A non-saturated soil freeze-thaw cycle device for applying wicking geotextile and a test method thereof

Abstract

The application belongs to the technical field of geotechnical engineering, and particularly relates to a non-saturated soil freeze-thaw cycle device with wicking geotextile and a test method thereof, which comprises a sample forming device, an illumination device, an environment device, a temperature and humidity control device, a water supply device, a data monitoring device and a control terminal, the illumination device is used for ultraviolet radiation on the part of the wicking geotextile exposed outside the soil column, the environment device is used for providing a closed test environment for the sample forming device, the temperature and humidity control device is used for regulating the temperature and humidity in the environment device, and the water supply device is used for providing a constant water head supply for the sample forming device. The application has the advantages of reasonable design, simple structure, convenient processing, and can truly simulate the boundary condition that the geotextile supplies water to the non-saturated soil body through the wicking effect in the actual engineering, so as to more accurately study the water and heat migration law and the mechanical property evolution of the non-saturated soil body in the freeze-thaw cycle process under the complex condition.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, and particularly relates to a freeze-thaw cycle device for applying wicking geotextiles to unsaturated soil and its testing method. Background Technology

[0002] In seasonally and perennially frozen soil regions, the soil undergoes phase changes, migration, and redistribution of internal moisture under cyclical positive and negative temperature variations, leading to significant deterioration of its physical and mechanical properties. This results in a series of engineering problems, such as uneven settlement of roadbeds, slope instability, canal lining damage, and frost heave of building foundations. To further investigate the hydrothermal migration patterns and mechanical property evolution of unsaturated soils during freeze-thaw cycles, freeze-thaw cycle testing devices have become an indispensable research tool in the field of geotechnical engineering.

[0003] In practical engineering, geotextiles and other reinforcing materials are widely used in roadbeds, slopes, and other engineering projects to serve functions such as drainage, filtration, and reinforcement. When wicking geotextiles are laid in roadbeds with high humidity, the outer geotextiles are exposed to the air along the embankment and moisture evaporates, while the inner geotextiles have increased moisture content in the high humidity environment. The humidity difference between the inside and outside creates a difference in matrix suction from the inside to the outside of the geotextiles, thus forming a water conveyance channel composed of wicking geotextiles. The external natural environment acts like a natural pump, continuously draining gravitational water and capillary water from the soil from the roadbed.

[0004] Existing freeze-thaw cycle testing devices and methods are unable to effectively simulate the special drainage boundary conditions controlled by the wicking effect of geotextiles. Due to the idealization of the boundary conditions, the freeze-thaw characteristic parameters of unsaturated soil obtained based on existing devices (such as unfrozen water content, frost heave rate, permeability coefficient, strength index, etc.) may produce large errors when applied to actual engineering design and safety assessment of geotextiles, and cannot provide accurate theoretical basis and data support for the durability and stability of such composite structures.

[0005] Therefore, developing an unsaturated soil freeze-thaw cycle test device and method that can accurately simulate the boundary conditions of geotextile core absorption and replenishment is of great theoretical and practical significance for deepening the understanding of the water-thermal-mechanical coupling mechanism of reinforced soil structures in cold regions and improving the design level and long-term service performance of related projects. Summary of the Invention

[0006] This invention addresses the technical problems existing in the freeze-thaw cycle test process mentioned above. It proposes a freeze-thaw cycle device and test method for unsaturated soil with applied wicking geotextile, which is reasonably designed, simple in structure, easy to process, and can realistically simulate the boundary conditions in actual engineering where geotextiles replenish water to unsaturated soil through wicking effect. This allows for a more accurate study of the water and heat migration law and mechanical property evolution of unsaturated soil during the freeze-thaw cycle under these complex conditions.

[0007] To achieve the above objectives, the present invention employs a technical solution of a freeze-thaw cycle device and test method for applying wicking geotextiles to unsaturated soil. The device includes a sample preparation unit, an illumination unit, an environmental unit, a temperature and humidity control unit, a water supply unit, a data monitoring unit, and a control terminal. The sample preparation unit receives the prepared soil column and places the wicking geotextiles on it. The illumination unit provides ultraviolet radiation to the portion of the wicking geotextiles exposed to the outside of the soil column. The environmental unit provides a sealed test environment with insulation and humidity control for the sample preparation unit. The temperature and humidity control unit regulates the temperature and humidity within the environmental unit. The water supply unit provides a constant head supply to the sample preparation unit. The data monitoring unit monitors the changes in temperature, moisture content, and displacement inside the soil column in real time. The control terminal is electrically connected to the illumination unit, the temperature and humidity control unit, and the data monitoring unit, and freely controls the test parameters and collects test data.

[0008] Preferably, the environmental device includes a constant temperature and humidity cabinet, and a constant temperature and humidity control system is provided on the outside of the constant temperature and humidity cabinet.

[0009] Preferably, the sample preparation device is placed inside the constant temperature and humidity cabinet of the environmental device. The sample preparation device includes a base plate, a column above the base plate, a top plate above the column, a jack on the lower inner side of the top plate, and a bottom cylinder, a middle cylinder, and a top cylinder arranged sequentially from bottom to top above the base plate. There are at least two middle cylinders, which are connected to the bottom cylinder and the top cylinder respectively by flanges. The bottom cylinder and the top cylinder in the sample preparation device have the same height and are greater than the height of the middle cylinder. Soil column samples are placed in the middle cylinder, the bottom cylinder, and the top cylinder. One end of the geotextile is sealed inside the soil column sample, and the other end extends into the light irradiation device. The side walls of the bottom cylinder, the middle cylinder, and the top cylinder are also provided with transparent observation windows.

[0010] Preferably, the data monitoring device includes a temperature sensor, a moisture content sensor, and a displacement sensor installed at different locations within the soil column sample, for monitoring the state of the soil column's temperature field, moisture field, and deformation field.

[0011] Preferably, the temperature and humidity control device includes an upper temperature control plate installed at the top of the soil column sample inside the top cylinder and a lower temperature control plate installed at the bottom of the soil column sample inside the bottom cylinder. The temperature and humidity control device also includes a cold bath box installed outside the environmental device.

[0012] Preferably, the water supply device is a Marshall bottle, which includes a water storage bottle, a water outlet control pipe, and an air compensation pipe. By adjusting the overall placement height of the Marshall bottle, a continuously adjustable constant water head is provided to the system.

[0013] Preferably, multiple sets of lighting devices are provided, and they are respectively located on one side of the middle cylinder and the top cylinder. The lighting device includes a lamp box, and the lamp box is provided with an angle adjustment mechanism that can be freely adjusted according to different irradiation angles. The adjustment end of the angle adjustment mechanism is provided with an ultraviolet lamp tube.

[0014] Preferably, two sets of angle adjustment mechanisms are provided at the front and rear, and are centrally symmetrical about the geometric center of the lamp box, and are located on the inner side of the lamp box. The angle adjustment mechanism includes a mounting plate, a rotating rod is provided on one side of the mounting plate, a rotating plate is provided on the outer periphery of the rotating rod located on the inner side of the mounting plate, a rotating shaft is provided on the other side of the mounting plate, a key plate is provided on the rotating shaft, a key groove is provided in the key plate, a moving block is provided in the key groove, and one side of the moving block is rotatably connected to the rotating plate. A moving frame with a ring key design is provided on one side of the moving block, and a rack is provided in the moving frame. Two sets of racks are centrally symmetrical about the geometric center of the moving frame. A rotating sleeve is provided at the end of the key plate, and a miniature electromagnetic clutch is provided at the end of the rotating sleeve. A drive gear is provided at one end of the miniature electromagnetic clutch and meshes with the rack. The ultraviolet lamp is placed inside one side of the rotating sleeve.

[0015] Preferably, a method for conducting unsaturated soil freeze-thaw cycle tests using wicking geotextiles includes the following steps:

[0016] S1: Prepare soil samples and fill them into the sample preparation device in layers. At the same time, arrange wicking geotextile at the preset flange connection interface, so that one end is buried in the soil and the other end is led out.

[0017] S2: Bury the sensors of each data monitoring device into the soil column at the preset positions and connect them to the data acquisition instrument;

[0018] S3: Sealed environment device, which sets the target temperature, humidity and ultraviolet light intensity through the control terminal;

[0019] S4: Cool the soil column by using a temperature and humidity control device, start the freeze-thaw cycle process, and simulate groundwater recharge through a water supply device;

[0020] S5: During the freeze-thaw cycle, the temperature, volumetric water content and displacement data of the soil column are collected in real time through the data monitoring device;

[0021] S6: By recording and analyzing data through the control terminal, the hydrothermal migration law of unsaturated soil under the action of wicking geotextile is studied.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0023] This invention provides a freeze-thaw cycle device and test method for applying wicking geotextiles to unsaturated soil. Utilizing an angle adjustment mechanism, the position of the ultraviolet lamp can be freely adjusted to simulate different ultraviolet radiation intensities, particularly the effect of ultraviolet radiation on unsaturated soil under varying angles. This more accurately simulates different environmental characteristics, enhancing the diversity of the test process. The device can realize the freeze-thaw cycle process of unsaturated soil with multiple layers of wicking geotextiles, reproducing environmental characteristics such as ultraviolet radiation, temperature and humidity changes, and groundwater recharge. It can accurately obtain the regulation law of wicking geotextiles on the moisture field, temperature field, and deformation field of unsaturated soil in permafrost regions, laying the foundation for research on wicking geotextile-unsaturated soil subgrades in plateau permafrost regions. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The structural schematic diagram provided for this invention;

[0026] Figure 2 This is a schematic diagram of the overall structure of the device provided by the present invention;

[0027] Figure 3 An exploded view of a portion of the sample-forming device provided by the present invention;

[0028] Figure 4 This is a schematic diagram of the angle adjustment mechanism provided by the present invention;

[0029] Figure 5 A schematic diagram of part of the internal structure of the angle adjustment mechanism provided by the present invention;

[0030] In the above figures, 1. Constant temperature and humidity cabinet; 2. Constant temperature and humidity control system; 3. Base plate; 4. Column; 5. Top plate; 6. Jack; 7. Bottom cylinder; 8. Middle cylinder; 9. Top cylinder; 10. Transparent observation window; 11. Temperature sensor; 12. Moisture content sensor; 13. Displacement sensor; 14. Upper temperature control panel; 15. Lower temperature control panel; 16. Cold bath chamber; 17. Marshall bottle; 171. Water storage bottle; 172. Water outlet control pipe; 173. 18. Air compensation tube; 19. Lamp box; 10. Angle adjustment mechanism; 11. Mounting plate; 12. Rotating rod; 13. Rotating plate; 14. Rotating shaft; 15. Key plate; 16. Key groove; 17. Moving block; 18. Moving frame; 199. Rack; 100. Rotating sleeve; 1910. Miniature electromagnetic clutch; 20. Drive gear; 21. Ultraviolet lamp tube; 22. Control terminal; 23. Core-absorbing geotextile. Detailed Implementation

[0031] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0032] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0033] Examples, such as Figures 1-5As shown, an unsaturated soil freeze-thaw cycle device and its testing method for applying wicking geotextile include a sample preparation device, an illumination device, an environmental device, a temperature and humidity control device, a water supply device, a data monitoring device, and a control terminal 21. The sample preparation device is used to receive the prepared soil column and place the wicking geotextile 22 on the soil column. The illumination device is used to irradiate the part of the wicking geotextile 22 exposed to the outside of the soil column with ultraviolet radiation. The environmental device is used to provide a closed test environment for the sample preparation device with heat preservation and humidity control. The temperature and humidity control device is used to regulate the temperature and humidity inside the environmental device. The water supply device is used to provide a constant water head supply to the sample preparation device. The data monitoring device is used to monitor the changes in temperature, moisture content, and displacement inside the soil column in real time. The control terminal 21 is connected to the illumination device and the temperature and humidity control device. The device and data monitoring device are electrically connected and can freely control the test parameters and collect test data. That is to say, the control terminal 21 is mainly used to control the light intensity of the fluorescent ultraviolet lamp, regulate the temperature and humidity in the soil column environment, and monitor the temperature, volumetric water content and overall displacement changes of the soil column at different locations in real time. Furthermore, the cooperation between the above devices can realize the freeze-thaw cycle process of unsaturated soil with multiple layers of wicking geotextile 22, restore the environmental characteristics such as ultraviolet radiation, temperature and humidity changes and groundwater recharge, and accurately obtain the regulation law of wicking geotextile 22 on the moisture field, temperature field and deformation field of unsaturated soil in permafrost areas, laying the foundation for the research of wicking geotextile-unsaturated soil subgrade in plateau permafrost areas.

[0034] To ensure a constant environment for the sample preparation device and to simulate different scenarios, thereby increasing the diversity of experiments, the environmental device includes a constant temperature and humidity chamber 1. A constant temperature and humidity control system 2 is installed on the outside of the constant temperature and humidity chamber 1. Specifically, the constant temperature and humidity chamber 1 is a polyurethane foam insulated and humidified chamber. The top of the chamber is equipped with a temperature and humidity control device, which generally includes an air outlet, compressor, condenser, evaporator, four-way valve, humidity sensor, etc. The composition of the device components is based on existing mature and conventional technologies, and will not be elaborated further. During use, the humidity inside the constant temperature and humidity chamber 1 can be freely adjusted to simulate various experimental environments.

[0035] To facilitate the convenient preparation of soil column samples, the sample preparation device is placed inside a constant temperature and humidity chamber 1 of the environmental apparatus. The sample preparation device includes a base plate 3, a column 4 above the base plate 3, a top plate 5 above the column 4, and a jack 6 located on the lower inner side of the top plate 5. Above the base plate 3, a bottom cylinder 7, a middle cylinder 8, and a top cylinder 9 are arranged sequentially from bottom to top. There are at least two middle cylinders 8, which are connected to the bottom cylinder 7 and the top cylinder 9 respectively via flanges. The bottom cylinder 7 and the top cylinder 9 in the sample preparation device have the same height and are larger than the middle cylinder 8. The middle cylinder 8, bottom cylinder 7, and top cylinder 9 contain soil column samples. One end of the wicking geotextile 22 is sealed inside the soil column sample, and the other end extends into the lighting device. Transparent observation windows 10 are also provided on the side walls of the bottom cylinder 7, middle cylinder 8, and top cylinder 9. Specifically, the bottom cylinder 7, the two middle cylinders 8, and the top cylinder 9 mentioned above are all columnar cylinders, that is, sample preparation cylinders used to prepare soil columns. They are made of steel. A specific specification is provided: the height of the top and bottom steel cylinders is 27cm, and the height of the two middle sample preparation cylinders is... The cylindrical tubes are 23cm high, and the inner diameter of each steel cylinder is 20cm. The entire device can prepare soil columns with a diameter of 20cm and a height of 100cm. The top and bottom steel cylinders, which are slightly taller than the middle steel cylinders, are used to place permeable stones and temperature control plates, respectively. A 90° central angle blank is reserved on one side of the steel cylinder, where plexiglass is spliced ​​to observe changes in the freezing state of the internal soil sample and to observe the flatness of compaction during the filling process. This is the aforementioned transparent observation window 10. The four steel cylinders are connected by flanges, and the flanges are connected by... Bolted connections are used. At the junction of the flanges, between the upper and lower gaskets, core-absorbing geotextile 22 is placed. Up to three core-absorbing geotextile 22s can be placed in the four sample tubes. One end of the core-absorbing geotextile 22 is sealed in the soil column, and the other end extends into the lighting device. The bottom steel cylinder 7 is placed on a steel support, i.e., the base plate 3. The base plate 3 is supported by a top plate 5 by four steel columns 4. A jack 6 with a maximum lifting capacity of 2t is installed below the top plate 5. The jack 6 can be connected to a force transmission rod for compaction of the soil column.

[0036] To facilitate the collection of test data, the data monitoring device includes a temperature sensor 11, a moisture content sensor 12, and a displacement sensor 13 installed at different locations within the soil column sample. These sensors are used to monitor the temperature field, moisture field, and deformation field of the soil column. Specifically, the data monitoring device mainly consists of necessary components such as the temperature sensor 11, moisture content sensor 12, displacement sensor 13, and a data acquisition instrument. The temperature sensor 11 is used to monitor the temperature changes inside the soil column in real time. The moisture content sensor 12 is used to monitor the volumetric moisture content within the soil column. The displacement sensor 13, installed in the top steel cylinder, is used to monitor the changes in frost heave and thaw settlement displacement in real time. The temperature sensor 11, moisture content sensor 12, and displacement sensor 13 are connected to the data acquisition instrument to collect real-time data on temperature and volumetric moisture content changes at different locations within the soil column, as well as the overall frost heave and thaw settlement deformation of the soil column.

[0037] To facilitate convenient control of the temperature and humidity of the soil column sample, the temperature and humidity control device includes an upper temperature control plate 14 located at the top of the soil column sample inside the top cylinder 9 and a lower temperature control plate 15 located at the bottom of the soil column sample inside the bottom cylinder 7. The temperature and humidity control device also includes a cold bath box 16 located outside the environmental device. Specifically, the temperature control device mainly controls the temperature of the environmental device through the upper and lower temperature control plates 15. The upper and lower temperature control plates 15 are respectively connected to the cold bath box 16 outside the polyurethane foam insulation and humidity cabinet through conduits. The conduits are sealed with foam at the points where they pass through the cabinet to ensure the insulation and humidity of the cabinet. The cold bath box 16 regulates the temperature of the upper and lower temperature control plates 15 by delivering antifreeze through conduits, thereby achieving the control of the soil column temperature.

[0038] To further simulate the groundwater environment, a Marshall bottle 17 is used as the water supply device, which includes a water storage bottle 171, an outlet control pipe 172, and an air compensation pipe 173. By adjusting the overall placement height of the Marshall bottle 17, a continuously adjustable constant water head is provided to the system. Specifically, the water supply device mainly consists of a Marshall bottle 17 and an air compensation pipe 173. Internally, it includes a large-volume water storage bottle 171, an outlet control pipe 172 that is higher than the bottom of the bottle, and an air compensation pipe 173 that connects the top space of the bottle to the atmosphere. When the system starts supplying water, by adjusting the overall placement height of the Marshall bottle 17, the top elevation of its outlet control pipe 172 can be set and fixed, thereby providing a constant reference water level at the inlet. By placing the main body of the Marshall bottle 17 at different heights, the constant reference water head value acting at the inlet can be continuously and accurately adjusted.

[0039] To simulate an ultraviolet irradiation environment for the soil column sample, multiple sets of illumination devices are installed, located on one side of the middle cylinder 8 and the top cylinder 9, respectively. In this embodiment, three sets of illumination devices are installed on the outer side of the cylinders except for the bottom cylinder 7, and their positions are opposite to the transparent observation window 10, each corresponding to a set of wicking geotextile 22. The illumination device includes a lamp box 18, which contains an angle adjustment mechanism 19 that can be freely adjusted according to different irradiation angles. The adjustment end of the angle adjustment mechanism 19 is equipped with an ultraviolet lamp tube. Specifically, the selected ultraviolet lamp tube is a UVA340 fluorescent ultraviolet lamp tube with an ultraviolet radiation intensity of 150W / m². 2 Of course, depending on different usage requirements, ultraviolet lamps with adjustable radiation intensity can be selected. At the same time, the angle adjustment mechanism 19 can be used to move it to different angles to meet different test conditions. The adjustable position of the ultraviolet lamp can more accurately simulate the irradiation situation under actual working conditions.

[0040] To better simulate the effect of ultraviolet (UV) irradiation, and especially to facilitate convenient adjustment of the irradiation angle to meet various irradiation needs, two sets of angle adjustment mechanisms 19 are provided at the front and rear, and are centrally symmetrical about the geometric center of the lamp box 18, located inside the lamp box 18. The two sets of angle adjustment mechanisms 19 cooperate with each other, not only adjusting the angle of the UV lamp tube, but also adjusting the irradiation angle of the UV lamp tube, ensuring that it always irradiates the soil column sample according to its position. The angle adjustment mechanism 19 includes a mounting plate 191, with a rotating rod 192 on one side of the mounting plate 191. This rotating rod 192 serves as the main drive rod, receiving external driving power. The outer periphery of the rotating rod 192, located inside the mounting plate 191, is provided with... The rotating plate 193 and the rotating rod 192 can drive the rotating plate 193 to rotate circumferentially. A rotating shaft 194 is provided on the other side of the mounting plate 191. A key-shaped plate 195 is provided on the rotating shaft 194. A key-shaped groove 1951 is formed in the key-shaped plate 195, and a moving block 196 is provided in the key-shaped groove 1951. One side of the moving block 196 is rotatably connected to the rotating plate 193. When the rotating rod 192 drives the rotating plate 193 to rotate, one end of the rotating plate 193 acts on the moving block 196. On one hand, the moving block 196 moves horizontally relative to the key-shaped plate 195; on the other hand, it also drives the key-shaped plate 195 to rotate relative to the mounting plate 191 under the action of the rotating shaft 194. One side of the moving block 196 is provided with a ring-shaped key design. The movable frame 197 has racks 1971 inside, and the two sets of racks 1971 are centrally symmetrical about the geometric center of the movable frame 197. The movable frame 197 and the movable block 196 move horizontally relative to the key plate 195. It should be further noted that the racks 1971 in the two sets of angle adjustment mechanisms 19 are centrally symmetrical about the geometric center of the rotating sleeve 198. The end of the key plate 195 is provided with a rotating sleeve 198, and a miniature electromagnetic clutch 199 is provided inside the end of the rotating sleeve 198. One end of the miniature electromagnetic clutch 199 is provided with a drive gear 1910, which meshes with the racks 1971. The ultraviolet lamp is placed inside one side of the rotating sleeve 198. Regarding 9, it can rotate together with the rotating sleeve 198. When it is engaged, the drive gear 1910 can receive the driving power and act on the rotating sleeve 198 to make it rotate. When it is not working, the drive gear 1910 rotates relative to the rotating sleeve 198 without affecting the rotation process of the rotating sleeve 198. It should be further explained that when it is necessary to control the operation of the angle adjustment mechanism 19 to adjust the position of the ultraviolet lamp, a specific operating mode is provided: control the rotating rod 192 in the angle adjustment mechanism 19 located on the rear side to rotate counterclockwise, which drives the rotating plate 193 to rotate counterclockwise together. In this state, the miniature electromagnetic clutch 199 located on the rear side is engaged, while the miniature electromagnetic clutch 199 located on the front side is not engaged.The movable block 196 receives the driving power and moves relative to the key plate 195 towards a position closer to the rotating sleeve 198. Simultaneously, the key plate 195, receiving the driving power from the movable block 196, rotates clockwise under the action of the rotating shaft 194. During this process, the movable frame 197 also moves along with the movable block 196. Its internal and lower rack 1971 meshes with the drive gear 1910, and under the engagement of the electromagnetic clutch, drives the rotating sleeve 198 to rotate counterclockwise. That is, the downward rotation of the key plate 195 adjusts the downward rotation of the ultraviolet lamp, while the movable block 196 drives the ultraviolet lamp to rotate upward, ensuring it always irradiates the outer side of the soil column sample. When the rotating plate 193 rotates from horizontal to vertical, it reaches the farthest rotation position of the key plate 195. The moving block 196 moves to half of its maximum travel distance. As the rotating plate 193 continues to rotate, it rotates from vertical to horizontal. Due to the setting of the rack 1971 inside the moving frame 197, the drive gear 1910 disengages from the lower rack 1971 and re-engages with the upper rack 1971. As it runs, the engagement of the drive gear 1910 with the upper rack 1971 drives the rotating sleeve 198 from an upward angle to a horizontal position until the moving block 196 reaches its farthest travel distance. At this point, the ultraviolet lamp returns to its initial position, and the rotating plate... When the rotating plate 193 rotates to a horizontal position opposite to its initial state, and it is necessary to continue controlling the rotating plate 193 to rotate counterclockwise, the micro electromagnetic clutch 199 located on the rear side is disengaged, and the micro electromagnetic clutch located on the front side is engaged, so that the drive gear 1910 located on the front side can control the rotation of the rotating sleeve 198. Thus, as the rotating plate 193 rotates from a horizontal to an upward vertical state, the key plate 195 rotates diagonally upward. The rack 1971 located in the moving frame 197 on the front side, that is, the rack 1971 located away from the rotating sleeve 198 and located below in the moving frame 197, meshes with the drive gear 1910, and uses its return movement to drive the drive gear 1910. Gear 1910 and rotating sleeve 198 rotate clockwise until rotating plate 193 is fully rotated to the upper vertical position. As rotating plate 193 continues to rotate, it is driven to change from a vertical position back to its initial horizontal position. At this time, the rack 1971 at the lower part of the front moving frame 197 is not engaged with the drive gear 1910, but the rack 1971 above it is engaged with the connecting pipe. This drives rotating sleeve 198 to change from a downward-sloping position back to a horizontal position, thus completing one simulation. The irradiation direction of the ultraviolet lamp can be freely adjusted according to different experimental needs to meet various requirements. Furthermore, the simulation process is more realistic, greatly improving the functionality of the device.

[0041] To ensure the successful completion of the test, a method for conducting unsaturated soil freeze-thaw cycle tests with applied wicking geotextile 22 is provided, specifically utilizing an unsaturated soil freeze-thaw cycle device to conduct such tests, including the following steps:

[0042] S1: Prepare soil samples and fill them into the sample preparation device in layers. At the same time, arrange the core-absorbing geotextile 22 at the preset flange connection interface, so that one end is buried in the soil and the other end is led out.

[0043] S2: Bury the sensors of each data monitoring device into the soil column at the preset positions and connect them to the data acquisition instrument;

[0044] S3: Sealed environment device, which sets the target temperature, humidity and ultraviolet light intensity through the control terminal 21;

[0045] S4: Cool the soil column by using a temperature and humidity control device, start the freeze-thaw cycle process, and simulate groundwater recharge through a water supply device;

[0046] S5: During the freeze-thaw cycle, the temperature, volumetric water content and displacement data of the soil column are collected in real time through the data monitoring device;

[0047] S6: Record and analyze data through control terminal 21 to study the water and heat migration law of unsaturated soil under the action of wicking geotextile 22;

[0048] Specifically, the following steps should be taken: First, the device should be assembled and the soil column prepared. The sample preparation device should be placed inside the polyurethane foam constant temperature and humidity cabinet 1. The sample preparation device consists of four steel cylinders with an inner diameter of 20cm, a top and bottom height of 27cm, and two middle steel cylinders with a height of 23cm. The total height after connection is 100cm. When splicing the steel cylinders, ensure that the plexiglass observation windows within the 90° central angle range reserved on the side wall of each steel cylinder are aligned to form a continuous observation surface.

[0049] When installing the bottom sample tube (bottom tube 7), it should be fixed to the base plate 3 with bolts. Before filling with soil, permeable stones should be installed at the bottom of the soil and placed above the lower temperature control plate 15. Then, the soil sample should be filled in layers. During the filling process, according to the experimental design requirements, a temperature sensor 11 and a moisture content sensor 12 should be precisely embedded at specific locations in each sample tube to monitor the temperature and volumetric moisture content at different locations in the soil column in real time. The soil column filling process is as follows: take test soil material and fill it into the sample tube in layers. Install the force transmission rods according to different lengths under the jack 6 so that the force transmission rods can contact the soil material. Connect a steel plate with a diameter of 20cm to the bottom of the force transmission rod, which is consistent with the diameter of the soil column. Then, use the jack 6 to compact the soil material to ensure that the soil material compaction degree reaches 95%. By controlling the height and quality of each layer of soil material, the dry density in the soil column is kept consistent. The two sides of the middle tube 8 and the bottom tube 7 and the top tube are connected to the middle tube 8. The flanges used for connection between 9 are bolted together and sealed with gaskets. The core-absorbing geotextile 22 is placed between the upper and lower gaskets. The core-absorbing geotextile 22 should be cut into a semicircle with a diameter of 20cm at one end and a rectangle with a diameter of more than 30cm at the other end. The semicircular part of the core-absorbing geotextile 22 is laid flat to cover the bottom soil, and the rectangular end extends into the lighting device. After the core-absorbing geotextile 22 is applied, the flanges are tightened with bolts to prevent moisture from migrating outward from the connection of the sample tube. Then, the filling is continued to be carried out in layers in the sample tube. During the filling process, the preset compaction degree and moisture content requirements should be strictly followed. The soil is evenly filled into the mold cavity composed of multiple sample tubes from bottom to top using the layered compaction method. Each layer is compacted using jacks 6 and dowel bars to ensure that the internal structure of the soil column is uniform and meets the target state. The filling is carried out in the order from bottom to top until the top sample tube is filled. After the soil column sample is formed, the upper temperature control plate 14 is tightly placed at the open end of the top sample forming tube, and then a high-precision displacement sensor 13 is installed to monitor the overall vertical deformation of the soil column in real time during the freeze-thaw process. The gap between the temperature control plate and the top sample forming tube is sealed with plastic wrap to prevent the soil column from exchanging moisture with the external environment.

[0050] Secondly, all subsystems should be interconnected and debugged. The environmental device is connected to the temperature and humidity control device. The inlet and outlet of the upper and lower temperature control panels are connected to two high and low temperature circulating cold baths 16 outside the cabinet through insulated conduits. The conduits are tightly sealed with expanding foam where they pass through the cabinet. The program of the cold bath 16 is set through the control terminal 21. For example, the cycle process can be set as follows: rapid cooling to -15℃ and maintaining for 24 hours (freezing process), then heating to +10℃ and maintaining for 24 hours (thawing process), thus forming a freeze-thaw cycle. The illumination device is connected to the sample preparation device. An independent lamp box 18 is installed at the position directly opposite each wicking geotextile 22. Each lamp box 18 contains a UVA340 fluorescent ultraviolet lamp tube, whose spectrum can effectively simulate the ultraviolet band in sunlight. The lamp tube switching and light intensity can be adjusted through the control terminal 21. In this embodiment, each group of lamp tubes is set to provide a total radiation intensity of 450W / m² to simulate the strong ultraviolet environment of the plateau region. In addition, the angle adjustment mechanism 19 allows for adjustment of the UV lamp position according to different usage requirements, creating an angle that simulates sunlight between the UV lamp and the soil column sample to ensure effective UV irradiation while simulating real working conditions. The water supply device is connected to the sample preparation device, using a Marvin bottle 17 as a constant pressure water source. Specifically, the outlet of the Marvin bottle 17 is connected to the inlet of the bottom temperature control plate via a flexible hose. By adjusting the placement height of the Marvin bottle 17, a height difference is created between the top of the water outlet control pipe 172 and the bottom of the soil column, providing a constant water head to simulate capillary recharge of groundwater. The data monitoring device is connected to the control terminal 21, connecting the signal outputs of all temperature sensors 11, moisture content sensors 12, and displacement sensors 13 at the top of the soil column to a multi-channel data acquisition instrument. The data acquisition instrument communicates with the control terminal 21, setting timed acquisition intervals to achieve fully automatic, real-time synchronous monitoring and storage of temperature, moisture content, and deformation.

[0051] After completing the above steps, the door of the constant temperature and humidity chamber 1 should be closed, the button of the cold bath chamber 16 should be turned on, and the test should be started. The temperature circulation program of the cold bath chamber 16 and the ultraviolet radiation program of the light device should be started simultaneously through the control terminal 21, and the water supply of the Marshall bottle 17 should be confirmed to be unobstructed. Throughout the process, the test personnel can qualitatively observe the water migration in the soil column and the advancement of the wet front of the wicking geotextile 22 through the plexiglass observation window. At the same time, the data curves of each sensor are displayed and recorded in real time on the screen of the control terminal 21.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A freeze-thaw cycle device for unsaturated soil by applying wicking geotextile, characterized in that, The system includes a sample preparation device, an illumination device, an environmental device, a temperature and humidity control device, a water supply device, a data monitoring device, and a control terminal. The sample preparation device is used to receive the prepared soil column and place wicking geotextile on the soil column. The illumination device is used to irradiate the exposed portion of the wicking geotextile with ultraviolet light. The environmental device is used to provide a closed test environment with insulation and humidity for the sample preparation device. The temperature and humidity control device is used to regulate the temperature and humidity within the environmental device. The water supply device is used to provide a constant water head supply to the sample preparation device. The data monitoring device is used to monitor the changes in temperature, moisture content, and displacement inside the soil column in real time. The control terminal is electrically connected to the illumination device, temperature and humidity control device, and data monitoring device, and can freely control the test parameters and collect test data.

2. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 1, characterized in that, The environmental device includes a constant temperature and humidity cabinet, and a constant temperature and humidity control system is installed on the outside of the constant temperature and humidity cabinet.

3. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 2, characterized in that, The sample preparation device is placed in the constant temperature and humidity cabinet of the environmental device. The sample preparation device includes a base plate, a column above the base plate, a top plate above the column, a jack on the lower inner side of the top plate, and a bottom cylinder, a middle cylinder, and a top cylinder arranged sequentially from bottom to top above the base plate. There are at least two middle cylinders, which are connected to the bottom cylinder and the top cylinder respectively by flanges. The bottom cylinder and the top cylinder in the sample preparation device have the same height and are greater than the height of the middle cylinder. Soil column samples are placed in the middle cylinder, the bottom cylinder, and the top cylinder. One end of the geotextile is sealed inside the soil column sample, and the other end extends into the light irradiation device. The side walls of the bottom cylinder, the middle cylinder, and the top cylinder are also provided with transparent observation windows.

4. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 3, characterized in that, The data monitoring device includes a temperature sensor, a moisture content sensor, and a displacement sensor installed at different locations within the soil column sample, which are used to monitor the state of the soil column's temperature field, moisture field, and deformation field.

5. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 4, characterized in that, The temperature and humidity control device includes an upper temperature control plate installed at the top of the soil column sample inside the top cylinder and a lower temperature control plate installed at the bottom of the soil column sample inside the bottom cylinder. The temperature and humidity control device also includes a cold bath box installed outside the environmental device.

6. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 5, characterized in that, The water supply device is a Marshall bottle, which includes a water storage bottle, a water outlet control pipe, and an air compensation pipe. By adjusting the overall placement height of the Marshall bottle, a continuously adjustable constant water head is provided to the system.

7. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 6, characterized in that, Multiple lighting devices are provided, and they are respectively located on one side of the middle cylinder and the top cylinder. The lighting device includes a lamp box, and the lamp box is provided with an angle adjustment mechanism that can be freely adjusted according to different irradiation angles. The adjustment end of the angle adjustment mechanism is provided with an ultraviolet lamp tube.

8. The unsaturated soil freeze-thaw cycle device for applying wicking geotextile according to claim 7, characterized in that, Two sets of angle adjustment mechanisms are provided at the front and rear, and are centrally symmetrical about the geometric center of the lamp box. They are located inside the lamp box. The angle adjustment mechanism includes a mounting plate. A rotating rod is provided on one side of the mounting plate. A rotating plate is provided on the outer periphery of the rotating rod located inside the mounting plate. A rotating shaft is provided on the other side of the mounting plate. A key-shaped plate is provided on the rotating shaft. A key-shaped groove is opened in the key-shaped plate. A moving block is provided in the key-shaped groove, and one side of the moving block is rotatably connected to the rotating plate. A moving frame with a ring-shaped key design is provided on one side of the moving block. A rack is provided in the moving frame. Two sets of racks are centrally symmetrical about the geometric center of the moving frame. A rotating sleeve is provided at the end of the key-shaped plate. A miniature electromagnetic clutch is provided at the end of the rotating sleeve. A drive gear is provided at one end of the miniature electromagnetic clutch and meshes with the rack. The ultraviolet lamp is placed inside one side of the rotating sleeve.

9. A method for testing unsaturated soil freeze-thaw cycles using wicking geotextiles, characterized in that, Conducting a freeze-thaw cycle test on unsaturated soil using the unsaturated soil freeze-thaw cycle device described in any of claims 1-8, with the following steps: S1: Prepare soil samples and fill them into the sample preparation device in layers. At the same time, arrange wicking geotextile at the preset flange connection interface, so that one end is buried in the soil and the other end is led out. S2: Bury the sensors of each data monitoring device into the soil column at the preset positions and connect them to the data acquisition instrument; S3: Sealed environment device, which sets the target temperature, humidity and ultraviolet light intensity through the control terminal; S4: Cool the soil column by using a temperature and humidity control device, start the freeze-thaw cycle process, and simulate groundwater recharge through a water supply device; S5: During the freeze-thaw cycle, the temperature, volumetric water content and displacement data of the soil column are collected in real time through the data monitoring device; S6: By recording and analyzing data through the control terminal, the hydrothermal migration law of unsaturated soil under the action of wicking geotextile is studied.

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