type detector arranged in the suction cylinder to record cone tip resistance and pore pressure data; and an image acquisition module arranged in the water to acquire images of the soil in the suction cylinder and the water film height.

[0010] In some embodiments, the suction cylinder comprises: a cylinder body enclosed by a cylinder wall and a cylinder cover; the first through hole and the second through hole are arranged in the cylinder cover; and a diffusion plate is arranged in the cylinder body and has a preset distance from the cylinder cover; the diffusion plate is uniformly provided with a plurality of hydrophobic holes, so that the water injected by the sinking device is uniformly released into the cylinder body after passing through the hydrophobic holes.

[0011] In some embodiments, the vertical loading device comprises: a first sliding unit arranged at the top of the simulation box and capable of sliding in a first direction; a second sliding unit arranged at the top of the first sliding unit and capable of sliding in a second direction; the second direction and the first direction are two different directions in a horizontal plane; a bottom plate unit arranged at the top of the second sliding unit; and a loading unit arranged at the bottom plate unit and connected to the suction cylinder.

[0012] In some embodiments, the sinking device comprises: a water pump comprising a second motor and being controllable to adjust frequency; a water pipe having a first end connected to an outlet of the water pump and a second end connected to the second through hole; and a flow detector arranged at the outlet of the water pump to monitor water pumping speed / water injection speed of the water pump in real time.

[0013] In some embodiments, the test method for simulating offshore wind turbine suction cylinder foundations is applicable to the aforementioned test device for simulating offshore wind turbine suction cylinder foundations. The test method for simulating offshore wind turbine suction cylinder foundations includes: controlling the activation of a vertical loading device to penetrate the suction cylinder into the soil to a first preset depth; controlling a sinking device to pump water, allowing the suction cylinder to continue penetrating the soil to a second preset depth; controlling a grouting device to inject grout into the suction cylinder, stopping grouting when grout overflows from the second through-hole of the suction cylinder; after the grout in the suction cylinder has solidified, controlling the vertical loading device to apply a cyclic load to the suction cylinder; controlling the sinking device to inject water into the suction cylinder to generate positive pressure inside the suction cylinder, and controlling the vertical loading device to pull the suction cylinder upwards; when the pressure inside the suction cylinder no longer rises, controlling the vertical loading device to stop pulling upwards, completing the recovery of the suction cylinder.

[0014] In some embodiments, controlling the pumping of water by the sinking device includes: firstly correcting the initial pumping speed based on the penetration resistance or soil strength during the penetration of the suction cylinder into the first preset depth; secondly correcting the pumping speed after the first correction based on the heave height of the soil inside the suction cylinder and the actual penetration depth of the suction cylinder, so that the heave speed of the soil inside the suction cylinder is less than a speed threshold; or, controlling the grouting device to inject grout into the suction cylinder includes: determining the initial grouting speed based on the soil strength; firstly correcting the initial grouting speed based on the pumping speed during the penetration of the suction cylinder; and secondly correcting the initial grouting speed based on the fluidity of the grout. The grouting speed is corrected a second time; based on the soil disturbance, the grouting speed after the second correction is corrected a third time; or, after the grout in the suction cylinder has solidified, the vertical loading device is controlled to apply a cyclic load to the suction cylinder, including: after the grout in the suction cylinder has solidified for a first preset time, the vertical loading device is controlled to apply a first preset frequency cyclic load to the suction cylinder; when the first preset frequency cyclic load is completed, the vertical loading device is controlled to maintain the load on the suction cylinder, so that the soil at the bottom of the suction cylinder is consolidated for a second preset time; the vertical loading device is controlled to apply a second preset frequency cyclic load to the suction cylinder.

[0015] In some embodiments, controlling the submersion device to inject water into the suction cylinder includes: determining an initial water injection rate based on the soil strength inside the suction cylinder; correcting the initial water injection rate once based on the grouting rate during the grouting process; and correcting the water injection rate after the first correction a second time based on the attenuation range of the first-stage resistance value, the increase range of the second-stage resistance value, and the attenuation range of the third-stage resistance value experienced by the suction cylinder; wherein, the first-stage resistance value is the resistance value borne by the suction cylinder when the first preset frequency cyclic load is applied to the suction cylinder; the second-stage resistance value is the resistance value borne by the suction cylinder after the soil at the bottom of the suction cylinder has consolidated; the third-stage resistance value is the resistance value borne by the suction cylinder when the second preset frequency cyclic load is applied to the suction cylinder; and correcting the water injection rate after the second correction a third time based on the disturbance of the soil inside the suction cylinder or when the turbidity inside the suction cylinder reaches a preset level.

[0016] In some embodiments, a spherical probe is used to detect the soil condition inside the suction cylinder; the soil disturbance is determined by: obtaining the calibration coefficient of the spherical probe and the detected real-time resistance / pressure; determining the initial strength of the soil based on the calibration coefficient and the real-time resistance / pressure; and correcting the initial strength based on a first correction coefficient, a second correction coefficient, and a third correction coefficient to obtain the final soil strength.

[0017] The present disclosure provides an experimental apparatus and method for simulating offshore wind turbine suction cylinder foundations, which can achieve the following technical effects:

[0018] A vertical loading device is installed at the top of the simulation chamber and connected to the suction cylinder. It provides downward or upward loads to the suction cylinder, allowing it to penetrate the soil or be pulled upwards. A grouting device is connected to the suction cylinder through a first through-hole, allowing grout to be injected into it. A sinking device is connected to the suction cylinder through a second through-hole, allowing water to be pumped out of the suction cylinder to facilitate deeper penetration and subsequent grouting. It can also inject water into the suction cylinder to assist the vertical loading device in pulling it upwards. A monitoring device is located inside the simulation chamber, monitoring the soil strength to adjust the pumping / grouting / water injection speed in real time, reducing disturbance to the soil during these stages. The monitoring device also monitors the water film height inside the suction cylinder to determine if the water injection requirements have been met. In this way, from the gravity penetration and negative pressure penetration of the suction cylinder, to the grouting inside the cylinder, cyclic loading, grout solidification, and then to the recycling of the suction cylinder, the entire life cycle of the suction cylinder from installation, service and recycling is simulated, providing an experimental basis for the actual use of the suction cylinder.

[0019] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein:

[0021] Figure 1 This is a schematic diagram of the structure of an experimental device for simulating the foundation of an offshore wind turbine suction cylinder, provided in an embodiment of this disclosure;

[0022] Figure 2 This is a schematic diagram of the suction cylinder provided in an embodiment of the present disclosure from one perspective;

[0023] Figure 3 This is a structural schematic diagram of the suction cylinder provided in an embodiment of this disclosure from another perspective;

[0024] Figure 4 This is a schematic diagram of the grouting device provided in the embodiments of this disclosure;

[0025] Figure 5 This is a schematic diagram of the structure of the diffusion plate provided in the embodiments of this disclosure;

[0026] Figure 6 This is a three-dimensional structural diagram of the first sliding unit, the second sliding unit, and the base plate unit provided in the embodiments of this disclosure;

[0027] Figure 7 This is a top view of the first sliding unit, the second sliding unit, and the base plate unit provided in the embodiments of this disclosure;

[0028] Figure 8 This is a front view of the first sliding unit, the second sliding unit, and the base plate unit provided in the embodiments of this disclosure;

[0029] Figure 9 This is a schematic diagram of the structure of the loading unit provided in the embodiments of this disclosure;

[0030] Figure 10 This is a schematic diagram of the submersion device provided in the embodiments of this disclosure;

[0031] Figure 11 This is a schematic diagram of the structure of the simulation box provided in the embodiments of this disclosure;

[0032] Figure 12 This is a schematic diagram of a test method for simulating offshore wind turbine suction cylinder foundations provided in an embodiment of this disclosure;

[0033] Figure 13 This is a schematic diagram of a method for controlling the pumping of water by a submerged device according to an embodiment of this disclosure;

[0034] Figure 14 This is a schematic diagram of a method for controlling a grouting device to inject grout into a suction cylinder, provided in an embodiment of this disclosure;

[0035] Figure 15 This is a schematic diagram of a method for controlling a vertical loading device to apply a cyclic load to a suction cylinder, provided in an embodiment of this disclosure;

[0036] Figure 16 This is a schematic diagram of a method for controlling the submersion device to inject water into a suction cylinder, provided in an embodiment of this disclosure.

[0037] Figure label:

[0038] 10. Suction cylinder; 11. First through hole; 12. Second through hole; 13. Cylinder body; 131. Cylinder wall; 132. Cylinder cover; 14. Diffuser plate; 141. Drainage hole; 15. Third through hole;

[0039] 20. Simulation box; 21. Side panel; 22. Bottom panel; 23. Tempered glass; 24. Drain pipe;

[0040] 30. Vertical loading device; 31. First sliding unit; 311. First reaction frame; 312. First support plate; 313. First slide rail; 314. First slider; 32. Second sliding unit; 321. Second reaction frame; 322. Second support plate; 323. Second slide rail; 324. Second slider; 33. Base plate unit; 331. Base plate; 332. Third reaction frame; 34. Loading unit; 341. Servo motor; 342. Electric cylinder; 343. Loading arm; 344. Inner push rod; 345. Through hole; 346. Tension / compression sensor; 347. Fixing ring; 348. Circular fastener; 349. Limiting rod; 350. Limiting hole;

[0041] 40. Grouting device; 41. Grouting pump; 42. Grout outlet pipe; 43. Pressure sensor; 44. Flow sensor;

[0042] 50. Submersion device; 51. Water pump; 52. Water pipe; 53. Flow detector;

[0043] 60. Controller;

[0044] 70. External support. Detailed Implementation

[0045] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0046] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0047] In this disclosure, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better description of the embodiments of this disclosure and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this disclosure according to the specific circumstances.

[0048] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0049] Unless otherwise stated, the term "multiple" means two or more.

[0050] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0051] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0053] Combination Figure 1 As shown, this disclosure provides a test apparatus for simulating offshore wind turbine suction cylinder foundations. The apparatus includes: a suction cylinder 10, a simulation box 20, a vertical loading device 30, a grouting device 40, a sinking device 50, and a monitoring device. Combined with... Figure 2 and Figure 3 As shown, the suction cylinder 10 is provided with a first through hole 11 and a second through hole 12. Grout can be injected into the suction cylinder 10 through the first through hole 11, and water can be extracted from or injected into the suction cylinder 10 through the second through hole 12. The simulation box 20 is a box with an open top, filled with soil and water, used to simulate the installation environment of the suction cylinder 10. The vertical loading device 30 is installed on the top of the simulation box 20, and the loading end is connected to the suction cylinder 10, used to apply a load to the suction cylinder 10 and lower it to a preset position in the soil. The grouting device 40 is connected to the first through hole 11 to inject grout into the suction cylinder 10. The sinking device 50 is connected to the second through hole 12, used to extract water from or inject water into the suction cylinder 10. The monitoring device is installed inside the simulation chamber 20 to monitor the soil strength and determine the soil disturbance during the grouting, pumping, and water injection stages. The monitoring device can also monitor the water film height inside the suction cylinder 10 to determine whether the water injection requirements have been met.

[0054] During the simulation, the vertical loading device 30 is first controlled to apply a downward load to the suction cylinder 10, lowering it to a suitable position. Then, the sinking device 50 is activated to pump out the water from the suction cylinder 10, allowing it to penetrate deeper into the soil. Subsequently, the grouting device 40 is activated to inject grout into the suction cylinder 10. After grouting, the grout is allowed to solidify. Once solidified, the vertical loading device 30 is activated to apply a cyclic load to the suction cylinder 10, consolidating the soil at the bottom. Then, the sinking device 50 is activated again to inject water into the suction cylinder 10, creating positive pressure inside. Simultaneously, the vertical loading device 30 is activated to provide an upward load to the suction cylinder 10. Thus, under the combined effect of the positive pressure inside the suction cylinder 10 and the vertical loading device 30, the suction cylinder 10 is pulled upwards. When the pressure inside the suction cylinder 10 stops rising, it indicates that the suction cylinder 10 has been pulled out. Then, the vertical loading device 30 is stopped, thus completing the recovery of the suction cylinder 10.

[0055] The test apparatus for simulating offshore wind turbine suction cylinder foundations provided in this embodiment includes a vertical loading device 30 installed on top of the simulation chamber 20 and connected to the suction cylinder 10. This device provides downward or upward loads to the suction cylinder 10, allowing it to penetrate the soil or be pulled upwards. A grouting device 40 is connected to the suction cylinder 10 via a first through-hole 11, allowing grout to be injected into the suction cylinder 10. A sinking device 50 is connected to the suction cylinder 10 via a second through-hole 12, allowing water to be pumped from the suction cylinder 10 to facilitate deeper penetration and subsequent grouting. It can also inject water into the suction cylinder 10 to assist the vertical loading device 30 in pulling it upwards. A monitoring device is installed inside the simulation chamber 20 to monitor soil strength, allowing for real-time adjustment of the pumping / grouting / water injection speed to reduce disturbance to the soil during the pumping / grouting / water injection stages. The monitoring device can also monitor the water film height inside the suction cylinder 10 to determine whether the water injection requirements have been met. In this way, from the gravity-driven penetration and negative pressure penetration of the suction cylinder 10, to the grouting inside the cylinder, cyclic loading, grout solidification, and then to the recycling of the suction cylinder 10, the entire life cycle of the suction cylinder 10 from installation, service and recycling is simulated, providing an experimental basis for the actual use of the suction cylinder 10.

[0056] Optionally, the controller 60 is communicatively connected to the vertical loading device 30, the grouting device 40, the sinking device 50, and the monitoring device, and is used to receive data monitored by the monitoring device and control the start and stop of the vertical loading device 30, the grouting device 40, and the sinking device 50.

[0057] Optionally, combined Figure 4 As shown, the grouting device 40 includes: a grouting pump 41, a grout outlet pipe 42, a pressure sensor 43, and a flow sensor 44. The grouting pump 41 includes a first motor, and a controller 60 is communicatively connected to the first motor to control its frequency, thereby controlling the grouting speed. The first end of the grout outlet pipe 42 is connected to the outlet of the grouting pump 41, and the second end is connected to a first through hole 11. The pressure sensor 43 is located in the first through hole 11 and is communicatively connected to the controller 60, used to detect the pressure of the suction cylinder 10 in real time and send the pressure to the controller 60. The flow sensor 44 is located in the grout outlet pipe 42 and is communicatively connected to the controller 60, used to monitor the grout flow rate in real time and send the grout flow rate to the controller 60. The controller 60 can control the frequency of the first motor based on the received pressure and grout flow rate of the suction cylinder 10, achieving refined control of the grouting and reducing disturbance to the soil within the suction cylinder 10.

[0058] Optionally, the grouting pump 41 is a single screw pump, and the flow rate of a single screw pump is generally 0.1 m³ / s. 3 / h to 0.5 m 3 / h, with an inlet and outlet diameter of 25 mm, connected to a screw air compressor hose with an inner diameter of 25 mm via a ring fastener.

[0059] Optionally, the first through hole 11 is a steel threaded interface that can be connected to a 25 mm pipe.

[0060] Slurry typically incorporates cement, with a certain amount of bentonite used to replace it. The slurry is usually described by its bentonite content; for example, 20% bentonite slurry means the mass ratio of bentonite to (bentonite + cement) is 20%. 0% bentonite slurry represents pure cement, and 100% bentonite slurry represents 100% bentonite.

[0061] Optionally, the monitoring device includes a spherical probe and an image acquisition module. The spherical probe is installed inside the suction cylinder 10. As the suction cylinder 10 is inserted / pulled out, it records the cone tip resistance and pore pressure data (from a pore pressure sensor installed on the cylinder cover 132) in real time. The spherical probe communicates with the controller 60 via a data acquisition unit to send the data recorded by the spherical probe to the controller 60. The controller 60 determines the soil mass based on the received cone tip resistance and pore pressure data, and thus judges the soil disturbance status.

[0062] An image acquisition module is positioned underwater and communicates with the controller 60 to acquire images of the soil and water film height within the suction cylinder 10 and transmit these images to the controller 60. Correspondingly, the suction cylinder 10 is made of transparent acrylic material to facilitate image acquisition by the image acquisition module. Optionally, the image acquisition device includes a camera, a base, and a support frame. The camera is fixed to the simulation box 20 via the support frame, which allows the underwater camera to move with three degrees of freedom to adjust the optimal shooting angle. The support frame consists of two mutually perpendicular steel pipes. The horizontal steel pipe is mounted on the model box, and the upper and lower parts of the vertical steel pipe are connected to the horizontal steel pipe and the base via screws. Unscrewing the upper screw allows the vertical steel pipe to move along the horizontal steel pipe. Unscrewing the lower screw allows the camera to move vertically along the steel pipe. The camera is mounted on the base and rotates up and down via a screw connected to the base.

[0063] Optionally, see again Figure 2 , Figure 3 and Figure 5The suction cylinder 10 includes a cylinder body 13 and a diffuser plate 14. The cylinder body 13 is formed by a cylinder wall 131 and a cylinder cover 132. A first through hole 11 and a second through hole 12 are provided on the cylinder cover 132. The outer diameter of the diffuser plate 14 is equal to the inner diameter of the cylinder body 13. Optionally, the diffuser plate 14 is made of stainless steel with a thickness of 5 mm and a diameter of 100 mm. The diffuser plate 14 is horizontally disposed inside the cylinder body 13 and maintains a preset distance from the cylinder cover 132. Optionally, the preset distance is 30 mm. In this way, the diffuser plate 14 divides the interior of the suction cylinder 10 into a buffer cavity, namely the space between the cylinder cover 132 and the diffuser plate 14. The diffuser plate 14 is provided with a plurality of hydrophobic holes 141, which are evenly arranged in multiple rings along the surface of the diffuser plate 14. Optionally, the hydrophobic holes 141 are circular holes with a diameter of 1 mm, and the number of hydrophobic holes 141 is 50 to 100. When the sinking device 50 injects water into the suction cylinder 10, the water first enters the buffer chamber and then flows downward through the drainage hole 141. The water flow is released evenly and flexibly through the small-diameter drainage hole 141, which can avoid the strong jet directly impacting the soil inside the cylinder and effectively reduce the impact and disturbance of water injection on the soil inside the cylinder.

[0064] Optionally, the cylinder 13 is made of plexiglass, with an outer diameter of 300 mm and a wall thickness of 10 mm, and the cylinder cover 132 is 40 mm thick.

[0065] Optionally, the second through hole 12 is equipped with a silicone membrane and a filter screen, and a scale is provided on the wall of the cylinder 13. During the test, the depth of the suction cylinder 10 penetrating the soil and the thickness of the water film can be observed through the scale. The second through hole 12 is a pagoda-shaped steel interface that can be connected to a pipe with an inner diameter of 6 mm. To prevent soil from entering the water pump and flow meter during the negative pressure pumping process, a steel filter screen is installed below the second through hole 12.

[0066] Optionally, valves are installed in both the first through hole 11 and the second through hole 12, which can be opened and closed independently. A third through hole 15 is provided above the cylinder cover 132 for installing a pore pressure sensor.

[0067] Optionally, combined Figures 6 to 9As shown, the vertical loading device 30 includes: a first sliding unit 31, a second sliding unit 32, a base plate unit 33, and a loading unit 34. The first sliding unit 31 is disposed on the top of the simulation box 20 and can slide along a first direction. The second sliding unit 32 is disposed on the top of the first sliding unit 31 and can slide along a second direction. The first and second directions are two different directions on a horizontal plane. For example, the first direction is left-right, and the second direction is front-back. Or, the first direction is front-back, and the second direction is left-right. The base plate unit 33 is disposed on the top of the second sliding unit 32 and is used to support the loading unit 34. The loading unit 34 is disposed on the base plate unit 33, and its loading end is connected to the top of the suction cylinder 10. Thus, by controlling the first sliding unit 31 and the second sliding unit 32 to slide in their respective directions, the loading unit 34 can carry the suction cylinder 10 and move it together, thereby moving the suction cylinder 10 to a suitable position, and then controlling the loading unit 34 to lower the suction cylinder 10 into the soil. In this way, the suction cylinder 10 can be placed anywhere in the soil.

[0068] Optionally, see again Figures 6 to 8 The first sliding unit 31 includes two first reaction frames 311 and two first support plates 312. The two first reaction frames 311 are bolted to opposite sides of the top of the simulation box 20 along a first direction. Each first reaction frame 311 has a first slide rail 313 fixed along its length by a screw. The bottom of each of the two first support plates 312 has a first slider 314 fixed along its length (which is also the length of the first reaction frame 311) by a screw, and the two first slide rails 313 are slidably embedded within the two first sliders 314. The second sliding unit 32 is disposed on the two first support plates 312. Thus, through the cooperation of the first slide rails 313 and the first sliders 314, the loading unit 34 can be driven to move along the first direction. Optionally, the length of the first reaction frame 311 is 1705 mm. The length of the first slide rail 313 is 1660 mm and it is made of steel. The height of the first slider 314 is 22 mm. The first pallet 312 is 620 mm long, 106 mm wide, and 9 mm thick.

[0069] Optionally, see again Figures 6 to 8The second sliding unit 32 includes two second reaction frames 321 and two second support plates 322. The two second reaction frames 321 are arranged side-by-side on top of the first sliding unit 31. Specifically, the two second reaction frames 321 are arranged side-by-side along a second direction, and both ends of the second reaction frames 321 are fixed to the tops of the two first support plates 312 by screws. Each second reaction frame 321 is provided with a second slide rail 323 along its own length. The bottom of each of the two second support plates 322 is provided with a second slider 324 along its own length (which is also the length direction of the second reaction frame 321), and the two second slide rails 323 are slidably embedded in the two second sliders 324. A base plate unit 33 is disposed on the two second support plates 322. Thus, through the cooperation of the second slide rails 323 and the second sliders 324, the loading unit 34 can be driven to move along the second direction. Optionally, the length of the second reaction frame 321 is 1705 mm. The distance between the two second reaction frames 321 is 460 mm. The length of the second slide rail 323 is 1660 mm, and it is made of steel. The height of the second slider 324 is 22 mm. The second support plate 322 is 620 mm long, 106 mm wide, and 9 mm thick.

[0070] Optionally, see again Figures 6 to 8 The base plate unit 33 includes a base plate 331 and two third reaction frames 332. The two third reaction frames 332 are disposed on top of the second sliding unit 32. Specifically, the two third reaction frames 332 are arranged side-by-side along a first direction, and both ends of the third reaction frames 332 are respectively fixed to the top of the two second support plates 322 by screws. The base plate 331 is fixed to the top of the two third reaction frames 332 by screws. The loading unit 34 is disposed on the base plate 331. Optionally, the length of the second reaction frame 321 is 645 mm. The distance between the two third reaction frames 332 is 460 mm.

[0071] Optionally, see again Figure 9 The loading unit 34 includes a servo motor 341, an electric cylinder 342, and a loading arm 343. The electric cylinder 342 is connected to the servo motor 341 and can be driven by the servo motor 341 to push down and pull up, thereby raising and lowering the lower structure. The maximum pushing height is 430 mm. The electric cylinder 342 is mounted on the base plate 331 of the base plate unit 33. For easy movement of the inner push rod 344 of the electric cylinder 342, see [reference needed]. Figure 6 and Figure 7The base plate 331 has a through hole 345 through which the inner push rod 344 passes. The bottom of the inner push rod 344 is connected to the top of the loading arm 343 via a tension / compression sensor 346. The bottom of the loading arm 343 is connected to the suction cylinder 10. In this way, the servo motor 341 transmits power to the electric cylinder 342, thereby driving the inner push rod 344 to move up and down, and the inner push rod 344 then drives the suction cylinder 10 to move up and down via the loading arm 343. The loading unit 34 can ensure various controls such as vertical static load, vertical cyclic load, and vertical displacement of the suction cylinder 10.

[0072] Optionally, see [link to relevant documentation] Figure 9 The loading unit 34 also includes a retaining ring 347 and an annular fastener 348. The top of the retaining ring 347 is connected to the bottom of the loading arm 343. The inner wall of the retaining ring 347 is adhered to the side wall of the cap 132 of the suction cylinder 10 by a silicone film, increasing the friction between the retaining ring 347 and the suction cylinder 10. The annular fastener 348 is sleeved on the outside of the retaining ring 347, and tightening the screw on the annular fastener 348 can further strengthen the connection between the retaining ring 347 and the suction cylinder 10.

[0073] Optionally, the loading unit 34 further includes a limiting rod 349. See also Figure 6 and Figure 7 The base plate unit 33 is provided with a limiting hole 350, and a limiting rod 349 passes through the limiting hole 350 and is connected to the fixing ring 347. In this way, the limiting rod 349 restricts the horizontal displacement and rotation of the fixing ring 347 and the suction cylinder 10. Specifically, the limiting hole 350 is provided on the base plate 331.

[0074] Optionally, combined Figure 10 As shown, the submersion device 50 includes a water pump 51, a water pipe 52, and a flow detector 53. The water pump 51 includes a second motor, and a controller 60 is communicatively connected to the second motor to control its frequency, thereby controlling the pumping / injection speed. The first end of the water pipe 52 is connected to the outlet of the water pump 51, and the second end is connected to a second through-hole 12. The flow detector 53 is located at the outlet of the water pump 51 and is used to detect the pumping / injection speed of the water pump 51 in real time, sending the pumping / injection speed to the controller 60. The controller 60 can control the frequency of the second motor based on the received pumping / injection speed to reduce disturbance to the soil within the suction cylinder 10 caused by pumping / injection.

[0075] Pump 51 extracts water from the suction cylinder 10, creating a pressure difference between the inside and outside of the cylinder, and lowers the suction cylinder 10 to a certain position within the soil. The adjustable frequency range of pump 51 is generally from 800 Hz to 3000 Hz, corresponding to a second motor speed of 800 r / min to 3000 r / min. At different frequencies, the inlet flow rate of pump 51 ranges from 1.5 L / min to 6 L / min. Both the inlet and outlet of pump 51 are connected to a 6 mm inner diameter silicone hose (water pipe 52) via hose clamps. The silicone hose connected to the outlet of pump 51 is connected to a flow detector 53 via a hose clamp to ensure a sealed interface. The flow detector 53 visualizes the pumping / injection rate of pump 51 and ultimately calculates the pumping volume.

[0076] Optionally, combined Figure 11 As shown, the simulation chamber 20 is composed of four side panels 21 and one bottom panel 22. The side panels 21 and bottom panel 22 are all 1500 mm long, wide, and high, and 10 mm thick, made of PVC. One side panel 21 has a rounded rectangular mounting hole 150 mm from the bottom panel, with a length of 1150 mm and a height of 1230 mm. Double-layered tempered glass 23 is installed in the mounting hole, and a scale is provided on the tempered glass 23. By combining the tempered glass 23 and the scale, the soil and water levels inside the simulation chamber 20, as well as the conditions inside the suction cylinder 10, can be observed in real time. The bottom of each of the four side panels 21 has multiple drainage holes with a diameter of 25 mm, and the center-to-center distance between adjacent drainage holes is 500 mm. The drainage holes are connected to 24 external PVC drainage pipes via threads, and each of the 24 drainage pipes can be independently controlled to open and close.

[0077] Optionally, the simulation box 20 is wrapped with an outer support 70 made of square steel pipe. The outer support 70 has a square cross-section with a side length of 40 mm, which can support and protect the simulation box 20 and prevent excessive deformation when soil is added or load is placed inside the simulation box 20.

[0078] Based on the aforementioned experimental device for simulating offshore wind turbine suction cylinder foundations, combined with Figure 12 As shown in the embodiments of this disclosure, a test method for simulating offshore wind turbine suction cylinder foundations is provided, including:

[0079] S101, control the vertical loading device to start, and insert the suction cylinder into the soil to the first preset depth;

[0080] S102, control the sinking device to pump water so that the suction cylinder continues to penetrate the soil to the second preset depth;

[0081] S103, control the grouting device to inject grout into the suction cylinder, and stop grouting when grout overflows from the second through hole of the suction cylinder;

[0082] S104. After the slurry in the suction cylinder has solidified, control the vertical loading device to apply a cyclic load to the suction cylinder.

[0083] S105, control the sinking device to inject water into the suction cylinder to generate positive pressure inside the suction cylinder, and control the vertical loading device to pull the suction cylinder upward;

[0084] S106, when the pressure inside the suction cylinder no longer rises, control the vertical loading device to stop pulling upwards, thus completing the recovery of the suction cylinder.

[0085] First, with both the first and second through holes of the suction cylinder open, the vertical loading device is used to lower the suction cylinder into the soil at a speed of approximately 0.2 mm / s using static pressure. Using an underwater camera, when turbidity is observed in the simulated soil, it indicates that the suction cylinder wall has begun to penetrate the soil, disturbing it. At this point, the vertical loading device is used to further penetrate the suction cylinder by an additional 2 cm, reaching the first preset depth. This ensures a sealed space is formed inside the cylinder, sufficient to create a pressure difference between the inside and outside of the suction cylinder during negative pressure pumping.

[0086] Then, the sinking device is activated, and water is pumped out of the suction cylinder to create negative pressure for penetration. When the suction cylinder penetrates to the second preset depth in the soil, it is in place. Ensure that the water film between the cylinder cover and the mud surface inside the cylinder is 2 cm or 4 cm.

[0087] Then, start the grouting device to pump water to lubricate the pipe, and then drain the water from the pipe. Connect the grouting pipe to the first through hole. Start the grouting device to inject grout into the suction cylinder. The hose connected to the first through hole drains the water film displaced by the injected grout into the measuring cylinder. Optionally, the grouting pressure is generally less than or equal to 10 kPa, and grout is injected slowly into the cylinder to avoid excessive grouting pressure that could lift the suction cylinder or disturb the soil inside the cylinder. Start timing when water begins to emerge from the second through hole and record the volume change of water in the measuring cylinder. When grout overflows from the second through hole, the grouting is considered complete. Close the valve of the second through hole and the grouting pump to stop grouting. Disconnect the grout outlet pipe from the suction cylinder, clean the grouting pump and the grout outlet pipe, and measure the final volume of the displaced water film.

[0088] Then, wait for the grout inside the suction cylinder to solidify. After the grout has solidified, control the vertical loading device to start and apply cyclic loads to the suction cylinder to consolidate the soil at the bottom of the suction cylinder. Optionally, control the vertical loading device to apply multiple rounds of cyclic loads to the suction cylinder.

[0089] Then, the valve of the second through hole is opened, the sinking device is started and water is injected into the suction cylinder to create positive pressure inside the suction cylinder. At the same time, the vertical loading device is controlled to pull the suction cylinder upward with a fixed load of 500N.

[0090] Finally, when the pressure in the second through hole stops rising, the vertical loading device is switched to a displacement null value, the upward pull is stopped, and the retrieval of the suction cylinder is completed.

[0091] Optionally, combined Figure 13 As shown, S102, controlling the pumping of water by the settling device, includes:

[0092] S112, Based on the penetration resistance or soil strength during the process of the suction cylinder penetrating to the first preset depth, the initial pumping speed is corrected once.

[0093] S122, based on the heave height of the soil inside the suction cylinder and the actual penetration depth of the suction cylinder, the pumping speed after the first correction is corrected a second time so that the heave speed of the soil inside the suction cylinder is less than the speed threshold.

[0094] During the process of the vertical loading device applying force to the suction cylinder to penetrate to the first preset depth (in order to form a sealed space in preparation for subsequent negative pressure penetration), the tension and compression sensors will provide feedback on the penetration resistance of the suction cylinder. Simultaneously, a spherical probe located inside the suction cylinder can detect the strength of the soil within the cylinder. The controller obtains the penetration resistance or soil strength and then corrects the initial pumping speed. Optionally, the initial pumping speed can be preset based on experience. Optionally, the motor frequency corresponding to the initial pumping speed is 800 Hz. Optionally, when the penetration resistance is greater than a resistance threshold or the soil strength is greater than a first strength threshold, the initial pumping speed is corrected; specifically, the motor frequency corresponding to the pumping speed is corrected to be greater than the first frequency. Optionally, the resistance threshold is 200 N, the first strength threshold is 10 kPa, and the first frequency is 2000 Hz. This increases the pumping speed, ensuring a sufficiently large negative pressure to maintain a certain speed for continuous penetration.

[0095] During subsequent pumping (under negative pressure penetration), the soil inside the suction cylinder will inevitably bulge due to the negative pressure. The faster the pumping, the higher the bulge. The controller uses a camera to acquire the bulge height of the soil inside the suction cylinder and the actual penetration depth of the suction cylinder. The penetration depth of the suction cylinder is the displacement of the loading arm. Based on the soil bulge rate and the actual penetration rate, the pumping speed, after the initial correction, is further adjusted to ensure that the bulge rate of the soil inside the suction cylinder is less than a speed threshold. Optionally, the speed threshold is set to 1 cm / min. For example, the ratio of the bulge height h to the actual penetration depth L of the suction cylinder is calculated. When h / L is greater than the ratio threshold, the pumping speed is adjusted to reduce the penetration speed of the suction cylinder, thereby ensuring that the bulge rate of the soil inside the suction cylinder is less than the speed threshold. Optionally, the ratio threshold is set to 0.1.

[0096] In this way, the first adjustment to the initial pumping rate can prevent soil disturbance caused by excessively rapid pumping. The second adjustment to the initial pumping rate ensures that the soil heave rate is less than the rate threshold, thereby minimizing soil disturbance.

[0097] Optionally, combined Figure 14 As shown, S103, controlling the grouting device to inject grout into the suction cylinder includes:

[0098] S113, Determine the initial grouting speed based on the soil strength;

[0099] S123, the initial grouting speed is corrected once based on the pumping speed during the penetration process of the suction cylinder;

[0100] S133, based on the fluidity of the grout, the grouting speed after the first correction is adjusted a second time;

[0101] S143, based on the soil disturbance, the grouting speed after the second correction is corrected a third time.

[0102] The controller obtains the soil strength inside the suction cylinder through a spherical probe, and then determines the initial grouting speed based on the soil strength. Optionally, when the soil strength is greater than a second strength threshold, the soil is relatively hard and can withstand higher grouting pressure and speed, and is not easily disturbed; in this case, the initial grouting speed is the first speed. When the soil strength is less than or equal to the second strength threshold, the initial grouting speed is the second speed. Optionally, the second strength threshold is 10 kPa. The first speed is (100±20) mL / min, and the second speed is less than 60 mL / min.

[0103] Subsequently, the initial grouting speed was corrected based on the measured pumping speed during the negative pressure penetration process of the suction cylinder. Grouting is essentially the reverse process of pumping; grouting can easily push the suction cylinder up, so it needs to be done slowly to allow sufficient time for the water to drain. Throughout the entire penetration process of the suction cylinder, the pumping speed varies according to the changes in soil strength. Therefore, it is necessary to ensure that the actual grouting speed is less than or equal to 1 / 5 of the maximum measured pumping speed during penetration to avoid excessively fast grouting speed that could push the suction cylinder up.

[0104] Subsequently, the grouting speed, after the initial correction, is further adjusted based on the grout's fluidity. Optionally, the grout's fluidity is pre-determined through a fluidity test. Once the grout's fluidity is determined, the required grouting pressure can be determined, thus allowing for speed adjustments.

[0105] Finally, the controller acquires images of the soil inside the suction cylinder via a camera and analyzes these images to determine whether the soil has been disturbed by the injected grout. If the soil is disturbed, for example, by the grout creating craters, the grouting speed, which has already undergone secondary correction, is adjusted a third time. Specifically, a pre-set threshold is used to define the degree of soil disturbance. If the degree of soil disturbance is greater than or equal to the threshold, the greater the disturbance, the greater the negative correction to the grouting speed, meaning the grouting speed is reduced more significantly. If the degree of soil disturbance is less than the threshold, the current grouting speed remains unchanged.

[0106] Thus, the initial grouting speed is first determined based on the soil strength inside the suction cylinder to avoid excessive grouting speed that could impact the soil. Then, the initial grouting speed is corrected based on the pumping speed during the suction cylinder's penetration, ensuring the pumping speed is less than or equal to 1 / 5 of the maximum measured pumping speed during penetration, preventing the suction cylinder from being lifted due to excessive grouting speed. A second correction to the initial pumping speed reduces the disturbance to the soil caused by the grout's fluidity. A third correction ensures that the disturbance to the soil caused by grouting is minimized.

[0107] Optionally, combined Figure 15 As shown, in step S104, after the slurry inside the suction cylinder has completely solidified, the vertical loading device is controlled to apply a cyclic load to the suction cylinder, including:

[0108] S114 After the slurry in the suction cylinder has completed the first preset time of curing, control the vertical loading device to apply a first preset frequency of cyclic load to the suction cylinder.

[0109] S124, after the first preset frequency cycle load is completed, control the vertical loading device to maintain the load on the suction cylinder, so that the soil at the bottom of the suction cylinder is consolidated for a second preset time.

[0110] S134, control the vertical loading device to apply a second preset frequency cyclic load to the suction cylinder.

[0111] After grouting is completed, wait for a first preset time period to allow the grout to solidify. Optionally, the first preset time period is 24 hours. Then, keeping the first and second through holes of the suction cylinder closed, start the vertical loading device to push the suction cylinder downwards and apply a first preset frequency of cyclic loads. Optionally, the first preset frequency of loads is greater than or equal to 10,000 cycles. After the first preset frequency of loads is applied, maintain the load to allow the soil at the bottom of the suction cylinder to consolidate for a second preset time period. Optionally, the second preset time period is greater than or equal to 7 days. After the second preset time period, continue to control the vertical loading device to apply a second preset frequency of cyclic loads to the suction cylinder. Optionally, the second preset frequency of cyclic loads is greater than or equal to 10,000 cycles. This makes the grout and the soil at the bottom of the suction cylinder more solid.

[0112] Optionally, combined Figure 16 As shown, S105, controlling the sinking device to inject water into the suction cylinder includes:

[0113] S115, Determine the initial water injection rate based on the soil strength inside the suction cylinder;

[0114] S125, the initial water injection speed is corrected once based on the grouting speed during the grouting process;

[0115] S135, based on the attenuation range of the first-stage resistance value, the increase range of the second-stage resistance value, and the attenuation range of the third-stage resistance value, the water injection speed after the first correction is adjusted a second time; wherein, the first-stage resistance value is the resistance value borne by the suction cylinder when a first preset frequency cyclic load is applied to the suction cylinder; the second-stage resistance value is the resistance value borne by the suction cylinder after the soil at the bottom of the suction cylinder has consolidated; and the third-stage resistance value is the resistance value borne by the suction cylinder when a second preset frequency cyclic load is applied to the suction cylinder.

[0116] S145, during water injection, the water injection speed is adjusted three times based on the disturbance of the soil in the suction cylinder or the turbidity in the suction cylinder reaching a preset level.

[0117] The controller obtains the soil strength inside the suction cylinder through a spherical probe, and then determines the initial water injection rate based on the soil strength. Subsequently, the initial water injection rate is corrected based on the grouting rate. Here, the grouting rate refers to the maximum grouting rate during the grouting process. Grouting needs to be slow, but when recovering the suction cylinder by injecting water, it needs to be injected quickly, otherwise the suction cylinder cannot be lifted. After grouting, the grout will block the second through hole to some extent, so a relatively high speed is required when injecting water. Optionally, the water injection rate is greater than or equal to 10 times the grouting rate, and less than or equal to 5 times the pumping rate, to avoid the suction cylinder rising too quickly, which is inconsistent with actual usage.

[0118] During the application of cyclic loads to the suction cylinder by the vertical loading device, the resistance value borne by the suction cylinder is divided into three stages. The first stage resistance value is the resistance value borne by the suction cylinder when the first preset frequency of cyclic loads is applied. At this stage, the greater the soil disturbance, the greater the decrease in resistance value. The second stage resistance value is the resistance value borne by the suction cylinder after the soil at the bottom of the suction cylinder has consolidated. During consolidation, the soil strength recovers, and the resistance value increases. The third stage resistance value is the resistance value borne by the suction cylinder when the second preset frequency of cyclic loads is applied. At this stage, the greater the soil disturbance, the greater the decrease in resistance value. The resistance values ​​are detected by tensile and compressive strength sensors. Therefore, by combining the decrease in resistance value in the first stage, the increase in resistance value in the second stage, and the decrease in resistance value in the third stage, a second correction is made to the water injection rate after the first correction.

[0119] During water injection, the controller uses a camera to acquire images of the soil and water inside the suction cylinder, and analyzes these images to determine if the soil has been disturbed by the injected grout. If the soil is disturbed, for example, if the grout washes out depressions, the grouting speed, which has already undergone secondary correction, is adjusted a third time. Specifically, a pre-set threshold is used to define the degree of soil disturbance. If the degree of soil disturbance is greater than or equal to the threshold, the greater the disturbance, the greater the negative correction to the water injection speed, meaning the water injection speed is reduced more significantly. If the degree of soil disturbance is less than the threshold, the current water injection speed remains unchanged. Alternatively, if the turbidity inside the suction cylinder reaches a preset level, the greater the soil disturbance, the greater the negative correction to the water injection speed, meaning the water injection speed is reduced more significantly. If the turbidity inside the suction cylinder is less than the preset level, the current water injection speed remains unchanged.

[0120] Thus, the initial water injection rate is first determined based on the soil strength within the suction cylinder to avoid excessive water injection that could impact the soil. Then, the initial water injection rate is adjusted based on the grouting rate to ensure sufficient water pressure to lift the suction cylinder. Next, the soil strength is reflected by the resistance values ​​experienced by the suction cylinder at three stages, leading to a second adjustment to the initial water injection rate to reduce soil disturbance. Finally, a third adjustment to the initial water injection rate ensures that the disturbance to the soil caused by water injection is minimized.

[0121] Alternatively, the soil disturbance can be determined in the following ways:

[0122] Obtain the calibration coefficients of the spherical probe and the detected real-time resistance / pressure;

[0123] The initial strength of the soil is determined based on the calibration coefficient and real-time resistance / pressure.

[0124] The initial strength is corrected using the first, second, and third correction factors to obtain the final soil strength.

[0125] The controller retrieves the calibration coefficients of the spherical probe pre-stored in the memory and measures the real-time resistance / pressure detected by the probe of the spherical probe during the penetration of the suction cylinder into the soil. Soil strength is used to characterize the soil disturbance. The initial soil strength is determined based on the real-time resistance / pressure of the calibration coefficients. The initial strength is then corrected using a first correction coefficient, a second correction coefficient, and a third correction coefficient to obtain the final soil strength.

[0126] Specifically, according to the formula Calculate the final soil strength. Among them, S For the final soil strength, F The real-time resistance / pressure detected by the probe of the spherical detector. N For the calibration coefficients of the spherical detector, f cyc This is the first correction factor. f con This is the second correction factor. f post This is the third correction factor. The first, second, and third correction factors can be preset or calculated.

[0127] In this way, by correcting the initial strength of the soil using a correction factor, a more accurate soil strength can be obtained, which in turn allows for a more accurate assessment of soil disturbance.

[0128] Optionally, when a first preset cyclic load is applied to the suction cylinder, the ratio of the resistance value experienced by the suction cylinder during the last loading cycle to the resistance value experienced by the suction cylinder during the first loading cycle is determined as the first correction factor. Taking a vertical loading device applying 10,000 cyclic loads to the suction cylinder (10,000 cycles for the first preset frequency load and 10,000 cycles for the second preset frequency load), totaling 20,000 cyclic loads, as an example, the resistance value experienced by the suction cylinder during the 10,000th loading cycle is divided by the resistance value experienced during the first loading cycle (resistance value reduction percentage), and this result is determined as the first correction factor. The first correction factor indirectly reflects the reduction in the strength of the surrounding soil when the suction cylinder is subjected to the first cyclic load.

[0129] Optionally, the ratio of the resistance value experienced by the suction cylinder during the first loading after soil consolidation to the resistance value experienced by the suction cylinder during the last loading before soil consolidation is determined as the second correction coefficient. Taking a vertical loading device applying 10,000 cycles of loading to the suction cylinder (10,000 cycles for the first preset frequency and 10,000 cycles for the second preset frequency), totaling 20,000 cycles, as an example, the result of dividing the resistance value experienced by the suction cylinder during the 10,001st loading (the first loading after soil consolidation) by the resistance value during the 10,000th loading (the last loading before soil consolidation) is determined as the second correction coefficient. This second correction coefficient indirectly reflects the extent of soil strength recovery during consolidation.

[0130] Optionally, when a second preset cyclic load is applied to the suction cylinder, the ratio of the resistance value experienced by the suction cylinder during the last loading to the resistance value experienced by the suction cylinder during the first loading is determined as the third correction factor. Taking a vertical loading device applying 10,000 cyclic loads to the suction cylinder (10,000 cycles for the first preset frequency load and 10,000 cycles for the second preset frequency load), totaling 20,000 cyclic loads, as an example, the resistance value experienced by the suction cylinder during the 20,000th loading (the 10,000th loading after soil consolidation) divided by the resistance value during the 10,001st loading (the 1st loading after soil consolidation) is determined as the third correction factor. The third correction factor indirectly reflects the reduction in soil strength when subjected to cyclic loads again.

[0131] The foregoing description and accompanying drawings fully illustrate embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included or substituted for parts and features of other embodiments. Embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A test method for simulating offshore wind turbine suction cylinder foundations, characterized in that, A test apparatus suitable for simulating offshore wind turbine suction cylinder foundations; the test apparatus includes: The suction cylinder is provided with a first through hole and a second through hole; The simulation chamber contains soil and water to simulate the installation environment. A vertical loading device is installed on the top of the simulation box and connected to the suction cylinder, used to lower the suction cylinder to a preset position in the soil. A grouting device, connected to the first through hole, is used to inject grout into the suction cylinder; A settling device, connected to the second through hole, is used to draw water from the suction cylinder or inject water into the suction cylinder; A monitoring device is installed inside the simulation box to monitor the strength of the soil and the height of the water film inside the suction cylinder; The test method includes: The vertical loading device is activated to drive the suction cylinder into the soil to a first preset depth. Control the sinking device to pump water so that the suction cylinder continues to penetrate the soil to a second preset depth; The grouting device is controlled to inject grout into the suction cylinder. Grouting is stopped when grout overflows from the second through hole of the suction cylinder. After the slurry inside the suction cylinder has solidified, the vertical loading device is controlled to apply a cyclic load to the suction cylinder. The sinking device is controlled to inject water into the suction cylinder to generate positive pressure inside the suction cylinder, and the vertical loading device is controlled to pull the suction cylinder upward. When the pressure inside the suction cylinder stops rising, the vertical loading device is controlled to stop pulling upwards, thus completing the recovery of the suction cylinder; The controlled submersion device for pumping water includes: The initial pumping speed is corrected once based on the penetration resistance or the strength of the soil during the process of the suction cylinder penetrating the first preset depth. Based on the heave height of the soil inside the suction cylinder and the actual penetration depth of the suction cylinder, the pumping speed after the first correction is adjusted a second time so that the heave speed of the soil inside the suction cylinder is less than the speed threshold. The controlled grouting device injects grout into the suction cylinder, including: The initial grouting rate is determined based on the strength of the soil. The initial grouting speed is corrected once based on the pumping speed during the penetration process of the suction cylinder. Based on the fluidity of the grout, the grouting speed, which has been corrected once, is adjusted a second time. Based on the soil disturbance, the grouting speed, which had been corrected twice, was adjusted a third time.

2. The test method for simulating offshore wind turbine suction cylinder foundations according to claim 1, characterized in that, The grouting device includes: The grouting pump includes a first motor with a controllable and adjustable frequency; The discharge pipe has a first end connected to the outlet of the discharge pump and a second end connected to the first through hole; A pressure sensor is installed in the first through hole to monitor the pressure inside the suction cylinder in real time; A flow sensor is installed in the slurry outlet pipe to measure the slurry flow rate in real time.

3. The test method for simulating offshore wind turbine suction cylinder foundations according to claim 1, characterized in that, The monitoring device includes: A spherical probe is installed inside the suction cylinder to record cone tip resistance and pore pressure data; An image acquisition module is installed in the water to acquire images of the soil and water film height inside the suction cylinder.

4. The test method for simulating offshore wind turbine suction cylinder foundations according to claim 1, characterized in that, The suction cylinder includes: The cylindrical body is formed by a cylindrical wall and a cylindrical cover; wherein the first through hole and the second through hole are provided in the cylindrical cover; A diffuser plate is disposed inside the cylinder and is spaced at a predetermined distance from the cylinder cover; wherein, the diffuser plate is uniformly provided with a plurality of water-repellent holes, so that the water injected by the submersion device is flexibly and uniformly released into the cylinder after passing through the water-repellent holes.

5. A test method for simulating offshore wind turbine suction cylinder foundations according to any one of claims 1 to 4, characterized in that, The vertical loading device includes: The first sliding unit is disposed on the top of the simulation box and is capable of sliding along the first direction; The second sliding unit is disposed on top of the first sliding unit and is capable of sliding along a second direction; wherein the second direction and the first direction are two different directions on a horizontal plane; The base plate unit is disposed on top of the second sliding unit; A loading unit is disposed on the base plate unit and connected to the suction cylinder.

6. A test method for simulating offshore wind turbine suction cylinder foundations according to any one of claims 1 to 4, characterized in that, The immersion device includes: The water pump includes a second motor, and its frequency can be controlled and adjusted. The water pipe has its first end connected to the outlet of the water pump and its second end connected to the second through hole. A flow detector is installed at the outlet of the water pump to monitor the pumping speed / injection speed of the water pump in real time.

7. A test method for simulating offshore wind turbine suction cylinder foundations according to any one of claims 1 to 4, characterized in that, After the slurry inside the suction cylinder has solidified, the vertical loading device is controlled to apply a cyclic load to the suction cylinder, including: After the slurry in the suction cylinder has solidified for a first preset time, the vertical loading device is controlled to apply a first preset frequency of cyclic load to the suction cylinder. When the first preset frequency cycle load is completed, the vertical loading device is controlled to maintain the load on the suction cylinder, so that the soil at the bottom of the suction cylinder is consolidated for a second preset time. The vertical loading device is controlled to apply a second preset frequency of cyclic load to the suction cylinder.

8. The test method for simulating offshore wind turbine suction cylinder foundations according to claim 7, characterized in that, The control of the submersion device to inject water into the suction cylinder includes: The initial water injection rate is determined based on the soil strength inside the suction cylinder; The initial water injection rate is corrected once based on the grouting rate during the grouting process; Based on the attenuation range of the first-stage resistance value, the increase range of the second-stage resistance value, and the attenuation range of the third-stage resistance value, the water injection rate after the first correction is adjusted a second time. The first-stage resistance value is the resistance value borne by the suction cylinder when the first preset frequency cyclic load is applied. The second-stage resistance value is the resistance value borne by the suction cylinder after the soil at the bottom of the suction cylinder has consolidated. The third-stage resistance value is the resistance value borne by the suction cylinder when the second preset frequency cyclic load is applied. During water injection, the water injection speed is adjusted three times based on the disturbance of the soil in the suction cylinder or the turbidity in the suction cylinder reaching a preset level.

9. The test method for simulating offshore wind turbine suction cylinder foundations according to claim 8, characterized in that, The soil condition inside the suction cylinder is detected using a spherical detector; the soil disturbance is determined by the following methods: Obtain the calibration coefficients of the spherical detector and the detected real-time resistance / pressure; The initial strength of the soil is determined based on the calibration coefficient and the real-time resistance / pressure. The initial strength is corrected according to the first correction factor, the second correction factor, and the third correction factor to obtain the final soil strength.

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