Phase change-moisture absorption and drainage composite roadbed structure in seasonal frozen region and intelligent regulation and control method

Abstract

The invention provides a phase change-moisture absorption and drainage composite roadbed structure in a seasonal frozen region and an intelligent regulation and control method, and relates to the technical field of roadbed design and renovation. The roadbed structure is characterized in that a plurality of gradient phase change material layers are arranged on the top surface of a roadbed surface layer; the multi-layer gradient phase change material layer, the high moisture absorption and drainage geotextile layer and the drainage pipe system are arranged from top to bottom; the phase change temperature intervals and the phase change latent heat of the phase change layers in the multiple gradient phase change material layers are different; the high moisture absorption and drainage geotextile layer is used for guiding water in the soil body into the drainage pipe system; the drainage pipe system is of a porous structure with the inclination angle within the set angle range and is used for guiding water in the soil into the drainage ditch. And the intelligent regulation and control system is used for dynamically regulating the thermal resistance of each phase change layer and the opening degree of the drainage pipe. According to the invention, the time of the roadbed in a relatively stable physical state can be prolonged, so that the purpose of preventing and treating winter frost heaving, frost boiling and mud rising in a spring melting period and other diseases caused by temperature change of the roadbed in severe cold areas is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of roadbed design and reconstruction, in particular to the technical field of frozen soil engineering in cold regions, and more particularly to a phase change-moisture absorption and drainage composite roadbed structure in seasonally frozen regions and an intelligent control method thereof. Background Art

[0002] In recent years, extreme weather events have become more frequent, and freeze-thaw cycles in seasonally frozen regions have become more frequent and intense. This environmental change poses severe challenges to infrastructure construction in permafrost areas. For example, important structures such as railway and highway subgrades are often plagued by frost heave, thaw settlement, and cumulative plastic deformation, which significantly impact the stability and operational safety of these structures. In the face of these challenges, traditional subgrade antifreeze measures, such as the use of insulation boards, the installation of heating rods, and chemical modification, can provide some assistance. However, they are often unable to fully and effectively address the drastic temperature fluctuations, complex soil moisture migration, and variability of frost heave mechanisms during freeze-thaw cycles. This results in the subgrade being unable to maintain a relatively stable physical state for a long time, leading to various roadbed defects such as uneven deformation and mud oozing. Summary of the Invention

[0003] The embodiments of the present invention provide a phase change-moisture absorption and drainage composite roadbed structure and an intelligent control method to solve the problem that the roadbed cannot be in a relatively stable physical state for a long time.

[0004] In a first aspect, an embodiment of the present invention provides a seasonally frozen area phase change-hygroscopic drainage composite roadbed structure, comprising: a multi-layer gradient phase change material layer, a high moisture absorption drainage geotextile layer, a drainage pipe system, and an intelligent control system;

[0005] Wherein, the multi-layer gradient phase change material layer is arranged on the top surface of the roadbed surface; the multi-layer gradient phase change material layer, the high moisture absorption drainage geotextile layer and the drainage pipe system are arranged from top to bottom;

[0006] The phase change temperature range and phase change latent heat of each phase change layer in the multi-layer gradient phase change material layer are different;

[0007] The highly hygroscopic drainage geotextile layer is used to guide water in the soil into the drainage pipe system;

[0008] The drainage pipe system adopts a porous structure with an inclination angle within a set angle range to guide water in the soil into the drainage ditch;

[0009] The intelligent control system includes a microcontroller, a feedback module, temperature and humidity sensors distributed in each phase change layer in the multi-layer gradient phase change material layer and the high moisture absorption drainage geotextile layer, and an electric heating component, which is used to dynamically adjust the thermal resistance of each phase change layer and the opening of the drainage pipe.

[0010] In a possible implementation, the groove spacing of the deep groove structure is 5 to 12 μm; the diameter of the water-conducting fiber is 30 to 50 μm; and the specific surface area of the water-conducting fiber is greater than 3650 cm 2 / g.

[0011] In a possible implementation, the setting angle range is 2° to 15°; the porous structure is an Ω-shaped porous structure; the apparent pore size satisfies AOS<2.5d 85 Filtering criteria.

[0012] In a possible implementation, the phase change temperature range of each phase change layer in the multi-layer gradient phase change material layer gradually decreases from bottom to top, and the phase change latent heat gradually decreases.

[0013] In a possible implementation, the temperature difference between adjacent phase change layers is ≥3° C., the phase change latent heat of each phase change layer is ≥160 kJ / kg, and the thermal conductivity of each phase change layer is 0.15-0.25 W / (m·K).

[0014] In one possible implementation, the multi-layer gradient phase change material layer is made of a composite phase change material; the composite phase change material is formed by adsorbing a matrix phase change material through a porous medium and encapsulating it through epoxy resin or styrene acrylic emulsion; the compressive strength is 16 to 20 MPa, and the flexural strength is 2.0 to 3.1 MPa.

[0015] Wherein, the porous medium includes expanded perlite and vermiculite.

[0016] In a possible implementation, graphite or metal powder is added to the multi-layer gradient phase change material layer, the thermal conductivity is increased to 0.20-0.25 W / (m·K), and the latent heat release uniformity deviation is less than 5%.

[0017] In a second aspect, an embodiment of the present invention provides an intelligent control method, characterized in that the composite roadbed structure in the first aspect or any possible implementation of the first aspect is applied, including:

[0018] Get temperature and humidity sensor data;

[0019] According to the temperature and humidity sensor data and the PID algorithm, the power of the electric heating components of each phase change layer and the opening of the drain pipe are adjusted.

[0020] In one possible implementation, adjusting the power of each phase change layer electric heating component and the opening of the drain pipe according to the temperature and humidity sensor data and the PID algorithm includes:

[0021] When it is determined according to the temperature and humidity sensor data that the soil temperature is lower than the set temperature, the electric heating component is started to heat;

[0022] When it is determined according to the temperature and humidity sensor data that the soil humidity exceeds the set humidity, the drain pipe valve is opened to accelerate drainage.

[0023] In this embodiment of the present invention, the phased temperature control of multiple layers of gradient phase change material, combined with the synergistic effect of highly hygroscopic drainage geotextiles, achieves dynamic stabilization of the subgrade temperature field and active control of moisture migration. Each phase change layer, with its differentiated phase change temperature ranges and latent heat parameters, forms a stepped temperature buffer barrier, gradually attenuating the impact of external temperature fluctuations, including winter cooling and spring warming, on the subgrade. The deeply grooved fiber structure of the highly hygroscopic drainage geotextile and the inclined, porous design of the drainage pipes effectively channel capillary and seepage water through capillary action and gravity, preventing localized moisture accumulation that can cause frost heave or thaw settlement. An intelligent control system utilizes temperature and humidity sensors to monitor environmental information in real time and dynamically adjusts the electric heating components and drainage pipe openings to enhance subgrade stability during freeze-thaw cycles, thereby extending the time the subgrade remains in a relatively stable physical state. This, in turn, helps prevent subgrade damage in severely cold regions, such as winter frost heave and spring mud oozing caused by temperature fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of an application scenario of the intelligent control system for the phase change-moisture absorption and drainage composite roadbed structure in seasonally frozen areas provided by an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the phase change-moisture absorption and drainage composite roadbed structure provided by an embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the bidirectional regulation effect of the phase change layer provided by an embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of the construction process of the seasonally frozen zone phase change-hygroscopic drainage composite roadbed structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The embodiments of this application mainly break through the bottleneck of two-way control of temperature and moisture performance of traditional passive roadbed under complex freeze-thaw conditions by integrating material function gradient, structural layer coordination, and closed-loop control algorithm. From top to bottom, a gradient phase change material layer with gradually increasing phase change temperature and step-by-step enhancement of latent heat is set on the surface of the roadbed. Combined with high-efficiency moisture-absorbing geotextile with deep-grooved water-conducting fibers and a porous drainage pipe system, a heat-humidity control barrier covering the entire freeze-thaw cycle is formed; at the same time, relying on an intelligent feedback system with integrated temperature and humidity sensors and electric heating components, the thermal resistance of the phase change material and the opening of the drainage valve are dynamically adjusted based on real-time data, actively suppressing temperature fluctuations in winter and spring and the resulting moisture accumulation, thereby improving the structural stability and service life of the roadbed in the drastic temperature change environment of the seasonal freezing zone.

[0029] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] Figure 1 This is an application scenario diagram of the intelligent control system for the phase change-hygroscopic drainage composite roadbed structure in seasonally frozen areas provided by the embodiment of the present invention. In order to facilitate the understanding of the implementation process of the solution, Figure 1 It mainly shows the temperature and humidity sensor data transmission and the feedback control of the electric heating component, and the feedback control scenario reference of the drain pipe opening Figure 1 shown.

[0031] like Figure 1 As shown, the temperature and humidity sensors are illustrated as temperature sensors and moisture sensors. In other possible implementations, they may be integrated sensors. The electric heating component is illustrated as a stainless steel heating rod. In other possible implementations, the electric heating component may be a heating wire or a heating mesh.

[0032] The data acquisition device obtains the temperature and humidity information collected by the temperature sensor and moisture sensor, and sends the temperature and humidity information to the monitoring center for online monitoring through network relays and routers. The monitoring center controls the operation of the stainless steel heating rod based on the temperature and humidity information.

[0033] Figure 2 Schematic diagram of the phase change-hygroscopic drainage composite roadbed structure provided by an embodiment of the present invention. Figure 2 As shown, it includes: a multi-layer gradient phase change material layer, a high moisture absorption and drainage geotextile layer, a drainage pipe system and an intelligent control system.

[0034] Among them, the multi-layer gradient phase change material layer is arranged on the top surface of the roadbed surface; the multi-layer gradient phase change material layer, the high moisture absorption drainage geotextile layer and the drainage pipe system are arranged from top to bottom.

[0035] The phase change temperature range and phase change latent heat of each phase change layer in the multi-layer gradient phase change material layer are different.

[0036] Highly hygroscopic drainage geotextile layer used to channel water from the soil into the drainage pipe system.

[0037] The drainage pipe system adopts a porous structure with an inclination angle within a set angle range to guide water in the soil into the drainage ditch.

[0038] The intelligent control system includes a microcontroller, a feedback module, temperature and humidity sensors distributed at the bottom of the phase change layer in the multi-layer gradient phase change material layer and the high moisture absorption drainage geotextile layer, and an electric heating component, which is used to dynamically adjust the thermal resistance of each phase change layer and the opening of the drainage pipe.

[0039] Among them, the thermal response of phase change material (PCM) is used to control the temperature, and the drainage and moisture absorption function of geotextiles is combined to form a dynamic heat-humidity bidirectional control mechanism, thereby achieving active regulation of the impact of freeze-thaw cycles on roadbed stability.

[0040] The core mechanism of the multi-layer gradient phase change material layer is to form an adaptive thermal resistance adjustment mechanism through the staged phase change latent heat regulation and gradient temperature buffer effect, thereby achieving dynamic stability of the roadbed temperature field. Optionally, the multi-layer gradient phase change material layer has two or more layers. In actual implementation, the number of layers of the multi-layer gradient phase change material layer is set according to the ambient temperature, ambient humidity or geographical location. For example, 3 to 4 layers are used in extremely cold areas, 2 to 3 layers are used in medium and low temperature areas, and 1 layer is added in high humidity areas within the same temperature range.

[0041] In practice, the intelligent control system dynamically adjusts the thermal resistance of each phase change layer by switching the electric heating element on and off to alter the temperature of the phase change layer material. The intelligent control system also adjusts the opening of the drain pipe by controlling the water flow cross-sectional area through a solenoid valve, thereby varying the drainage rate and thus regulating humidity.

[0042] Figure 3 During spring (thaw) conditions, the surface phase change layer absorbs ambient heat, inhibiting permafrost thawing and reducing the risk of thaw subsidence. During winter (freeze) conditions, the middle and deep phase change layers release latent heat, delaying the downward movement of the freezing front and suppressing frost heave deformation. Unlike traditional insulation panels, which only provide a one-way heat barrier, the phase change layer can provide bidirectional regulation under both winter cooling and spring warming conditions, effectively controlling the temperature field.

[0043] The highly hygroscopic drainage geotextile layer and the drainage pipe system work together through capillary action and gravity to balance soil moisture fluctuations during freeze-thaw cycles, greatly improving drainage efficiency. The highly hygroscopic drainage geotextile layer is a dual-function geotextile that combines reinforcement and water conduction, making it particularly suitable for the coordinated drainage of gravity and capillary water in unsaturated soil conditions.

[0044] The intelligent control system integrates a network of temperature and humidity sensors distributed across the top surface of the roadbed and at key locations within the phase-change-hygroscopic drainage composite roadbed structure, collecting real-time temperature, humidity, and other data. Temperature and humidity sensors are deployed between the phase-change layer and the highly hygroscopic geotextile layer to monitor temperature changes in the soil beneath the phase-change layer, as well as water drainage and drainage pipe blockage. Remote data transmission is achieved through a feedback module and microcontroller.

[0045] The intelligent control system works as follows: Temperature and humidity sensors detect temperature and humidity data, which are processed in real time by a microcontroller and feedback control module. Based on a pre-set algorithm (such as PID control or adaptive control), the operating state of the stainless steel heating rods in the roadbed is adjusted. The PID control targets the temperature and humidity of the soil in the lowest phase change layer. The goal is to keep the roadbed soil temperature at a positive temperature and the soil moisture content below a threshold. The PID parameters for temperature and humidity are set as input.

[0046] Temperature control method: A stainless steel heating rod is inserted under the phase change material. When the temperature below the phase change material is lower than the set temperature (such as 0°C), that is, the phase change material is not enough to block the winter cold, the heating rod starts to work and add heat to the phase change material to keep it working. When the temperature is higher than the set temperature, the heating rod stops working to dissipate heat.

[0047] Method of controlling humidity regulation: The microcontroller controls the electronic valve, and uses the electronic valve to control the opening and closing of the drain pipe. When the moisture content is high and the humidity is high, the drain valve is opened; when the moisture content is low and the humidity is low, the drain valve is closed.

[0048] During the spring warming period, the phase change layer is isolated or reduced in heat transfer, absorbing ambient heat and delaying the thawing of frozen soil. During the winter cold period, the phase change layer is activated to absorb cold energy, suppressing excessive freezing depth and maintaining a stable temperature field.

[0049] Through the intelligent integration of temperature and humidity sensors and PID control, it can be further ensured that the roadbed does not accumulate moisture due to the temperature gradient caused by the existence of the phase change layer, and the roadbed soil is always controlled to not freeze. The dynamic adjustment of the control system enables the entire roadbed temperature field and moisture field to be actively regulated, thereby improving the roadbed soil temperature gradient and moisture changes caused by the freeze-thaw cycle of the external environment and enhancing the roadbed stability.

[0050] In this embodiment, the dynamic stabilization of the roadbed temperature field and active control of moisture migration are achieved through the synergistic effect of staged temperature control of multiple layers of gradient phase change material and high-hygroscopic drainage geotextiles. Each phase change layer forms a stepped temperature buffer barrier through differentiated phase change temperature ranges and phase change latent heat parameters, gradually attenuating the impact of external temperature fluctuations on the interior of the roadbed. The deep-grooved fiber structure of the high-hygroscopic drainage geotextile and the inclined porous design of the drainage pipe effectively drain water through capillary action and gravity, effectively channeling capillary water and seepage water in the soil and preventing local moisture accumulation from causing frost heave or thaw settlement. The intelligent control system uses real-time monitoring of temperature and humidity sensors and dynamic adjustment of electric heating components and drainage pipe openings to accurately maintain the phase change layer operating within the target temperature range, improve the stability of the roadbed under freeze-thaw cycles, and thus extend the time the roadbed remains in a relatively stable physical state.

[0051] On the basis of the aforementioned embodiments, in order to improve the drainage performance and thermal conductivity of the phase change-hygroscopic drainage composite roadbed structure, optimization is performed from different angles.

[0052] In a possible implementation, a deep groove structure is provided in the cross section of the water-conducting fibers of the high moisture absorption and drainage geotextile layer.

[0053] The optional high-absorbency drainage geotextile layer consists of a composite fiber structure and a water-conducting component. The composite fiber structure, composed of high-modulus polypropylene yarn, provides tensile strength and vertical support. The water-conducting component is composed of hydrophilic, moisture-absorbing fibers. The water-conducting fibers have deep grooves in their cross-section, significantly increasing their surface area and forming multi-channel water-conducting pathways.

[0054] In a possible implementation, the groove spacing of the deep groove structure is 5 to 12 μm; the diameter of the water-conducting fiber is 30 to 50 μm; and the specific surface area of the water-conducting fiber is greater than 3650 cm 2 / g.

[0055] In this embodiment, the highly absorbent drainage geotextile layer's deep groove structure and exceptionally large surface area enhance its ability to absorb capillary water and improve its water conduction efficiency. By increasing the fiber surface area and creating multi-channel water conduction pathways, the geotextile effectively transmits both gravity and capillary water in unsaturated soil conditions, improving drainage efficiency, effectively reducing soil moisture fluctuations, and inhibiting frost heave and thaw settlement deformation.

[0056] In a possible implementation, the angle range is set to 2° to 15°; the porous structure is an Ω-shaped porous structure; and the apparent pore size satisfies AOS<2.5d 85 Filtering criteria.

[0057] The drainage pipe is designed with an inclination angle of 5° to 15° to promptly drain the moisture in the soil in winter and spring, including gaseous water and liquid water, generated by temperature gradient and pumping action, to the slope drainage ditch to prevent local moisture accumulation causing frost heave or thaw settlement.

[0058] Apparent aperture meets AOS<2.5d 85 The filtration principle effectively intercepts soil particles and allows water to penetrate. The small groove design guides water to the Ω-shaped holes through capillary action and gravity, while limiting the migration of soil particles, forming a dynamic natural filter layer.

[0059] In this embodiment, the drainage pipe system adopts an Ω-shaped porous structure with an inclination angle of 2° to 15°, combined with an apparent pore size AOS < 2.5d 85The filtration principle achieves an optimal balance between drainage efficiency and anti-clogging performance. The inclined design uses gravity to accelerate water discharge. The Ω-shaped holes and small grooves guide the water flow through capillary action and intercept soil particles, forming a dynamic natural filter layer, preventing drain pipe blockage and ensuring the long-term stable operation of the drainage system. Furthermore, the tilt angle can be dynamically adjusted according to the freezing depth and groundwater level to adapt to different working conditions.

[0060] In one possible implementation, the drain pipe is made of a 2mm-thick plastic strip with a smooth, solid surface on one side and multiple Ω-shaped holes and interconnecting small slots on the other. The Ω-shaped holes have an inner diameter of 1.0mm, a slot width of 0.3mm, and a center-to-center spacing of 1.5mm. The apparent pore diameter of the drain pipe is 0.3mm.

[0061] During the specific implementation process, a drainage pipe is set under the high-hygroscopic drainage geotextile layer, a hole is drilled to a predetermined depth at the target location, and debris in the hole is cleaned; the drainage device is inserted into the drilled hole in sections, and the pipe sections are connected by connectors to ensure that the intervals are aligned; the inclination angle of the device is adjusted, and after fixing, the surrounding soil is backfilled and compacted; the outlet end is connected to a horizontal PVC pipe to divert water to the drainage ditch.

[0062] The highly hygroscopic drainage geotextile layer and drainage pipe system absorbs capillary water, seepage water and groundwater in the soil, thereby balancing the changes in soil moisture content caused by moisture migration and phase change due to the coupling of external temperature changes and traffic loads in winter, and discharges the water to the outside of the roadbed through the system, thereby reducing the risk of uneven frost heave deformation of the roadbed; in spring (permafrost thawing) working conditions, the system can absorb the moisture accumulated by moisture migration and phase change in the soil in spring, and then discharge it to the drainage ditch on one side of the roadbed through the drainage pipe, thereby reducing the possibility of roadbed melting or mud oozing due to rising temperatures.

[0063] In one possible implementation, the phase change temperature range of each phase change layer in the multi-layer gradient phase change material layer gradually decreases from top to bottom, and the phase change latent heat gradually decreases, forming a stepped temperature buffer barrier.

[0064] Figure 1 In the figure, the multi-layer gradient phase change material layer is shown as a three-layer structure, and the phase change temperature range and phase change latent heat of each phase change layer are as follows:

[0065] The first layer: The phase change temperature range is -1℃~-3℃, the phase change latent heat (△H) is 330~380 (J / g), covering the shallow freeze-thaw zone, and first absorbing the cold or heat generated by the surface temperature fluctuation;

[0066] The second layer: The phase change temperature range is -6℃~-8℃, and the phase change latent heat (△H) is 320~360 (J / g). It is aimed at the middle freezing depth area and delays the downward movement of the freezing front through the phase change layer.

[0067] The third layer: The phase change temperature range is -12℃ or lower, the phase change latent heat (△H) is 270~320 (J / g), which acts on the deep low temperature zone to inhibit the excessive development of freezing depth under extreme low temperatures.

[0068] The above layers form a stepped buffer barrier through gradient temperature intervals, which gradually reduces the conduction effect of external temperature disturbances on the internal temperature field of the roadbed.

[0069] When the ambient temperature drops to the phase transition temperature range of a certain layer, this layer of material releases latent heat through solid-liquid phase transition (for the first layer, ΔH = 27 to 46 J / g), offsetting the external cooling input and delaying the freezing process. When the first layer of phase change material ceases to function, the second layer begins to function. Similarly, during the gradual cooling process in winter, the phase change material releases latent heat, thereby controlling the freezing of the roadbed filler, delaying or even eliminating frost heave and uneven deformation. During drastic temperature fluctuations in spring, especially with nighttime cooling and daytime warming, the phase change material can release latent heat at night and absorb heat during the day, thereby maintaining a relatively stable temperature gradient in the roadbed. This in turn slows the migration and redistribution of moisture, reducing the risk of uneven deformation and mud oozing that occurs during the frequent freezing and thawing of the roadbed during the early spring thaw period and the subsequent rapid thawing.

[0070] In this embodiment, the multi-layer gradient phase change material layer is designed with a gradually decreasing phase change temperature range and phase change latent heat from bottom to top, forming a three-level temperature buffer mechanism: "shallow layer speed control, middle layer delay, and deep layer slow release." During freezing conditions, the shallow phase change layer first releases latent heat to delay the downward movement of the freezing front, while the middle and shallow layers sequentially provide additional regulation to suppress frost heave. During thawing conditions, the shallow phase change layer preferentially absorbs heat to delay thawing, while the middle and deep layers coordinate regulation to reduce thaw settlement.

[0071] In a possible implementation, the temperature difference between adjacent phase change layers is ≥3° C., the phase change latent heat of each phase change layer is ≥160 kJ / kg, and the thermal conductivity of each phase change layer is 0.15-0.25 W / (m·K).

[0072] Among them, the gradient temperature difference (≥3°C) ensures the orderly connection of the phase change processes of each layer and avoids sudden changes in the temperature field.

[0073] In this embodiment, the limiting conditions ensure temperature buffer continuity and uniform heat diffusion within the phase change layer. The temperature gradient enables relay-style control of the phase change process within each layer. The matching of thermal conductivity and latent heat parameters optimizes the uniform distribution of heat across the depth of the subgrade, avoiding localized thermal stress concentration and improving the system's reliability and durability during long-term freeze-thaw cycles.

[0074] To enhance the stability of the roadbed structure, this application utilizes a composite phase change material (CPCM) to prevent liquid phase leakage. The composite phase change material, when mixed with concrete, forms a phase change layer test block with a compressive strength of 16-20 MPa and a flexural strength of 2.0-3.1 MPa. This layer combines energy storage with structural load-bearing capacity, ensuring no risk of delamination or cracking under long-term freeze-thaw cycles.

[0075] In one possible implementation, the multi-layer gradient phase change material layer is made of a composite phase change material; the composite phase change material is formed by adsorbing a matrix phase change material on a porous medium and encapsulating it through epoxy resin or styrene acrylic emulsion; the compressive strength is 16 to 20 MPa, and the flexural strength is 2.0 to 3.1 MPa.

[0076] Among them, the porous media include expanded perlite and vermiculite.

[0077] In this embodiment, the composite phase change material uses expanded perlite and vermiculite porous media to adsorb the matrix phase change material, which is then encapsulated in epoxy resin to form a high-strength, leak-resistant phase change energy storage structure. Mechanical properties of 16-20 MPa compressive strength and 2.0-3.1 MPa flexural strength ensure that the phase change layer will not delaminate or crack during long-term freeze-thaw cycles. The epoxy resin encapsulation effectively prevents liquid leakage, extending the service life of the phase change material. The porous media also enhances the adsorption stability and thermal conductivity of the phase change material.

[0078] In a possible implementation, each phase change layer is bonded between layers using an environmentally friendly adhesive or a mechanically fixed frame to form a continuous gradient temperature buffer zone.

[0079] In one possible implementation, graphite or metal powder is added to the multi-layer gradient phase change material layer, the thermal conductivity is increased to 0.20-0.25 W / (m·K), and the latent heat release uniformity deviation is less than 5%.

[0080] In this embodiment, the addition of graphite or metal powder to the phase change material layer significantly improves its thermal diffusion properties. The highly thermally conductive filler accelerates the lateral and longitudinal conduction of latent heat from the phase change within the roadbed, enabling more uniform and efficient temperature control. This prevents localized overheating or overcooling caused by concentrated thermal stress, enhancing the system's adaptability to extreme temperature fluctuations.

[0081] The phase change-moisture absorption and drainage composite roadbed structure provided in the above embodiments can be used for both new roadbed construction and the reconstruction of existing freeze-thaw damaged roadbeds, and has high applicability and economy. Figure 4 A schematic diagram of the construction process of the phase change-hygroscopic drainage composite roadbed structure in the seasonally frozen area is shown.

[0082] like Figure 4As shown in the figure, the system construction adopts a modular design. First, the roadbed subgrade is pretreated (filling, leveling, and compacting). Sensors are placed at the bottom of the phase change material. Then, drainage pipes are laid at fixed intervals on the surface of the bottom layer to control the inclination angle from 5° to 15°. The drainage effect is checked, and a high-hygroscopic drainage geotextile layer is laid. Then, the drainage pipe system, geotextile layer, and gradient PCM layer are laid in sequence.

[0083] After the temperature sensor and control module are installed on site, a trial run and system debugging are conducted to ensure that the modules work together to achieve the expected temperature control and drainage effects. In order to verify the system operation effect, the following two specific examples are provided:

[0084] Example 1: Railway roadbed test section application

[0085] A test section approximately 20 meters long was selected on a railway subgrade in a typical seasonally frozen zone. After pre-treating the subgrade surface, three layers of gradient PCM (50 mm thick) were laid in sequence. The first layer had a phase transition temperature of -2°C to -3°C, the second layer had a temperature of -6°C to -8°C, and the third layer had a temperature of -12°C. A highly hygroscopic drainage geotextile was laid beneath the PCM layer, and drainage pipes were arranged at a 2° inclination. Temperature sensors were installed at key points on the subgrade surface and within it, and connected to a microcontroller to form a closed-loop control system. After continuous freeze-thaw cycles and on-site monitoring, data showed that the system can effectively stabilize the subgrade surface temperature, reduce frost heave and thaw settlement deformation, and extend the subgrade's service life.

[0086] Example 2: Highway roadbed reconstruction project

[0087] A phase change-moisture absorption and drainage composite system was used in a highway subgrade renovation project for frost protection. The construction process involved first laying a negative temperature phase change layer and a porous medium composite layer, then laying an optimized geotextile and drainage pipes underneath, and finally installing a temperature control feedback module. Field data showed that the system maintained a stable temperature distribution under continuous freeze-thaw cycles, effectively alleviating subgrade frost heave and thaw settlement issues. Its simple construction process and low cost suggest broad application prospects.

[0088] Based on the verification results of the above embodiments, it can be seen that the seasonally frozen zone phase change-hygroscopic drainage composite roadbed structure provided by the embodiments of the present application can be applied to different application scenarios of railway roadbed and highway roadbed, and has high applicability.

[0089] It should be understood that the execution order of each step in the above embodiment is determined by its function and internal logic, and does not constitute any limitation on the implementation process of the embodiment of the present invention. The following is an embodiment of the intelligent control method of the present invention. For details not described in detail, please refer to the relevant principle description in the corresponding device embodiment above.

[0090] The present application provides an intelligent control method, which uses the composite roadbed structure provided by any of the above embodiments. The method includes:

[0091] Get temperature and humidity sensor data;

[0092] According to the temperature and humidity sensor data and PID algorithm, the power of the electric heating components of each phase change layer and the opening of the drain pipe are adjusted.

[0093] In this embodiment, a dynamic intelligent control method based on temperature and humidity sensor data and a PID algorithm achieves precise response to freeze-thaw cycles. By identifying whether the current operating condition is frozen or thawed, the system automatically adjusts the phase change layer electric heating power and the drain pipe opening, achieving intelligent control.

[0094] In one possible implementation, the power of the electric heating components of each phase change layer and the opening of the drain pipe are adjusted according to the temperature and humidity sensor data and the PID algorithm, including:

[0095] When the soil temperature is determined to be lower than the set temperature according to the temperature and humidity sensor data, the electric heating component is started to heat;

[0096] When the soil humidity is determined to exceed the set humidity according to the temperature and humidity sensor data, the drain pipe valve is opened to accelerate drainage.

[0097] Optionally, the set temperature is between 0°C and 3°C. In one possible implementation, the set temperature is 0°C, where 0°C is the critical freezing point. When the soil temperature is detected to be below 0°C, a thermal barrier is quickly formed to inhibit freezing. In other possible implementations, the set temperature is 1°C, 2°C, or 3°C. When the soil temperature is detected to be below the set temperature and approaching the critical freezing point, freezing is prevented in advance.

[0098] Optionally, the humidity is set to 12% to 20%. In practice, the humidity setting may vary depending on the soil composition in different regions. For example, the humidity setting for sandy soil is 12%, for silty clay soil is 18%, and for clay soil is 20%.

[0099] In this embodiment, when the soil temperature falls below a set point, the system automatically activates the electric heating components of the corresponding phase change layer, actively compensating for heat and maintaining the layer within its effective operating temperature range. When the soil humidity exceeds the set point, the drain valve rapidly opens to accelerate drainage, preventing moisture accumulation and frost heave. This threshold triggering mechanism, combined with the dynamic adjustment of the PID algorithm, improves system response time and control accuracy, enabling refined control and rapid response of temperature and humidity.

[0100] Another possible implementation involves adjusting the soil temperature and moisture content beneath the phase change layer based on data from temperature and humidity sensors and a PID algorithm. When the temperature drops below a set point (e.g., 0°C), the heating rods are triggered for preheating or heat dissipation compensation, enabling dynamic regeneration and continuous control of the phase change material. This mechanism ensures that the phase change layer replenishes energy promptly after the solid-liquid phase transition, maintaining its temperature control efficiency, extending the system's effective operating cycle, and reducing the need for manual intervention.

[0101] In the above embodiments, the descriptions of each embodiment have their own focus. For parts not described or recorded in detail in one embodiment, please refer to the relevant descriptions of other embodiments. Unless otherwise specified or there is a logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced to each other. The technical features of different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0102] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A seasonally frozen zone phase change-hygroscopic drainage composite roadbed structure, characterized in that: include: Multi-layer gradient phase change material layer, high moisture absorption and drainage geotextile layer, drainage pipe system and intelligent control system; Wherein, the multi-layer gradient phase change material layer is arranged on the top surface of the roadbed surface; The multi-layer gradient phase change material layer, the high moisture absorption drainage geotextile layer and the drainage pipe system are arranged from top to bottom; The phase change temperature range and phase change latent heat of each phase change layer in the multi-layer gradient phase change material layer are different; The highly hygroscopic drainage geotextile layer is used to guide water in the soil into the drainage pipe system; The drainage pipe system adopts a porous structure with an inclination angle within a set angle range to guide water in the soil into the drainage ditch; The intelligent control system includes a microcontroller, a feedback module, temperature and humidity sensors distributed in each phase change layer in the multi-layer gradient phase change material layer and the high moisture absorption drainage geotextile layer, and an electric heating component, which is used to dynamically adjust the thermal resistance of each phase change layer and the opening of the drainage pipe.

2. The structure according to claim 1, characterized in that The cross section of the water-conducting fibers of the high moisture absorption and drainage geotextile layer is provided with a deep groove structure.

3. The structure according to claim 2, characterized in that The groove spacing of the deep groove structure is 5 to 12 μm; the diameter of the water-conducting fiber is 30 to 50 μm.

4. The structure according to claim 1, characterized in that The setting angle range is 2° to 15°; and the porous structure is an Ω-shaped porous structure.

5. The structure according to claim 1, characterized in that The phase change temperature range of each phase change layer in the multi-layer gradient phase change material layer gradually decreases from bottom to top, and the phase change latent heat gradually decreases.

6. The structure according to claim 5, characterized in that The temperature difference between adjacent phase change layers is ≥3°C, and the phase change latent heat of each phase change layer is ≥160kJ / kg.

7. The structure according to claim 5, characterized in that The multi-layer gradient phase change material layer is made of a composite phase change material; the composite phase change material is formed by adsorbing a matrix phase change material on a porous medium and encapsulating it with epoxy resin or styrene acrylic emulsion; Wherein, the porous medium includes expanded perlite and vermiculite.

8. The structure according to claim 5, characterized in that Graphite or metal powder is doped into the multi-layer gradient phase change material layer.

9. An intelligent control method, characterized in that: The seasonally frozen zone phase change-hygroscopic drainage composite roadbed structure according to any one of claims 1 to 8 comprises: Get temperature and humidity sensor data; According to the temperature and humidity sensor data and the PID algorithm, the power of the electric heating component under the phase change layer and the opening of the drain pipe are adjusted.

10. The method according to claim 9, characterized in that The method of adjusting the power of the electric heating components of each phase change layer and the opening of the drain pipe according to the temperature and humidity sensor data and the PID algorithm includes: When it is determined according to the temperature and humidity sensor data that the soil temperature is lower than the set temperature, the electric heating component is started to heat; When it is determined according to the temperature and humidity sensor data that the soil humidity exceeds the set humidity, the drain pipe valve is opened to accelerate drainage.

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