A structure and method for active air-heat synergistic regulation of frost heave prevention in cold-region roadbeds

Abstract

This invention relates to the field of road and railway engineering technology, and discloses an active air-heat synergistic regulation structure and method for preventing frost heave in cold-region roadbeds. Sensors embedded in the roadbed acquire real-time temperature and humidity data, and a controller automatically switches operating modes based on data feedback and preset logic. In active drying mode, hot, dry air is injected into the pipeline network to reduce the roadbed moisture content below the critical frost heave threshold, eliminating the root cause of frost heave. In adaptive barrier mode, a low-energy "thermal barrier" is formed using slightly warm air, and in the event of sudden water intrusion, a "freezing barrier," or ice curtain, is creatively formed using a low-temperature refrigerant for emergency water isolation. In assisted thaw drainage mode, low-pressure air is used to accelerate the discharge of thawed water. This invention transforms frost heave prevention from reactive remediation and passive defense into proactive, intelligent, full-cycle management, achieving a unified approach to both symptomatic and fundamental treatment. It has advantages such as strong adaptability, high reliability, and integrated functional synergy.

Description

Technical Field

[0001] This invention relates to the field of road and railway engineering technology, and in particular to an active air-heat synergistic regulation structure and method for preventing frost heave in cold regions. Background Technology

[0002] Seasonally frozen soil areas account for over 50% of my country's land area, and transportation infrastructure such as highways and railways in these regions generally face severe roadbed frost heave problems. Roadbed frost heave is a complex hydrothermal coupling physical process that requires three basic conditions to occur simultaneously: the presence of frost-sensitive soil, a sustained ambient temperature below freezing point, and sufficient moisture supply. In winter, the negative temperature gradient drives unfrozen thin film water in the soil to migrate and accumulate towards forming ice crystals (i.e., ice lenses), causing the ice lenses to grow continuously and resulting in uneven roadbed heave. In spring, the ice lenses melt, leading to supersaturation of the roadbed soil, a sharp decrease in strength, and melting settlement deformation under external loads, seriously affecting traffic safety and route smoothness, and generating huge annual maintenance costs.

[0003] Studies have shown that the severity of frost heave is closely related to the initial moisture content of the soil. When the volumetric water content (VWC) of the soil is below a certain threshold, known as the "critical frost heave content," large-scale water migration and accumulation are difficult to occur due to the discontinuous nature of water in the pores, resulting in minimal or even no frost heave. Therefore, the core of preventing and controlling frost heave in roadbeds lies in the effective control of moisture within the roadbed.

[0004] To address the aforementioned problems, existing technologies have proposed various prevention and control solutions, which can be broadly categorized into passive and active approaches.

[0005] Passive prevention technologies mainly include replacement filling, insulation layer installation, and traditional drainage methods. Replacement filling involves replacing the frost-sensitive fill layer of the roadbed with non-frost-sensitive coarse-grained materials such as graded gravel. While effective, this method is extremely resource-intensive, resulting in high engineering costs. Furthermore, it requires large-scale excavation for existing roads, severely disrupting traffic. Insulation layers such as XPS extruded polystyrene boards aim to reduce freezing depth, but these layers cannot address the moisture problem within the roadbed and are prone to creating cold bridges at edges such as shoulders, leading to poor results. Traditional drainage facilities such as blind drains and seepage ditches are effective for soils with good permeability, but for frost-sensitive soils with extremely low permeability, such as silty clay, gravity drainage alone is inefficient and has limited effectiveness. These passive methods are essentially static defense strategies, designed based on historical data and assumed operating conditions, unable to adapt to dynamically changing hydrothermal environments, and lacking resilience.

[0006] Active prevention technologies are currently being explored by the engineering community. For example, active heating methods use ground source heat pumps to deliver heat to pipes buried in the roadbed, forming a "thermal barrier" to prevent soil freezing. This is an energy-intensive "containment" strategy; it does not remove moisture from the roadbed, addressing the symptoms but not the root cause. Once heating stops or extreme cold waves occur, the risk of frost heave remains, and it may exacerbate roadbed softening during the spring thaw. Another example is passive water absorption methods, which use highly absorbent geotextiles to "dry" the roadbed. However, this method is limited by the limited capacity and lifespan of the absorbent materials (approximately 5 years), requiring regular replacement and incurring high maintenance costs. Furthermore, its passive absorption process may be insufficient for sections with strong external water supply. Another technical concept is to introduce hot, dry compressed air into the roadbed to "dry" the soil. The principle of this method is correct, but the scheme is too simplistic, lacks scientific basis for pipeline layout, adopts a high-energy-consuming "continuous delivery" mode, and has a single function, only considering autumn dryness and unable to cope with other seasonal challenges such as sudden water supply in winter and spring melting and subsidence.

[0007] In summary, existing technologies for preventing frost heave in cold regions have several problems, including treating the symptoms but not the root cause, high energy consumption, poor adaptability, and inability to cope with dynamic water and heat changes throughout the year. There is an urgent need for a comprehensive solution that can actively, intelligently, and throughout the entire lifecycle regulate the water and heat status of the roadbed. Summary of the Invention

[0008] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention provides a structure and method for active air-heat synergistic regulation of roadbeds in cold regions to prevent frost heave.

[0009] The first technical solution is:

[0010] A method for preventing frost heave in roadbeds in cold regions through active air-heat synergistic regulation.

[0011] Includes the following steps:

[0012] S1, Real-time monitoring step: Through sensors buried in the roadbed, continuously monitor the volumetric water content and temperature of the target area of ​​the roadbed to obtain real-time status data as input for subsequent steps;

[0013] S2, Intelligent decision-making step: The real-time status data is input to the controller, and the controller compares and judges the real-time status data with the preset control logic to output a decision command for executing a specific control mode;

[0014] S3, Coordinated Control Step: Based on the received decision instruction, the ground integrated processing unit is activated to execute the control mode corresponding to the decision instruction, generate a corresponding control medium, and input the control medium into the underground pipe network system to control the hydrothermal state of the roadbed. The control mode includes at least:

[0015] Active drying mode: Supply hot dry gas to reduce the volumetric moisture content of the roadbed;

[0016] Thermal barrier mode: Supplying slightly warm gas to prevent the freezing front from penetrating deeper;

[0017] Freezing barrier mode: Low-temperature refrigerant is supplied to form a water-proof frozen soil barrier within the roadbed.

[0018] Furthermore, in the intelligent decision-making step S2, when it is determined that the real-time status data meets the following conditions: the roadbed temperature is higher than 0°C and the volumetric water content is higher than the preset critical frost heave threshold, a decision instruction to execute the active drying mode is output.

[0019] Furthermore, in the active drying mode, the hot dry gas is air with a relative humidity of less than 20% and a temperature of 40-60°C, and this mode adopts pulsed operation.

[0020] Furthermore, in the heat barrier mode, the slightly heated gas is air at a temperature of 5-10°C.

[0021] Furthermore, in the intelligent decision-making step S2, when it is determined that the real-time status data shows that the rate of change of the volumetric water content of the roadbed exceeds a preset alarm threshold, a decision instruction to execute the freezing barrier mode is output.

[0022] Furthermore, the control mode also includes a spring-assisted fusion mode;

[0023] In the intelligent decision-making step S2, when the real-time status data meets the following conditions: the roadbed temperature is stably higher than 0℃ and the volumetric water content increases due to ice melting, a decision instruction to execute the spring auxiliary melting mode is output.

[0024] Furthermore, in the spring-assisted molten water drainage mode, ambient temperature low-pressure air is supplied to the underground pipeline system to accelerate the drainage of molten water from the roadbed.

[0025] The second technical solution is:

[0026] A frost heave prevention structure for roadbeds in cold regions with active air-heat synergistic regulation.

[0027] Includes: underground pipeline systems, buried within the frost-sensitive soil layer of the roadbed, used for transporting and distributing control media;

[0028] A ground-based integrated processing unit, fluidly connected to the underground pipeline system, is characterized in that the ground-based integrated processing unit is configured to selectively generate and supply to the underground pipeline system, according to an operating command, one of a variety of control media including at least hot dry gas, slightly hot gas, and low-temperature refrigerant;

[0029] Intelligent monitoring and control systems include:

[0030] At least one sensor buried in the roadbed is used to monitor the volumetric water content and / or temperature of the roadbed in real time and output monitoring data;

[0031] A controller, electrically connected to the sensor and the ground integrated processing unit, is used to receive the monitoring data and, based on the comparison result of the monitoring data and preset control logic, generate and send an operation command to the ground integrated processing unit.

[0032] Furthermore, the underground pipeline system includes multiple parallel porous pipes, and each porous pipe is wrapped with a geotextile filter sleeve.

[0033] The porous pipe is made of high-density polyethylene.

[0034] The ground integrated processing unit also includes a valve group and a manifold system, which are controlled by the controller and are used to precisely guide the generated control medium to a designated area of ​​the underground pipe network system according to the operating instructions.

[0035] The sensor is a time-domain reflectometer sensor;

[0036] The controller is an industrial-grade programmable logic controller;

[0037] The intelligent monitoring and control system also includes a remote monitoring and data acquisition platform, which is connected to the controller via a wireless communication module.

[0038] Furthermore, the ground integrated processing unit is a skid-mounted unit, which integrates the following:

[0039] Gas booster device;

[0040] A gas dehumidification device is used to dehumidify the gas from the gas pressurization device to generate dry gas;

[0041] A gas heating device for heating gas from the gas pressurization device or the gas dehumidification device;

[0042] The ground-based integrated processing unit also integrates a low-temperature cooling system for preparing the low-temperature refrigerant;

[0043] The cryogenic cooling system includes a refrigeration unit for cooling the brine secondary refrigerant to below 0°C.

[0044] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0045] This invention not only suppresses frost heave through the "winter adaptive barrier" mode (treating the symptoms), but also actively removes the core disaster-causing factor—moisture—from the roadbed before the freezing period through the "autumn active drying" mode, reducing the moisture content to below the critical frost heave threshold, thereby fundamentally eliminating the material basis for frost heave (treating the root cause), and achieving full-chain, root-cause prevention and control of frost heave disease.

[0046] This invention constructs a closed-loop control system based on real-time sensor data feedback. This system can automatically determine and switch to the optimal operating mode (autumn drying, winter thermal barrier, winter freezing barrier, spring thawing) based on the dynamic changes in temperature and humidity within the roadbed. This achieves refined and intelligent management of the roadbed's hydrothermal state, effectively addressing various complex and sudden climatic and hydrogeological conditions, significantly outperforming traditional static and passive prevention and control methods.

[0047] This invention fully considers long-term operational reliability in its structural design. For example, it uses low-temperature resistant and corrosion-resistant HDPE pipes and creatively incorporates geotextile filter sleeves on the outside of the pipes, effectively solving the long-standing technical problem of underground pipe networks being easily blocked in fine-grained soils such as silty clay. Simultaneously, the core control equipment uses an industrial-grade fail-safe PLC, ensuring long-term stable operation of the system in unattended environments.

[0048] This invention achieves multiple functions, including drying, insulation, waterproofing, and drainage assistance, through a unified hardware system (underground pipe network and surface IPU). This high degree of functional integration maximizes the value of the engineering investment. More importantly, by creatively integrating soil vapor extraction (SVE) technology (for efficient drying), artificial ground freezing (AGF) technology (for emergency waterproofing), and active thermal management technology, this invention achieves synergistic effects among different functions. Its comprehensive effect far exceeds the simple sum of any single technology, representing a significant advancement in addressing this technical challenge.

[0049] Additional aspects and advantages 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. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but cannot be used to limit the scope of this invention.

[0051] The core idea of ​​this invention is to transform the prevention and control of frost heave in cold-region roadbeds from the traditional "passive defense" or "single intervention" model to a "proactive management" and "intelligent collaboration" paradigm. It constructs a closed-loop system that can dynamically regulate the hydrothermal state of the roadbed throughout the year based on changes in the external environment and feedback from the internal state of the roadbed.

[0052] The present invention provides an active air-heat coordinated regulation anti-frost heave structure for roadbeds in cold regions, which mainly consists of three core subsystems: an underground pipeline system, a ground integrated processing unit (IPU), and an intelligent monitoring and control system.

[0053] 1. Underground pipe network system

[0054] The underground pipeline system is the physical foundation for realizing all functions, and it is directly buried inside the roadbed where water and heat regulation is required.

[0055] The system consists of a series of parallel porous pipes that traverse the roadbed laterally, positioned within frost-sensitive soil layers within the local maximum freezing depth range. The burial depth and spacing of the pipes require scientific design. The burial depth is determined based on relevant standards such as the "Highway Subgrade Design Specification" (JTG D30-2015), combined with specific meteorological and soil data, to ensure it targets the most critical areas prone to frost heave. The pipe spacing is determined through numerical simulation or analytical models, drawing on the Radius of Influence (ROI) theory from soil vapor-phase extraction (SVE) technology and based on parameters such as soil air permeability measured in in-situ permeability tests. This ensures that the airflow completely covers the roadbed area requiring treatment, achieving optimal efficiency and economy.

[0056] The materials and structure of the piping are crucial to the long-term reliability of the system. Porous pipes are made of high-density polyethylene (HDPE) PE100 grade. HDPE has excellent low-temperature resistance and can... It maintains flexibility and impact resistance in harsh environments, fully meeting the requirements of cold-region engineering. Furthermore, its excellent flexibility makes it ideal for trenchless horizontal directional drilling (HDD) installation, minimizing disruption to existing road traffic. Small-diameter pipes of 50-75 mm are recommended to reduce disturbance to the existing roadbed structure and lower the risk of uneven settlement caused by the pipes.

[0057] To address the fundamental problem of underground pipe networks being easily clogged in fine-grained soil in existing technologies, a key technical feature of this invention is that, before installation, each porous pipe must be tightly wrapped with a seamless geotextile filter sleeve made of knitted polyester fibers. This filter sleeve has excellent water and air permeability, yet its pore size is small enough to effectively prevent fine soil particles from entering the pipe, thereby ensuring the permanent unobstructed flow of air. This is one of the decisive measures to ensure the effective operation of the system for decades.

[0058] 2. Ground Integrated Processing Unit (IPU)

[0059] The ground integrated processing unit (IPU) is the power and processing core of the entire system, responsible for generating and regulating various required gaseous or fluid media.

[0060] The IPU is designed as a modular, skid-mounted unit prefabricated in the factory and integrated onto a steel base. The unit is transported to the site as a whole and hoisted onto a pre-cast concrete foundation next to the roadbed, requiring only final piping and electrical connections. This design ensures manufacturing quality, shortens on-site construction time, and facilitates future maintenance and replacement.

[0061] The IPU integrates the following core components:

[0062] Gas booster devices, such as high-pressure blowers or air compressors, provide the required airflow and pressure to the system. Their specifications are selected based on the total length of the pipeline network, soil permeability, and the required operating pressure (e.g., 10-50 kPa).

[0063] Gas dehumidification device: An industrial-grade rotary dehumidifier is preferred. This device utilizes the principle of solid adsorption to stably generate low dew point dry air with a relative humidity (RH) of less than 20%, and is the core equipment of the "autumn active drying mode".

[0064] Gas heating devices: such as electric heaters, used to precisely heat the air in "dry mode" and "heat barrier mode".

[0065] Cryogenic cooling systems: For example, a compact industrial refrigeration unit used to prepare cryogenic media in "freezing barrier mode". This system can cool secondary refrigerants such as brine to... about.

[0066] Valve manifold and piping system: Composed of a series of electrically or pneumatically controlled multi-way valves and main pipelines, it is key to achieving switching between different operating modes. The controller precisely guides the processed medium (such as dry hot air, slightly warm air, or cryogenic refrigerant) to designated pipeline areas by controlling the opening and closing of these valves.

[0067] 3. Intelligent monitoring and control system

[0068] This system is the nerve center that enables "intelligent" and "adaptive" operation.

[0069] The system includes a gridded array of soil sensors within the roadbed. Time-Domain Reflectometry (TDR) sensors are preferred, as this technology is a recognized method in geotechnical engineering capable of long-term, stable, and accurate measurement of soil volumetric moisture content and temperature, and the real-time data it provides serves as the basis for the decisions of the entire intelligent control logic.

[0070] The core of the system is the controller, preferably an industrial-grade, high-reliability programmable logic controller (PLC). To ensure absolute safety in unattended environments, the PLC must employ a fail-safe design, integrating hardware redundancy, self-diagnostics, and a watchdog timer. This means that a failure of any single component will cause the system to automatically enter a preset safe state (such as shutdown and alarm), preventing it from performing erroneous operations that could damage the roadbed or equipment. The controller connects to a remote Supervisory Control and Data Acquisition (SCADA) platform via cellular networks or other communication modules, enabling maintenance personnel to remotely monitor system status, adjust control parameters, and analyze historical data.

[0071] The core value of this invention lies in its multi-mode operation strategy based on real-time data feedback and designed to address different seasonal challenges. The controller automatically switches between several modes based on real-time data collected by soil sensors and in conjunction with preset control logic.

[0072] Mode 1: Autumn Active Drying Mode

[0073] This model is the cornerstone of the entire prevention and control strategy, with the goal of actively reducing the volumetric water content (VWC) of the core area of ​​the roadbed to below the critical frost heave threshold by 1 before the start of large-scale freezing in winter.

[0074] Triggering conditions: When the controller detects a significant drop in the average ambient temperature (e.g., below 10°C) but the subgrade soil temperature remains above freezing, and the average volumetric water content of the subgrade is... Higher than the preset critical frost heave threshold This mode will be automatically activated when needed.

[0075] Operating Process: The IPU activates the gas pressurization, dehumidification, and heating devices. Outside air is compressed, deeply dehumidified (e.g., treated to RH < 20%), and moderately heated (e.g., to 40–60°C) to form a high-temperature, low-humidity forced airflow. This airflow is injected into the underground pipe network system through a valve system and infiltrates into the surrounding soil at a certain pressure through micropores in porous pipes. The hot, dry air flows through the soil pores, creating a significant water vapor partial pressure difference with the pore water. This pressure difference becomes a powerful driving force for moisture evaporation, causing the liquid water in the soil to rapidly transform into gaseous water vapor. This humid, hot air, rich in water vapor, is ultimately discharged outside the roadbed, thus efficiently removing moisture from the soil.

[0076] To improve energy efficiency, this mode preferably adopts a pulsed operation, such as "running for 12 hours and then resting for 12 hours". During the resting period, moisture in the low-permeability zone has time to diffuse into the high-permeability channels that have been drained, and can be efficiently removed during the next operation.

[0077] Stopping condition: When the VWC detected by soil sensors at all key locations has decreased to the preset target value. Once the system stabilizes, the controller automatically stops operating in this mode.

[0078] Mode 2: Winter Adaptive Barrier Mode

[0079] The goal of this mode is to maintain low moisture content in the core area of ​​the roadbed throughout the winter and prevent excessive intrusion of freezing fronts. This mode includes two sub-modes that intelligently switch based on threat level and energy consumption considerations.

[0080] Sub-mode A: Thermal barrier mode

[0081] This is a low-energy-consumption prevention mode.

[0082] Triggering condition: This mode is automatically activated when the controller detects that the internal temperature of the roadbed is approaching 0°C (e.g., below 2°C), but the VWC is still at a safe level.

[0083] Operating process: The IPU only activates the gas pressurization and gas heating devices to slightly heat the outside air (e.g., to 5–10°C) and circulate it in the pipeline network at a low flow rate. Through forced thermal convection, a zone with a temperature slightly above 0°C is formed in the soil around the pipeline, creating a "thermal barrier" that prevents the freezing front from penetrating.

[0084] Sub-mode B: Freeze Barrier Mode

[0085] This is a high-energy-consuming emergency response mode, which is an important innovation of this invention. Its principle is derived from the creative application of mature artificial ground freezing (AGF) technology.

[0086] Triggering conditions: When a serious threat from external water sources is detected, such as abnormally warm and humid weather in winter leading to a large amount of snowmelt or rainfall infiltration, the soil sensor will detect an abnormally rapid increase in the roadbed VWC. The controller then determines the rate of change of VWC. Exceeding the preset alarm threshold This emergency mode will be automatically triggered when [the situation is as described].

[0087] Operating procedure: The IPU immediately activates the cryogenic cooling system. Cryogenic refrigerant (such as...) The brine is pumped into specific pipelines, typically on the water-facing side of the roadbed or at the slope. The low-temperature refrigerant exchanges heat efficiently with the surrounding soil through the pipe walls, rapidly freezing the pore water in the soil into ice. As the freezing zone expands, the frozen zones of adjacent pipelines converge, forming a continuous, extremely low-permeability frozen soil barrier—an ice curtain. This ice curtain acts like a temporary underground dam, effectively blocking lateral liquid water flow and protecting the already dried core area of ​​the roadbed from re-wetting.

[0088] Stop conditions: When the external water source threat is eliminated, or when VWC is detected to have stabilized, the system will automatically switch back to thermal barrier mode or standby mode.

[0089] Mode 3: Spring Auxiliary Reduction Mode

[0090] This model is designed to address the problem of "melt subsidence" where the roadbed strength decreases significantly during the spring thawing period.

[0091] Triggering conditions: This mode is automatically activated when the controller detects that the roadbed temperature begins to stabilize above 0℃ and the VWC rises rapidly due to ice melting.

[0092] Working process: The IPU only activates the gas pressurization device, blowing ambient air at low pressure and low speed into the underground pipe network system. In this mode, the airflow mainly serves two purposes: first, it physically clears blockages, helping to maintain unobstructed drainage channels; second, it accelerates drainage, as the slight positive pressure helps to "push" the accumulated meltwater out of the pores and quickly discharge it from the roadbed area through the drainage system, thereby effectively alleviating the problem of roadbed melting and softening.

[0093] Stop condition: When monitoring data shows that the VWC inside the roadbed has dropped to a normal unsaturated state, indicating that the melt water has been basically drained, the system will automatically stop this mode.

[0094] At all other times, the system is in a very low-power monitoring / standby mode, with only the sensors and control system operating to continuously monitor the roadbed condition.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for active air-heat synergistic regulation to prevent frost heave in roadbeds in cold regions, characterized in that, Includes the following steps: S1, Real-time monitoring step: Through sensors buried in the roadbed, continuously monitor the volumetric water content and temperature of the target area of ​​the roadbed to obtain real-time status data as input for subsequent steps; S2, Intelligent decision-making step: The real-time status data is input to the controller, and the controller compares and judges the real-time status data with the preset control logic to output a decision command for executing a specific control mode; S3, Coordinated Control Step: Based on the received decision instruction, the ground integrated processing unit is activated to execute the control mode corresponding to the decision instruction, generate a corresponding control medium, and input the control medium into the underground pipe network system to control the hydrothermal state of the roadbed. The control mode includes at least: Active drying mode: Supply hot dry gas to reduce the volumetric moisture content of the roadbed; Thermal barrier mode: Supplying slightly warm gas to prevent the freezing front from penetrating deeper; Freezing barrier mode: Low-temperature refrigerant is supplied to form a water-proof frozen soil barrier within the roadbed.

2. The method for active air-heat synergistic regulation to prevent frost heave in cold-region roadbeds according to claim 1, characterized in that, In the intelligent decision-making step S2, when the real-time status data meets the following conditions: the roadbed temperature is higher than 0℃ and the volumetric water content is higher than the preset critical frost heave threshold, a decision command to execute the active drying mode is output.

3. The method for active air-heat synergistic regulation to prevent frost heave in cold-region roadbeds according to claim 2, characterized in that, In the active drying mode, the hot dry gas is air with a relative humidity of less than 20% and a temperature of 40-60°C, and the mode operates in a pulsed manner.

4. The method for active air-heat synergistic regulation to prevent frost heave in cold-region roadbeds according to claim 1, characterized in that, In the aforementioned thermal barrier mode, the slightly heated gas is air at a temperature of 5-10°C.

5. The method for active air-heat synergistic regulation to prevent frost heave in cold-region roadbeds according to claim 4, characterized in that, In the intelligent decision-making step S2, when it is determined that the real-time status data shows that the rate of change of the volumetric water content of the roadbed exceeds the preset alarm threshold, a decision command to execute the freezing barrier mode is output.

6. The method for active air-heat synergistic regulation to prevent frost heave in cold-region roadbeds according to claim 1, characterized in that, The control mode also includes a spring-assisted fusion elimination mode; In the intelligent decision-making step S2, when the real-time status data meets the following conditions: the roadbed temperature is stably higher than 0℃ and the volumetric water content increases due to ice melting, a decision instruction to execute the spring auxiliary melting mode is output.

7. The method for active air-heat synergistic regulation to prevent frost heave in cold-region roadbeds according to claim 6, characterized in that, In the spring auxiliary drainage mode, ambient temperature and low pressure air is supplied to the underground pipeline system to accelerate the drainage of melted water from the roadbed.

8. A structure for preventing frost heave in cold-region roadbeds through active air-heat synergistic regulation, characterized in that, include: The underground pipeline system is buried in the frost-sensitive soil layer of the roadbed and is used to transport and distribute the control medium. A ground-based integrated processing unit, fluidly connected to the underground pipeline system, is characterized in that the ground-based integrated processing unit is configured to selectively generate and supply to the underground pipeline system, according to an operating command, one of a variety of control media including at least hot dry gas, slightly hot gas, and low-temperature refrigerant; Intelligent monitoring and control systems include: At least one sensor buried in the roadbed is used to monitor the volumetric water content and / or temperature of the roadbed in real time and output monitoring data; A controller, electrically connected to the sensor and the ground integrated processing unit, is used to receive the monitoring data and, based on the comparison result of the monitoring data and preset control logic, generate and send an operation command to the ground integrated processing unit.

9. The active air-heat synergistic regulation anti-frost heave structure for cold-region roadbeds according to claim 8, characterized in that, The underground pipeline system includes multiple parallel porous pipes, and each porous pipe is wrapped with a geotextile filter sleeve. The porous pipe is made of high-density polyethylene. The ground integrated processing unit also includes a valve group and a manifold system, which are controlled by the controller and are used to precisely guide the generated control medium to a designated area of ​​the underground pipe network system according to the operating instructions. The sensor is a time-domain reflectometer sensor; The controller is an industrial-grade programmable logic controller; The intelligent monitoring and control system also includes a remote monitoring and data acquisition platform, which is connected to the controller via a wireless communication module.

10. The active air-heat synergistic regulation anti-frost heave structure for cold-region roadbeds according to claim 8, characterized in that, The ground integrated processing unit is a skid-mounted unit, which integrates the following: Gas booster device; A gas dehumidification device is used to dehumidify the gas from the gas pressurization device to generate dry gas; A gas heating device for heating gas from the gas pressurization device or the gas dehumidification device; The ground-based integrated processing unit also integrates a low-temperature cooling system for preparing the low-temperature refrigerant; The cryogenic cooling system includes a refrigeration unit for cooling the brine secondary refrigerant to below 0°C.