An experimental device and method for the migration of water vapor to ice in subgrade fillers in cold regions

Abstract

The present invention provides a test device and a test method for water-vapor migration and ice formation of subgrade fillers in cold regions. The test device includes a model box, above which is a load loading device, and the bottom of the model box is connected to a vibration device. The inner cavity of the model box includes two cold bath cavities, a soil specimen cavity, and a gas storage cavity. The two cold bath cavities are communicated with a cold bath device, and the gas storage cavity is communicated with a humidifier. The top of the model box is provided with a sealing cover, the outer diameter of the sealing cover is the same as the inner diameter of the model box, and the load loading device drives the sealing cover to move vertically in the inner cavity of the model box. A plurality of sensor groups are arranged in the soil specimen cavity, and the sensor groups and the load loading device are both electrically connected to the processor. The test device of the present invention has a simple structure, is convenient to install, and has flexible test operations, and can meet the test conditions for the water-vapor migration and frost heaving mechanism and performance evolution of subgrade fillers such as railways and expressways.

Description

Technical Field

[0001] The present invention belongs to the field of instrument and equipment development, and particularly relates to a test device and test method for water-vapor migration and ice formation of subgrade fillers in cold regions. Background Technique

[0002] With the needs of national development and the rapid economic growth in the Qinghai-Tibet alpine region, some highway and railway engineering projects have to cross permafrost regions. Affected by the special properties of permafrost, the diseases of transportation infrastructure in permafrost regions are more serious and complex than those in ordinary regions, and the economic losses caused by diseases are huge every year. Scientifically revealing the dynamic distribution characteristics of the subgrade moisture field under the coupling action of temperature and traffic load, and reducing or preventing the occurrence of frost heaving and thaw settlement diseases of the subgrade are of great significance for improving the stability and economy of transportation infrastructure in the Qinghai-Tibet region.

[0003] The subgrade is the basic structure that supports the superstructure and running vehicles, and is long-term affected by the coupling action of complex environment and traffic load, thus various adverse engineering diseases will occur. The traditional view holds that in permafrost or seasonal frozen soil regions, the formation of ice lenses and frost heaving are mainly attributed to the migration of liquid water in the subgrade soil under the temperature gradient, while the migration of gaseous water and its liquefaction and sublimation account for a very low proportion in the ice formation process and can be ignored. However, with the large-scale development of transportation infrastructure construction in cold and arid regions in northern China, the latest engineering practice has found that even when the soil water content is very low and far from the groundwater recharge, the railways, highways and other infrastructure in these regions still have frost damage problems that cannot be explained by traditional theories, which provides an opportunity for studying the mechanism of gaseous water migration and ice formation in soil.

[0004] The migration of water and vapor in soil induces subgrade frost heaving. Especially during the ice formation process, not only does the liquid water in the soil pores migrate and flow, but also the gaseous water migrates. Domestic and foreign scholars first adopted some scaled model test methods to investigate the influence laws of internal and external factors such as particle gradation, density, void ratio, temperature and overlying load on water-vapor migration and ice formation, but lacked a comprehensive, accurate and systematic revelation of problems such as the disaster-causing mechanism of water-vapor migration frost damage diseases and the evolution law of service performance; secondly, although domestic and foreign scholars have gradually realized that water-vapor migration is the key inducement for the formation of ice lenses in soil and the occurrence of frost damage diseases, there is no consensus on how to quickly detect and identify and adopt scientific and effective prevention and control methods to inhibit the occurrence of water-vapor migration frost heaving; finally, domestic and foreign scholars have successively developed some model test devices for water-vapor migration and ice formation focusing on this problem, but due to the inconsistent temperature control methods, air supply and boundary conditions adopted by different scholars, the discreteness of research results is relatively large and the reliability cannot be verified.

[0005] In terms of temperature control technology, the Chinese utility model patent CN214585421U proposed a soil frost heave water migration test device, whose temperature control module is provided by frozen sodium chloride ice packs in a metal container. Its obvious defect is the poor temperature control accuracy, because the refrigeration capacity of the sodium chloride solution will gradually decrease during the heat exchange process. At the same time, in order to simulate the low ground temperature or temperature gradient conditions in the real roadbed, a large number of sodium chloride ice packs need to be made before the test, and the process is cumbersome. In addition, in terms of loading conditions, the Chinese invention patent CN106525661A discloses a temperature-controlled soil gaseous water migration measurement device, which can accurately control the temperature and relative humidity of the specimen, but the device itself cannot apply static and dynamic loads, which is significantly different from the stress and strain conditions borne by the real roadbed, and the engineering applicability of relevant achievements is difficult to be guaranteed. Although the Chinese invention patent CN104655823A proposed a frost heave meter considering the action of overlying load, its loading method is to change the number of weights on the soil surface. Therefore, this type of frost heave meter is only applicable to analyzing the frost heave problems of soil under some static loads, and is helpless when studying the frost heave characteristics of water and gas migration in the roadbed under the coupled action of long-term structural static load and vehicle dynamic load.

[0006] It can be seen from this that in the study of the frost heave mechanism of the roadbed, there is currently a lack of an effective and low-cost physical model test system for water and gas migration and ice formation, which is used to systematically study the characteristics of water and gas migration in soil under the coupled action of environment-traffic load, as well as the whole-phase change ice formation disaster-causing mechanism and disaster-causing process such as water and gas solidification and sublimation. The construction of a test device for water and gas migration and ice formation of subgrade fillers in cold regions can not only provide verification for numerical simulation, but more importantly, it is of great academic and engineering application value for revealing the gestation and disaster-causing mechanism of water and gas migration frost heave diseases in the roadbed and the law of performance evolution, expounding the formation, evolution of the deformation and strength characteristics of frost-damaged roadbeds and their influence mechanism on engineering, and improving the construction and maintenance capabilities of transportation infrastructure in cold regions and serving the high-quality development of transportation in the Qinghai-Tibet Plateau. Summary of the Invention

[0007] The present invention aims to provide a test device and test method for simulating water and gas migration and ice formation in frozen soil roadbeds. The test device is convenient, fast and reliable in precision, and the test method can carry out model tests under various combinations of simulated dynamic loads, temperature gradients, water and gas supply conditions and soil physical properties at the same time.

[0008] To solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0009] A test device for water and gas migration and ice formation of subgrade fillers in cold regions, the test device includes a model box, a load loading device is arranged above the model box, and a vibration device is connected to the bottom of the model box;

[0010] The inner cavity of the model box includes a first cold bath cavity at the bottom and a soil specimen cavity at the upper part. A gas storage cavity is provided between the first cold bath cavity and the soil specimen cavity. The gas storage cavity is communicated with the soil specimen cavity through a porous plate, and is separated from the first cold bath cavity by a sealing partition. The gas storage cavity is communicated with a humidifier.

[0011] A sealing cover is provided at the top of the model box. The load loading device drives the sealing cover to move vertically within the inner cavity of the model box. A second cold bath cavity is provided inside the sealing cover. Both the first cold bath cavity and the second cold bath cavity are communicated with a cold bath device.

[0012] A plurality of sensor groups are provided in the soil specimen cavity. Both the sensor groups and the load loading device are electrically connected to the processor.

[0013] Thus, the load loading device above the model box and the vibration device at the bottom of the model box respectively simulate and apply vibration loads. Through the first cold bath cavity and the second cold bath cavity at both ends of the soil specimen cavity, the test soil sample is cooled, and water vapor is added into the gas storage cavity to simulate the water vapor migration phenomenon in frozen soil subgrade, so as to study the factors and water vapor migration mechanism that induce the water vapor migration phenomenon in frozen soil subgrade under various combinations of dynamic loads, temperature, humidity and soil properties.

[0014] Further, the load loading device includes a platform above the model box. A screw jack is provided on the upper end surface of the platform. A screw rod is provided on the screw jack. The screw rod penetrates through the platform and is connected to the sealing cover below. The screw jack controls the movement of the screw rod through a driving device.

[0015] Further, the driving device includes a motor. The motor is connected to the screw jack through a coupling. The motor is electrically connected to a servo driver. The servo driver is electrically connected to the processor. An EMC filter and an air switch are installed between the main power supply interface of the servo driver and the three-phase alternating current power supply.

[0016] Still further, the lower end surface of the sealing cover is a loading plate, and the loading plate has the same inner diameter as the model box.

[0017] The upper end surface of the sealing cover is connected to the load loading device. A second cold bath cavity liquid outlet and a second cold bath cavity liquid inlet are provided on the upper end surface of the sealing cover. The second cold bath cavity liquid outlet and the second cold bath cavity liquid inlet respectively communicate the second cold bath cavity with the cold bath device through pipelines.

[0018] Still further, a displacement sensor is provided on the upper end surface of the sealing cover.

[0019] Furthermore, the vibration device includes a vibrator, a base panel is provided above the vibrator, a compression spring is provided between the base panel and the vibrator, a clamp is provided on the upper end surface of the base panel, and the bottom of the model box is installed on the base panel through the clamp.

[0020] Furthermore, a first cold bath cavity outlet and a first cold bath cavity inlet are provided on the side wall of the model box for the first cold bath cavity, and the first cold bath cavity outlet and the first cold bath cavity inlet communicate the first cold bath cavity with the cold bath through a pipeline;

[0021] A wire passing hole is also provided on the side wall of the model box, and the sensor group is electrically connected to the processor through the wire passing hole. The sensor group includes an earth pressure sensor, a pore water pressure sensor, a humidity sensor, and a temperature sensor.

[0022] In addition, the outer periphery of the model box is wrapped with heat insulating cotton.

[0023] Based on the same inventive concept, the present invention also provides a method for conducting an experiment using the above-described experimental device for water-vapor migration and ice formation in cold region subgrade fillers, including the following steps:

[0024] Step 1: Calculate and weigh the test soil sample, fill the test soil sample into the soil specimen cavity, and bury the sensor group at the designed height position. After reaching the designed sample filling height, the filling of the test soil sample is completed;

[0025] Step 2: After installing the sealing cover, start the load loading device, control the load loading device through the processor, so that the load loading device drives the sealing cover to gradually descend. When the sealing cover descends to contact the test soil sample, turn off the load loading device;

[0026] Step 3: Turn on the cold bath, so that the cold bath liquid flows into the first cold bath cavity and the second cold bath cavity;

[0027] Step 4: After the temperature of the test soil sample no longer changes, turn on the humidifier. After the water vapor enters the gas storage cavity, it enters the soil specimen cavity through the through holes on the porous plate;

[0028] Step 5: Start the load loading device and the vibration device, and record in real time the magnitude, frequency, amplitude of the load, and the data output by the sensor group;

[0029] Step 6: After the number of loading cycles reaches the designed value of the test plan, turn off the test device and end the test.

[0030] Preferably, before step 2, a layer of vaseline is evenly applied on the outer side wall surface of the sealing cover.

[0031] The test device and test method for water-vapor migration and ice formation in subgrade fillers in cold regions of the present invention have the following advantages:

[0032] 1). Using the device of the present invention, model test research on the induced water-vapor migration phenomenon in frozen soil subgrade under various combinations of simulated dynamic loads, temperature gradients, moisture conditions, and soil physical properties can be carried out. Different magnitudes, frequencies, and forms of dynamic loads, and test soil samples with various particle compositions, gradations, saturations, and densities can be simulated.

[0033] 2). The test device applies vertical pressure using a motor and achieves the purpose of simulating dynamic loads through combination with a vibrator. The motor realizes closed-loop control of position, speed, and torque, overcomes the problem of step motor out-of-step, has high precision, and operates smoothly at low speeds.

[0034] 3). The base of the test device designed with a vibrator can set different vibration frequencies according to the test design scheme to simulate different traffic volumes. At the same time, compression springs are set to avoid the separation between the rigid loading plate and the soil sample surface during the test process, ensuring the continuous application of dynamic loads.

[0035] 4). The air storage cavity and porous plate inside the test model box realize the simulation of water-vapor recharge inside the subgrade soil body, and at the same time, the height of the test soil sample and the temperature difference between the top and bottom of the soil sample can be flexibly controlled.

[0036] 5). The device of the present invention has a simple structure, is convenient to install, and has flexible test operations, meeting various test conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of a test device for simulating the water-vapor migration phenomenon in a frozen soil subgrade of the present invention;

[0038] Figure 2 is Figure 1 a schematic cross-sectional view of the model box Ⅰ—Ⅰ in

[0039] Figure 3 is a schematic structural diagram of the sealing cover of the present invention.

[0040] Description of the markings in the figure: 1. Platform; 2. Column; 3. Base; 4. Lead screw; 5. Lead screw lift; 6. Flange; 7. Load cell; 8. Loading rod; 9. Outlet of the second cold bath chamber; 10. Liquid outlet control valve of the second cold bath chamber; 11. Displacement sensor; 12. Inlet of the second cold bath chamber; 13. Liquid inlet control valve of the second cold bath chamber; 14. Second cold bath chamber; 15. Insulating cotton cylinder; 16. Model box; 17. Soil sample chamber; 18. Perforated plate; 19. Gas storage chamber; 20. Sealing partition; 21. First cold bath chamber; 22. Liquid inlet control valve of the first cold bath chamber; 23. Inlet of the first cold bath chamber; 24. Liquid outlet control valve of the first cold bath chamber; 25. Outlet of the first cold bath chamber; 26. Water and gas inlet valve; 27. Water and gas inlet pipe; 28. Fixture; 29. Vibrator; 30. Base panel; 31. Compression spring; 32. Coupling; 33. Motor; 34. Cable; 35. Servo drive; 36. EMC filter; 37. Air switch; 38. Transformer; 39. Processor; 40. Humidifier outlet control valve; 41. Humidifier; 42. Support of the heat preservation cabinet; 43. Heat preservation cabinet; 44. Cold bath; 45. Liquid inlet control valve of the cold bath; 46. Liquid outlet control valve of the cold bath; 47. Waterproof connector; 48. Earth pressure sensor; 49. Pore water pressure sensor; 50. Humidity sensor; 51. Temperature sensor; 52. Insulating cotton; 53. Vibration device; 54. Loading plate; 55. Sensor group; 56. Sealing cover; 57. Load loading device; 58. Threading hole; 59. Driving device. Detailed implementation mode

[0041] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. For the convenience of narration, words such as "upper", "lower", "left", and "right" in the following text only represent the same as the upper, lower, left, and right of the drawings themselves, and do not limit the structure.

[0042] A test device for water-vapor migration and ice formation of subgrade fillers in cold regions in this embodiment is as Figure 1 shown. The test device includes a model box 16, above which is a load loading device 57, and the bottom of the model box 16 is connected to a vibration device 53.

[0043] The model box 16 is a cylindrical transparent plexiglass barrel, which is used to fill the test soil sample, and the height of the filled test soil sample, the movement of the test soil sample particles during the test, and the changes such as the freezing of water in the soil body can be conveniently observed through the transparent side wall of the model box 16.

[0044] As Figure 1 and Figure 2As shown, a heat-insulating cotton cylinder 15 is wrapped around the outer periphery of the model box 16. The inner cavity of the model box 16 includes a first cold bath cavity 21 at the bottom and a soil specimen cavity 17 at the upper part. A plurality of sensor groups 55 are arranged in the soil specimen cavity 17. The sensor group 55 includes an earth pressure sensor 48, a pore water pressure sensor 49, a humidity sensor 50, and a temperature sensor 51. The sensor group 55 and the load loading device 57 are both electrically connected to the processor 39. Preferably, the processor 39 is a computer. A wire passing hole 58 is formed in the side wall of the model box 16, and a waterproof joint 47 is arranged at the wire passing hole 58. The sensor group 55 is electrically connected to the processor 39 through the wire passing hole 58.

[0045] In this embodiment, according to the test requirements, a series of earth pressure sensors 48, pore water pressure sensors 49, humidity sensors 50, and temperature sensors 51 for measuring the stress distribution, pore water pressure, temperature, and humidity in the soil are pre-buried at different thicknesses of the test soil sample, and their leads are led out through the wire passing hole 58.

[0046] As Figure 1 and Figure 3 shown, a gas storage cavity 19 is provided between the first cold bath cavity 21 and the soil specimen cavity 17. The gas storage cavity 19 is communicated with the soil specimen cavity 17 through a porous plate 18. The material of the porous plate 18 is transparent organic glass. Circular holes are arranged on the surface of the porous plate 18 in a matrix form, and the diameter of the circular holes can be 3 - 5 mm. If the diameter is too small, it will affect the water and gas passing efficiency, and it is easy to form blockage after the soil particles fall. If the diameter is too large, the soil particles may leak out from the circular holes and stay in the gas storage cavity 19. The gas storage cavity 19 is separated from the first cold bath cavity 21 by a sealing partition 20. A pillar with a certain height is distributed on the sealing partition 20 to support the porous plate 18. A circular hole is drilled in the side wall of the model box 16 at the position of the gas storage cavity 19, and a waterproof joint 47 is arranged at the circular hole. The water and gas inlet pipe 27 connected to the humidifier 41 passes through the circular hole to transmit the water and gas into the gas storage cavity 19. By adjusting the water and gas inlet valve 26, the humidifier outlet control valve 40, and the humidifier 41, the humidity in the model box 16 can be changed.

[0047] The gas storage cavity 19 communicates with the humidifier 41. A sealing cover 56 is provided on the top of the model box 16. The sealing cover 56 is provided with heat-insulating cotton 52, and a second cold bath cavity 14 is arranged inside the sealing cover 56. Both the first cold bath cavity 21 and the second cold bath cavity 14 communicate with the cold bath device 44. Preferably, the first cold bath cavity 21 and the second cold bath cavity 14 are respectively connected to a cold bath device 44. The upper end surface of the sealing cover 56 is connected to the load loading device 57. A second cold bath cavity liquid outlet 9 and a second cold bath cavity liquid inlet 12 are provided on the upper end surface of the sealing cover 56. Waterproof connectors 47 are provided at the second cold bath cavity liquid outlet 9 and the second cold bath cavity liquid inlet 12. The second cold bath cavity liquid outlet 9 and the second cold bath cavity liquid inlet 12 respectively communicate the second cold bath cavity 14 with the cold bath device 44 through pipelines, and corresponding second cold bath cavity liquid outlet control valves 10 and second cold bath cavity liquid inlet control valves 13 are provided on the pipelines to control the flow rate of the refrigerant and prevent backflow. The first cold bath cavity 21 is provided with a first cold bath cavity liquid outlet 25 and a first cold bath cavity liquid inlet 23 on the side wall of the model box 16. The first cold bath cavity liquid outlet 25 and the first cold bath cavity liquid inlet 23 communicate the first cold bath cavity 21 with the cold bath device 44 through pipelines, and corresponding first cold bath cavity liquid outlet control valves 24 and first cold bath cavity liquid inlet control valves 22 are provided on the pipelines to control the flow rate of the refrigerant and prevent backflow.

[0048] As Figure 1 shown, the load loading device 57 includes a platform 1 located above the model box 16. A screw jack 5 is provided on the upper end surface of the platform 1. A screw rod 4 is provided on the screw jack 5. The screw rod 4 penetrates through the platform 1 and is connected to the sealing cover 56 below. The screw jack 5 controls the movement of the screw rod 4 through a driving device 59. The driving device 59 includes a motor 33. The motor 33 is connected to the screw jack 5 through a coupling 32. The motor 33 is electrically connected to a servo driver 35. The servo driver 35 is electrically connected to a processor 39. An EMC filter 36 and an air switch 37 are installed between the main power interface of the servo driver 35 and the three-phase AC power supply.

[0049] In this embodiment, a base 3 is provided below the model box 16. There are columns 2 between the platform and the base. The columns 2 can be fixed on the upper surface of the base 3 by welding or bolt connection, mainly for bearing the self-weight of the test device installed on the platform 1. And it is integrally fixed in the heat preservation cabinet 43, so that the test device has a good heat preservation effect. The bottom of the heat preservation cabinet 43 is provided with a heat preservation cabinet support 42. A screw jack 5 is installed at the center position of the platform 1 by bolts. The servo driver 35 is connected to the motor 33 through a cable 34, provides power supply and digital signals for the motor 33, and controls the motor 33 in three ways of position, speed and torque to achieve high-precision positioning of the transmission system. An EMC filter 36 and an air switch 37 are installed between the main power interface of the servo driver 35 and the three-phase alternating current power supply. The EMC filter 36 can eliminate strong electromagnetic interference and electric spark interference in the circuit. The air switch 37 will automatically disconnect when the current in the circuit is too large to cut off the circuit.

[0050] In this embodiment, the screw 4 in the screw jack 5 passes through the center of the platform 1. A flange 6, a load cell 7, and a loading rod 8 are sequentially installed at the lower end of the screw 4. The lower end of the loading rod 8 is connected to the sealing cover 56. A displacement sensor 11 is provided on the upper end surface of the sealing cover 56. The displacement sensor 11 is placed on the upper surface of the sealing cover 56 and is hinged and fixed to the column 2. The displacement sensor 11 and the sealing cover 56 move up and down together in the vertical direction to measure the amplitude of the dynamic load. The outer diameter of the sealing cover 56 is the same as the inner diameter of the model box 16. The load loading device 57 drives the sealing cover 56 to move vertically in the inner cavity of the model box 16. To avoid scratching the inner wall of the model box 16 by the edge of the sealing cover 56 and weakening the friction effect with the model box 16, a layer of vaseline can be evenly applied on the outside of the sealing cover 56 during the test. Specifically, the lower end surface of the sealing cover 56 is a loading plate 54, and the loading plate 54 has the same inner diameter as the model box 16. The above-mentioned loading rod 8 and the lower loading plate 54 of the sealing cover 56 are made of aluminum. Its advantages are light texture, easy machining, and can be customized into different specifications of loading mechanisms according to test needs. And the thermal conductivity of aluminum is better than that of iron, which can transfer the low temperature of the second cold bath cavity 14 of the sealing cover to the upper surface of the test soil sample more quickly and efficiently.

[0051] As Figure 1 shown, the vibration device 53 includes a vibrator 29. There is a base panel 30 above the vibrator 29. There is a compression spring 31 between the base panel 30 and the vibrator 29. A fixture 28 is provided on the upper end surface of the base panel 30. The bottom of the model box 16 is installed on the base panel 30 through the fixture 28.

[0052] In this embodiment, the vibrator 29 is fixedly installed on the base 3 by bolts, and the vibration frequency can be adjusted according to the test requirements. Together with the load loading device 57, the purpose of simulating dynamic loads is achieved. The base panel 30 is connected to the vibrator 29 through a compression spring 31 to achieve the purpose of transmitting vibration. The fixture 28 is fixedly welded on the base panel 30, and mounting holes are provided at corresponding positions on the side wall of the model box 16 and the locking fixture 28. The inner surface of the mounting hole is tapped so that it can be fixed to the locking fixture 28 by bolts to achieve the purpose of fixing the model box 16.

[0053] The method of conducting tests using a test device for water-vapor migration and ice formation in subgrade fillers in cold regions according to this embodiment specifically includes the following steps:

[0054] Step 1: Check whether all structural devices of the entire test system are intact, including the working performance of the motor 33 and the vibrator 29, whether the model box 16 leaks, whether there are damages to various liquid inlet and gas inlet pipes, and the sensitivity calibration and calibration of sensors, etc.

[0055] Step 2: Fix the model box 16 on the base panel 30 through the fixture 28.

[0056] Step 3: Sequentially place the sealing partition 20 and the porous plate 18 into the model box 16. At this time, an air storage cavity 19 is formed between the sealing partition 20 and the porous plate 18. Connect the air storage cavity 19 to the humidifier 41 through the water-vapor inlet pipe 27, and connect the second cold bath cavity liquid inlet 12, the second cold bath cavity liquid outlet 9, the first cold bath cavity liquid inlet 23, and the first cold bath cavity liquid outlet 25 to the cold bath 44. At this time, the control valves in each pipeline are all in the closed state.

[0057] Step 4: Calculate and weigh the test soil sample, and uniformly fill the test soil sample into the soil sample cavity 17 of the model box 16 using the sand-falling method. Bury the earth pressure sensor 48, the pore water pressure sensor 49, the humidity sensor 50, and the temperature sensor 51 at the designed height position. The leads of the sensors are all led out through drilling holes in the side wall of the model box 16 and sealed with a waterproof joint 47. When loading the sample, pay close attention to the height and surface flatness of the test soil sample. When the designed loading height is reached, the filling of the test soil sample is completed.

[0058] Step 5: Apply a layer of vaseline evenly on the side of the sealing cover 56. After aligning the sealing cover 56 with the model box 16, start the motor 33, and control the motor 33 through the processor 39 and the servo driver 35 to gradually lower the lead screw 4 in the lead screw lift 5, thereby driving the sealing cover 56 to contact the surface of the test soil sample. When the compression spring 31 of the base shows a slight compression deformation, that is, the surface of the test soil sample is in close contact with the loading plate 54, turn off the motor 33 and stabilize the position of the model box 16 for marking.

[0059] Step 6: Turn on the cold bath 44, open each control valve connected to the cold bath 44, and input the refrigerant at the temperature specified in the test plan into the first cold bath chamber 21 and the second cold bath chamber 14 to form a temperature difference in the test soil sample in the vertical direction.

[0060] Step 7: When the temperature measured by the temperature sensor 51 in the test soil sample no longer changes, it indicates that the temperature gradient in the test soil sample has stabilized. Then turn on the humidifier 41, the water-vapor intake valve 26, and the humidifier outlet control valve 40 to allow the water-vapor to enter the gas storage chamber 19 and be transmitted to the bottom of the test soil sample through the round holes on the porous plate 18.

[0061] Step 8: According to the magnitude and frequency of the dynamic load designed in the test plan, start the motor 33 and the vibrator 29. The motor 33 is connected to the screw jack 5 through the coupling 32, so as to generate a vertical load and evenly transmit the load to the test soil sample through the loading plate 54. During the loading process, the compression spring 31 on the vibrator 29 should be in a compressed state, realizing the use of the elastic constraint structure of the test device, which not only improves the overall stability of the loading structure but also ensures the close contact between the loading plate 54 and the surface of the test soil sample to achieve continuous loading.

[0062] Step 9: During the test, record in real time the magnitude, frequency, and amplitude of the dynamic load, the dynamic stress value in the test soil sample along the vertical direction, the pore water pressure, temperature, and humidity in the soil at different layers, and after the test, analyze the distance from the position where the ice lens appears to the surface of the test soil sample and the thickness. After the number of loading cycles reaches the value designed in the test plan, turn off the power supply of each device and the valve to end the test.

[0063] It can be understood that the present invention is described through some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A test device for water vapor migration and ice formation in subgrade fillers in cold regions, characterized in that, It includes a model box (16), above which is a load loading device (57), and the bottom of the model box (16) is connected to a vibration device (53); The inner cavity of the model box (16) includes a first cold bath cavity (21) at the bottom and a soil specimen cavity (17) at the upper part. Between the first cold bath cavity (21) and the soil specimen cavity (17) is a gas storage cavity (19). The gas storage cavity (19) is communicated with the soil specimen cavity (17) through a porous plate (18). The gas storage cavity (19) is separated from the first cold bath cavity (21) by a sealing partition (20). The gas storage cavity (19) is communicated with a humidifier (41); The top of the model box (16) is provided with a sealing cover (56). The load loading device (57) drives the sealing cover (56) to move vertically in the inner cavity of the model box (16). Inside the sealing cover (56) is a second cold bath cavity (14). Both the first cold bath cavity (21) and the second cold bath cavity (14) are communicated with a cold bath device (44); Inside the soil specimen cavity (17) are provided multiple sensor groups (55). Both the sensor groups (55) and the load loading device (57) are electrically connected to a processor (39); The load loading device (57) includes a platform (1) above the model box (16). On the upper end face of the platform (1) is installed a screw jack (5). On the screw jack (5) is a screw rod (4). The screw rod (4) penetrates through the platform (1) and is connected to the sealing cover (56) below. The screw jack (5) controls the movement of the screw rod (4) through a driving device (59); The vibration device (53) includes a vibrator (29). Above the vibrator (29) is a base panel (30). Between the base panel (30) and the vibrator (29) is a compression spring (31). On the upper end face of the base panel (30) is a fixture (28). The bottom of the model box (16) is installed on the base panel (30) through the fixture (28).

2. The ice formation test device for water vapor migration in subgrade fillers in cold regions according to claim 1, wherein, The driving device (59) includes a motor (33). The motor (33) is connected to the screw jack (5) through a coupling (32). The motor (33) is electrically connected to a servo driver (35). The servo driver (35) is electrically connected to the processor (39). Between the main power interface of the servo driver (35) and the three-phase alternating current power supply are installed an EMC filter (36) and an air switch (37).

3. The test device for water-vapor migration and ice formation in subgrade fillers in cold regions according to claim 1, characterized in that, The lower end face of the sealing cover (56) is a loading plate (54), and the loading plate (54) has the same inner diameter as the model box (16); The upper end face of the sealing cover (56) is connected to the load loading device (57). On the upper end face of the sealing cover (56) are opened a second cold bath cavity liquid outlet (9) and a second cold bath cavity liquid inlet (12). The second cold bath cavity liquid outlet (9) and the second cold bath cavity liquid inlet (12) respectively connect the second cold bath cavity (14) with the cold bath device (44) through pipes.

4. The test device for water-vapor migration and ice formation in subgrade fillers in cold regions according to claim 1 or 3, characterized in that, A displacement sensor (11) is provided on the upper end face of the sealing cover (56).

5. The test device for water-vapor migration and ice formation of subgrade fillers in cold regions according to any one of claims 1-3, characterized in that, The first cold bath cavity (21) is provided with a first cold bath cavity liquid outlet (25) and a first cold bath cavity liquid inlet (23) on the side wall of the model box (16). The first cold bath cavity liquid outlet (25) and the first cold bath cavity liquid inlet (23) communicate the first cold bath cavity (21) with the cold bath device (44) through pipelines; The side wall of the model box (16) is further provided with a wire passing hole (58). The sensor group (55) is electrically connected to the processor (39) through the wire passing hole (58). The sensor group (55) includes an earth pressure sensor (48), a pore water pressure sensor (49), a humidity sensor (50), and a temperature sensor (51).

6. The ice formation test device for water vapor migration in subgrade fillers in cold regions according to any one of claims 1 to 3, characterized in that, The outer periphery of the model box (16) is wrapped with heat insulating cotton.

7. A testing method for the water-vapor migration and ice formation test device of the subgrade filler in cold regions as described in any one of claims 1 to 6, characterized in that, It includes the following steps: Step 1: Calculate and weigh the test soil sample, fill the test soil sample into the soil specimen cavity (17), and bury the sensor group (55) at the designed height position. After reaching the designed sample filling height, the filling of the test soil sample is completed; Step 2: After installing the sealing cover (56), start the load loading device (57). Control the load loading device (57) through the processor (39) to drive the sealing cover (56) to gradually descend. When the sealing cover (56) descends to contact the test soil sample, turn off the load loading device (57); Step 3: Turn on the cold bath device (44) to make the cold bath liquid flow into the first cold bath cavity (21) and the second cold bath cavity (14); Step 4: After the temperature of the test soil sample no longer changes, turn on the humidifier (41). After the water vapor enters the air storage cavity (19), it enters the soil specimen cavity (17) through the through holes on the porous plate (18); Step 5: Start the load loading device (57) and the vibration device (53), and record the magnitude, frequency, amplitude of the load, and the data output by the sensor group (55) in real time; Step 6: After the number of loading cycles reaches the designed value of the test scheme, turn off the test device to end the test.

8. The test method according to claim 7, wherein Before step 2, apply a layer of vaseline evenly on the outer side wall surface of the sealing cover (56).

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