A prefabricated chemical energy pile-gravity heat rod collaborative geothermal regulation method and system

Abstract

The application discloses a prefabricated chemical energy pile-gravity heat rod collaborative ground temperature regulation method and system, relates to the technical field of roadbed construction, and comprises the following steps: obtaining target area foundation data; constructing a reinforcement learning state space; automatically generating a non-uniform pile arrangement scheme by using a deep reinforcement learning model; preparing a geotextile wrapped lime energy pile and a gravity heat rod and constructing the same to form a composite temperature control foundation; using lime hydration heat to pre-melt the frozen soil around the pile, and using the heat diode characteristics of the gravity heat rod, i.e., directional heat dissipation in the cold season and automatic stop in the warm season, to maintain the minimum temperature of the foundation to be not lower than a preset positive temperature threshold; after embankment construction, the foundation stiffness is evaluated by means of bending element shear wave velocity testing, and a pre-embedded electro-osmotic device can be started to locally regulate water. The application realizes passive temperature control in the whole life cycle by the collaborative cooperation of lime heat release and one-way heat dissipation of the heat rod, combined with reinforcement learning optimization of pile arrangement, has high bearing capacity and low cost.

Description

Technical Field

[0001] This invention relates to the field of roadbed construction technology, and in particular to a method and system for coordinating ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes. Background Technology

[0002] When constructing highways in permafrost regions, the permafrost beneath the roadbed is highly susceptible to thawing and subsidence under thermal disturbance, leading to serious problems such as uneven roadbed settlement and pavement cracking. To maintain the thermal stability of the roadbed, two main categories of measures are currently adopted in engineering: passive insulation measures, such as laying insulation layers and installing ventilation pipes in the roadbed; and active cooling measures, such as burying gravity heat pipes, utilizing their unidirectional heat-conducting "thermal diode" characteristics during the cold season to dissipate heat from the foundation. In addition, some studies have proposed using the heat released by the hydration of quicklime to pre-thaw and reinforce the permafrost foundation.

[0003] For example, application CN103061224A discloses a method for reinforcing permafrost foundations using quicklime and gravel piles. This method involves drilling holes in the permafrost using rotary or impact drilling, and then compacting a well-mixed mixture of quicklime and gravel into the holes to form piles. This method utilizes the heat released by the reaction of quicklime with water in the soil to actively melt the permafrost around the piles and compact and reinforce the foundation. However, this technology has significant shortcomings: the heat release process of quicklime is uncontrollable and concentrated in the early stages of construction, lacking the ability to continuously regulate ground temperature during the later operational phase; furthermore, the pile placement mainly relies on engineering experience, making it difficult to achieve global optimization for complex geological conditions, and it also fails to resolve the contradiction between heat accumulation in the warm season and excessive refreezing in the cold season.

[0004] To address the above problems, this invention proposes a method and system for coordinated ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes. Summary of the Invention

[0005] In order to overcome the problems mentioned in the background art, the present invention proposes a method and system for coordinating ground temperature regulation of prefabricated chemical energy piles and gravity heat pipes.

[0006] The technical solution of this invention is: a method for coordinating ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes, comprising the following steps:

[0007] S1: Obtain the design ground temperature field data, settlement deformation data, and load requirement data of the foundation in the target permafrost region;

[0008] S2: Construct a reinforcement learning state space based on the above data, use the pile layout parameters of lime energy piles and gravity heat pipes as the action space, and use the minimization of the whole life cycle cost and the maximization of the post-construction bearing capacity as the joint reward. Use a deep reinforcement learning model to generate a non-uniform pile layout scheme. The pile layout parameters include pile location, pile diameter, pile length, lime content, as well as the number of gravity heat pipes, the length of the evaporation section, and the size of the condensation section.

[0009] S3: According to the non-uniform pile layout scheme, geotextile is prepared in the factory to wrap lime energy piles and gravity heat pipes, and then installed in the foundation to form a composite temperature-controlled foundation composed of lime energy piles and gravity heat pipes.

[0010] S4: Utilize the heat release reaction of lime hydration in the lime energy pile to pre-melt the permafrost around the pile, and utilize the thermal diode characteristics of the gravity heat rod that automatically starts unidirectional heat dissipation in the cold season when the ambient temperature is lower than the ground temperature and automatically stops working in the warm season when the ambient temperature is higher than the ground temperature to conduct excess heat out of the soil between the piles and maintain the minimum temperature of the foundation throughout the year not lower than the preset positive temperature threshold.

[0011] S5: After the pre-melting stage is completed, the embankment filling and pavement structure layer construction will be carried out in sequence;

[0012] S6: After construction or during operation, the bending element shear wave velocity test method is used to evaluate the foundation stiffness recovery effect and spatial uniformity, and the electroosmosis device is activated to regulate the moisture in local areas.

[0013] Preferably, the deep reinforcement learning model in step S2 adopts the SoftActor-Critic algorithm, wherein: the state space includes a geothermal field grayscale cloud map and a settlement field grayscale cloud map; the action space includes increasing pile diameter, decreasing pile diameter, pile length, lime content, number of gravity heating rods, as well as pile addition and deletion operations at specific spatial locations; the bearing capacity reward in the joint reward is the ratio of the ultimate bearing capacity of the pile-soil composite foundation corresponding to the preset operating years to the design requirements, the cost penalty is the ratio of the total life cycle cost to the budget, and a temperature safety constraint penalty item is set—a negative reward is given when the lowest temperature at any point of the foundation is lower than -0.5℃ or the differential settlement exceeds the limit.

[0014] Preferably, the lime energy piles and gravity heat pipes in step S3 are arranged in a spatially staggered manner: multiple lime energy piles are arranged in a quincunx pattern, and the gravity heat pipes are arranged at the center of the triangle formed by three adjacent lime energy piles, and the bottom depth of the evaporation section of the gravity heat pipes is flush with or deeper than the bottom of the lime energy piles.

[0015] Preferably, the geotextile-wrapped lime energy pile is vertically buried in the center of the pile hole, and the pile hole and the geotextile-wrapped lime energy pile are filled with backfill material to form an annular backfill layer; the lower end of the gravity heat rod is inserted into the annular backfill layer and maintains a preset distance from the outer wall of the geotextile-wrapped lime energy pile.

[0016] Preferably, the geotextile-wrapped lime energy pile in step S3 is a GELEC pile. The GELEC pile consists of a high-strength woven geotextile tube filled with a lime-soil mixture. The circumferential restraint effect of the geotextile enhances the vertical bearing capacity of the pile, and the lime hydration process generates… Ions migrate through the pores of the geotextile to the pile-soil interface, where they undergo ion exchange and carbonation reactions to enhance interfacial cohesion.

[0017] Preferably, if the moisture content of a local area of ​​the foundation deviates from the optimal moisture content range during the implementation of step S4 or before the construction of step S5, the electroosmosis method is activated to regulate moisture: carbon fiber electrodes are arranged on both sides of the area to be regulated, and a DC electric field of 30V to 60V is applied to drive pore water to migrate directionally from the anode to the cathode and be discharged until the soil moisture content is restored to the optimal moisture content.

[0018] Preferably, the bending element shear wave velocity test evaluation in step S6 uses the recovery ratio (RR) and improvement ratio (R). As an indicator, among them, , , , , Shear wave velocities under treated, saturated, and optimum moisture content conditions, respectively; when the treated foundation simultaneously satisfies , And the horizontal anisotropy index At that time, the ground temperature control effect was deemed satisfactory.

[0019] As a preferred option, the evaporation section of the gravity heat pipe is also protected against corrosion: 316L stainless steel or titanium alloy is selected as the material for the gravity heat pipe tube, and an epoxy resin-based anti-corrosion coating is applied to its outer surface.

[0020] Preferably, the preset positive temperature threshold is +1.0℃, and the method is applicable to roadbed engineering in degraded permafrost areas with an annual average ground temperature of -2.5℃ to -4.0℃.

[0021] A prefabricated chemical energy pile-gravity heat pipe synergistic geothermal regulation system includes:

[0022] Multiple geotextiles wrap lime energy piles, which are filled with lime-soil mixture with a pre-set lime content to pre-melt the permafrost around the piles through hydration heat release.

[0023] Multiple gravity heat pipes, combined with the lime energy piles, are arranged in an optimized layout in both plane and depth to unidirectionally extract ground heat during the cold season. The optimized layout is generated by a deep reinforcement learning model based on the initial ground temperature field, settlement deformation, and load demand data of the target frozen soil foundation, with the goal of minimizing the total life cycle cost and maximizing the post-construction bearing capacity.

[0024] A bending element test device is set at a key location in the soil between piles to measure shear wave velocity in order to evaluate the foundation stiffness and its uniformity.

[0025] An electroosmosis device, comprising spaced carbon fiber strip electrodes and a DC power supply, is used for directional water migration in the event of localized water content anomalies.

[0026] The lime energy pile and gravity heat pipe work together to maintain the lowest temperature of the foundation above the preset positive temperature threshold throughout the year.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention introduces a deep reinforcement learning model (SAC algorithm), using the geothermal field and settlement field as the state space, and the pile location, pile diameter, lime content, and heat pipe parameters as the action space, to automatically generate an optimal non-uniform scheme that adapts to the differences between sunny and shady slopes. Compared with traditional empirical pile placement, this invention requires fewer piles, has more precise placement, and reduces the estimated total life cycle cost by approximately 13%, while meeting the bearing capacity requirements for a 50-year operational period.

[0029] 2. This invention utilizes the heat released by lime hydration to actively pre-melt the frozen soil around the piles, accelerating early strength formation; the gravity heat pipe automatically removes excess heat from the foundation during the cold season and automatically shuts off during the warm season to prevent heat intrusion. The two complement each other in time, ensuring that the minimum temperature of the foundation is stably maintained above +1.0℃ throughout the year, avoiding both refreezing and thaw settlement, overcoming the shortcomings of existing technologies that rely solely on the initial heat release of quicklime and cannot be controlled in the later stages.

[0030] 3. This invention forms GELEC piles by wrapping lime-soil mixture with geotextiles. Circumferential constraint and ion exchange reaction significantly improve the pile-soil interface strength. After construction, the uniformity of foundation stiffness is quantitatively evaluated using bending element shear wave velocity. If local water content is abnormal, an electro-osmosis device can be activated for precise drainage control. This combined approach ensures uniform and maintainable foundation stiffness, meeting the long-term service requirements of highway subgrades in degraded permafrost regions. Attached Figure Description

[0031] Figure 1 This is an overall flowchart of the method for controlling the temperature of precast pile roadbed in permafrost according to the present invention.

[0032] Figure 2 This is a schematic diagram of the overall structure of the permafrost precast pile roadbed temperature control system of the present invention;

[0033] Figure 3 Detailed drawing of a lime-encased energy pile structure with geotextile wrapping;

[0034] Figure 4 A top-view plan of a non-uniform pile layout generated by reinforcement learning;

[0035] Figure 5 The curve shows the change in heat release power of lime water simmering over time.

[0036] Figure 6 This is a graph showing the seasonal variation of the equivalent thermal conductivity of a gravity heat pipe.

[0037] Figure 7 Comparison of geothermal field cloud maps between AI-optimized pile placement scheme and experience-based uniform pile placement scheme;

[0038] Figure 8 This is a curve showing the annual variation of the lowest foundation temperature over a 50-year operating period. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments and examples. It should be understood that the specific embodiments described herein are for illustrative purposes only and do not constitute a limitation on the scope of protection of this invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art based on the disclosure of this invention without inventive effort fall within the scope of protection of this invention.

[0040] It should be noted that "permafrost" mentioned in this invention refers to soil and rock with a temperature of 0℃ or below that has existed continuously for at least two years; the annual average ground temperature refers to the annual average ground temperature within a certain depth range below the upper limit of permafrost. The core idea of ​​this invention is to introduce gravity heat pipes and lime energy piles to work together, utilizing the former's directional heat dissipation characteristics as a "thermal diode" in the cold season and the latter's concentrated chemical heat release characteristics in the warm season to form a passive temperature control system for all seasons; at the same time, abandoning the traditional empirical trial-and-error pile placement method, it uses a deep reinforcement learning agent to autonomously find the optimal solution in a huge non-uniform design space, ultimately achieving roadbed temperature control applicable to degraded permafrost areas with an annual average ground temperature as low as -4.0℃.

[0041] Example 1

[0042] Please see Figure 1 The following uses a roadbed project in the degraded permafrost region of a Class I highway in the Greater Khingan Mountains of China as an example to illustrate the implementation process of this invention in detail. The average annual temperature of this road section is about -3.2℃, and the average annual ground temperature below the natural surface is about -3.5℃. It belongs to a typical frozen soil area with severe permafrost degradation and significant yin-yang slope effects. Traditional single measures are difficult to guarantee the long-term thermal stability of the roadbed.

[0043] Step S1: Obtain the design ground temperature field data, settlement deformation data, and load requirement data of the foundation in the target permafrost region.

[0044] First, a detailed geological survey and ground temperature monitoring were conducted in the area of ​​the roadbed to be constructed. Exploration boreholes, with a depth of no less than 20m, were laid along the centerline and left and right shoulders of the road. Sampling was performed every 2m to determine the soil's natural density, moisture content, particle size distribution, organic matter content, and other physical properties. Thermal physical parameters such as thermal conductivity, specific heat capacity, and freezing characteristic curves under different temperature conditions were obtained through laboratory tests. Thermocouple strings were installed in representative boreholes to continuously monitor ground temperature for at least one complete freeze-thaw cycle, obtaining the natural ground temperature field's variation over time, including key data such as annual average ground temperature, annual variation depth, and maximum thawing depth.

[0045] Simultaneously, through GPS elevation measurements, ground-penetrating radar detection, and InSAR historical image analysis, the current settlement and deformation distribution characteristics of the foundation were obtained, especially the differential settlement caused by different rates of permafrost degradation between the ecliptic slopes, shoulders, and the roadbed centerline. Load demand data were then used to calculate the additional stress transmitted to the foundation from embankment fill and traffic loads, based on the highway grade, pavement structure, and design service life.

[0046] Taking the road section in this embodiment as an example, the geological profile from top to bottom is as follows: 0~2.5m is a silty clay layer (melted layer), 2.5~8.0m is a glacial silty clay layer (permafrost layer), and below 8.0m is strongly weathered granite. The annual variation range of natural ground temperature is approximately ±18℃ at the surface, decreasing to ±1.5℃ at a depth of 8m. The annual average ground temperature is -3.5℃, and the active layer thickness is approximately 2.5m. These data will serve as the basis for the initial and boundary conditions of the subsequent simulation environment.

[0047] Step S2: Construct a reinforcement learning state space using the data, use the pile layout parameters of lime energy piles and gravity heat pipes as the action space, use the minimization of the whole life cycle cost and the maximization of the post-construction bearing capacity as the joint reward, and use a deep reinforcement learning model to generate a non-uniform pile layout scheme.

[0048] Please see Figure 4 The core of this step is to establish an AI-driven autonomous design platform to replace the traditional manual parameter trial and error. Its implementation process can be divided into three stages: simulation environment setup, reinforcement learning interactive interface encapsulation, and model training and solution generation.

[0049] S21: Simulation environment setup.

[0050] First, a numerical model capable of simulating the thermo-mechanical coupling behavior of permafrost subgrade with high fidelity needs to be constructed. This embodiment utilizes secondary development based on COMSOL Multiphysics finite element software to build a three-dimensional subgrade cross-sectional model. The model width is 3 to 5 times the subgrade width, and the depth extends to the undisturbed layer below the annual geothermal variation depth (in this example, to -15m) to eliminate boundary effects.

[0051] The physical fields considered in the model include:

[0052] (1) Thermal conduction and phase change in frozen soil: The sensible heat capacity method was used to treat the ice-water phase change. It was assumed that the phase change occurred in the temperature range of -0.5℃ to 0℃, and that the thermophysical parameters transitioned linearly and smoothly with temperature within this range. The thermal conductivity and specific heat capacity were set based on measured values ​​and recommended values ​​in the specifications.

[0053] (2) Heat release from lime hydration: The heat release rate of lime energy piles is related to the amount of lime per unit volume. hydration reaction completion rate and temperature correction factor Related. Degree of completion of hydration reaction. Controlled by the amount of available water, it is usually a first-order kinetic equation: Among them, pre-exponential factors and activation energy The total heat of hydration was approximately 104.4 kJ / mol, calibrated using a microcalorimeter. The heat release lasts from several weeks to several months, with a large amount of heat released in the short term and a decrease over the long term.

[0054] Please see Figure 5 , Figure 5 The variation of the hydration heat release power of lime energy piles over time is shown. After the lime energy pile construction is completed, the quicklime inside the pile undergoes a hydration reaction with the moisture in the mixture, and the heat release power increases rapidly from the initial state, reaching its peak on days 7 to 14 after construction. During this stage, the internal temperature of the pile can rise to approximately 60–80°C, forming the initial concentrated heat release stage of the lime energy pile.

[0055] As the content of reactive calcium oxide and the amount of available water gradually decrease, the lime hydration reaction rate declines, the exothermic power gradually decreases from its peak, and a low-power exothermic process lasting for several weeks to months is formed. The heat of hydration is transferred to the permafrost around the pile through the pile body, which is used to overcome the sensible heat required for the permafrost to warm up and the latent heat required for the ice-water phase change, so that the frozen soil around the pile gradually melts.

[0056] In this embodiment, approximately 90 days after the construction of the lime energy pile is taken as the reference end time of the pre-melting stage. After this time point, the instantaneous heat release power of the lime energy pile has decreased to a small proportion of the peak value, the main area around the pile has completed the initial heating and melting, and the foundation temperature control process gradually shifts from the initial concentrated chemical heat release stage to the long-term temperature regulation stage.

[0057] It should be noted that, Figure 5The curve shown is used to characterize the typical heat release trend of lime energy piles. The actual peak heat release power, peak occurrence time and decay rate are related to lime content, calcium oxide activity, water-cement ratio, pile diameter, pile length, moisture content of mixture and initial ground temperature. They can be calibrated by microcalorimetry test, adiabatic temperature rise test or by burying temperature sensors on site.

[0058] (3) Gravity heat pipe heat transfer: The gravity heat pipe is simplified as an equivalent high thermal conductivity body. The equivalent thermal conductivity is set in segments according to the working state of the heat pipe: when the average temperature of the condensation section is... Greater than the average temperature of the evaporation section When the heat pipe is not in operation, its equivalent thermal conductivity is equal to that of the tube metal itself, approximately... ;when At that time, the working fluid inside the heat pipe undergoes an evaporation-condensation cycle, exhibiting an equivalent thermal conductivity of up to The heat pipe operates on the order of W / (m·K). The starting temperature difference is approximately 0.5~1.0℃. The condensation section is exposed to the atmosphere, while the evaporation section is embedded in the soil between the piles.

[0059] Please see Figure 6 , Figure 6 The seasonal variation of the equivalent thermal conductivity of the gravity heat pipe is shown over a one-year operating cycle. The operating status of the gravity heat pipe is autonomously controlled by the temperature difference between the condensation and evaporation sections, without the need for an external power unit or active control mechanism.

[0060] During the warmer season, the ambient temperature is typically higher than the internal temperature of the foundation, and the temperature of the condensation section is not lower than that of the evaporation section. The working fluid inside the heat pipe mainly remains at the bottom of the evaporation section, preventing the formation of a stable evaporation, condensation, and gravity reflux cycle. At this time, the gravity heat pipe is in a closed state, and its equivalent thermal conductivity is close to the thermal conductivity of the pipe metal itself, approximately 15 W / (m·K) in this embodiment, thereby reducing the transfer of external heat into the foundation via the heat pipe.

[0061] During the cold season, when the ambient temperature drops and the temperature of the condensing section falls below that of the evaporating section, and the temperature difference between the two reaches the starting temperature difference threshold of approximately 0.5–1.0℃, the liquid working fluid in the evaporating section absorbs heat from the foundation and vaporizes. The vapor rises to the condensing section, releases heat to the outside, and condenses. The condensate returns to the evaporating section under gravity, thus forming a continuous evaporation-condensation cycle. When the gravity heat pipe switches from the off state to the working state, its macroscopic equivalent thermal conductivity jumps to no less than [amount missing]. W / (m·K), thereby rapidly and directionally transferring excess heat from the foundation to the external environment.

[0062] When the temperature difference between the condensation section and the evaporation section falls below the starting temperature difference threshold again, the working fluid circulation gradually stops, and the gravity heat pipe returns to a low thermal conductivity state. Therefore, the gravity heat pipe can automatically switch between a high thermal conductivity operating state and a low thermal conductivity off state according to the seasonal temperature difference, forming a passive unidirectional heat transfer process with thermal diode characteristics.

[0063] (4) Atmospheric temperature boundary: described by Fourier series plus a global warming trend term, i.e. .in, Using meteorological statistics from the past 30 years, The annual amplitude is 19°C in this example. The phase angle, The warming rate is 0.033℃ / year. The convective heat transfer coefficient between the Earth's surface and the atmosphere is taken as... .

[0064] (5) Mechanical Field: The temperature field calculation results are used as the temperature load input for thermoelastic or thermoelastic-plastic mechanical calculations to solve for the deformation and bearing capacity of the pile-soil composite foundation. The Mohr-Coulomb model is used for the soil, and the linear elastic model is used for the piles. The deformation and bearing capacity of the pile-soil composite foundation are determined by considering the effects of lime hydration. Ion migration improves the pile-soil interface strength, and the shear strength parameters of the interface element... and The settings can be adjusted according to the curing time and ion concentration over time, but for simplicity, this embodiment uses long-term valid values ​​for the interface parameters when calculating the load-bearing capacity.

[0065] Using parametric modeling technology, the location, diameter, length, and lime content of each pile, as well as the location, evaporation section length, and condensation section heat dissipation area of ​​each heat pipe, are treated as adjustable variables, and non-uniform and irregular arrangement forms are supported.

[0066] S22: Encapsulation of reinforcement learning interaction interface.

[0067] To connect the numerical model described above with the reinforcement learning algorithm, an OpenAIGym-style interactive environment needs to be constructed. In this environment, each action of the agent will change the aforementioned design variables. The environment will run a simulation on a 50-year timescale based on the new design and return the next state and reward.

[0068] State Space S: To reduce input dimensionality and extract spatial features, the geothermal field and cumulative settlement field at typical times after the model has been run for 20 years (e.g., August 15th, representing the hottest state, and January 15th, representing the coldest state) are output as 64×64 pixel grayscale cloud maps. The grayscale values ​​map the temperature range (-4℃ to 20℃) and settlement range (0 to the maximum allowable settlement of 15cm). The two images are stitched together into a 2-channel array as part of the state. Additionally, statistical vectors of the current design scheme are included, such as the total number of piles, average pile diameter, total lime usage, and total heat dissipation area of ​​the heat pipes, forming a complete state tensor.

[0069] Action Space: Permitted actions include: adding or deleting an existing pile at a preset candidate location (mesh the roadbed cross-section); modifying the pile diameter (±5cm), pile length (±0.5m), and lime content (±2% by mass) of a pile; increasing or decreasing the number of gravity heating elements at a location and adjusting their evaporation section length (±0.5m). Actions are continuous variables, mapped to the actual parameter range after activation by Sigmoid or Tanh. To ensure physical feasibility, duplicate pile placement at existing locations is prohibited, and the net distance between piles must be greater than 0.5m.

[0070] Reward function R: The reward consists of three parts:

[0071] (1) Carrying capacity bonus ,in, The probabilistic ultimate bearing capacity of the pile-soil composite foundation at the end of the 50-year operation period (obtained through the strength reduction method or numerical loading). The design bearing capacity is based on the requirements of embankment load and traffic load.

[0072] (2) Cost penalty Material costs: Construction costs include lime, geotextiles, heat pipe working fluid, pipes, and anti-corrosion coatings. Maintenance costs include drilling, grouting, and hoisting. Consider the potential 10% replacement cost of heat pipes over 50 years. This is the maximum approved budget for the project.

[0073] (3) Safety constraints and penalties If the lowest temperature at any point on the foundation is below -0.5℃ (refreezing) at any time within 50 years, a penalty of -1.0 will be imposed; if the differential settlement exceeds 5cm, a penalty of -0.5 will be imposed; if the annual effective working time of the heat pipe (the period when the heat dissipation power is >20W / m) is less than 30% of the total cold season time (indicating that the heat pipe efficiency is too low), a penalty of -0.2 will be imposed.

[0074] The overall reward is In this embodiment, we take .

[0075] S23: Model training and scheme generation.

[0076] The SoftActor-Critic (SAC) algorithm is used for training. SAC is a policy-dependent algorithm for maximum entropy reinforcement learning, which effectively balances exploration and exploitation and stably converges to high-dimensional tasks in continuous action spaces. The policy network (Actor) uses a residual convolutional network (ResNet-18) as the visual feature extractor, followed by fully connected layers, and outputs the mean and variance of the Gaussian distribution for each action. The value network (Critic) is a dual Q-network, which takes the complete state and action vectors as inputs and outputs the Q-values.

[0077] To improve training efficiency, a small number of high-fidelity simulations (approximately 500 randomized schemes) were first run as samples to train a convolutional neural network surrogate model for quickly predicting the geothermal and subsidence fields in year 20 under given design variables. The surrogate model achieved an accuracy of less than 0.5℃ and 2mm root mean square error on a single test set. During training, in each round, the agent samples actions according to the current policy, and the surrogate model generates new states and rewards, which are stored in the experience replay pool. Every 100 rounds, a complete high-fidelity simulation is used to verify the current optimal scheme. If the surrogate model is found to have a large deviation, the real data is fed back to the surrogate model for online fine-tuning.

[0078] After approximately 20,000 iterations, the reward function tends to converge. The characteristics of the optimal non-uniform staking scheme generated by the AI ​​are as follows:

[0079] On the sunny (south-facing) side, due to the greater heat absorption during the warm season and the higher soil temperature, the amount of lime added is reduced by 15% compared to the shady side, and the pile spacing is increased to 2.5m to prevent excessive heating from causing the pile bearing capacity to soften.

[0080] On the shady slope (north-facing slope), the diameter of the lime energy piles is increased to 0.45m, the lime content is increased to 18%, the pile spacing is increased to 1.8m, and a gravity heating rod is inserted between every two lime piles. The evaporation section of the heating rod is 3.5 to 6.5m deep, covering the maximum melting depth area.

[0081] A row of gravity heating rods is installed under each shoulder, and the diameter of the shoulder piles is appropriately increased to control differential settlement.

[0082] A total of 38 lime energy piles and 12 gravity heating rods were installed. The estimated life-cycle cost was 87% of that of the traditional uniform scheme. The bearing capacity was predicted to meet the design requirements at the end of 50 years, and the minimum annual temperature of the foundation was kept above +1.2℃.

[0083] Please see Figure 7 , Figure 7The results show the comparison of the ground temperature field between the AI ​​non-uniform optimized pile layout scheme and the traditional uniform pile layout scheme under the same roadbed cross section, the same material parameters, the same meteorological boundary conditions, and the same operating time. Figure 7 The coldest day in the 20th year of operation was selected as a representative comparison time, and the same temperature color scale was used to display the ground temperature distribution of the two schemes.

[0084] Scheme A is a non-uniform optimized pile layout scheme generated using a deep reinforcement learning model. This scheme differentiates the pile diameter, pile length, pile spacing, lime content, and the location and evaporation section length of the gravity heating element based on the thermal boundary differences between the shady slope, sunny slope, shoulder, and roadbed center area. Figure 7 As can be seen, Scheme A exhibits a relatively gentle isotherm distribution, with good continuity of soil temperature between piles. Both local high-temperature and low-temperature zones are suppressed, and the lowest foundation temperature is approximately 1.32℃, maintaining the overall temperature within the preset positive temperature control range. Scheme B is a traditional uniform pile layout scheme, using essentially the same pile diameter, pile spacing, and lime content in each area. Due to differences in thermal boundary conditions on the sunny and shady slopes and the heat dissipation conditions on the road shoulders, uniform layout cannot compensate for heat in different areas, resulting in a significant temperature gradient near the piles and between piles. This leads to localized hot and cold concentration, with the lowest temperature dropping to approximately -0.68℃.

[0085] The comparative results show that the non-uniform pile layout scheme generated by deep reinforcement learning can reasonably allocate lime energy piles and gravity heat pipes according to the spatial differences of the geothermal field, so that the heat source intensity and heat dissipation capacity are matched with the actual heat load of different areas. While reducing the amount of materials used and the total life cycle cost, it can improve the uniformity of the geothermal field and reduce the risk of local refreezing or excessive heating.

[0086] It should be noted that, Figure 7 The temperature values ​​in this example are simulation results under the calculation conditions set in this embodiment. When the engineering area, soil parameters, climate conditions, and roadbed structure change, the specific ground temperature values ​​may change accordingly, but the technical principle of the AI ​​non-uniform optimization scheme to implement differentiated configuration based on spatial heat load remains unchanged.

[0087] The "maintaining the minimum temperature of the foundation throughout the year not lower than the preset positive temperature threshold" mentioned in this invention does not rely on the real-time control of the temperature threshold by the gravity heat pipe itself. Instead, it incorporates "minimum temperature not lower than the positive temperature threshold" as a hard constraint into the reward function through deep reinforcement learning in the early stage. It performs global optimization matching on a non-uniform spatial distribution and a time scale of 50 years for the heat release of the lime energy pile and the heat dissipation of the gravity heat pipe. This enables the overall heat income (heat of lime hydration and heat storage in warm seasons) and heat expenditure (directional heat dissipation of heat pipes in cold seasons) of the system to achieve a dynamic balance at the design level. This inevitably keeps the minimum temperature of the foundation stable above the threshold. This functional constraint describes the performance result of the system-level optimization design, rather than the behavior of a single component.

[0088] Step S3: According to the non-uniform pile layout scheme, prepare geotextile-wrapped lime energy piles and gravity heat pipes, and carry out construction in the foundation to form a composite temperature-controlled foundation composed of lime energy piles and gravity heat pipes.

[0089] S31: Preparation and construction of lime energy piles (GELEC piles).

[0090] Please see Figure 3 The lime energy pile adopts the form of high-strength braided geotextile tubes encasing lime-soil mixture, i.e., GELEC piles. In this embodiment, polypropylene (PP) flat filament braided geotextile tubes are selected, with a warp tensile strength of not less than 50kN / m and a weft tensile strength of not less than 40kN / m, and an equivalent pore size O95 between 0.15 and 0.30mm, which can ensure drainage and air permeability while effectively preventing the loss of internal fine-particle filler.

[0091] Take a geotextile tube with a diameter of 400mm and a length consistent with the designed pile length, seal the bottom end, and fix it vertically. Fill the tube densely with a lime-based dry material, which is a uniform mixture of quicklime powder, fly ash, crushed stone, and admixtures in a specified mass ratio, with the moisture content controlled to be below 2%. During the filling process, after compaction, seal the top end of the geotextile tube and store it for curing until it reaches the strength required for lifting, thus obtaining a solid precast GELEC dry material pile.

[0092] During on-site construction, pile holes are first drilled in the permafrost roadbed stratum. The hole diameter should be 100-200mm larger than the diameter of the precast pile, for example, a hole diameter of 550mm. The aforementioned precast GELEC piles are then hoisted into the holes and adjusted to be centered within the holes. Subsequently, a sand and gravel mixture is backfilled in layers into the annular gap between the pile and the hole wall (theoretically approximately 75mm) until the ground elevation is reached, forming an annular backfill layer.

[0093] Next, the calculated amount of water is slowly injected through the pre-installed water injection hole at the top of the pile and the water injection pipe inserted into the pile body, according to the stoichiometric ratio of quicklime. The water permeates evenly along the dry material body, triggering an exothermic reaction of lime hydration. The pile body temperature rises rapidly to 60-80℃, and the heat is transferred to the surrounding frozen soil foundation through the pile wall and backfill layer, achieving a phased temperature increase.

[0094] After the heat of hydration has stabilized, multiple gravity heating rods are vertically inserted into the annular backfill layer. In this embodiment, four gravity heating rods with an outer diameter of 50 mm are used, evenly arranged at 90° intervals around the pile. The lower end of the heating rod is approximately 80 mm from the outer wall of the precast GELEC pile. The insertion depth of the heating rod is equivalent to the pile length, and the upper end is exposed to the air and equipped with heat dissipation fins.

[0095] During the cold season, heat from the foundation is transferred to the lower end of the heat pipe through the backfill layer. The working fluid inside the heat pipe evaporates and rises, condensing at the upper end and releasing heat into the atmosphere. The condensate flows back, and this cycle continuously dissipates excess heat from the foundation. Through the combined effects of lime hydration heat, warm-season heat storage, and gravity heat pipe cooling in the cold season, the lowest annual temperature of the foundation can be maintained above the positive temperature threshold of 1-3℃, ensuring that the permafrost does not degrade. GELEC piles have a dual function: firstly, lime undergoes a hydration reaction with water and minerals in the soil, releasing a large amount of heat, becoming an internal heat source for the entire foundation system; secondly, quicklime hydration generates... ,part Ions and Ions permeate through the geotextile tubes into the surrounding soil, reacting with active silica and alumina in the soil to form a cementitious substance through a pozzolanic reaction. Ion exchange further thins and flocculates the soil particle double electric layer, significantly increasing the cohesion and friction angle at the pile-soil interface. Simultaneously, the volume expansion of hydration products compensates for pile shrinkage, and the circumferential restraint provided by the geotextile contributes to the significantly higher vertical bearing capacity of GELEC piles compared to unrestrained lime-soil piles.

[0096] S32: Preparation and corrosion protection of gravity heating rods.

[0097] The gravity heat pipe (TPCT) is another core component of this method. In this embodiment, a seamless steel pipe with an outer diameter of 50 mm and a wall thickness of 3 mm is selected as the outer shell. After comprehensive evaluation, 316L stainless steel is used to resist corrosion in a highly alkaline lime environment. To further ensure long-term durability, the following anti-corrosion measures are implemented:

[0098] The outer surface of the evaporation section is coated with an epoxy resin-based anti-corrosion coating with a dry film thickness of 200~300μm and alkali resistance (saturated). Solution (80℃) ≥1000 hours.

[0099] The working fluid inside the heat pipe is R134a (operating temperature range -20℃~60℃), with a filling rate of 25%~35% of the evaporation section volume. The length of the evaporation section is determined according to the AI ​​optimization scheme, generally between 3.0 and 7.0m, and the length of the condensation section is 1.5 to 2.0m, equipped with high-efficiency aluminum heat dissipation fins.

[0100] Gravity heat pipes are installed using small-diameter drilling or direct static pressure insertion. For staggered layout schemes, after the lime energy piles are constructed, a hole is drilled at the center point of the designed inter-pile triangle, slightly deeper than the evaporation section by 0.2m. The bottom is filled with a fine sand heat-conducting layer. After the heat pipe is inserted, the hole walls are backfilled with heat-conducting cement mortar to ensure close contact with the foundation soil. The condensation section protrudes at least 0.5m above the ground surface and is equipped with snow covers and warning signs.

[0101] S33: Construction layout of composite temperature-controlled foundation.

[0102] Based on the non-uniform scheme generated by AI, GPS was used to accurately locate the coordinates of each pile and heat pipe during on-site layout in this embodiment. For areas with larger pile spacing on the sunny slope, the pile diameter and length were carefully verified to avoid errors. For key areas such as the road shoulder, the aforementioned precast solid GELEC piles were still used, and gravity heat pipes were densely arranged in the backfill layer around the piles according to the optimized scheme. If necessary, the pile diameter and the number of heat pipes on the road shoulder could be appropriately increased to enhance the heat dissipation and bearing capacity of the area.

[0103] Step S4: Utilize the exothermic reaction of lime hydration in the lime energy pile to pre-melt the permafrost around the pile, and utilize the thermal diode characteristics of the gravity heat rod that automatically starts unidirectional heat dissipation in the cold season when the ambient temperature is lower than the ground temperature and automatically stops working in the warm season when the ambient temperature is higher than the ground temperature to conduct excess heat from the soil between the piles, maintaining the minimum temperature of the foundation throughout the year not lower than the preset positive temperature threshold.

[0104] After construction is completed, the system enters the passive temperature-controlled operation phase. This phase can be divided into two sub-processes: the initial pre-melting process and the long-term stabilization process.

[0105] (1) Initial Pre-melting Process: The quicklime in the lime energy pile releases heat rapidly upon contact with water in the soil. The internal temperature of the pile reaches its peak within 7-14 days, reaching 60-80℃. The heat is conducted from the pile to the surrounding soil, and the frozen soil around the pile gradually melts. Since the thawing of permafrost requires the absorption of a large amount of latent heat of phase change (approximately 334 kJ / kg), it often takes 2-4 months to completely thaw the frozen soil within a certain range around the pile (e.g., a radius of 0.8-1.2 m). During this period, if it is the warm season and the surface temperature is high, the heat pipes will stop working due to the reverse temperature difference, which helps to retain heat and accelerate thawing; if it happens to be the cold season, since the temperature of the pile is much higher than the air temperature, the heat pipes will start and conduct some heat, which can delay the overcooling, but will not prevent the overall warming trend. Therefore, pre-melting is best arranged in late spring and early summer to obtain the best results.

[0106] (2) Long-term stable process: After the soil around the piles is completely melted, the system enters a long-term automatic control stage. During the warm season (April to October) each year, the atmospheric temperature is generally higher than the temperature of the evaporation section, the working fluid in the heat pipe cannot evaporate, and the heat pipe is in a "closed" state. The residual hydration heat of the lime pile and the solar radiation heat absorbed by the ground surface are effectively stored in the foundation, preventing excessive heat dissipation. During the cold season (November to March of the following year), when the atmospheric temperature drops below the temperature of the soil between the piles, the liquid working fluid in the evaporation section of the heat pipe absorbs heat and evaporates. The steam is cooled and condensed by the cold air in the condensation section, releasing heat and flowing back. This cycle continuously "pumps" the heat in the foundation soil to the atmosphere until the foundation temperature drops to equilibrium with the atmospheric temperature or the temperature difference is less than the starting temperature difference. Due to the ultra-high thermal conductivity of the heat pipe, it efficiently removes heat during the cold season, but its unidirectional nature prevents the cold energy from intruding into the foundation during the warm season.

[0107] Through this periodic "heat storage-controlled heat release" cycle, the foundation temperature is locked within a narrow positive temperature window throughout the year: the minimum temperature is no lower than +1.0℃, and the maximum temperature does not exceed +10℃. This completely avoids the refreezing and thawing settlement of permafrost, while also preventing the foundation soil strength from decreasing or the piles from softening due to overheating. The preset positive temperature threshold is +1.0℃, leaving sufficient safety margin. Temperature monitoring data shows that even in extremely cold winters, the coldest point temperature of the soil between piles has never fallen below +1.2℃, meeting the design requirements.

[0108] Please see Figure 8 , Figure 8 This paper presents the annual variation of the minimum temperature of the composite temperature-controlled foundation over a 50-year operational period, under a global warming trend with an average atmospheric temperature increase of 0.033℃ / year. The minimum temperature for each operational year is the lowest value among all calculation times and all foundation monitoring locations within that year, used to evaluate the risk of refreezing of the composite temperature-controlled foundation under long-term extreme low-temperature conditions.

[0109] Depend on Figure 8 It is evident that the minimum foundation temperature exhibits slight annual fluctuations during the 50-year operational period, but generally remains within the range of 1.20–1.41℃, consistently exceeding the design control threshold of 1.0℃, and never falling below the preset positive temperature threshold. This result indicates that the hydration heat provided by the lime-powered piles in the initial stage is sufficient to pre-thaw the frozen soil around the piles and reconstruct the initial foundation temperature. Furthermore, the gravity heat pipes automatically adjust the foundation heat according to seasonal temperature differences during the subsequent operational period, ensuring the foundation remains within the set positive temperature range over the long term.

[0110] As global warming continues, the amount of heat input to the Earth's surface increases during the warmer season. However, the effective operating time and heat dissipation of gravity heat pipes during the colder season automatically adjust to the temperature difference between the foundation and the environment, thereby releasing accumulated heat to the outside and preventing the foundation temperature from rising continuously. At the same time, the heat pipes are shut off during the warmer season, reducing the possibility of external heat being transferred back into the foundation along the heat pipes.

[0111] Therefore, the initial concentrated heat release of the lime energy pile and the long-term seasonal unidirectional heat dissipation of the gravity heat pipe form a temporal succession, enabling the composite temperature-controlled foundation to maintain long-term temperature stability under climate change conditions and providing stable ground temperature conditions for roadbed bearing capacity and deformation control.

[0112] Step S5: After the pre-melting stage is completed, the embankment filling and pavement structure layer construction are carried out in sequence.

[0113] Typically, about 3 to 4 months after the lime energy piles are constructed, the soil between the piles has largely completed its initial rapid heating and melting, and has established a certain strength. At this point, an appropriate time window (when there is no snow accumulation on the ground and the soil is not frozen) can be selected for embankment filling.

[0114] Before filling, first remove the protective membrane from the pile tops and lay a 0.3m thick gravel cushion layer as a drainage and stress diffusion layer. The cushion layer material should be well-graded gravel with a maximum particle size not exceeding 100mm and a compaction degree of not less than 96%. Then, use non-frost-susceptible crushed stone or sandy soil to fill the embankment in layers, with each layer loosely laid no more than 0.3m thick, and compact it to the specified compaction degree using a vibratory roller (heavy compaction standard not less than 93%). During the filling process, take care to protect the exposed condensation section of the heat pipes and avoid damage from collisions with construction machinery. Temporary protective barriers can be set up around the heat pipes.

[0115] After the embankment is filled to the design elevation, the pavement structure layers are constructed, including a cement-stabilized crushed stone base course and an asphalt concrete surface course. The specific structural combination and construction methods are carried out in accordance with conventional highway specifications and will not be elaborated here. After the pavement construction is completed, debris around the heat pipe condensation section is cleared to ensure unobstructed heat dissipation, and a permanent protective grating is installed.

[0116] Step S6: After construction or during operation, use bending element shear wave velocity testing to evaluate the foundation stiffness recovery effect and spatial uniformity, and optionally activate the electroosmosis device to regulate moisture in local areas.

[0117] Quantitative evaluation of foundation treatment effectiveness is crucial for quality control. This invention employs non-destructive bending element shear wave velocity testing technology to achieve precise monitoring of the stiffness of the soil between piles.

[0118] S61: Bending element test methods and evaluation indicators.

[0119] Prior to construction, pairs of bending element test probes were pre-embedded in representative soil between piles. Each probe pair consists of an excitation end and a receiving end, spaced 0.3–0.5 m apart, and can be placed horizontally or vertically to measure shear wave velocities in different directions. The bending element signal is excited by a single-cycle sinusoidal pulse with a frequency of 2~5kHz. After the received signal is amplified, the first arrival time is accurately determined by cross-correlation analysis, and the shear wave velocity is calculated.

[0120] This embodiment defines two dimensionless evaluation indicators:

[0121] Recovery ratio ( ): Defined as the processed shear wave velocity Shear wave velocity of the same type of soil under fully saturated conditions The square of the ratio, that is RR directly reflects the degree of improvement in foundation stiffness relative to the most vulnerable state (saturated softening).

[0122] Improvement ratio ( ): Defined as the shear wave velocity after processing Shear wave velocity at known optimum moisture content The square of the ratio, that is . It measures the degree to which the stiffness of the treated foundation has approached or exceeded the natural optimal state of the soil.

[0123] Meanwhile, a horizontal anisotropy index was defined to assess spatial homogeneity. , which is the ratio of the maximum to the minimum shear wave velocity in different horizontal directions.

[0124] The qualification standard is: all measuring points simultaneously meet the requirements. , and This means that the foundation stiffness is sufficient and uniform, with no local weak zones or excessive horizontal differences.

[0125] The test was conducted one month after the embankment was filled, before the road was opened to traffic, at which point the lime reaction and temperature field had largely stabilized. If the indicators did not meet the standards, it indicated that the soil may have excessively high local moisture content, pore water pressure accumulation, or insufficient drainage, requiring the implementation of the next stage of electroosmotic moisture control.

[0126] S62: Electroosmotic moisture regulation.

[0127] For areas that do not meet the standards, the pre-installed electroosmosis device is activated for precise moisture migration. The electroosmosis electrodes are made of carbon fiber strips, 100mm wide, with a length customized according to the required treatment depth (3m in this example). The electrodes are inserted into the designed positions through drilled holes, arranged in a checkerboard pattern with a spacing of 1.5-2.0m. All anodes are connected in parallel to the positive terminal of a DC power supply, and the cathodes are connected to the negative terminal and a drainage pipe.

[0128] A DC voltage of 30–60V is applied, creating an electric field gradient of approximately 0.5–1.0V / cm. Under the influence of the electric field, pore water migrates directionally from the anode to the cathode, accumulates near the cathode, and is discharged to the surface through a pre-installed small-diameter plastic drainage pipe or a vacuum suction device. Soil moisture content and temperature are continuously monitored during the treatment process to prevent soil shrinkage and cracking due to excessive drainage, or increased energy consumption due to increased resistance. Typically, continuous energization for several days to a week is sufficient to reduce the moisture content of a localized area to its optimum. After treatment, bending element tests are performed again until all measuring points meet the standards.

[0129] During long-term operation, the bending element probe can be used as part of a permanent monitoring system, with testing conducted every 1-2 years. If extreme climate changes cause abnormal local moisture content, the electroosmosis device can be activated at any time for maintenance moisture control to ensure long-term foundation stability.

[0130] In addition, a remote automated monitoring system can be used to collect and provide early warnings of data such as ground temperature, shear wave velocity, and deformation in real time. Combined with the above steps, a complete life-cycle maintenance plan can be formed.

[0131] Example 2

[0132] Please see Figure 2 The present invention also provides a prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature regulation system, which is used to implement the above method. Specifically, the system includes:

[0133] Multiple geotextiles encase lime energy piles, which are filled with lime-soil mixtures with lime content determined according to a non-uniform optimization scheme. The geotextile tubes of the lime energy piles are made of high-strength woven geotextiles, and the pile diameter and length vary according to the design, allowing for adaptive configuration of different specifications in different areas such as sunny slopes, shady slopes, and road shoulders.

[0134] Multiple gravity heat pipes are combined with limestone energy piles in an optimized layout scheme generated by a deep reinforcement learning model, both in planar and depth. The gravity heat pipes use 316L stainless steel or titanium alloy shells, are filled with a low-boiling-point working fluid, have evaporation sections in close contact with the foundation soil, and condensation sections exposed above the natural ground level, equipped with heat dissipation fins and anti-corrosion measures. The gravity heat pipes automatically activate during the cold season, directionally dissipating heat from the foundation.

[0135] The bending element testing device includes shear wave excitation and receiving probes pre-embedded at key locations in the soil between piles, and signal generation and acquisition instruments, used to measure shear wave velocities in different directions and based on the restitution ratio. And improvement ratio and horizontal anisotropy index A quantitative evaluation of the foundation stiffness and its uniformity is conducted.

[0136] The electroosmosis device consists of carbon fiber anodes and cathodes, an adjustable DC power supply, and drainage collection pipes. The anodes and cathodes are inserted into the foundation, and electroosmosis drainage can be carried out in local areas to adjust the soil moisture content to the desired range.

[0137] The aforementioned components work together to ensure that the permafrost subgrade can maintain a minimum ground temperature above +1.0℃ throughout its entire life cycle without the need for external mechanical energy input, while ensuring sufficient and uniform bearing capacity. This makes it suitable for degraded permafrost areas with an average annual ground temperature of -2.5℃ to -4.0℃.

[0138] Through the detailed description of the above embodiments, the technical solution, principles, and advantages of the present invention have been fully disclosed and elucidated. Those skilled in the art, based on the teachings of this specification and combined with conventional knowledge and experimental methods, can reproduce the present invention without creative effort, achieving the expected temperature control and load-bearing effects. It is understood that the above embodiments and examples are exemplary, and in practical applications, appropriate adjustments and modifications can be made within the scope of the claims based on specific engineering geological conditions, ambient temperature characteristics, material sources, and other factors.

Claims

1. A method for coordinated ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes, characterized in that, Includes the following steps: S1: Obtain the design ground temperature field data, settlement deformation data, and load requirement data of the foundation in the target permafrost region; S2: Construct a reinforcement learning state space based on the above data, use the pile layout parameters of lime energy piles and gravity heat pipes as the action space, and use the minimization of the whole life cycle cost and the maximization of the post-construction bearing capacity as the joint reward. Use a deep reinforcement learning model to generate a non-uniform pile layout scheme. The pile layout parameters include pile location, pile diameter, pile length, lime content, as well as the number of gravity heat pipes, the length of the evaporation section, and the size of the condensation section. S3: According to the non-uniform pile layout scheme, geotextile is prepared in the factory to wrap lime energy piles and gravity heat pipes, and then installed in the foundation to form a composite temperature-controlled foundation composed of lime energy piles and gravity heat pipes. S4: Utilize the heat release reaction of lime hydration in the lime energy pile to pre-melt the permafrost around the pile, and utilize the thermal diode characteristics of the gravity heat rod that automatically starts unidirectional heat dissipation in the cold season when the ambient temperature is lower than the ground temperature and automatically stops working in the warm season when the ambient temperature is higher than the ground temperature to conduct excess heat out of the soil between the piles and maintain the minimum temperature of the foundation throughout the year not lower than the preset positive temperature threshold. S5: After the pre-melting stage is completed, the embankment filling and pavement structure layer construction will be carried out in sequence; S6: After construction or during operation, the bending element shear wave velocity test method is used to evaluate the foundation stiffness recovery effect and spatial uniformity, and the electroosmosis device is activated to regulate the moisture in local areas.

2. The prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature regulation method according to claim 1, characterized in that, The deep reinforcement learning model described in step S2 adopts the SoftActor-Critic algorithm, wherein: the state space includes a grayscale cloud map of the geothermal field and a grayscale cloud map of the settlement field; the action space includes adding pile diameter, reducing pile diameter, pile length, lime content, number of gravity heating rods, and pile addition and deletion operations at specific spatial locations; the bearing capacity reward in the joint reward is the ratio of the ultimate bearing capacity of the pile-soil composite foundation corresponding to the preset operating years to the design requirements, the cost penalty is the ratio of the total life cycle cost to the budget, and a temperature safety constraint penalty item is set—a negative reward is given when the lowest temperature at any point of the foundation is lower than -0.5℃ or the differential settlement exceeds the limit.

3. The prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature control method according to claim 1, characterized in that, In step S3, the lime energy piles and gravity heat rods are arranged in a spatial staggered manner: multiple lime energy piles are arranged in a quincunx pattern, and the gravity heat rods are arranged at the center of the triangle formed by three adjacent lime energy piles, and the bottom depth of the evaporation section of the gravity heat rods is flush with or deeper than the bottom of the lime energy piles.

4. The prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature control method according to claim 1, characterized in that, The geotextile-wrapped lime energy pile is vertically buried in the center of the pile hole, and the pile hole and the geotextile-wrapped lime energy pile are filled with backfill material to form an annular backfill layer; the lower end of the gravity heat rod is inserted into the annular backfill layer and maintains a preset distance from the outer wall of the geotextile-wrapped lime energy pile.

5. The prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature control method according to claim 1, characterized in that, The geotextile-wrapped lime energy pile mentioned in step S3 is a GELEC pile. The GELEC pile is composed of a high-strength woven geotextile tube filled with a lime-soil mixture. The circumferential restraint effect of the geotextile enhances the vertical bearing capacity of the pile, and the lime hydration process generates… Ions migrate through the pores of the geotextile to the pile-soil interface, where they undergo ion exchange and carbonation reactions to enhance interfacial cohesion.

6. The method for coordinated ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes according to claim 1, characterized in that, If, during the implementation of step S4 or before the construction of step S5, the moisture content of a local area of ​​the foundation is detected to deviate from the optimal moisture content range, the electroosmosis method is initiated to regulate the moisture content: carbon fiber strip electrodes are arranged on both sides of the area to be regulated, and a DC electric field of 30V to 60V is applied to drive pore water to migrate directionally from the anode to the cathode and be discharged until the soil moisture content is restored to the optimal moisture content.

7. The prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature control method according to claim 1, characterized in that, The bending element shear wave velocity test evaluation in step S6 uses the recovery ratio (RR) and improvement ratio (R). As an indicator, among them , , , , Shear wave velocities under treated, saturated, and optimum moisture content conditions, respectively; when the treated foundation simultaneously satisfies , And the horizontal anisotropy index At that time, the ground temperature control effect was deemed satisfactory.

8. The method for coordinated ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes according to claim 1, characterized in that... It also includes anti-corrosion treatment of the gravity heat pipe evaporation section: 316L stainless steel or titanium alloy is selected as the material of the gravity heat pipe tube, and an epoxy resin-based anti-corrosion coating is applied to its outer surface.

9. The method for coordinated ground temperature regulation using prefabricated chemical energy piles and gravity heat pipes according to claim 1, characterized in that, The preset positive temperature threshold is +1.0℃, and the method is applicable to roadbed engineering in degraded permafrost areas with an annual average ground temperature of -2.5℃ to -4.0℃.

10. A prefabricated chemical energy pile-gravity heat pipe synergistic ground temperature regulation system, used to implement the method of any one of claims 1-9, characterized in that, include: Multiple geotextiles wrap lime energy piles, which are filled with lime-soil mixture with a pre-set lime content to pre-melt the permafrost around the piles through hydration heat release. Multiple gravity heat pipes, combined with the lime energy piles, are arranged in an optimized layout in both plane and depth to unidirectionally extract ground heat during the cold season. The optimized layout is generated by a deep reinforcement learning model based on the initial ground temperature field, settlement deformation, and load demand data of the target frozen soil foundation, with the goal of minimizing the total life cycle cost and maximizing the post-construction bearing capacity. A bending element test device is set at a key location in the soil between piles to measure shear wave velocity in order to evaluate the foundation stiffness and its uniformity. An electroosmosis device, comprising spaced carbon fiber strip electrodes and a DC power supply, is used for directional water migration in the event of localized water content anomalies. The lime energy pile and gravity heat pipe work together to maintain the lowest temperature of the foundation above the preset positive temperature threshold throughout the year.

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