Three-dimensional pile-soil interaction test method and test system based on magnetic induction tracing and quick freezing soil consolidation technology

Abstract

The present invention relates to a three-dimensional pile-soil interaction test method and test system based on magnetic induction tracing and quick freezing soil consolidation technology, including a horizontal cyclic loading test platform for simulating the long-term vibration environment of offshore wind turbine pile foundations, a magnetic induction tracing system for real-time monitoring of the position and motion characteristics of sand particles, a terrain modeling and analysis system for real-time recording of terrain changes around piles, and a quick freezing soil sectioning system for observing the motion morphology of sand particles inside a sand bed. Using the horizontal cyclic loading test platform, according to the designed test conditions, horizontal cyclic loads of different amplitudes and frequencies are applied to aluminum alloy semi-cylinder model piles; the three-dimensional pile-soil interaction under different loading conditions is studied by using the magnetic induction tracing system, the terrain modeling and analysis system, and the quick freezing soil sectioning system.

Description

Technical Field

[0001] The invention relates to a three-dimensional pile-soil interaction test method and a test system based on magnetic induction tracing and quick freezing soil consolidation technology, and belongs to the technical field of offshore wind turbine pile-soil interaction test under long-term vibration. Background Art

[0002] Offshore wind power has advantages that are difficult to match with onshore wind power, such as higher wind energy quality, closer distance to electricity loads, and no occupation of arable land.

[0003] The dynamic environment of offshore wind turbines is very complex. The continuous cyclic vibration caused by their own operation and the cyclic load of the marine environment poses a great threat to the stability of the offshore wind turbine pile foundation structure. Based on the previous research of relevant scholars and the experience of existing projects, it is mainly reflected in the settlement and uplift of the bed soil around the pile and the convection phenomenon caused by the deep soil around the pile under the action of continuous cyclic vibration. The above process will increase the length of the free end of the wind turbine structure and cause resonance damage. At the same time, it affects the scouring process around the pile, resulting in an increased risk of instability and collapse of the wind turbine. At the same time, predicting the maximum settlement depth of the soil around the pile under a complex marine dynamic environment is the most challenging part of the offshore wind turbine design process. Insufficient or overly conservative predictions may cause a decrease in the overall stability of the wind turbine structure or a significant increase in construction costs. Therefore, it is of great significance to study the interaction between piles and soil under long-term cyclic vibration.

[0004] The interaction between the pile foundation and the sand around the pile under continuous vibration has complex three-dimensional characteristics, and there are obvious differences in soil settlement, uplift and convection phenomena along the area around the pile. Based on existing experimental techniques, Li Jialong et al. (Two-dimensional pile-soil interaction test system and test method based on PIV technology) simplified the three-dimensional cylindrical pile into a two-dimensional rectangular pile, generalized the three-dimensional characteristics of the pile-soil interaction, and used PIV technology to observe the process of soil settlement and convection phenomena under continuous vibration. Although this test technology uses non-contact means to analyze the movement process of sand particles and protect the original soil, it has the following three defects: First, it oversimplifies the three-dimensional characteristics of the pile-soil interaction. The rectangular piles used in this test technology do not have three-dimensional rotational symmetry, and the movement of sand particles is blocked and restricted by the tempered glass on the front of the box, resulting in significant differences in the settlement and uplift of the soil on the bed surface around the pile and the three-dimensional cylindrical pile; second, there is an obvious stiffness difference between the rectangular piles and cylindrical piles used in this test technology. Under the condition of applying the same horizontal cyclic load, the horizontal deflection of the rectangular piles on the surface of the sand bed is greater than that of the cylindrical piles, resulting in the convection area of ​​the deep soil on both sides of the rectangular piles being wide and deep, which is quite different from the convection area morphology obtained from existing related studies; third, this experimental technology can only capture and record the movement characteristics of sand particles on the plane of the tempered glass, and cannot observe the movement characteristics and convection area morphology of sand particles in the inner layer of the sand bed. Considering the above three defects, the test results cannot accurately reflect the three-dimensional pile-soil interaction of cylindrical piles in actual offshore wind turbine projects.

[0005] After long-term experiments and analysis, magnetic induction tracing technology, as a tracking and monitoring method based on magnetic tracer particles, has been tried to be applied in the three-dimensional pile-surrounding sand movement characteristic test. Magnetic induction tracing technology originated in the biomedical field in the early 20th century. With the development of materials science, the preparation and functionalization of magnetic tracer particles have been improved, so that the application scope of this technology has gradually expanded to environmental science, geological engineering and materials science. In geological exploration and environmental monitoring, magnetic induction tracing technology can monitor water flow, sedimentation process and underground mineral migration. In the field of materials science and nanotechnology, researchers use this technology to reveal the microstructure of materials and the movement behavior of nanoparticles. Magnetic induction tracing technology is also widely used in geological engineering, material labeling, environmental pollution monitoring and liquid flow research. The magnetic induction tracing technology is introduced into the field of offshore wind turbine pile-soil interaction test technology. The cylindrical model pile with material stiffness fitting the actual engineering is used to restore the real offshore wind turbine cyclic vibration environment, which solves the problem of poor three-dimensional characteristics and significant stiffness gap of existing experimental technology.

[0006] Therefore, it is necessary to design a test system based on magnetic induction tracing technology that fully considers the three-dimensional characteristics of pile-soil interaction, observes and analyzes the entire process of sand movement under continuous cyclic vibration, and can section the soil in a way that minimizes soil disturbance after the test. Summary of the invention

[0007] The present invention provides a three-dimensional pile-soil interaction test method and test system based on magnetic induction tracing and quick freezing soil consolidation technology, and studies the three-dimensional pile-soil interaction under different loading conditions through a magnetic induction tracing system, a terrain modeling analysis system and a quick freezing soil consolidation sectioning system.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] The three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology specifically includes the following steps:

[0010] Step S1: according to the actual test conditions, the amplitude of the horizontal cyclic loading test platform for simulating the long-term vibration environment of the offshore wind turbine pile foundation is set, the model of each component in the horizontal cyclic loading test platform is determined, and each component is assembled; during the assembly, an oil-based synthetic lubricant needs to be applied on the bottom of the test sand box and around the inner side walls;

[0011] Step S2: according to the actual test conditions, the output power of the unidirectional adjustable speed motor in the horizontal cyclic loading test platform is set, and based on the operating principle of converting rotary motion into linear motion, the rotary motion of the motor shaft of the unidirectional adjustable speed motor is converted into a sinusoidal reciprocating motion at the top of the aluminum alloy semi-cylinder model pile to simulate test conditions of different frequencies;

[0012] Step S3: preparing magnetic tracer sand particles for laying on the inner surface of the test sand box of the horizontal cyclic loading test platform; at the intersection of the four outer side walls of the test sand box, the intersection of two oppositely arranged side walls is a group, one group is equipped with a steady magnetic field applying device, and the other group is equipped with a magnetic field monitoring device; the magnetic tracer sand particles, the steady magnetic field applying device and the magnetic field monitoring device constitute a magnetic induction tracing system;

[0013] Step S4: according to the actual test conditions, the mass M of quartz sand required for each layer of test to form a thickness H is calculated and slowly poured into the test sand box through the aggregate standard funnel. Each time a layer of quartz sand of thickness H is filled, the sand bed surface is first smoothed with a spatula, then compacted evenly with a rectangular iron block, and finally flattened with an iron plate until the sand bed surface is flush with the scale value of the test sand box; this operation is repeated repeatedly to make the sand bed thickness meet the test condition setting requirements;

[0014] Step S5: Based on the quartz sand bed formed in step S4, a layer of sand particles mixed with prepared magnetic tracer sand particles and quartz sand particles is laid in a circular area on the surface of the sand bed with the aluminum alloy semi-cylindrical model pile as the center, and the compaction operation in step S4 is repeated to make the thickness of the top layer of the sand bed meet the setting requirements of the test working condition;

[0015] Step S6: Determine the test condition type. If a saturated sand test is to be conducted, connect the direct water valve to the PVC soft water pipe, and then connect the other end of the PVC soft water pipe to the funnel, keep the height of the funnel higher than the height of the sand bed surface, and fill the funnel with water. When the water level in the test sand box is above the sand bed surface, stop filling water, close the direct water valve, and proceed to step S7;

[0016] If a dry sand test is performed, proceed directly to step S7 until step S10 is completed and the water injection operation of this step is performed before proceeding to step S11;

[0017] Step S7: Turn on the power of the constant magnetic field applying device, start the Hall effect sensor receiving program in the magnetic field monitoring device, and after the computer calculates the magnetic field strength and distribution inside the test sand box, check whether it is the same as the initial setting and whether the stability is good. If there is a problem, recalibrate and calibrate the Hall effect sensor in the magnetic field monitoring device;

[0018] Step S8: four high-definition network cameras are installed at the four top corners of the opening end of the test sand box, with the cameras of the high-definition network cameras facing the inside of the test sand box, forming a terrain modeling and analysis system; the indoor light source is adjusted, and the python program of the high-performance computer is started to call the four high-definition network cameras; after the timed shooting interval is preset according to the test requirements, the high-definition network camera is adjusted to a preset position so that it faces the aluminum alloy semi-cylindrical model pile and the sand bed area to be studied;

[0019] Step S9: Check the magnetic induction tracing system and the terrain modeling and analysis system, start the unidirectional adjustable speed motor, and vibrate the aluminum alloy semi-cylinder model pile continuously in a cycle, and the duration is set to 120 hours;

[0020] Step S10: After the test lasts for 120 hours, the unidirectional adjustable speed motor and the four high-definition network cameras are turned off;

[0021] Step S11: remove the unidirectional adjustable speed motor, the constant magnetic field applying device, the magnetic field monitoring device and four high-definition network cameras in the horizontal cyclic loading test platform, and hoist the test sand box into the ultra-low temperature freezer by a small indoor crane. The ultra-low temperature freezer starts full-power refrigeration, and takes out the test sand box from the freezer after the sand particles are fixed;

[0022] Step S12: insert the visual sand cutting system as a whole into the test sand box, pull out the organic glass plates in front and behind the test sand box, clean the test sand in the non-cutting area with a soil cutter, take out the sand bed that has been cut into blocks, and take photos to record the final shape of the cross-section convection area;

[0023] Step S13: using an electromagnetic signal open source algorithm to calculate and analyze the motion trajectory and motion properties of sand particles, and obtaining the time-averaged velocity field and vorticity field of sand motion; using the image-to-3D model software 3DF Zephyr to reconstruct a 3D model of sand around the aluminum alloy semi-cylindrical model pile under continuous vibration, and obtaining the range, size and volume data of the settlement and uplift of the sand around the pile, and the test is finished;

[0024] As a further preferred embodiment of the present invention, the relationship between the vibration frequency of the test condition setting in step S2 and the output power of the unidirectional adjustable speed motor is as follows:

[0025] ;

[0026] As a further preferred embodiment of the present invention, in step S4, the calculation steps of the mass M of the quartz sand required for each layer to form a thickness H are as follows:

[0027] Step S41: Setting the relative density of the sand bed sand according to the test conditions ;

[0028] Step S42: Derivation of the density of sand in the experimental sand box according to the basic formula of soil relative density The basic formula of soil relative density is: ,Depend on: , , the following formula can be derived: , converted into the relative density of soil: ;

[0029] Step S43: Perform a density test in accordance with the geotechnical test method standard GBT 50123-2019 of the People's Republic of China to obtain the maximum dry density of the quartz sand used in the test and minimum dry density ;

[0030] Step S44: Based on the maximum dry density and the minimum dry density obtained in step S43, substitute them into the soil relative density formula in step S43 to obtain the density of the sand in the experimental sand box. ;

[0031] Step S45: According to the radius r of the aluminum alloy semi-cylindrical model pile, the mass M of the quartz sand required for each layer to be filled to form a thickness H is obtained, and the calculation formula is: ;

[0032] A three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology for the three-dimensional pile-soil interaction test method, including a horizontal cyclic loading test platform for simulating the long-term vibration environment of offshore wind turbine pile foundations, a magnetic induction tracing system for real-time monitoring of the position and movement characteristics of sand particles, a terrain modeling and analysis system for real-time recording of terrain changes around piles, and a quick freezing soil sectioning system for observing the movement morphology of sand particles inside a sand bed;

[0033] As a further preferred embodiment of the present invention, the horizontal cyclic loading test platform comprises an open and unsealed test sand box made of organic glass, wherein the four sides of the test sand box are defined as the front side, the left side, the back side and the right side, and the front and the back side of the test sand box are detachable organic glass plates;

[0034] A straight-through water valve is installed at the bottom of the test sand box;

[0035] An aluminum alloy semi-cylindrical model pile is vertically inserted at the center of the test sand box, the top of which is connected to the transmission structure through a semi-circular ring component, and the bottom of the aluminum alloy semi-cylindrical model pile is fastened to the center of the bottom of the test sand box through a circular ring component;

[0036] A transmission structure and a one-way adjustable speed motor are fixed on the right outer side of the test sand box through a loading device mounting platform, the transmission structure includes an eccentric wheel and a transmission rod, and the one-way adjustable speed motor is installed on the top of the loading device mounting platform. The eccentric wheel is sleeved on the motor shaft, and the eccentric wheel is connected to one end of the transmission rod through a limiter. The other end of the transmission rod is connected to the top of the aluminum alloy semi-cylindrical model pile through a semi-circular ring component, wherein the transmission rod is arranged parallel to the bottom surface of the test sand box;

[0037] As a further preferred embodiment of the present invention, the invention comprises two semicircular ring parts, which are arranged opposite to each other to form a space in the middle for fixing the top of the aluminum alloy semi-cylindrical model pile, and the ends of the two adjacent semicircular ring parts are fixed by a pile top connecting part;

[0038] As a further preferred embodiment of the present invention, the magnetic induction tracing system comprises magnetic tracing sand particles, a constant magnetic field applying device and a magnetic field monitoring device;

[0039] The magnetic tracer sand particles are made of quartz sand particles, on the outside of which ferrite magnetic paint is coated;

[0040] The constant magnetic field applying devices are respectively installed at the intersection of the left side and the back side, and at the intersection of the right side and the front side of the test sand box; a group of electromagnetic coils are installed in each constant magnetic field applying device;

[0041] The magnetic field monitoring devices are installed at the intersection of the left side and the front side, and at the intersection of the right side and the back side of the test sand box respectively; a Hall effect sensor is installed in each magnetic field monitoring device; the Hall effect sensor is connected to a computer, and the Hall voltage measured by the Hall effect sensor is converted into a voltage or current signal, and then the motion trajectory and motion properties of the magnetic tracer sand particles are recorded and saved in real time through an open source algorithm;

[0042] As a further preferred embodiment of the present invention, the terrain modeling and analysis system comprises a high-definition network camera installed at four corners of the opening end of the test sand box, the high-definition network camera is connected to the computer, and the shooting mode is set to timed interval shooting through a python program call, and the captured images are remodeled by software to calculate and analyze the terrain changes around the aluminum alloy semi-cylinder model piles and the changes in the density of the sand;

[0043] As a further preferred embodiment of the present invention, the quick-frozen soil cutting system comprises an ultra-low temperature freezer, a circular cutting fixed frame and a plurality of sand bed separation base plates, two symmetrically arranged extended fixed brackets are vertically mounted at the end of the circular cutting fixed frame, and the ends of the two extended fixed brackets are connected and fixed by a top fixed bracket;

[0044] A plurality of substrate grooves for inserting a sand bed to cut the substrate are evenly arranged on the circumferential wall of the circular section fixing frame, and a plurality of substrate grooves are distributed to form a cylindrical structure;

[0045] The sand bed cutting base plate is made of stainless steel plate, a T-shaped base is arranged at the connecting end, and the cutting section of the sand bed cutting base plate is ground to open a single edge.

[0046] Through the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology provided by the present invention introduces magnetic induction tracing technology into the field of offshore wind turbine pile-soil interaction test technology, which is an innovative exploration in this field, realizes non-contact, high-precision motion trajectory measurement and motion property analysis, can accurately observe and record the complex interaction process between the pile foundation and the sand around the pile, helps to deeply understand the comprehensive characteristics of the pile-soil interaction under vibration, and provides reliable experimental support for the engineering design of offshore wind turbine pile foundations and the further development of particle flow and force chain network theory;

[0048] 2. The three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology provided by the present invention adopts a cylindrical model pile that matches the actual engineering situation, so that the test results are more practical and can more accurately reflect the characteristics of the actual pile-soil interaction. In particular, under the consideration of the three-dimensional characteristics, the cylindrical model pile can more comprehensively simulate the vibration response in different directions, providing more convincing data support for in-depth research on the behavior of the interaction between pile foundation and sand particles in different spatial dimensions;

[0049] 3. The three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology provided by the present invention can apply different amplitudes and frequencies to the cylindrical model pile according to the set test conditions, and quantitatively evaluate and analyze the interaction between soils with different engineering characteristics and vibrating pile foundations; at the same time, the sand bed can be sectioned and analyzed after the test to reveal the convection area morphology generated by deep soil under continuous cyclic vibration, which provides a new way to deeply understand the movement mechanism of sand particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0051] Figure 1 It is a schematic diagram of the overall structure of a preferred embodiment provided by the present invention;

[0052] Figure 2 It is a structural front view of a preferred embodiment provided by the present invention;

[0053] Figure 3 is a top view of the structure of a preferred embodiment provided by the present invention;

[0054] Figure 4 It is a structural left view of a preferred embodiment provided by the present invention;

[0055] Figure 5 It is a structural schematic diagram of a quick-frozen soil cutting system in a preferred embodiment provided by the present invention;

[0056] Figure 6 is a top view of a quick-frozen soil cutting system in a preferred embodiment provided by the present invention;

[0057] Figure 7 It is a schematic diagram of installing the quick-freezing soil cutting system in a test sand box in a preferred embodiment provided by the present invention.

[0058] In the figure: 1 is an aluminum alloy semi-cylindrical model pile, 2 is a test sand box, 3 is a unidirectional adjustable speed motor, 4 is a transmission rod, 5 is a limiter, 6 is an eccentric wheel, 7 is an organic glass instrument box, 8 is a semi-circular ring body component, 9 is a pile top connecting component, 10 is an organic glass plate, 11 is a loading device installation platform, 12 is a stainless steel wing plate, 13 is a magnetic field monitoring device, 14 is a high-definition network camera, 15 is a motor controller, 16 is a computer, 17 is a straight-through water valve, 18 is a circular cut-out fixed frame, 19 is a substrate groove, 20 is an extended fixed bracket, 21 is a sand bed separating substrate, 22 is a T-type base, and 23 is a top fixed bracket. DETAILED DESCRIPTION

[0059] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "left side", "right side", "upper part", "lower part", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and "first", "second", etc. do not indicate the importance of the components, and therefore cannot be understood as a limitation on the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution by example, and do not limit the scope of protection of the present invention.

[0060] As explained in the background technology, under actual working conditions, the interaction between the pile foundation and the sand around the pile under continuous vibration has complex three-dimensional characteristics, and the existing test systems for three-dimensional characteristics have the following main defects: the test simulation is not carried out using pile foundations close to actual working conditions, and the dynamic response of the pile foundation and sand particles in the sand bed in a complex vibration environment cannot be captured in real time in a non-contact manner, resulting in the test results being unable to accurately reflect the three-dimensional pile-soil interaction of offshore wind turbines in actual engineering.

[0061] In order to solve the above problems, the present application provides a three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology, introduces magnetic induction tracing technology into the offshore wind turbine pile-soil interaction test, and cooperates with the aluminum alloy semi-cylinder model pile 1 with more three-dimensional characteristics and rigidity. It can perform non-contact measurement of sand particles in the sand bed under the condition of fully considering the three-dimensional characteristics of pile-soil interaction, monitor and record the three-dimensional motion information of sand particles in real time and continuously, and provide a more comprehensive analysis of pile-soil interaction behavior. Here, the three-dimensional motion information includes the response of the aluminum alloy semi-cylinder model pile in the horizontal, vertical and lateral directions, so as to further study the dynamic response of the pile foundation and sand particles in a complex vibration environment. At the same time, by monitoring the movement of the tracer particles through a magnetic field sensor, displacement data with submillimeter or even higher precision can be obtained, and high-precision measurement of the position and displacement of sand particles can be achieved, so as to accurately capture the tiny deformation and displacement in the pile-soil interaction.

[0062] Next, this application first describes the three-dimensional pile-soil interaction test system based on this test method, such as Figure 1 As shown, it includes a horizontal cyclic loading test platform for simulating the long-term vibration environment of offshore wind turbine pile foundations, a magnetic induction tracing system for real-time monitoring of the position and movement characteristics of sand particles, a terrain modeling and analysis system for real-time recording of terrain changes around piles, and a quick-freezing soil sectioning system for observing the movement morphology of sand particles inside the sand bed.

[0063] The horizontal cyclic loading test platform includes an open and unclosed test sand box 2 made of organic glass, and the four sides of the test sand box are defined as the front, left, back and right sides. The front and back of the test sand box are detachable organic glass plates 10. This test sand box is made of high-strength organic glass integrated molding, and the quartz sand used for the test is loaded from the unclosed opening. The front and back sides of the test sand box and the bottom edges adjacent to the front and back are all provided with chute with a width of 5 cm. The organic glass is inserted into the chute to achieve the purpose of detachability, and prepare for the subsequent removal of the sand bed for frozen soil tests. Since it is necessary to inject water into the test sand box during the test, in order to prevent the organic glass plates at the front and back from leaking, a rubber sealing strip is set at the intersection of the organic glass plate and the side of the test sand box. A straight water valve 17 is installed at the bottom of the test sand box to inject water into the sand in the test sand box to saturate it. The other end of the straight water valve can be connected to a PVC soft water pipe. A nylon filter is fixed at the connection between the straight water valve 17 and the bottom plate of the test sand box. The pore size of the nylon filter is much smaller than the particle size of the test sand.

[0064] An aluminum alloy semi-cylindrical model pile for simulating the pile foundation of an offshore wind turbine is vertically inserted in the center of the test sand box, and its top is connected to the transmission structure through a semi-circular ring component 8, which includes two semi-circular ring components, and the space between the two relatively arranged semi-circular ring components is formed to fix the top of the aluminum alloy semi-cylindrical model pile, and the ends of the two adjacent semi-circular ring components are fixed by the pile top connection component 9; one of the semi-circular ring components is welded to the transmission rod 4 of the transmission structure, and the two semi-circular ring components are clamped and fixed by four bolts. After the test is completed, the relevant system can be disassembled and replaced by unscrewing the bolts. The bottom end of the aluminum alloy semi-cylindrical model pile is fastened to the center of the bottom of the test sand box through a ring component anchored to the bottom plate of the test sand box, and the ring component is fastened to the aluminum alloy semi-cylindrical model pile by two hexagon socket head screws; it is ensured that during the vibration process, the aluminum alloy semi-cylindrical model pile does not deviate as a whole.

[0065] The transmission structure and the one-way adjustable speed motor 3 are fixed on the right outer side of the test sand box through the loading device mounting platform 11. The transmission structure includes an eccentric wheel 6 and a transmission rod. The one-way adjustable speed motor is installed on the top of the loading device mounting platform. The eccentric wheel is sleeved on the motor shaft. The eccentric wheel is connected to one end of the transmission rod through a limiter 5. The limiter includes two and is fixed on the angle steel installed on the top of the loading device platform to ensure that the transmission rod can reciprocate. The other end of the transmission rod is connected to the top of the aluminum alloy semi-cylindrical model pile through a semi-circular ring component, wherein the transmission rod is arranged parallel to the bottom surface of the test sand box. After the one-way adjustable speed motor is started by the motor controller 15, based on the operating principle of converting rotational motion into linear motion, the rotational motion of the motor shaft of the one-way adjustable speed motor is converted into a sinusoidal reciprocating motion at the top of the aluminum alloy semi-cylindrical model pile; Figure 2 It can be seen from the viewing angle that the motor shaft is arranged upward (perpendicular to the ground), and the eccentric wheel is fastened to the motor drive shaft with screws. The displacement amplitude applied to the top of the aluminum alloy semi-cylindrical model pile can be adjusted by replacing eccentric wheels with different eccentric distances to simulate test conditions with different vibration amplitudes.

[0066] Next, another innovative point of the present application is described, the magnetic induction tracing system, which includes magnetic tracing sand particles, a constant magnetic field applying device and a magnetic field monitoring device 13; the principle of magnetic tracing sand particles is to give ordinary sand particles magnetic properties by coating the surface of ordinary sand particles with magnetic coating, and to monitor the motion trajectory of magnetic tracer particles in real time by applying an external magnetic field and using a magnetic field monitoring device. The production method includes the following steps: first, select suitable ordinary sand particles to ensure that they meet the experimental requirements; then, select a magnetic coating containing ferrite and an adhesive; then, immerse the sand particles in the magnetic coating to ensure that the coating is evenly attached to the surface of the sand particles, and control the thickness of the coating through the immersion process; then, the surface of the ferrite sand particles is silicified by a silane coupling agent, so that the surface of the particles has a silicon oxide layer, which enhances the hydrophilicity and compatibility of the particles. Finally, a drying method is used to make the coating form a stable attachment on the surface of the sand particles.

[0067] During the test, the magnetic tracer sand particles are mixed with ordinary quartz sand particles and laid on the top layer of the sand bed according to the laying thickness and relative density of the sand designed in the test. The constant magnetic field applying device is symmetrically placed in the organic glass instrument box 7 outside the left rear and right front walls of the test sand box, and each of the constant magnetic field applying devices has a group of electromagnetic coils with exactly the same geometric structure and winding number. Through precise current supply and control, it can be ensured that the magnetic field intensity generated by the electromagnetic coil remains stable and the required magnetic field parameters are achieved during the test. The magnetic field monitoring device is placed outside the left front and right rear walls of the test sand box, and Hall effect sensors are alternately placed in the magnetic field monitoring device. The sensor is connected to a high-performance computer 16, and the Hall voltage measured by the Hall effect sensor is converted into a voltage (current) signal, and then the motion trajectory and motion properties of the magnetic tracer sand particles are recorded and saved in real time through an open source algorithm.

[0068] The terrain modeling and analysis system includes a high-definition network camera 14 installed at four corners of the opening end of the test sand box. Figure 3-Figure 4 As shown, each high-definition network camera is fixed on the stainless steel wing plate 12 at the four corners of the outside of the test sand box. The high-definition network camera is connected to the computer and called by the python program. The shooting mode is set to timed interval shooting. The captured image is re-modeled by the image-to-three-dimensional model software 3DF Zephyr to obtain the length, width, angle, volume and other geometric data of the pile periphery subsidence and uplift, and the terrain changes around the pile and the changes in the density of the sand can be calculated and analyzed.

[0069] Another innovative point of this application is the quick-freezing soil sectioning system included. In terms of studying the three-dimensional pile-soil interaction, the observation of the movement morphology of sand and soil particles inside the sand bed is also of great significance, that is, observing the convection area morphology generated by the deep soil around the pile under the action of continuous cyclic vibration. Based on the quick-freezing soil technology of the quick-freezing soil sectioning system, the sand bed after cyclic vibration is placed in an ultra-low temperature freezer for shaping. After the sand bed is shaped, the convection area morphology is analyzed by modular sectioning according to polar coordinates, which solves the problem that existing experimental technology cannot observe the convection area morphology of sand and soil particles in the inner layer of the sand bed.

[0070] Specific as Figure 5-Figure 7 As shown, the quick-freezing soil cutting system includes an ultra-low temperature freezer (for rapid freezing of saturated sand in the test sand box), a circular cutting fixed frame 18 and a plurality of sand bed segmentation substrates 21. Two symmetrically arranged extension fixed brackets 20 are vertically installed at the end of the circular cutting fixed frame. The ends of the two extension fixed brackets are connected and fixed by a top fixed bracket 23 to prevent the circular cutting fixed frame from being dislocated during the cutting process and affecting the cutting effect. The circumferential wall of the circular cutting fixed frame is evenly provided with a plurality of substrate grooves 19 for inserting the sand bed segmentation substrate. In the preferred embodiment, the plurality of substrate grooves are distributed at intervals of 30° or 15° to form a cylindrical structure. The design of different interval angles realizes the multi-section analysis of the sand bed and reduces the influence of the expansion and deformation of the sand at the same time. The sand bed segmentation substrate is made of extremely thin stainless steel plate. The front end of the stainless steel plate is machine-polished to open a single blade. A T-shaped base 22 is provided at its connection end so that it can be hammered when it is difficult to insert the sand bed manually. After the saturated sand is frozen and fixed, the sand bed segmentation substrates are inserted into the sand bed in sequence to minimize the expansion and deformation of the sand.

[0071] After the test system is explained clearly, the key point of this application is the three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology, which specifically includes the following steps:

[0072] Step S1: according to the actual test conditions, the amplitude of the horizontal cyclic loading test platform for simulating the long-term vibration environment of the offshore wind turbine pile foundation is set, the model of each component in the horizontal cyclic loading test platform is determined, and each component is assembled; during assembly, an oil-based synthetic lubricant needs to be applied to the bottom of the test sand box and around the inner side walls to facilitate freezing and demolding after the test.

[0073] Step S2: according to the actual test conditions, the output power of the unidirectional adjustable speed motor in the horizontal cyclic loading test platform is set, and based on the operating principle of converting rotary motion into linear motion, the rotary motion of the motor shaft of the unidirectional adjustable speed motor is converted into a sinusoidal reciprocating motion at the top of the aluminum alloy semi-cylinder model pile to simulate test conditions of different frequencies;

[0074] The relationship between the set vibration frequency and the output power of the unidirectional adjustable speed motor is as follows:

[0075]

[0076] Through preliminary experiments, the power range of this device is 210W-745W. Turn on the motor to check the working status of the loading system. After checking that it is correct, adjust the motor to the standby mode.

[0077] Step S3: prepare magnetic tracer sand particles for laying on the inner surface of the test sand box of the horizontal cyclic loading test platform. At the intersection of the four external side walls of the test sand box, the intersection of two oppositely arranged side walls is a group, one group is installed with a steady magnetic field applying device, and the other group is installed with a magnetic field monitoring device; the magnetic tracer sand particles, the steady magnetic field applying device and the magnetic field monitoring device constitute a magnetic induction tracing system.

[0078] Step S4: according to the actual test conditions, the mass M of quartz sand required for each layer of test to form a thickness H is calculated and slowly poured into the test sand box through the aggregate standard funnel. Each time a layer of quartz sand of thickness H is filled, the sand bed surface is first smoothed with a spatula, then compacted evenly with a rectangular iron block, and finally flattened with an iron plate until the sand bed surface is flush with the scale value of the test sand box; this operation is repeated repeatedly to make the sand bed thickness meet the test condition setting requirements;

[0079] The calculation steps for the mass M of quartz sand required for each layer to form a thickness H are:

[0080] Step S41: Setting the relative density of the sand bed sand according to the test conditions ;

[0081] Step S42: Derivation of the density of sand in the experimental sand box according to the basic formula of soil relative density The basic formula of soil relative density is: ,Depend on: , , the following formula can be derived: , converted into the relative density of soil: ;

[0082] Step S43: Perform a density test in accordance with the geotechnical test method standard GBT 50123-2019 of the People's Republic of China to obtain the maximum dry density of the quartz sand used in the test and minimum dry density ;

[0083] Step S44: Based on the maximum dry density and the minimum dry density obtained in step S43, substitute them into the soil relative density formula in step S43 to obtain the density of the sand in the experimental sand box. ;

[0084] Step S45: According to the radius of the aluminum alloy semi-cylindrical model pile r , the mass M of quartz sand required for each layer to form a thickness H is obtained, and the calculation formula is: .

[0085] Step S5: Based on the quartz sand bed formed in step S4, a layer of sand particles mixed with prepared magnetic tracer sand particles and quartz sand particles is laid on the surface of the sand bed in a circular area centered on the aluminum alloy semi-cylindrical model pile, and the compaction operation in step S4 is repeated to make the thickness of the top layer of the sand bed meet the requirements of the test condition setting.

[0086] Step S6: Determine the test condition type. If a saturated sand test is to be conducted, connect the direct water valve to the PVC soft water pipe, and then connect the other end of the PVC soft water pipe to the funnel, keep the height of the funnel higher than the height of the sand bed surface, and fill the funnel with water. When the water level in the test sand box is above the sand bed surface, stop filling water, close the direct water valve, and proceed to step S7;

[0087] If a dry sand test is performed, directly proceed to step S7 until step S10 is completed and the water injection operation of this step is performed, and then proceed to step S11.

[0088] Step S7: Turn on the power of the constant magnetic field application device, start the Hall effect sensor receiving program in the magnetic field monitoring device, and after the computer calculates the magnetic field strength and distribution inside the test sand box, check whether it is the same as the initial setting and whether the stability is good. If there is a problem, recalibrate and calibrate the Hall effect sensor in the magnetic field monitoring device.

[0089] Step S8: four high-definition network cameras are installed at the four top corners of the opening end of the test sand box, with the cameras of the high-definition network cameras facing the inside of the test sand box, forming a terrain modeling and analysis system; the indoor light source is adjusted, and the python program of the high-performance computer is started to call the four high-definition network cameras; after the timed shooting interval is preset according to the test requirements, the high-definition network camera is adjusted to the preset position so that it faces the aluminum alloy semi-cylindrical model pile and the sand bed area to be studied.

[0090] Step S9: Check the magnetic induction tracing system and the terrain modeling and analysis system, start the unidirectional adjustable speed motor, and vibrate the aluminum alloy semi-cylindrical model pile continuously in a cycle, and the duration is set to 120 hours.

[0091] Step S10: After checking that the magnetic induction tracing system and the terrain modeling and analysis system are working properly, the one-way adjustable speed motor is turned on. After the test lasts for 120 hours, the one-way adjustable speed motor and the four high-definition network cameras are turned off.

[0092] Step S11: Remove the unidirectional adjustable speed motor, the constant magnetic field application device, the magnetic field monitoring device and four high-definition network cameras in the horizontal cyclic loading test platform, and use the indoor small crane to lift the test sand box into the ultra-low temperature freezer. The ultra-low temperature freezer starts full-power refrigeration, and takes out the test sand box from the freezer after the sand particles are fixed.

[0093] Step S12: insert the visual sand cutting system as a whole into the test sand box, pull out the plexiglass plates in front and behind the test sand box, use a soil cutter to clean the test sand in the non-cutting area, take out the cut sand bed in blocks, and take photos to record the final shape of the cross-section convection area.

[0094] Here through Figure 5-Figure 7 The process of cutting with the sand and soil cutting system is as follows: insert the circular cutting fixed frame from above the aluminum alloy semi-cylindrical model pile, fix the extended fixing brackets on both sides of the circular cutting fixed frame to the top of the aluminum alloy semi-cylindrical model pile to prevent the circular cutting fixed frame from moving during the cutting process; insert the sand bed dividing substrates into the sand bed in sequence, and when the insertion is difficult, use a small hammer to hit the base at the tail of the sand bed dividing substrate to make the whole sand bed dividing substrate completely penetrate into the sand bed; slowly pull out the organic glass plates in front and behind the test sand box from the waterproof card slot, clean the test sand and soil in the non-cutting area with a soil cutter, carefully take out the cut sand bed into blocks, and take pictures to record the final shape of the cross-section convection area.

[0095] Step S13: Using the electromagnetic signal open source algorithm to calculate and analyze the motion trajectory and motion properties of the sand particles, the time-averaged velocity field and vorticity field of the sand movement are obtained; using the image-to-3D model software 3DF Zephyr to reconstruct the 3D model of the sand around the aluminum alloy semi-cylindrical model pile under continuous vibration, the range, size and volume data of the settlement and uplift of the sand around the pile are obtained, and the test is completed.

[0096] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0097] The meaning of "and / or" described in this application means that the situations where each exists alone or both exist at the same time are included.

[0098] The term “connection” as used in this application may mean a direct connection between components or an indirect connection between components via other components.

[0099] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology, characterized in that: The specific steps include: Step S1: according to the actual test conditions, the amplitude of the horizontal cyclic loading test platform for simulating the long-term vibration environment of the offshore wind turbine pile foundation is set, the model of each component in the horizontal cyclic loading test platform is determined, and each component is assembled; during assembly, an oil-based synthetic lubricant needs to be applied to the bottom of the test sand box and around the inner wall; an aluminum alloy semi-cylindrical model pile is vertically inserted at the center of the test sand box, the top end of which is connected to the transmission structure through a semi-circular ring component, and the bottom end of the aluminum alloy semi-cylindrical model pile is fastened to the center of the bottom of the test sand box through the semi-circular ring component; Step S2: according to the actual test conditions, the output power of the unidirectional adjustable speed motor in the horizontal cyclic loading test platform is set, and based on the operating principle of converting rotational motion into linear motion, the rotational motion of the motor shaft of the unidirectional adjustable speed motor is converted into a sinusoidal reciprocating motion at the top of the aluminum alloy semi-cylinder model pile to simulate test conditions of different frequencies; Step S3: preparing magnetic tracer sand particles for laying on the inner surface of the test sand box of the horizontal cyclic loading test platform, at the intersection of the four outer side walls of the test sand box, the intersection of two oppositely arranged side walls is a group, one group is equipped with a steady magnetic field applying device, and the other group is equipped with a magnetic field monitoring device; The magnetic tracer sand particles, the constant magnetic field applying device and the magnetic field monitoring device constitute the magnetic induction tracer system; Step S4: Calculate the thickness of each layer according to the actual test conditions H The quality of quartz sand required for the test M , slowly pour into the test sand box through the aggregate standard funnel, and fill each layer with a thickness of H First, use a spatula to smooth the sand bed surface, then use a rectangular iron block to compact it evenly, and finally use an iron plate to flatten the entire surface until the sand bed surface is flush with the scale value of the test sand box; repeat this operation repeatedly to make the sand bed thickness meet the test condition setting requirements; Step S5: Based on the quartz sand bed formed in step S4, a layer of sand particles mixed with prepared magnetic tracer sand particles and quartz sand particles is laid in a circular area on the surface of the sand bed with the aluminum alloy semi-cylindrical model pile as the center, and the compaction operation in step S4 is repeated to make the thickness of the top layer of the sand bed meet the setting requirements of the test working condition; Step S6: Determine the test condition type. If a saturated sand test is to be conducted, connect the direct water valve to the PVC soft water pipe, and then connect the other end of the PVC soft water pipe to the funnel, keep the height of the funnel higher than the height of the sand bed surface, and fill the funnel with water. When the water level in the test sand box is above the sand bed surface, stop filling water, close the direct water valve, and proceed to step S7; If a dry sand test is performed, proceed directly to step S7 until step S10 is completed and the water injection operation of this step is performed before proceeding to step S11; Step S7: Turn on the power of the constant magnetic field applying device, start the Hall effect sensor receiving program in the magnetic field monitoring device, and after the computer calculates the magnetic field strength and distribution inside the test sand box, check whether it is the same as the initial setting and whether the stability is good. If there is a problem, recalibrate and calibrate the Hall effect sensor in the magnetic field monitoring device; Step S8: four high-definition network cameras are installed at the four top corners of the opening end of the test sand box, with the cameras of the high-definition network cameras facing the inside of the test sand box, forming a terrain modeling and analysis system; the indoor light source is adjusted, and the python program of the high-performance computer is started to call the four high-definition network cameras; after the timed shooting interval is preset according to the test requirements, the high-definition network camera is adjusted to a preset position so that it faces the aluminum alloy semi-cylindrical model pile and the sand bed area to be studied; Step S9: Check the magnetic induction tracing system and the terrain modeling and analysis system, start the unidirectional adjustable speed motor, and vibrate the aluminum alloy semi-cylinder model pile continuously in a cycle, and the duration is set to 120 hours; Step S10: After the test lasts for 120 hours, the unidirectional adjustable speed motor and the four high-definition network cameras are turned off; Step S11: remove the unidirectional adjustable speed motor, the constant magnetic field applying device, the magnetic field monitoring device and four high-definition network cameras in the horizontal cyclic loading test platform, and hoist the test sand box into the ultra-low temperature freezer by a small indoor crane. The ultra-low temperature freezer starts full-power refrigeration, and takes out the test sand box from the freezer after the sand particles are fixed; Step S12: insert the visual sand cutting system as a whole into the test sand box, pull out the organic glass plates in front and behind the test sand box, clean the test sand in the non-cutting area with a soil cutter, take out the sand bed that has been cut into blocks, and take photos to record the final shape of the cross-section convection area; Step S13: Using the electromagnetic signal open source algorithm to calculate and analyze the motion trajectory and motion properties of the sand particles, the time-averaged velocity field and vorticity field of the sand movement are obtained; using the image-to-3D model software 3DF Zephyr to reconstruct the 3D model of the sand around the aluminum alloy semi-cylindrical model pile under continuous vibration, the range, size and volume data of the settlement and uplift of the sand around the pile are obtained, and the test is completed.

2. The three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 1 is characterized in that: The relationship between the vibration frequency of the test condition setting in step S2 and the output power of the unidirectional adjustable speed motor is as follows: 。 3. The three-dimensional pile-soil interaction test method based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 1 is characterized in that: In step S4, each layer is filled to form a thickness H The quality of quartz sand required for the test M The calculation steps are: Step S41: Setting the relative density of the sand bed sand according to the test conditions ; Step S42: Derivation of the density of sand in the experimental sand box according to the basic formula of soil relative density The basic formula of soil relative density is: ,Depend on: , , the following formula can be derived: , converted into the relative density of soil: ; Step S43: Perform a density test in accordance with the geotechnical test method standard GBT 50123-2019 of the People's Republic of China to obtain the maximum dry density of the quartz sand used in the test and minimum dry density ; Step S44: Based on the maximum dry density and the minimum dry density obtained in step S43, substitute them into the soil relative density formula in step S42 to obtain the density of sand in the experimental sand box. ; Step S45: According to the radius r of the aluminum alloy semi-cylindrical model pile, the mass M of the quartz sand required for each layer to be filled to form a thickness H is obtained, and the calculation formula is: .

4. A three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology for the three-dimensional pile-soil interaction test method according to claim 2 or 3, characterized in that: It includes a horizontal cyclic loading test platform for simulating the long-term vibration environment of offshore wind turbine pile foundations, a magnetic induction tracing system for real-time monitoring of the position and movement characteristics of sand particles, a terrain modeling and analysis system for real-time recording of terrain changes around piles, and a quick-freezing soil sectioning system for observing the movement morphology of sand particles inside the sand bed.

5. The three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 4 is characterized in that: The horizontal cyclic loading test platform comprises an open and unsealed test sand box made of organic glass, wherein the four sides of the test sand box are defined as the front side, the left side, the back side and the right side, and the front side and the back side of the test sand box are detachable organic glass plates; A straight-through water valve is installed at the bottom of the test sand box; A transmission structure and a one-way adjustable speed motor are fixed on the right outer side of the test sand box through a loading device mounting platform. The transmission structure includes an eccentric wheel and a transmission rod. The one-way adjustable speed motor is installed on the top of the loading device mounting platform. The eccentric wheel is sleeved on the motor shaft. The eccentric wheel is connected to one end of the transmission rod through a limiter, and the other end of the transmission rod is connected to the top of the aluminum alloy semi-cylindrical model pile through a semi-circular ring component, wherein the transmission rod is arranged parallel to the bottom surface of the test sand box.

6. The three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 5 is characterized in that: It comprises two semicircular ring parts, which are arranged relatively to form a space in the middle for fixing the top of the aluminum alloy semi-cylindrical model pile, and the ends of two adjacent semicircular ring parts are fixed by a pile top connecting part.

7. The three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 4 is characterized in that: The magnetic induction tracing system includes magnetic tracing sand particles, a constant magnetic field applying device and a magnetic field monitoring device; The magnetic tracer sand particles are made of quartz sand particles, on the outside of which ferrite magnetic paint is coated; The constant magnetic field applying devices are respectively installed at the intersection of the left side and the back side, and at the intersection of the right side and the front side of the test sand box; a group of electromagnetic coils are installed in each constant magnetic field applying device; The magnetic field monitoring devices are installed at the junction of the left and front sides and the right and back sides of the test sand box respectively; a Hall effect sensor is installed in each magnetic field monitoring device; the Hall effect sensor is connected to a computer, and the Hall voltage measured by the Hall effect sensor is converted into a voltage or current signal, and then the motion trajectory and motion properties of the magnetic tracer sand particles are recorded and saved in real time through an open source algorithm.

8. The three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 4 is characterized by: The terrain modeling and analysis system includes a high-definition network camera installed at the four corners of the opening end of the test sand box. The high-definition network camera is connected to the computer and is called by a python program. The shooting mode is set to timed interval shooting. The captured images are re-modeled by software to calculate and analyze the terrain changes around the aluminum alloy semi-cylindrical model piles and the changes in the density of the sand.

9. The three-dimensional pile-soil interaction test system based on magnetic induction tracing and quick freezing soil consolidation technology according to claim 4 is characterized by: The quick-freezing soil cutting system comprises an ultra-low temperature freezer, a circular cutting fixed frame and a plurality of sand bed separation base plates, two symmetrically arranged extended fixed brackets are vertically installed at the end of the circular cutting fixed frame, and the ends of the two extended fixed brackets are connected and fixed by a top fixed bracket; A plurality of substrate grooves for inserting a sand bed to cut the substrate are evenly arranged on the circumferential wall of the circular section fixing frame, and a plurality of substrate grooves are distributed to form a cylindrical structure; The sand bed cutting base plate is made of stainless steel plate, a T-shaped base is arranged at the connecting end, and the cutting section of the sand bed cutting base plate is ground to open a single edge.

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