Multi-dimensional multi-field coupling high-pressure frozen soil frost heaving and thaw collapse test device

Abstract

The invention provides a multi-dimensional multi-field coupling high-pressure frozen soil frost heaving and thaw collapse test device, which belongs to the technical field of frozen soil, and comprises a loading frame, a loading system, a water replenishing system, a temperature control system, a control system, a test box and a sensor group electrically connected with the control system, the temperature control system comprises a multi-channel temperature adjusting control device, a thermostatic bath A, a thermostatic bath B and a thermostatic water tank which are electrically connected with the control system, the thermostatic water tank comprises a plurality of thermotanks which are sequentially arranged from bottom to top, and the thermostatic bath A and the thermostatic bath B are communicated with the multi-channel temperature adjusting control device through pipelines. The multi-channel temperature regulation control device is respectively communicated with the plurality of thermotanks through pipelines with valves, and the plurality of thermotanks are respectively communicated with the thermostatic bath A and the thermostatic bath B through pipelines with peristaltic pumps. According to the invention, frost heaving and thaw collapse behaviors of frozen soil under different environmental conditions can be evaluated more comprehensively, and more real and reliable test data can be provided.

Description

Technical Field

[0001] This invention relates to a multidimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device, belonging to the field of frozen soil technology. Background Technology

[0002] Permafrost refers to soil that remains frozen for extended periods when the ambient temperature is below freezing. Frost heave and thaw settlement are among the most prominent characteristics of permafrost, affecting not only soil stability but also significantly impacting infrastructure and engineering construction (such as roads, bridges, and railways). With the increasing influence of global climate change, the freeze-thaw cycle in permafrost regions is gradually lengthening, making frost heave and thaw settlement an increasingly important issue in engineering construction. Existing permafrost heave and thaw settlement testing devices primarily measure axial frost heave force, and most studies are limited to investigating soil behavior under a single frozen state. However, frost heave and thaw settlement in natural environments are influenced not only by temperature but also by factors such as pressure, water level, soil type, and freezing rate, resulting in a multi-dimensional, multi-temperature field of frost heave and thaw settlement. Therefore, current technologies cannot comprehensively and accurately assess the frost heave and thaw settlement behavior of permafrost, especially when simulating frost heave and thaw settlement behavior under complex environmental conditions, where limitations exist. Summary of the Invention

[0003] The purpose of this invention is to provide a multidimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device to solve the problems existing in the prior art.

[0004] To address the aforementioned technical problems, this invention provides a multi-dimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device, comprising: a loading frame, a loading system, a water replenishment system, a temperature control system, a control system, a test chamber, and a sensor group electrically connected to the control system. The temperature control system includes a multi-channel temperature regulation and control device electrically connected to the control system, a constant temperature bath A, a constant temperature bath B, and a constant temperature water tank arranged on a reaction plate under the loading frame. The constant temperature water tank comprises multiple constant temperature chambers arranged sequentially from bottom to top, with a ring for arranging the test chambers in each of the middle chambers. Constant temperature baths A and B are connected to the multi-channel temperature regulation and control device via pipes. The multi-channel temperature regulation and control device is connected to each of the multiple constant temperature chambers via pipes equipped with valves. Each of the multiple constant temperature chambers is connected to constant temperature bath A via pipes equipped with peristaltic pumps, and to constant temperature bath B via pipes equipped with peristaltic pumps. The test chamber is placed in the constant temperature water tank, with the bottom of the test chamber in contact with the upper surface of the bottom constant temperature chamber. Soil is loaded into the test chamber layer by layer through compaction. A soil column is formed, with the number of soil layers matching the number of constant-temperature chambers equipped with circular rings. The height of each soil layer matches the height of the corresponding constant-temperature chamber. Each soil layer has a through-hole A, through-hole B, and through-hole C on its side. The water replenishment system supplies water to the soil column in the test chamber according to preset conditions via water replenishment pipes. The water replenishment system includes a height adjustment mechanism, an electronic scale placed on the height adjustment mechanism, a water storage tank arranged on the electronic scale, and water replenishment pipes arranged in each soil layer through the corresponding through-hole C. The system includes an electronic scale electrically connected to the control system, a water storage tank connected to pipe A with a valve and pipe B with a valve, pipe C with a valve at the other end of pipe A, pipe D with a valve at the other end of pipe B, pipe E connecting pipes A and B, pipe C extending from the upper surface of the top layer of soil into the top layer of soil, pipe E connected to the water supply pipes of each layer of soil, and pipe D extending from the lower surface of the bottom layer of soil into the bottom layer of soil. Each layer of soil's water supply pipe is equipped with a valve.

[0005] In one specific embodiment, the loading system is installed on the upper reaction plate of the mounting frame. The loading system is electrically connected to the control system and is used to apply vertical downward pressure to the soil column to simulate the overburden load of the soil column. The loading system includes a pressure applying mechanism and a pressure bar. The pressure applying mechanism is installed on the upper reaction plate of the mounting frame. A pressure column is provided at the bottom of the pressure applying mechanism. The top end of the pressure bar is connected to the pressure column. The bottom end of the pressure bar presses against the bottom surface of the constant temperature tank on the top layer of the constant temperature water tank. The pressure applying mechanism is electrically connected to the control system.

[0006] In one specific embodiment, the sensor group includes a thermometer and hygrometer arranged in each soil layer through a corresponding through hole A, a pore water pressure gauge arranged in each soil layer through a corresponding through hole B, a pressure sensor and a displacement gauge arranged on the loading system, and each thermometer, hygrometer, pore water pressure gauge, displacement gauge and pressure sensor are electrically connected to the control system.

[0007] In one specific embodiment, the temperature-controlled tank at the top of the temperature-controlled water tank is connected to an elastic bag, and the bottom plate of the temperature-controlled tank at the top of the temperature-controlled water tank is provided with holes that match the elastic bag.

[0008] In one specific embodiment, the bottom end of the pressure rod is connected to a pressure plate, which presses against the bottom of the elastic bag so that the elastic bag comes into contact with the permeable stone on top of the soil.

[0009] In one specific embodiment, the pressure sensor is arranged between the pressure column and the pressure rod.

[0010] In one specific embodiment, the constant temperature water tank is made of stainless steel, and the outer surface of the constant temperature water tank is provided with heat insulation material, and the contact parts between multiple constant temperature tanks are also provided with heat insulation material.

[0011] In one specific embodiment, a water bath with a temperature range of -30 to -5°C is arranged in constant temperature bath A, and a water bath with a temperature range of 0°C to room temperature is arranged in constant temperature bath B. The water bath is a mixture of ethylene glycol and water in a 1:1 ratio.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0013] This invention provides a multi-dimensional high-pressure frozen soil frost heave and thaw settlement testing device. Through the coordinated action of a temperature control system, a water supply system, a loading system, and an intelligent control system, it achieves multi-dimensional simulation testing and dynamic monitoring of frozen soil under complex environmental conditions. The device can accurately simulate and measure the frost heave and thaw settlement behavior of frozen soil samples under different directions, pressures, and groundwater levels, providing reliable experimental data for cold region engineering design and frozen soil mechanics research. The core design and innovative functions of this invention include the following aspects.

[0014] 1. Multi-dimensional frost heave test function

[0015] This invention employs a multi-channel temperature control system to achieve independent temperature control and water bath circulation control for each layer of soil in a soil column. The system not only simulates the traditional axial frost heave process but also enables radial frost heave testing through a radial temperature adjustment device. This simulates temperature changes and frost heave deformation of the soil in both axial and radial directions, while simultaneously measuring frost heave force. This multi-dimensional temperature control design accurately reflects non-uniform frost heave behavior, providing a more comprehensive assessment of the anisotropic frost heave characteristics of frozen soil than existing technologies, thus broadening the applicability of frost heave testing.

[0016] 2. Freeze-thaw cycle simulation function

[0017] Through precise adjustment of the temperature control system and water bath circulation control, this invention can simulate long-term, multiple freeze-thaw cycles, study the cumulative deformation law and mechanical property changes of soil under repeated freezing and thawing, and obtain data on freeze-thaw heave and thaw settlement characteristics that are closer to the natural environment.

[0018] 3. High-pressure cryogenic loading system

[0019] This invention combines a temperature control system and a loading system, employing high-pressure freezing technology to conduct frozen soil tests. It can apply constant or variable axial pressure (pressure accuracy 0.01 MPa) within the range of 0–8 MPa. By controlling the temperature and pressure conditions of the samples, the frost heave characteristics and deformation mechanisms of frozen soil under different stress states can be studied. This device is particularly suitable for testing frost heave behavior in deep frozen soil and under high-pressure environments, providing scientific reference for engineering construction in complex geological environments and under extreme conditions.

[0020] 4. Groundwater level regulation and replenishment function

[0021] This invention features an adjustable water replenishment system. A height adjustment mechanism controls the position of the water storage tank and the opening and closing of pipeline valves, enabling water replenishment tests under different groundwater level conditions. Combined with temperature and pressure control, it can simulate the impact of groundwater level changes on the freezing rate, frost heave, and thaw settlement behavior of permafrost, thus more realistically reproducing the natural geological environment and providing experimental evidence for the stability analysis of permafrost under different water level conditions.

[0022] 5. Two-dimensional temperature and force field simulation function

[0023] This invention employs a uniformly distributed cooling element arrangement within the temperature control system to create a two-dimensional temperature field within the test chamber. Simultaneously, a distributed loading system enables coordinated adjustment of axial and radial stresses. This design can simulate temperature and stress gradient changes in different directions, allowing for the study of bidirectional frost heave effects in both vertical and horizontal directions, and providing data support for the mechanistic analysis of complex frost heave behavior.

[0024] 6. Multi-layer frozen soil structure simulation function

[0025] This invention, through the layered arrangement of different types of soil and a layered temperature control system, allows for independent control of the temperature, water replenishment, and water bath circulation of each layer, simulating frost heave behavior under different depths and soil conditions. This multi-layered permafrost design can reproduce the interactions of multiple layers of permafrost in actual geological environments, improving the diversity and practicality of the experiments.

[0026] 7. Dynamic monitoring and intelligent control functions

[0027] This invention is equipped with multiple sensors, including a thermometer and hygrometer, a pore water pressure gauge, a displacement gauge, a pressure sensor, and an electronic balance, to achieve real-time monitoring of temperature, humidity, pressure, and displacement of a soil column during frost heave. All data is fed back to the control system, which automatically adjusts experimental environmental parameters (such as temperature, pressure, and water replenishment) based on the monitoring results, achieving dynamic control of the experimental process. This intelligent feedback mechanism can reproduce the actual changes in the frozen soil freezing process in real time, ensuring the accuracy and stability of the experiment.

[0028] Through the above structure and function, this invention can comprehensively study the coupling effect of temperature field, stress field and water level changes on frozen soil frost heave and thaw settlement, obtain more realistic, systematic and repeatable experimental data, and comprehensively evaluate the engineering stability and deformation characteristics of frozen soil under different environmental conditions. It is especially suitable for the research and simulation of complex working conditions such as non-uniform frost heave, high pressure environment, groundwater changes and long-term freeze-thaw cycles. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the multidimensional multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device of the present invention.

[0030] In the diagram: 1. Control system, 2. Loading frame, 3. Test chamber, 4. Soil column, 5. Permeable stone, 6. Constant temperature water tank, 7. Elastic bag, 8. Constant temperature bath A, 9. Constant temperature bath B, 10. Multi-channel temperature regulation and control device, 11. Peristaltic pump, 12. Thermometer and hygrometer, 13. Pore water pressure gauge, 14. Displacement gauge, 15. Pressure sensor, 16. Pressing mechanism, 17. Pressure bar, 18. Pressure plate, 19. Electronic scale, 20. Water storage tank, 21. Height adjustment mechanism, 22. Pipe A, 23. Pipe B, 24. Pipe C, 25. Pipe D, 26. Pipe E, 27. Water supply pipe. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0032] refer to Figure 1A multidimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device includes: a loading frame 2, a loading system, a water replenishment system, a temperature control system, a control system 1, a sensor group electrically connected to the control system 1, and a test chamber 3.

[0033] The temperature control system includes a multi-channel temperature regulation and control device 10 electrically connected to the control system 1, a constant temperature bath A8 containing a water bath solution with a temperature range of -30 to -5℃, a constant temperature bath B9 containing a water bath solution with a temperature range of 0℃ to room temperature, and a constant temperature water tank 6 arranged on the reaction plate under the loading frame 2. The constant temperature water tank 6 includes multiple constant temperature chambers arranged sequentially from bottom to top. Each of the multiple constant temperature chambers located in the middle is provided with a ring for arranging the test chamber 3. The constant temperature baths A8 and B9 are connected to the multi-channel temperature regulation and control device 10 through pipes. One side of each constant temperature chamber is connected to the multi-channel temperature regulation and control device 10 through a pipe with a valve. Each constant temperature chamber is connected to the constant temperature baths A8 and B9 through a pipe equipped with a peristaltic pump 11. The water bath solution in the constant temperature baths A8 and B9 is a mixture of ethylene glycol and water in a 1:1 ratio, which will not freeze or boil at -50 to 50℃.

[0034] The water bath liquid in constant temperature baths A8 and B9 can be input to the multi-channel temperature regulation and control device 10, and can be output to each constant temperature chamber through the multi-channel temperature regulation and control device 10. The temperature of the water bath liquid output to each constant temperature chamber can be any temperature between the water bath liquid temperatures of constant temperature baths A8 and B9, and the temperature accuracy can reach ±0.01℃.

[0035] According to the preset conditions, the temperature of the input water bath liquid is controlled by the multi-channel temperature regulation control device 10, and the input water bath liquid temperature is controlled for each constant temperature box, so that the soil column 4 is in different temperature environments at different heights, simulating the temperature difference of soil layers in the actual environment.

[0036] The temperature control system can be used to uniformly arrange cooling elements on the soil column 4 to simulate the frost heave changes of frozen soil in the axial and radial directions.

[0037] The water bath solution enters from one side of the constant temperature chamber through a multi-channel temperature regulation and control device 10, and then flows back from the constant temperature chamber to the constant temperature bath A8 or constant temperature bath B9 under the action of the peristaltic pump 11, completing the continuous circulation and heat exchange of the water bath solution. The water bath circulation can simulate the long-term freeze-thaw cycle of frozen soil.

[0038] The test chamber 3 is placed in the constant temperature water tank 6, with the bottom of the test chamber 3 in contact with the upper surface of the constant temperature box at the bottom of the constant temperature water tank 6. The bottom of the test chamber 3 is provided with a permeable stone 5 slot for arranging permeable stones 5. The soil is loaded into the test chamber 3 layer by layer by compaction to form a soil column 4. The number of soil layers in the soil column 4 is the same as the number of constant temperature boxes with rings. The height of each soil layer in the soil column 4 matches the height of the corresponding constant temperature box. The side of the test chamber 3 corresponding to each soil layer is provided with a through hole A, a through hole B and a through hole C. Preferably, the material of the test chamber 3 is plexiglass, and the height and diameter of the test chamber 3 can be selected according to the actual situation.

[0039] The constant temperature water tank 6 is arranged in layers. The test chamber 3 is placed on the bottom constant temperature box of the constant temperature water tank 6. After installing the soil column 4, sensor group and water supply pipe 27, the constant temperature boxes with rings are placed on the test chamber 3 layer by layer. Then the top constant temperature box is placed on the top constant temperature box with rings.

[0040] The loading system is installed on the upper reaction plate of the mounting frame. The loading system is electrically connected to the control system 1 and is used to apply a vertically downward pressure to the soil column 4 to simulate the overburden load of the soil column 4.

[0041] By combining the temperature control system and the loading system, the frost heave test of frozen soil is carried out using high-pressure freezing technology. By controlling the environmental pressure and temperature of soil column 4, the frost heave behavior of soil column 4 under different pressures is simulated.

[0042] The water replenishment system replenishes water to the soil column 4 of the test chamber 3 according to preset conditions through the water replenishment pipe 27.

[0043] The sensor group includes a thermometer and hygrometer 12 arranged in each soil layer through corresponding through holes A, a pore water pressure gauge 13 arranged in each soil layer through corresponding through holes B, a pressure sensor 15 and a displacement gauge 14 arranged on the loading mechanism. Each thermometer and hygrometer 12, each pore water pressure gauge 13, displacement gauge 14 and pressure sensor 15 are electrically connected to the control system 1. The pressure sensor 15, displacement gauge 14 and each thermometer and hygrometer 12 monitor the stress data of the soil column 4 during the frost heave process in real time and feed it back to the control system. The control system automatically adjusts the temperature and pressure of the test environment.

[0044] The loading system includes a pressure applying mechanism 16 and a pressure rod 17. The pressure applying mechanism 16 is installed on the upper reaction plate of the mounting frame. The bottom of the pressure applying mechanism 16 is provided with a pressure column. The top of the pressure rod 17 is connected to the pressure column. The bottom of the pressure rod 17 is pressed against the bottom surface of the constant temperature box on the top layer of the constant temperature water tank 6. The pressure applying mechanism 16 is electrically connected to the control system 1. The pressure range applied by the loading system is 0-8MPa, and the pressure accuracy is 0.01MPa.

[0045] The water replenishment system includes a height adjustment mechanism 21, an electronic scale 19 placed on the height adjustment mechanism 21, a water storage tank 20 arranged on the electronic scale 19, and water replenishment pipes arranged in each soil layer through corresponding through holes C. The electronic scale 19 is electrically connected to the control system 1. The water storage tank 20 is connected to pipes A22 and B23 with valves. The other end of pipe A22 is connected to pipe C24 with a valve, and the other end of pipe B23 is connected to pipe D25 with a valve. Pipe E26 connects pipes A22 and B23. The other end of pipe C24 extends from the upper surface of the top soil layer into the top soil layer. Pipe E26 is connected to the water replenishment pipes 27 of each soil layer. The other end of pipe D25 extends from the lower surface of the bottom soil layer into the bottom soil layer. Each water replenishment pipe 27 of each soil layer is equipped with a valve.

[0046] The water storage tank 20 can supply distilled water or salt solution to the soil column 4 as needed. Based on preset conditions, it controls the opening and closing of valves on the pipeline and the water supply pipeline 27 to regulate the water supply to the bottom, top, and sides of the soil. An electronic scale 19 monitors the water supply volume in real time and transmits the data to the control system 1. A height adjustment device adjusts the height of the water storage tank 20 to simulate the influence of groundwater level on soil frost heave and thaw settlement, helping to assess the frost heave behavior of frozen soil under different groundwater level conditions.

[0047] The control system controls the temperature, water replenishment, and water bath circulation of soil column 4 in layers. The soil type of each layer can be arranged as needed to simulate frost heave behavior under different depths and soil conditions.

[0048] The constant temperature tank 6 has an elastic bag 7 connected to the top layer of the constant temperature tank 6, and the bottom plate of the top layer of the constant temperature tank 6 has holes that match the elastic bag 7.

[0049] The bottom end of the pressure rod 17 is connected to a pressure plate 18, which is pressed against the bottom of the elastic bag 7 so that the elastic bag 7 comes into contact with the permeable stone 5 on the top of the soil.

[0050] The elastic bag 7 ensures that the temperature environment at the top of the soil column 4 can be freely adjusted, and also ensures that the water bath liquid will not leak into the soil column 4. The elastic bag 7 can freely expand and contract with the pressure rod 17 and the pressure plate 18 without generating frictional resistance.

[0051] The pressure sensor 15 is arranged between the pressure column and the pressure rod 17 to record the load condition and transmit it to the control system 1.

[0052] The constant temperature water tank 6 is made of stainless steel, which has good thermal conductivity. The outer surface of the constant temperature water tank 6 is covered with heat insulation material, and the contact parts between multiple constant temperature tanks are also covered with heat insulation material to ensure that the water tank temperature is constant. Preferably, the thickness of the heat insulation material is 0.5cm to ensure that the constant temperature water tank temperature is constant.

[0053] The bottom constant temperature chamber of the constant temperature water tank 6 is placed on the bottom reaction plate of the reaction frame. The test chamber 3 is placed on the bottom constant temperature chamber of the constant temperature water tank 6. After placing the permeable stones 5 and filter paper, the soil is compacted layer by layer into the test chamber 3. The soil quality of each layer can be determined according to the actual situation. Permeable stones 5 are placed on the top surface of the top layer of soil. The height of each layer of soil matches the corresponding constant temperature chamber, and the number of soil layers is consistent with the number of constant temperature chambers with rings. The ring-shaped constant temperature chambers are sequentially placed on top of test chamber 3. The constant temperature chamber at the top of the constant temperature water tank 6 is then positioned on top of test chamber 3. A hygrometer 12 and a pore water pressure gauge 13 are inserted into each soil layer through corresponding through holes on the constant temperature chambers, ensuring each soil layer has both a hygrometer 12 and a pore water pressure gauge 13. The corresponding through holes in the water supply pipes 27 of each soil layer are also inserted into the corresponding soil layer, ensuring each soil layer has a water supply pipe 27. Gaps in each through hole are filled with sealant to prevent water and soil leakage. Valves on control pipes A22, B23, C24, and D25, and on each water supply pipe 27, are all closed. The pressure rod 17 is lowered so that the elastic bag 7 and the permeable stone 5 of the uppermost soil layer are slightly in contact. Finally, the cover plate of the constant temperature chamber at the top of the constant temperature water tank 6 is closed, sealing and insulating the constant temperature water tank 6.

[0054] In the experiment, the constant temperature water tank 6 contains 7 layers of insulation, the soil is set in 5 layers, and the multi-channel temperature regulation and control device 10 is set in 7 channels. The soil is loaded into the test chamber 3 in 5 layers by compaction.

[0055] The process of frozen soil frost heave was simulated by setting the temperature and switching of seven insulated boxes to correspond to the water bath circulation of the insulated boxes. According to the actual situation, the frozen soil frost heave process was divided into three cases: 1. the bottom soil, top soil, or middle soil freezes; 2. the soil column freezes at a gradient temperature; 3. the bottom soil and top soil freeze, and the middle soil thaws.

[0056] All seven channels of the multi-channel temperature regulation and control device 10 are set to the same temperature, so that each layer of soil in the soil column 4 is in the same temperature environment. In this test, it was set to 5℃.

[0057] Frozen soil at the bottom, top, or middle: When simulating freezing of the top soil, the temperature of the top insulation box is set to -15℃, and the temperature of the other insulation boxes is set to 5℃. The water bath circulation of the six insulation boxes from bottom to top is turned off, and the temperature of soil column 4 gradually decreases from the top to induce frost heave. Similarly, when simulating freezing of the bottom soil, the temperature of the bottom insulation box is set to -15℃, and the temperature of the other insulation boxes is set to 5℃. The water bath circulation of the six insulation boxes from top to bottom is turned off, and the temperature of soil column 4 gradually decreases from the bottom to induce frost heave. When simulating freezing of the middle soil, the temperatures of the top and bottom insulation boxes remain unchanged at 5℃, and the temperatures of the five middle insulation boxes are all set to -15℃. The water bath circulation of the top and bottom insulation boxes is turned off, so that frost heave begins in the middle soil. 2. Simulating gradient temperature freezing: In real natural environments, soil temperature varies due to differences in depth and soil mineral composition. To simulate actual temperature environments, such as the formation of a cold source at the top during snowfall and cooling, different soil depths experience temperature differences and frost heave. Specifically, the temperatures of the six insulated boxes from bottom to top are set to 5℃, 4℃, 3℃, 2℃, 1℃, and 0℃ respectively, while the temperature of the top insulated box is set to -15℃. The water bath circulation in the bottom six insulated boxes is turned off. Temperature simulation can be performed according to actual environmental conditions. 3. Frozen bottom and top soil, thawing middle soil: Simulates the conditions in a permafrost region, i.e., the bottom soil layer is frozen, the middle soil layer is thawing, and the top soil layer is frozen. The temperature of the two bottom insulation boxes can be set to -15℃, the temperatures of the other insulation boxes are set to -5℃, 0℃, 5℃, and 10℃ respectively, and the temperature of the top insulation box is set to -15℃. The water bath circulation of the five middle insulation boxes is turned off, so that the top and bottom act as cold sources and the soil begins to freeze and expand.

[0058] After the above soil frost heave test is completed, the soil thaw settlement test is conducted: 1. During the complete thawing process, the temperature of the top insulation box is set to 10℃, and the water bath circulation of the other insulation boxes is turned off. 2. For the test where the top soil thaws while the bottom soil remains frost-sustaining, the temperature of the bottom two insulation boxes is set to -15℃, the temperature of the top insulation box is set to 10℃, and the water bath circulation of the five middle insulation boxes is turned off.

[0059] When performing freeze-thaw cycles, the above-mentioned freeze-thaw and thaw cycles can be repeated as needed, depending on the conditions of the simulated environment.

[0060] Soil moisture changes are involved during frost heave and thaw settlement. During the above test, water can be replenished at different locations as needed. Specifically: 1. Bottom water replenishment: Raise the bottom of water tank 20 above the top of soil column 4, open valves on pipes B23 and D25, and close valves on pipes A22, C24, and all water replenishment pipes 27; 2. Top water replenishment: Raise the bottom of water tank 20 above the top of soil column 4, open valves on pipes A22 and C24, and close valves on pipes B23, D25, and all water replenishment pipes 27; 3. Intermediate water replenishment: Raise the bottom of water tank 20 above the top of soil column 4, open valve on pipe A22, close valves on pipes B23, C24, and D25, and open valves on the corresponding water replenishment pipes 27 as needed. 4. Groundwater level regulation: In the natural environment, the groundwater level affects the soil's frost heave and thaw settlement process. The water storage tank 20 is positioned at different heights as needed. Water then enters the soil column 4 from the bottom of the test chamber 3, i.e., valves on pipes B23 and D25 are opened, while valves on pipes A22, C24, and all water supply pipes 27 are closed. The water absorption quality and rate of the soil column 4 can be monitored in real time using the electronic scale 19.

[0061] Monitoring of deformation and frost heave under different pressure conditions: 1. Based on the simulation conditions, frost heave and thaw settlement tests under different pressure conditions can be set up to simulate frost heave and thaw settlement tests with overlying loads of 0MPa, 0.5MPa, 1MPa, 2MPa, and 4MPa. The methods for frost heave or thaw settlement and water replenishment are the same as described above, with different settings as needed. During this process, the real-time data of each thermo-hygrometer 12, each pore water pressure gauge 13, displacement gauge 14, and electronic scale 19 are monitored. 2. Frost heave force is tested to simulate frost heave force under constant volume. The loading system is controlled to prevent the pressure rod 17 and pressure plate 18 of the loading system from moving. The methods for frost heave and water replenishment are the same as described above, with different settings as needed. The frost heave force during the test is obtained by real-time monitoring of the pressure sensor 15.

[0062] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions and substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A multidimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device, characterized in that, include: Loading frame, loading system, water supply system, temperature control system, control system, test chamber, and sensor group electrically connected to the control system; The temperature control system includes a multi-channel temperature regulation and control device electrically connected to the control system, a constant temperature bath A, a constant temperature bath B, and a constant temperature water tank arranged on the reaction plate under the loading frame. The constant temperature water tank includes multiple constant temperature chambers arranged sequentially from bottom to top. Each of the multiple constant temperature chambers located in the middle is provided with a ring for arranging test chambers. Both constant temperature bath A and constant temperature bath B are connected to the multi-channel temperature regulation and control device through pipes. The multi-channel temperature regulation and control device is connected to the multiple constant temperature chambers through pipes with valves. The multiple constant temperature chambers are connected to constant temperature bath A through pipes equipped with peristaltic pumps, and the multiple constant temperature chambers are connected to constant temperature bath B through pipes equipped with peristaltic pumps. The test chamber is placed in a constant temperature water tank, with the bottom of the test chamber in contact with the upper surface of the bottom constant temperature chamber. The soil is compacted layer by layer into the test chamber to form a soil column. The number of soil layers in the soil column is the same as the number of constant temperature chambers with rings. The height of each soil layer in the soil column matches the height of the corresponding constant temperature chamber. Each soil layer has a through hole A, through hole B, and through hole C on the side of the test chamber. The water replenishment system replenishes water to the soil column of the test chamber according to preset conditions through water replenishment pipes; The water replenishment system includes a height adjustment mechanism, an electronic scale placed on the height adjustment mechanism, a water storage tank arranged on the electronic scale, and water replenishment pipes arranged in each layer of soil through corresponding through holes C. The electronic scale is electrically connected to the control system. The water storage tank is connected to pipe A with a valve and pipe B with a valve. The other end of pipe A is connected to pipe C with a valve, and the other end of pipe B is connected to pipe D with a valve. Pipe E connects pipes A and B. The other end of pipe C extends from the upper surface of the top layer of soil into the top layer of soil. Pipe E is connected to the water replenishment pipes of each layer of soil. The other end of pipe D extends from the lower surface of the bottom layer of soil into the bottom layer of soil. Each layer of soil's water replenishment pipe is equipped with a valve.

2. The multidimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device as described in claim 1, characterized in that, The loading system is installed on the upper reaction plate of the installation frame and is electrically connected to the control system. It is used to apply vertical downward pressure to the soil column to simulate the overburden load of the soil column. The loading system includes a pressure applying mechanism and a pressure bar. The pressure applying mechanism is installed on the upper reaction plate of the installation frame. The pressure applying mechanism has a pressure column at the bottom and the top of the pressure bar is connected to the pressure column. The bottom end of the pressure bar is pressed against the bottom surface of the constant temperature tank on the top layer of the constant temperature water tank. The pressure applying mechanism is electrically connected to the control system.

3. The multidimensional multi-field coupled high-pressure frozen soil frost heave-thaw settlement test device as described in claim 2, characterized in that, The sensor group includes a thermometer and hygrometer arranged in each soil layer through a corresponding through hole A, a pore water pressure gauge arranged in each soil layer through a corresponding through hole B, a pressure sensor and a displacement gauge arranged on the loading system, and each thermometer, hygrometer, pore water pressure gauge, displacement gauge and pressure sensor are electrically connected to the control system.

4. The multidimensional multi-field coupled high-pressure frozen soil frost heave-thaw settlement test device as described in claim 3, characterized in that, The constant temperature tank at the top layer is connected to an elastic bag, and the bottom plate of the constant temperature tank at the top layer has holes that match the elastic bag.

5. The multidimensional, multi-field coupled high-pressure frozen soil frost heave and thaw settlement test device as described in claim 4, characterized in that, The bottom end of the pressure bar is connected to a pressure plate, which is pressed against the bottom of the elastic bag so that the elastic bag comes into contact with the permeable stone on top of the soil.

6. The multidimensional multi-field coupled high-pressure frozen soil frost heave-thaw settlement test device as described in claim 5, characterized in that, The pressure sensor is positioned between the pressure column and the pressure rod.

7. The multidimensional multi-field coupled high-pressure frozen soil frost heave-thaw settlement test device as described in claim 6, characterized in that, The constant temperature water tank is made of stainless steel, and the outer surface of the constant temperature water tank is covered with heat insulation material. The contact parts between multiple constant temperature tanks are also covered with heat insulation material.

8. The multidimensional multi-field coupled high-pressure frozen soil frost heave-thaw settlement test device as described in claim 7, characterized in that, The constant temperature bath A contains a water bath solution with a temperature range of -30 to -5℃, and the constant temperature bath B contains a water bath solution with a temperature range of 0℃ to room temperature. The water bath solution is a mixture of ethylene glycol and water in a 1:1 ratio.

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