Foundation frost heaving test system and method considering self-controlled groundwater recharge

Abstract

The application belongs to the technical field of electric power engineering. A foundation frost heaving test system and method considering self-control underground water recharge are provided, which comprises: the upper part of the water tank of the test soil box is arranged with at least two detachable cylinders arranged in layers, each detachable cylinder is placed with different water permeability materials; filter cotton is arranged between the water tank and the adjacent detachable cylinder, water permeable screen is arranged between the adjacent detachable cylinders, the top of the uppermost layer of the detachable cylinder is closed by a top low-temperature cold plate, and the bottom of the water tank is arranged with a bottom heating plate; the water pump is located in the water supplement cylinder, the water pump is connected with the water tank through the water supplement pipe, the water tank is arranged with a water level sensor in communication connection with a control end, and the control end is used for controlling the opening and closing of the water pump according to the sensing result of the water level sensor, so that the liquid surface of the water in the water tank is flush with the lower surface of the filter cotton or submerges the lower surface of the filter cotton; the application improves the comprehensiveness and accuracy of the foundation frost heaving test in cold regions.

Description

Technical Field

[0001] This invention relates to the field of power engineering technology, and in particular to a foundation frost heave test system and method that takes into account self-controlled groundwater recharge. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] When constructing power infrastructure projects such as transmission lines and new energy sources in cold regions, the most prominent problem encountered is the frost heave, frost pull-out, and thaw settlement damage to building foundations caused by frozen soil. This severely impacts the bearing capacity and stability of the foundations. Therefore, conducting indoor frozen soil tests to obtain reliable data has become an indispensable part of assessing the structural safety performance of buildings in cold regions, and is of great significance for enhancing structural safety and stability and preventing frost heave damage.

[0004] Existing research has shown that groundwater recharge conditions have a very important impact on the strength of frost heave of structures and are one of the core elements that cause and aggravate frost heave. The occurrence state, recharge conditions and migration law of groundwater directly determine the type, scale and degree of engineering impact of frost heave. Existing indoor foundation freezing systems have the following problems: (1) Inaccurate water level control, traditional experimental devices are difficult to simulate dynamic groundwater level fluctuations and capillary water recharge effect is poor; (2) Insufficient simulation of layered structure, natural foundations are usually multi-layered soil (such as clay-sand interlayer), and existing devices are difficult to reproduce interlayer water migration; (3) Lack of temperature-water coupling, lack of synchronous control of temperature gradient and water migration during freezing; (4) Lagging monitoring data, unreasonable sensor layout, resulting in discontinuous collection of water and temperature data. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a foundation frost heave test system and method that considers self-controlled groundwater recharge. This system can precisely control water level, temperature, and stratified structure, and is suitable for research on the frost heave mechanism of seasonally frozen soil and verification of engineering anti-freezing design. It greatly improves the comprehensiveness and accuracy of foundation frost heave tests in cold regions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a foundation frost heave test system that takes into account self-controlled groundwater recharge.

[0007] A foundation frost heave test system considering self-controlled groundwater recharge includes: a water supply cylinder, a water pump, and a test soil box. The test soil box includes a water tank, a permeable screen, filter cotton, a bottom heating plate, and a top low-temperature cooling plate. At least two detachable cylinders arranged in layers are arranged on the upper part of the water tank, and each detachable cylinder holds a material with different permeability. A filter cotton is arranged between the water tank and the adjacent detachable cylinder, a water-permeable screen is arranged between the adjacent detachable cylinders, the top of the uppermost detachable cylinder is sealed by a top low-temperature cold plate, and a bottom heating plate is arranged at the bottom of the water tank. The water pump is located inside the water supply cylinder and is connected to the water tank via a water supply pipe. A water level sensor, which is connected to a control terminal, is arranged inside the water tank. The control terminal is used to control the start and stop of the water pump based on the sensing result of the water level sensor so that the water level in the water tank is level with or submerges the lower surface of the filter cotton.

[0008] In one implementation of the first aspect of the present invention, the water supply pipe is attached to the lower surface of the filter cotton.

[0009] In one implementation of the first aspect of the present invention, the detachable cylinder is a cylindrical structure and the cross-section of the water tank is circular.

[0010] In one implementation of the first aspect of the present invention, the water supply cylinder, the water tank, and the detachable cylinder are all made of transparent glass.

[0011] In one implementation of the first aspect of the present invention, a plurality of annular semiconductor cooling chips are uniformly attached to each detachable cylinder.

[0012] In one implementation of the first aspect of the present invention, a moisture temperature sensor and a pore water pressure gauge are provided in the detachable cylinder of each layer.

[0013] In one implementation of the first aspect of the present invention, multiple unidirectional capillary fiber bundles are arranged at equal intervals on the side wall of the test soil box to enhance the migration of water in the unsaturated zone.

[0014] In one implementation of the first aspect of the present invention, the water level sensor is a multi-point infrared water level sensor.

[0015] Secondly, the present invention provides a method for testing the frost heave of a foundation that takes into account self-controlled groundwater recharge.

[0016] A method for testing the frost heave of a foundation considering self-controlled groundwater recharge, utilizing the frost heave testing system for a foundation considering self-controlled groundwater recharge as described in the first aspect of this invention, includes the following steps: When the water level in the tank drops due to water migration, the water level sensor transmits the current water level to the control terminal. The control unit controls the water pump to start working and replenish the water tank with water so that the water level in the tank is level with or submerges the lower surface of the filter cotton. When the water level is attached to or submerged on the lower surface of the filter cotton, the water level sensor transmits the current water level to the control terminal, which then controls the water pump to stop working. Cooling is achieved through temperature transfer via a top low-temperature cold plate, and refrigeration is achieved through PID control of a ring-shaped semiconductor cooling chip attached to the removable cylinder to simulate seasonal freezing. Heating is achieved through a bottom heating plate to prevent the freezing front from moving down too quickly.

[0017] In one implementation of the second aspect of the present invention, the proportional coefficient is adjusted according to the rate of temperature decrease, the integral time is adjusted according to the temperature fluctuation, and the derivative time is adjusted according to the temperature overshoot.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. In terms of precise control, the system achieves precise control of the water level in the tank through the coordinated work of the water level sensor, control terminal, and water pump. The control terminal, based on the real-time feedback from the water level sensor, precisely controls the start and stop of the water pump, ensuring that the water level in the tank is level with or submerges the lower surface of the filter cotton, creating a stable and compliant water level environment for the experiment. At the same time, the bottom heating plate and the top low-temperature cooling plate allow for independent adjustment of the bottom and top temperatures of the test soil box, thereby accurately simulating temperature changes in soil layers at different seasons and depths. Furthermore, the at least two detachable cylinders arranged in layers on the upper part of the tank can hold materials with different permeability, allowing for flexible construction of diverse layered structures to meet the experimental needs under different geological conditions.

[0019] 2. From an application perspective, the system's ability to precisely control water level, temperature, and stratified structure makes it highly suitable for studying the mechanism of seasonal frozen soil frost heave. Researchers can use the system to accurately simulate various actual working conditions and delve into the intrinsic laws of frozen soil frost heave. The system also performs excellently in engineering anti-freezing design verification. It can provide reliable test data and a scientific verification platform for foundation anti-freezing design in cold regions, effectively avoiding engineering hazards caused by unreasonable design.

[0020] 3. The unidirectional capillary fiber bundles of this invention possess unique unidirectional hydrodynamic properties, effectively enhancing water migration in unsaturated zones. During experiments, when the foundation soil is unsaturated, these fiber bundles guide water to move in a specific direction, more accurately simulating the migration path and patterns of water in actual foundations. This makes the experimental results closer to real-world conditions. The evenly spaced arrangement ensures the uniformity of water migration, avoiding localized water accumulation or loss, and improving the accuracy and reliability of the experiment. Through this design, researchers can more deeply study the impact mechanism of unsaturated zone water migration on foundation frost heave, providing a more scientific and accurate basis for the prevention and control of foundation frost heave in seasonally frozen soil regions. This, in turn, optimizes engineering anti-freezing design, ensures the quality and safety of engineering construction in cold regions, and promotes the further development of related technologies.

[0021] 4. This invention demonstrates significant technical effectiveness in temperature control. A top-mounted low-temperature cooling plate, coupled with a copper plate and continuous U-shaped condenser tubes connected to a low-temperature constant-temperature bath, efficiently conducts heat through external circulation, accurately simulating the low-temperature environment at the top of the soil. Ring-shaped semiconductor cooling pads are arranged around the outer wall of the soil tank, and PID control is used to adjust the cooling power, simulating seasonal freezing temperature ranges. Uniform arrangement ensures temperature field uniformity and avoids localized overcooling. It can also perform uniform or non-uniform temperature gradient control, flexibly forming different freezing fronts and controlling the direction of frost heave. PID control provides precise adjustment of cooling power; by reasonably setting proportional, integral, and derivative coefficients, the temperature can be quickly and stably controlled at the target value. During the -20℃ test, parameters can be dynamically adjusted based on the cooling effect and temperature changes. The bottom heating plate prevents the freezing front from moving too quickly, maintaining a stable temperature gradient. This provides reliable temperature conditions for accurately studying the mechanism of foundation frost heave, improving the accuracy and scientific rigor of the experiment.

[0022] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 A schematic diagram of a foundation frost heave test system considering self-controlled groundwater recharge, provided as an exemplary embodiment of the present invention; Figure 2 A cross-sectional view of a layered simulation unit provided as an exemplary embodiment of the present invention; Figure 3 A circuit connection diagram of a temperature control module provided for an exemplary embodiment of the present invention; The components include: 1. Water supply cylinder; 2. Water pump; 3. Water supply pipe; 4. Detachable cylinder; 5. Ring-shaped semiconductor cooling chip; 6. Water-permeable screen; 7. Filter cotton; 8. Bottom heating plate; 9. Top low-temperature cold plate; 10. Unidirectional capillary fiber bundle; 11. Pore water pressure gauge; 12. TDR probe moisture temperature sensor; 13. Multi-point water level sensor; and 14. Water tank. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] Example 1: As described in the background section, developing a simple, reliable, and easy-to-operate frozen soil freezing device and method capable of accurately simulating ground freezing under low-temperature conditions is an urgent problem to be solved in the field of power transmission engineering. In view of this, this implementation proposes a ground frost heave test system considering self-controlled groundwater recharge. The technical terms and related concepts involved in this solution are briefly introduced below: Temperature gradient refers to the degree of temperature difference between different depths or locations during the freezing process of soil, and is usually expressed as the temperature change per unit distance (°C / m). Moisture migration refers to the migration of liquid water in soil pores towards the freezing front (the interface between the frozen and unfrozen zones) driven by a temperature gradient. Soil thermal balance refers to the state of heat exchange and balance between the soil system and the external environment, as well as between different parts of the soil. Its core is that the heat input and output reach a dynamic balance. A freezing front is the interface between unfrozen and frozen soil during the formation or freezing of permafrost. It is a dynamic interface that changes as the temperature decreases and the freezing process extends from the surface of the earth or soil to deeper layers. The freezing front also moves into the soil as a result.

[0028] like Figure 1 and Figure 2 As shown, it includes: a water supply cylinder 1, a water pump 2, and a test soil box. The test soil box includes a water tank 14, a permeable screen 6, a filter cotton 7, a bottom heating plate 8, and a top low-temperature cooling plate 9. At least two detachable cylinders 4 arranged in layers are arranged on the upper part of the water tank 14, and each detachable cylinder 4 holds materials with different permeability. A filter cotton 7 is arranged between the water tank 14 and the adjacent detachable cylinder 4, and a water-permeable screen 6 is arranged between the adjacent detachable cylinder 4. The top of the uppermost detachable cylinder 4 is sealed by a top low-temperature cold plate 9, and a bottom heating plate 8 is arranged at the bottom of the water tank 14. The water pump 2 is located inside the water supply cylinder 1. The water pump 2 is connected to the water tank 14 through the water supply pipe 3. A water level sensor that is communicatively connected to the control terminal is arranged inside the water tank 14. The control terminal is used to control the opening and closing of the water pump 2 according to the sensing result of the multi-point water level sensor 13 so that the water level in the water tank 14 is level with or submerges the lower surface of the filter cotton 7.

[0029] In this implementation, preferably, the water supply cylinder 1 is made of transparent glass and houses a magnetic fully automatic optical infrared sensor water supply device (composed of an infrared-based multi-point water level sensor 13, a control terminal, and a water pump 2) to simulate the static or dynamic changes in the groundwater level.

[0030] In this implementation, the preferred test soil box is made of transparent plexiglass with a diameter of 40cm, and is filled with natural soil or artificial soil. Alternatively, a circular test soil box is used in this implementation, which facilitates the installation of the annular semiconductor cooling chip and promotes uniform cooling of the soil.

[0031] In this implementation, preferably, the test soil box is composed of multiple detachable cylinders 4 (40cm in diameter) stacked vertically, with each layer filled with a different permeable material (such as clay or sand). It is understood that the detachable cylinders 4 here can also be replaced with cylindrical structures such as cubes, cuboids, and prisms. Those skilled in the art can choose according to the specific working conditions, which will not be elaborated here.

[0032] In this implementation, preferably, a permeable screen 6 (1mm aperture) is provided between layers (i.e., between adjacent detachable cylinders 4) to prevent material mixing, and a filter cotton 7 is provided at the bottom layer to allow water to migrate vertically.

[0033] In this preferred embodiment, water from the water supply cylinder 1 is connected to the water tank 14 inside the test soil box via the water supply pipe 3. The position of the water supply pipe 3 is adjusted so that it always remains in close contact with the lower surface of the filter cotton 7. After the water tank 14 is filled with water and made to be in close contact with the filter cotton 7, when the water level in the water tank 14 drops due to water migration, the multi-point water level sensor 13 detects this and the water pump 2 starts working to replenish the water in the water tank 14. This ensures that the water level in the water tank 14 will always be level with the position of the filter cotton 7, thus continuously replenishing the water. When the water level is close to the filter cotton 7, the water pump 2 stops working.

[0034] In this implementation, preferably, a capillary water supply channel is set up. Specifically, it includes embedding unidirectional capillary fiber bundles 10 (such as polypropylene unidirectional fiber bundles) into the side wall of the test soil box, with one bundle every 5 cm, for a total of 25 bundles, evenly distributed to enhance the water migration capacity of the unsaturated area.

[0035] In this implementation, preferably, a pore water pressure gauge 11 and a TDR probe moisture temperature sensor 12 are arranged in the detachable cylinder 4 of each layer for monitoring pore water pressure and moisture temperature, thereby achieving better moisture, pressure and temperature testing.

[0036] In this implementation, preferably, a low-temperature cold plate is installed on the top of the detachable cylinder 4 of the uppermost pair for refrigeration. Specifically, a metal copper plate is placed on the top of the detachable cylinder 4, and a continuous U-shaped condenser tube is placed on the upper part of the metal copper plate with the lower part close to the soil. The U-shaped condenser tube is connected to a low-temperature constant temperature bath (-30℃~15℃), and energy is transferred through an external circulation mode.

[0037] In this implementation, preferably, a ring-shaped semiconductor cooling pad 5 is arranged around the outer wall of the test soil box, and the cooling power is adjusted by a PID temperature controller to simulate seasonal freezing (-20℃ to 25℃). The cooling pads are evenly arranged around the test soil box to ensure the uniformity of the temperature field and avoid local overcooling. By adjusting the temperature controller, the ring-shaped semiconductor cooling pad 5 can perform uniform temperature gradient control to form a flat freezing front, or it can perform non-uniform temperature gradient control to perform gradient freezing and control the direction of frost heave. In this implementation, such as Figure 3 As shown, the cooling power is adjusted using a PID temperature controller, with -20℃ as an example. For the -20℃ frozen soil test, the proportional coefficient can be initially set to around 15-20; if the cooling effect is poor, the proportional coefficient can be set to 20-25. During the test, if the temperature drop rate is too slow, the proportional coefficient can be increased appropriately by 5% each time; if temperature overshoot occurs, the proportional coefficient should be decreased by 5% to 10% each time, gradually finding a suitable value. Considering the long thermal equilibrium time of the system at low temperatures, the integral time can be initially set to 120-150s. If the temperature fails to reach the target value for a long time and static error exists, the integral time can be decreased by 10% to 15% each time; if large temperature fluctuations occur, the integral time can be increased by 10% to 20% each time. Since the temperature changes slowly in low-temperature environments, the derivative time can be initially set to 5-10s. If temperature overshoot occurs during the experiment, gradually increase the derivative time by 10% to 20% each time. After the overshoot is effectively suppressed, carefully observe whether the system response is slow to avoid affecting the temperature regulation speed due to excessive derivative time.

[0038] More specifically, the PID temperature controller achieves dynamic adjustment of cooling power through the coordinated action of three components: proportional (P), integral (I), and derivative (D), thereby accurately controlling the temperature in the frozen soil test.

[0039] The output of the PID controller (i.e., the cooling power regulation) is determined by the following formula: (1); in, This represents the output of the PID controller (the signal that controls the cooling power). This represents the difference between the target value and the actual value. The proportionality coefficient determines the weight of the current error's impact on the output. The integral coefficient represents the weighting of the cumulative historical error on the output. The coefficients represent the differential coefficients, which determine the weight of the impact of the error rate on the output. Taking the -20℃ test as an example, the initial proportionality coefficient Set it to 15-20. At this point, if the actual temperature is -18℃ (error...) e ( t If the temperature is -2℃, then the proportional circuit outputs: (2); The negative sign indicates that the cooling power needs to be increased. If the cooling effect is poor (e.g., the temperature drops slowly), it means that the proportional effect is insufficient and the power needs to be increased. Up to 20-25, to enhance the strength of the response to errors.

[0040] If the temperature drops too slowly (e.g., it takes too long to go from -18°C to -19°C), it indicates... If the value is still too low, increase it by 5% increments (e.g., from 20 to 21) to accelerate the adjustment of cooling power; if overshoot occurs (e.g., the temperature drops to -21℃), it indicates... If the size is too large, it needs to be reduced by 5% to 10% (e.g., from 20 to 18) to avoid overcooling.

[0041] At low temperatures, the system has a long thermal equilibrium time (e.g., it takes several hours to drop from -10°C to -20°C), and the integration time is long. (and Inversely proportional, The initial time is set to 120-150 seconds. During this time, the integral stage slowly accumulates historical errors and gradually corrects the cooling power. If the temperature cannot reach -20℃ for a long time (e.g., it stabilizes at -19℃), it indicates the presence of a static error, which needs to be reduced. (For example, reducing from 150s to 135s) enhances the integral action and accelerates error elimination; if the temperature fluctuation is large (e.g., fluctuating around -20℃ by 1℃), it indicates that the integral action is too strong and needs to be increased. (For example, increasing from 120s to 144s) reduces the cumulative effect of historical errors and stabilizes the output.

[0042] Low temperature environments have slow temperature changes, and the differential time... The initial setting is 5–10 seconds; at this time, the differential element is less sensitive to the rate of temperature change, so premature intervention should be avoided; if overshoot occurs during the experiment (e.g., the temperature drops suddenly from -19°C to -21°C), the setting needs to be increased. (For example, increasing from 5s to 6s) enhances the suppression of the error rate of change; when overshoot is effectively suppressed, if the system response is slow (e.g., the temperature rises too slowly to -20℃), it indicates... If the value is too large, it needs to be appropriately reduced (e.g., from 6s to 5.5s) to balance the need to suppress overshoot and the requirement for response speed.

[0043] In this implementation, a bottom heating plate 8 is added to the bottom of the water tank 14 to prevent the freezing front from moving down too quickly and to maintain the stability of the temperature gradient.

[0044] In this implementation, a data acquisition device is set up to transmit data to the control terminal in real time, generating a spatiotemporal distribution cloud map of moisture, temperature, and pressure. By observing the spatiotemporal movement of the 0℃ isotherm in the temperature cloud map, the location of the freezing or thawing front of the frozen soil is determined. Attention is paid to the temperature gradient. In high gradient areas (where isotherms are dense), there may be active zones of moisture migration or phase transition interfaces, which can easily cause soil frost heave. In the moisture cloud map, high water content areas (dark / bright areas) usually correspond to liquid water enrichment zones, and their diffusion direction reflects the migration trend of moisture infiltration or freeze-thaw cycles. In the pressure cloud map, high value areas (dark / dense texture areas) correspond to points of concentrated frost heave force or areas under external loads, and attention should be paid to whether they will cause soil cracking or structural deformation.

[0045] It should be noted that the PID temperature controller can also be integrated into the control terminal for a unified design. Similarly, the data acquisition unit can be connected to various sensors to achieve the acquisition and transmission of different sensor data.

[0046] In this implementation, the multi-point water level sensor 13 is an infrared sensor. Of course, other water level sensors can also be used, which will not be elaborated here. Understandably, the motor is fixed to the water supply cylinder 1 with a magnetic structure, or other fixing methods can be used, which will not be elaborated here.

[0047] Example 2: In other implementation methods, based on the pain points of water level control, a dynamic coupling model of temperature gradient and moisture migration can be established to predict water replenishment demand at different freezing stages, thereby achieving proactive control of groundwater levels. Specifically, these include: Construct a water migration rate prediction model: (3); in, Represents the water migration rate (m / s), which characterizes the amount of water that migrates to the freezing front per unit time. Represents the temperature-dependent permeability coefficient (m / s), satisfying , Reference temperature Permeability coefficient at (20℃) This refers to the temperature sensitivity coefficient. Represents the temperature gradient in the vertical direction (°C / m). Represents the moisture content-temperature coupling coefficient (1 / ℃). Dynamic water replenishment control for: (4); in, Represents the volume of water replenishment. Represents the cross-sectional area of ​​the soil box. This represents the evaporation compensation amount. t Represents time.

[0048] Optionally, in some other implementations, the PID control parameters are optimized in real time based on the location of the freezing front and the temperature gradient distribution obtained by the monitoring system to achieve precise control of the temperature field. Specifically, these include: Constructing a model of the movement rate of a frozen front: (5); in, This represents the rate of downward movement of the freezing front (m / s). This represents the comprehensive influence coefficient, which is related to soil porosity and moisture content. Represents the thermal conductivity of saturated / unsaturated soil (W / (m•K)).

[0049] An adaptive PID parameter adjustment rule was designed, including: (6); in, These are the real-time PID parameters (proportional coefficient, integral time, derivative time). These are the initial PID parameters; e Represents temperature error (°C); Represents the adjustment coefficient; This represents the error attenuation factor, which helps prevent parameter oscillations when there are large errors.

[0050] This implementation solves the problem of "inaccurate water level control" in traditional devices by using a temperature-moisture coupling algorithm, enabling predictive water replenishment based on the freezing physical process rather than passive induction control. By combining an adaptive PID algorithm with freezing front tracking, it compensates for the "lack of temperature-moisture coupling," enabling dynamic matching between temperature gradient regulation and moisture migration patterns. Relying on real-time data from the monitoring system (TDR probe, pore water pressure gauge 11), it strengthens the closed-loop logic of "monitoring-control" and improves the system's simulation accuracy of the natural foundation frost heave mechanism.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A foundation frost heave test system considering self-controlled groundwater recharge, characterized in that, include: The test soil box includes a water tank, a water pump, and a test soil box. The test soil box includes a water tank, a permeable screen, filter cotton, a bottom heating plate, and a top low-temperature cooling plate. At least two detachable cylinders are arranged in layers on the upper part of the water tank, and each detachable cylinder holds a material with different permeability. A filter cotton is arranged between the water tank and the adjacent detachable cylinder, a water-permeable screen is arranged between the adjacent detachable cylinders, the top of the uppermost detachable cylinder is sealed by a top low-temperature cold plate, and a bottom heating plate is arranged at the bottom of the water tank. Multiple annular semiconductor cooling chips are evenly attached to each detachable cylinder, and the cooling power of the annular semiconductor cooling chips is adjusted by a PID temperature controller. The water pump is located inside the water supply cylinder. The water pump is connected to the water tank through the water supply pipe. A water level sensor that is connected to the control terminal is arranged inside the water tank. The control terminal is used to control the start and stop of the water pump according to the sensing result of the water level sensor so that the water level in the water tank is level with or submerges the lower surface of the filter cotton. The water supply pipe is attached to the lower surface of the filter cotton; Multiple unidirectional capillary fiber bundles were arranged at equal intervals on the side wall of the test soil box to enhance water migration in the unsaturated zone.

2. The foundation frost heave test system considering self-controlled groundwater recharge as described in claim 1, characterized in that, The detachable cylinder has a cylindrical structure, and the water tank has a circular cross-section.

3. The foundation frost heave test system considering self-controlled groundwater recharge as described in claim 1, characterized in that, The water supply cylinder, water tank, and detachable cylinder are all made of transparent glass.

4. The foundation frost heave test system considering self-controlled groundwater recharge as described in claim 1, characterized in that, Each layer of the removable cylinder is equipped with a moisture temperature sensor and a pore water pressure gauge.

5. The foundation frost heave test system considering self-controlled groundwater recharge as described in claim 1, characterized in that, The water level sensor is a multi-point infrared water level sensor.

6. A method for testing frost heave of foundations considering self-controlled groundwater recharge, characterized in that, The foundation frost heave test system considering self-controlled groundwater recharge as described in any one of claims 1-5 includes the following process: When the water level in the tank drops due to water migration, the water level sensor transmits the current water level to the control terminal. The control unit starts the water pump to replenish the water tank, so that the water level in the tank is level with or submerges the lower surface of the filter cotton. When the water level is attached to or submerged on the lower surface of the filter cotton, the water level sensor transmits the current water level to the control terminal, which then controls the water pump to stop working. Cooling is achieved through temperature transfer via a top low-temperature cold plate, and refrigeration is achieved through PID control of a ring-shaped semiconductor cooling chip attached to the removable cylinder to simulate seasonal freezing. Heating is achieved through a bottom heating plate to prevent the freezing front from moving down too quickly.

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