Widely distributed cold storage gas freezing roadbed and refrigeration method

Abstract

The present application relates to frozen soil engineering technical field, it is a kind of widely distributed cold storage gas frozen soil subgrade and refrigeration method, its former includes air-cooled regulation unit, air power unit, refrigeration unit, temperature sensing unit and control unit;Air-cooled regulation unit includes phase-change heat storage body, air-cooled box, air exhaust passage and air circulation channel, multiple phase-change heat storage bodies are uniformly distributed in air-cooled box, multiple phase-change heat storage bodies are provided with multiple air circulation channels, and the air circulation channel is extended to the outside of air-cooled box, and the adjacent two air circulation channels in the inside of air-cooled box are staggered distribution;The present application is judged by temperature in air-cooled box and external environment temperature, and the mode of external circulation refrigeration and internal circulation refrigeration is set to complement each other, and the comprehensive utilization of forced convection, phase-change heat storage body is carried out slow-release heat absorption mode, to reach the effect of frozen soil subgrade efficient cooling.

Description

Technical Field

[0001] This invention relates to the field of frozen soil engineering technology, and in particular to a widely distributed cold storage frozen soil subgrade and a refrigeration method. Background Technology

[0002] In permafrost regions such as the Qinghai-Tibet Plateau and Northeast my country, thick layers of underground ice, ranging from several meters to tens of meters in thickness and exhibiting various shapes, have formed through long-term evolution, development, and changes. With changes in climate and the impact of human engineering activities, the permafrost and underground ice can degrade and melt, leading to various engineering disasters and significantly affecting the stability of major engineering projects.

[0003] The adoption of permafrost protection engineering measures, including active cooling of permafrost foundations, is a key approach to ensuring the long-term safe operation and stability of permafrost projects. Because the strength of permafrost is closely related to temperature, its strength can increase exponentially as the temperature decreases. At low temperatures, permafrost foundations can be as solid as rock, while at high temperatures or near 0°C, they can be as soft as soft soil. Therefore, by applying permafrost protection engineering measures to permafrost foundations, and by reducing the permafrost temperature to varying degrees and continuously channeling cold energy into the foundation, the long-term stability of the permafrost foundation can be effectively maintained. Thus, for any permafrost protection engineering measure, its cooling efficiency, or its overall regulation efficiency of the permafrost foundation's ground temperature field, is crucial to the success or failure of maintaining the long-term stability of the roadbed.

[0004] The use of riprap subgrade is a crucial engineering measure for protecting permafrost foundations. It primarily utilizes the different thermal conductivity of the riprap layer during the cold and warm seasons to cool the permafrost foundation, and has played a significant role in permafrost projects such as the Qinghai-Tibet Railway. However, with the increasing warming and humidification of the Qinghai-Tibet Plateau, the rate of permafrost degradation and thawing has increased dramatically, posing a significant threat to the stability of permafrost foundations. Actual observations show that the cooling efficiency of this measure is now insufficient to meet practical engineering needs, especially under highway conditions, where its effectiveness is even worse or nonexistent. Because the Qinghai-Tibet Railway and the world's first expressway, the Qinghai Gonghe-Yushu Expressway, extensively use this riprap subgrade structure in permafrost regions, uneven settlement and cracking of the subgrade are increasingly common, posing serious threats to project stability and traffic safety. Summary of the Invention

[0005] This invention provides a widely distributed cold storage and freezing method for frozen soil subgrade, which overcomes the shortcomings of the prior art. It can effectively solve the problems that the cooling effect of existing roadbeds using boulders as the base for frozen soil foundations is difficult to meet the actual engineering needs and the cooling effect is poor.

[0006] To solve the above problems, one of the technical solutions of the present invention is achieved through the following means: a widely distributed cold storage frozen soil roadbed, including a cold air control unit, an aerodynamic unit, a refrigeration unit, a power supply unit, a temperature sensing unit and a control unit; The power supply unit includes solar photovoltaic panels located above the roadbed slope; the power supply unit is connected to the control unit; The air-cooled control unit includes a phase change heat storage body, an air-cooled housing, an air exhaust channel, and an air circulation channel. Multiple phase change heat storage bodies are evenly distributed inside the air-cooled housing. Multiple parallel and spaced air circulation channels extend to the outside of the air-cooled housing between the multiple phase change heat storage bodies. Adjacent air circulation channels inside the air-cooled housing are staggered. Each air circulation channel inside the air-cooled housing has multiple air holes that connect the inside and outside on one side wall. Multiple air exhaust channels that communicate with the external environment are provided on the outer side wall of the air-cooled housing. The air circulation channel is located at one end of the outer side of the air-cooled box and is connected to the aerodynamic unit, which is connected to the refrigeration unit; temperature sensing units are provided on both the inner and outer sides of the air-cooled box; the control unit is connected to the temperature sensing unit, the aerodynamic unit, and the refrigeration unit respectively.

[0007] The aforementioned air-cooled enclosure is a hollow structure consisting of a top plate, a bottom plate, and an outer partition. Supporting columns are spaced apart inside the air-cooled enclosure.

[0008] The aforementioned air exhaust channel is located at one end of the outer side of the air-cooled box, with an angle of 0~45° between the inclined section of the pipe opening and the vertical direction. A damper is installed at the pipe opening on the inclined surface, with the damper having a hinge fixedly connected to the corresponding position of the pipe opening at the upper end. A counterweight is installed at the lower end of the damper.

[0009] The aforementioned aerodynamic unit includes an air circulation power device, a first three-way valve, and a second three-way valve. The output end of the air filter is fixedly connected to the air circulation power device and a first delivery pipe via the first three-way valve. The output end of the air circulation power device is fixedly connected to a second delivery pipe that is fixedly connected to an air circulation channel. A third delivery pipe is fixedly connected to the second delivery pipe. The third delivery pipe is fixedly connected to the first delivery pipe and the corresponding air circulation channel via the second three-way valve. The air circulation power device, the first three-way valve, and the second three-way valve are all connected to the control unit.

[0010] The aforementioned refrigeration unit includes a refrigeration heat exchanger and a refrigeration unit. The refrigeration heat exchanger is installed on the second delivery pipeline. The refrigeration heat exchanger is connected to the refrigeration unit, and the refrigeration unit is connected to the control unit.

[0011] The control unit includes a control module and a signal transmission module, and the control module is connected to the signal transmission module.

[0012] The aforementioned power supply unit also includes a battery, a solar photovoltaic panel connected to the battery, and the battery connected to the control unit.

[0013] The above also includes waterproof geotextile and thermal insulation material. Thermal insulation material is installed above the air-cooled control unit, and waterproof geotextile is installed above the thermal insulation material.

[0014] The second technical solution of this invention is achieved through the following method: a cooling method for widely distributed cold storage gas-frozen soil roadbed, including external circulation cooling and internal circulation cooling, the specific steps of which are as follows: Determine whether the temperature signal detected by the temperature sensing unit inside the air-cooled box is greater than the ambient temperature signal detected by the temperature sensing unit outside the air-cooled box. In response, only the aerodynamic unit is activated, while the refrigeration unit remains dormant. External air flows through the aerodynamic unit, enters through the air circulation channel, enters the inside of the air-cooled box through the air vents of the air circulation channel, and is then discharged through the air exhaust channel, thus achieving external circulation refrigeration. If no response is received, it is determined whether the temperature sensed by the temperature sensing unit inside the air-cooled box is greater than the temperature threshold set by the control unit. In response, the aerodynamic unit and the refrigeration unit are activated simultaneously. Air inside the air-cooled control layer flows out from one air circulation channel, passes through the refrigeration unit, cools the airflow, and then enters through another air circulation channel. The air then enters the inside of the air-cooled chamber through the vents on the air circulation channel. The air inside the air-cooled chamber then enters the air circulation channel through the vents on the other air circulation channel. This process is repeated to achieve internal circulation refrigeration.

[0015] This invention determines the temperature inside the air-cooled box and the external ambient temperature, sets up external circulation cooling and internal circulation cooling modes to complement each other, and comprehensively utilizes forced convection, phase change heat storage cold body for slow heat release and absorption, etc., to achieve efficient cooling of frozen soil subgrade through a widely distributed overall layer cooling method. Attached Figure Description

[0016] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention.

[0018] Figure 2 This is a planar schematic diagram of the air-cooling control unit in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the cross-sectional structure of the air-cooled control unit in an embodiment of the present invention.

[0020] Figure 4 for Figure 2 Schematic diagram of the cross section of the AA' roadbed.

[0021] Figure 5 for Figure 2 Schematic diagram of the cross section of the BB' roadbed.

[0022] Figure 6 for Figure 2 Schematic diagram of the cross section of the CC' roadbed.

[0023] Figure 7 This is a schematic diagram of the air circulation channel structure in an embodiment of the present invention.

[0024] Figure 8 This is a schematic diagram of the air exhaust channel structure in an embodiment of the present invention.

[0025] Figure 9 This is a schematic diagram of the external circulation cooling mode in an embodiment of the present invention.

[0026] Figure 10 This is a schematic diagram of the internal circulation cooling mode in an embodiment of the present invention.

[0027] Figure 11 This is a simulation result of the ground temperature on April 1st, the first year of the cold season for a widely distributed air-cooled roadbed with cold storage.

[0028] Figure 12 This is a simulation result of the ground temperature on October 1st of the first warm season for a widely distributed cold storage and air-cooled roadbed.

[0029] Figure 13 The above data represents the measured ground temperature of the ventilation duct subgrade on October 1, 2014 (Zhang et al., Cold Regions Science and Technology, 2020).

[0030] Figure 14 The measured ground temperature of the ventilation duct subgrade with automatic damper on October 1, 2015 (Zhang et al., ColdRegions Science and Technology, 2020).

[0031] Figure 15 The above is a map showing the measured ground temperature at the center of the Qinghai-Tibet Railway's block rock subgrade from 2003 to 2006 (Sun Zhizhong, Chinese Journal of Geotechnical Engineering, 2008).

[0032] In the diagram: 1-Air-cooled box; 2-Air exhaust channel; 3-Door hinge; 4-Damper; 5-Counterweight; 6-Air circulation channel; 7-Air vent; 8-Phase change heat storage body; 9-Temperature sensing unit; 10-Solar photovoltaic panel; 11-Battery; 12-Air filtration equipment; 13-Air circulation power equipment; 14-Refrigeration heat exchanger; 15-Refrigeration unit; 16-Control module; 17-Signal transmission module; 18-First three-way valve; 19-Second three-way valve; 20-First conveying pipe; 21-Second conveying pipe; 22-Third conveying pipe; 23-Supporting column; 24-Insulation material; 25-Waterproof geotextile; 26-Roadbed. Detailed Implementation

[0033] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0034] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: As Figure 1-10 As shown, this embodiment of the invention discloses a widely distributed cold storage air frozen soil roadbed, including an air-cooling control unit, an aerodynamic unit, a refrigeration unit, a power supply unit, a temperature sensing unit 9, and a control unit; The power supply unit includes a solar photovoltaic panel 10 located above the slope of roadbed 26; the power supply unit is connected to the control unit; The air-cooled control unit includes a phase change heat storage body 8, an air-cooled box 1, an air exhaust channel 2, and an air circulation channel 6. Multiple phase change heat storage bodies 8 are evenly distributed inside the air-cooled box 1. Multiple parallel and spaced air circulation channels 6 are provided between the multiple phase change heat storage bodies 8 and extend to the outside of the air-cooled box 1. Two adjacent air circulation channels 6 inside the air-cooled box 1 are staggered. One end of the side wall of each air circulation channel 6 inside the air-cooled box 1 is provided with multiple air holes 7 that are connected inside and outside. Multiple air exhaust channels 2 that are connected to the external environment are provided on the outer side wall of the air-cooled box 1. The air circulation channel 6 is located at one end of the outer side of the air-cooled box 1 and is connected to the aerodynamic unit, which is connected to the refrigeration unit; temperature sensing units 9 are provided on both the inner and outer sides of the air-cooled box 1; the control unit is connected to the temperature sensing unit 9, the aerodynamic unit and the refrigeration unit respectively.

[0035] During installation, the aforementioned air-cooled control unit is horizontally located inside the roadbed 26, with its bottom 0-1.0m above the original natural ground surface. It can be installed inside the fill soil of the roadbed 26 when the roadbed 26 has been filled to a certain height. The air-cooled box 1 is a hollow, sealed structure, which can be rectangular, cylindrical, or a combination thereof, with a thickness of 10cm-50cm. The outer shell of the air-cooled box 1 is a precast concrete component or a metal component. It forms a load-bearing structure through the top plate, bottom plate, and outer partition, meeting the load-bearing requirements of the roadbed 26 and ensuring its overall compressive strength. The air-cooled box 1 is equipped with supporting columns 23, which are made of concrete or steel frame structure and have high strength. The supporting columns 23 are evenly arranged at certain intervals to provide sufficient space for the phase change heat storage body 8 and form a natural channel to enhance the convective heat transfer of the air inside the air-cooled box 1.

[0036] The aforementioned phase change heat storage body 8 is a thin-shell sealed container. The phase change material inside can be one or more combinations of conventional phase change materials with a phase change temperature of 0 to -15℃. It is placed inside the air-cooled box 1 and on both sides of the air circulation channel 6. Its main purpose is to store the cold energy in the air-cooled box 1 through the phase change process and release the cold energy when the roadbed 26 needs to be cooled. By balancing and regulating the temperature inside the roadbed 26, the purpose of uniformly reducing the temperature of the roadbed 26 can be achieved.

[0037] The aforementioned air circulation channel 6 can be made of metal, PVC, PE, plastic, etc., and its shape can be round or rectangular. The air circulation channel 6 can serve as an airflow channel, as well as an air outlet channel and an air inlet channel. When used as an air outlet channel, it only flows outward in one direction. Air holes 7 are provided on the side wall of the air circulation channel 6 inside the air-cooled box 1 to facilitate uniform convective heat transfer of the air inside the air-cooled box 1 under forced convection heat transfer. At the same time, by setting two adjacent air circulation channels 6 arranged at intervals, parallel and staggered inside the air-cooled box 1, the convective heat transfer of the air in the center of the roadbed 26 is enhanced, ensuring its overall cooling effect.

[0038] The aforementioned solar photovoltaic panels 10 are located on one or both sides of the sunny slope of the roadbed 26 and are fixed at a certain height by conventional support rod materials, thereby further shading and cooling the slope and reducing the heat energy generated by solar radiation from being transferred into the roadbed 26. They can also be fixed on one or both sides of the roadbed 26.

[0039] The temperature sensing unit 9 mentioned above can be a known temperature probe, which is placed in the environment inside the air-cooled box 1, on the phase change heat storage body 8, and outside the air-cooled box 1 to measure the temperature change inside the roadbed 26 in real time, thus forming a multi-point sensing system.

[0040] This invention has two operating modes: an internal circulation cooling mode and an external circulation cooling mode, wherein: 1. The internal circulation cooling mode is as follows: the air flow in the air-cooled box 1 flows out from one of the air circulation channels 6 to the cooling unit. After the cooling unit cools the air flow, the output cold air enters the inside of the air-cooled box 1 from the other air circulation channel 6, so as to realize the forced internal circulation cooling of the air flow in the air-cooled box 1. 2. The external circulation cooling mode is as follows: external air flows through the aerodynamic unit and through different air circulation channels 6 to the inside of the air-cooled box 1, forcing the air inside the air-cooled box 1 to be discharged from the air exhaust channel 2, thereby achieving forced external circulation cooling.

[0041] like Figure 8 As shown, the air exhaust channel 2 is located at one end of the air-cooled box 1 with an inclined distribution. The angle between the inclined section of the pipe opening and the vertical direction is 0~45°. A damper 4 is installed at the pipe opening with the same inclined direction as the pipe opening. The upper end of the damper 4 is movably connected to a door hinge 3 that is fixedly connected to the corresponding position of the pipe opening. A counterweight 5 is installed at the lower end of the damper 4.

[0042] The above-mentioned air damper 4 and counterweight 5 are installed on the outside of the air exhaust channel 2 to increase the sealing of the damper 4. Thus, when the air pressure inside the air-cooled box 1 reaches a certain air pressure height, the damper 4 will automatically open, and at other times the damper 4 will be closed.

[0043] like Figure 1 , 4 As shown in -6, 9-10, the power supply unit also includes a storage battery 11, the solar photovoltaic panel 10 and the storage battery 11 are connected, and the storage battery 11 is connected to the control unit.

[0044] The aforementioned solar photovoltaic panel 10 is a known technology that can directly or indirectly convert solar radiation into electrical energy through the photoelectric effect or photochemical effect. The converted electrical energy is stored in the battery 11 and used to power the control unit. When no power supply is needed, the solar photovoltaic panel 10 is used to charge the battery 11, so that the battery 11 can serve as a backup power source when the solar photovoltaic panel 10 has no power output.

[0045] like Figure 1As shown, the aerodynamic unit includes an air filter 12, an air circulation power unit 13, a first three-way valve 18, and a second three-way valve 19. The output end of the air filter 12 is fixedly connected to the air circulation power unit 13 and the first delivery pipe 20 through the first three-way valve 18. The output end of the air circulation power unit 13 is fixedly connected to a second delivery pipe 21, which is fixedly connected to the air circulation channel 6. A third delivery pipe 22 is fixedly connected to the second delivery pipe 21. The third delivery pipe 22 is fixedly connected to the first delivery pipe 20 and the corresponding air circulation channel 6 through the second three-way valve 19. The air circulation power unit 13, the first three-way valve 18, and the second three-way valve 19 are all connected to the control unit.

[0046] The aforementioned air filtration device 12 is mainly used to filter the airflow, preventing dust carried by the outside wind from entering the air circulation power device 13 and preventing blockage of the air circulation channel 6. The aforementioned air circulation power device 13 is mainly used to increase the airflow pressure and deliver cooling energy to the air circulation channel 6 through the refrigeration unit. The first three-way valve 18 and the second three-way valve 19 control the airflow path.

[0047] like Figure 1 , 9 As shown in Figure 10, the refrigeration unit includes a refrigeration heat exchanger 14 and a refrigeration unit 15. The refrigeration heat exchanger 14 is installed on the second delivery pipe 21. The refrigeration heat exchanger 14 is connected to the refrigeration unit 15, and the refrigeration unit 15 is connected to the control unit.

[0048] The aforementioned refrigeration unit 15 is used to cool and reduce the airflow flowing out from the inside of the air-cooled box 1, and outputs the cooled airflow to the inside of the air-cooled box 1 to achieve convective heat transfer inside the air-cooled box 1.

[0049] like Figure 1 , 9 As shown in Figure 10, the control unit includes a control module 16 and a signal transmission module 17, and the control module 16 is connected to the signal transmission module 17.

[0050] The aforementioned control module 16 is used to compare and judge the received external ambient temperature, the temperature inside the air-cooled box 1, and the temperature set in the control module 16 based on the data received from the temperature sensing unit 9, thereby controlling the operation of all equipment and the conversion of the air flow process, and thus realizing the linkage between the external circulation cooling and internal circulation cooling modules; and to transmit its signal to the remote host computer (which can be a computer, tablet, mobile phone or other terminal control device) through the signal transmission module 17, so as to facilitate remote viewing of the temperature signal inside the air-cooled box 1 and control of the entire system.

[0051] like Figure 4-6As shown, it also includes a waterproof geotextile 25 and a thermal insulation material 24. The thermal insulation material 24 is provided above the air-cooled control unit, and the waterproof geotextile 25 is provided above the thermal insulation material 24.

[0052] The aforementioned thermal insulation material 24 can be one or a combination of polystyrene board (EPS), polyurethane board (PU), and injection-molded polystyrene board (XPS), with a thickness of 10~50 cm and a width of 5~15 m. It is buried at a position of 0~1.0 m above the air-cooled box 1. It can effectively block the heat transfer process inside the roadbed 26 from the outside and has the effect of eliminating the adverse effects of the roadbed 26 absorbing heat on the cooling of the engineering measures. In practical applications, its width is slightly narrower than the width of the roadbed fill at its burial depth, and its burial height is coordinated with the burial height of the air-cooled control unit.

[0053] The aforementioned geotextile can be a commonly used waterproof geotextile 25 in engineering. It is laid horizontally and continuously on the top of the air-cooled box 1, mainly to reinforce the soil and isolate water, preventing moisture from entering the insulation material 24 and the air-cooled box 1, thus affecting the air-cooling control performance.

[0054] Example 2: This embodiment of the invention discloses a cooling method for widely distributed cold storage gas-frozen soil roadbed, including external circulation cooling and internal circulation cooling. The specific steps are as follows: Determine whether the temperature signal detected by the temperature sensing unit 9 inside the air-cooled box 1 is greater than the ambient temperature signal detected by the temperature sensing unit 9 outside the air-cooled box 1. In response, only the aerodynamic unit is activated, while the refrigeration unit remains dormant. External air flows through the aerodynamic unit and enters through the air circulation channel 6, then through the air vents 7 of the air circulation channel 6 into the inside of the air-cooled housing 1, and is then discharged through the air exhaust channel, thus achieving external circulation refrigeration. If no response is received, it is determined whether the temperature sensed by the temperature sensing unit 9 inside the air-cooled box 1 is greater than the temperature threshold set by the control unit. In response, the aerodynamic unit and the refrigeration unit are activated simultaneously. Air inside the air-cooled control layer flows out from one air circulation channel 6, passes through the refrigeration unit, and after the refrigeration unit cools the airflow, it enters from another air circulation channel 6 and enters the inside of the air-cooled box 1 through the air holes 7 on the air circulation channel 6. The air inside the air-cooled box 1 flows into the air circulation channel 6 through the air holes 7 of the other air circulation channel 6, and the above process is repeated to achieve internal circulation refrigeration.

[0055] Example 3: This invention has two cooling modes: external circulation cooling and internal circulation cooling. The working principle is as follows: 1. External circulation cooling The control unit receives the temperature signal inside the air-cooled box 1 and the external ambient temperature signal detected by the temperature sensing unit 9. When it is determined that the external ambient temperature is lower than the temperature inside the air-cooled box 1, the external circulation open cooling mode is activated. Specifically, under the drive of the air circulation power device 13, the outside air flows through the air filter device 12 and enters different air circulation channels 6 through the first three-way valve 18, the refrigeration heat exchanger 14, the second delivery pipe 21, the third delivery pipe 22 and the second three-way valve 19 respectively. The air flows to the inside of the air-cooled box 1 through the air holes 7 on the air circulation channel 6, flows inside the entire air-cooled box 1, and finally is discharged from the air exhaust channel 2.

[0056] 2. Internal circulation cooling The control unit receives the temperature signal inside the air-cooled box 1 and the external ambient temperature signal detected by the temperature sensing unit 9. When it is determined that the external ambient temperature is greater than the temperature inside the air-cooled box 1, and the temperature inside the air-cooled box 1 is higher than the temperature threshold set by the control unit, the internal circulation cooling module is activated. Specifically, the refrigeration unit 15 is turned on, and the air inside the air-cooled box 1 flows out from an air circulation channel 6, and is cooled down through the second three-way valve 19, the first conveying pipe 20, the first three-way valve 18, the air circulation power equipment 13, the refrigeration heat exchanger 14, and the refrigeration unit 15. The cooled air then enters the air circulation channel 6 again through the second conveying pipe 21, and enters the inside of the air-cooled box 1 through the air holes 7 on the air circulation channel 6 for forced convection heat exchange, so that the gas inside the air-cooled box 1 circulates internally, thereby achieving internal cooling and circulation cooling of the roadbed 26 and promoting the permafrost evolution process.

[0057] During the external circulation cooling mode, the low-temperature air mainly cools the outer shell of the air-cooled box 1 and the bottom plate, that is, it widely and comprehensively cools the lower part of the roadbed 26 through the layer. At the same time, it exchanges heat and cools with the phase change heat storage body 8, accumulating cold energy and realizing the cooling process of the external open system of the roadbed 26. In addition, since the air circulation channels 6 are arranged alternately on both sides of the roadbed 26, a cold core is easily formed in the center of the roadbed 26, which further enhances the energy storage of cold air inside the roadbed 26.

[0058] In operation, during the cold season at night, the external circulation cooling mode can be activated based on the temperature. During the cold season during the day, either the external circulation cooling mode or the internal circulation cooling mode can be selected based on the temperature. During the warm season during the day, the internal circulation cooling mode can be activated based on the temperature. The phase change heat storage body 8 is used to store cold energy during winter nights or other low-temperature weather conditions for heat exchange during the day or other relatively high-temperature conditions. During the warm season, it stores cold energy in the internal circulation cooling mode during the day for heat exchange inside the roadbed 26 at night. When the phase change heat storage body 8 absorbs heat, and the roadbed 26 is in a low-temperature state and under operating conditions, the entire circulation system is in a dormant state.

[0059] In summary, this invention, by judging the temperature inside the air-cooled box 1 and the external ambient temperature, sets up external circulation cooling and internal circulation cooling modes to complement each other. It comprehensively utilizes forced convection, phase change heat storage body 8 for slow heat release and absorption, and other modes, and achieves efficient cooling of the entire frozen soil subgrade by widely distributed overall cooling method.

[0060] Compared with the prior art, the present invention has made changes to the heat exchange mechanism and working efficiency, as follows: 1. Change in heat exchange method In terms of heat exchange methods, ventilation ducts cool the roadbed by means of ventilation ducts arranged in parallel at certain intervals. In this cooling method, the ventilation ducts are local points or circles in the longitudinal and transverse sections of the roadbed, and a line in the cross section of the roadbed; that is, point-type or line-type cooling; while the present invention cools the roadbed through the overall level of the air-cooled control unit, which is a surface cooling mode; 2. Changes in heat exchange mechanism This invention first changes the convective heat transfer process of traditional ventilation duct roadbeds. Previously, the heat transfer process in ventilation duct roadbeds involved convective heat transfer between the inner wall of the ventilation duct and the outside environment, followed by heat conduction between the duct wall and the roadbed fill. Firstly, under engineering structural conditions with ventilation duct spacing of 1-2m, a roadbed height typically of 3m, and a ventilation duct diameter of approximately 0.4m, the heat transfer boundary of the ventilation duct wall accounts for a very small proportion (approximately 20-30%) of the entire longitudinal section of the roadbed. Furthermore, the low thermal conductivity of the soil (approximately 1-2 W / m·K) results in insufficient cooling efficiency of this engineering measure, making it difficult to meet practical engineering needs. Actual observations show that this engineering measure leads to continuous settlement and deformation of frozen soil roadbeds under highway conditions, and also makes it difficult to ensure long-term stability of the roadbed under railway conditions.

[0061] Secondly, this invention alters the heat exchange process of the rubble roadbed. In the cold season, when the temperature at the top of the rubble layer is lower than at the bottom, the air at the top of the layer cools, contracts in volume, increases in density, and begins to sink, while the relatively hot air at the bottom rises. Thus, the air continuously releases heat at the top and absorbs heat at the bottom, undergoing a natural convection heat exchange process. In the warm season, when the temperature at the top of the rubble layer is higher than at the bottom, the hot air is above and the cold air is below, preventing convection heat exchange. Therefore, the rubble layer provides heat release in the cold season and relative insulation in the warm season throughout the year. This heat exchange process is vertical. However, in this type of heat exchange, the air needs to pass through the rubble layer, resulting in a tortuous and variable flow path, naturally encountering significant resistance. Simultaneously, with the increase in ambient temperature in permafrost regions or under the condition of heat absorption by the black roadbed, the temperature at the top of the rubble layer increases, causing the working conditions required for cold-season operation of the rubble layer to continuously decrease or even disappear. Therefore, the heat exchange efficiency of the rock layer in the rock-based roadbed is very low or even lost, which is the main reason for the instability of the roadbed of the Qinghai-Tibet Railway and the Gongyu Expressway.

[0062] Therefore, this invention employs an air-cooled control unit to conduct convective heat exchange with the outside environment at the overall and layer level, thereby changing the slow "heat conduction" heat exchange mechanism between the ventilation duct roadbed and the ventilation duct itself. At the same time, this invention changes the vertical and weak natural convective heat exchange process of the boulders roadbed by employing a horizontal air-cooled control unit at the overall level and a strong forced convective heat exchange process. Furthermore, this invention uses a control unit for intelligent control, automatically conducting the overall heat exchange process according to temperature conditions, thus changing the previous measures that used an autonomous and passive heat exchange process.

[0063] Furthermore, this invention employs a highly efficient cooling process that operates year-round, every day and hour. During the cold season, when ambient temperatures are between -20°C and -30°C, it facilitates rapid convective heat exchange between the roadbed interior and the external environment. During the warm season, or during the day, the roadbed 26 is cooled by the refrigeration unit 15 according to the internal temperature conditions. Compared to previous methods, such as those for rubble-based roadbeds, which only involve weak, vertical convective heat exchange within the rubble layer during the cold season and cease operation during the warm season; or ventilated duct roadbeds, which, while cooling during the cold season, still experience increased roadbed temperature due to convective heat exchange during the warm season, this invention achieves continuous, uninterrupted operation and efficient cooling throughout the year, completely overcoming the shortcomings of previous methods that only offered cooling during the cold season or were inefficient.

[0064] 3. Changes in work efficiency The air-cooling control unit of this invention has a hollow structure. With the addition of upper insulation material 24 and internal phase change heat storage material 8, it can effectively block the downward transfer of heat from the upper part of the roadbed 26 and can also effectively preserve the cold energy stored by mechanical refrigeration during the cold season. This greatly improves the cooling efficiency of the roadbed 26 and enables the full utilization of the abundant cold energy and solar energy resources of the Qinghai-Tibet Plateau.

[0065] At the same time, due to the complete change in the refrigeration mechanism and efficiency, the temperature of the "whole" frozen soil in the bearing layer under the roadbed 26 is effectively reduced significantly and for a long time. Since the strength of frozen soil is closely related to the temperature of frozen soil, this invention enables the large-scale existence of "low-temperature" frozen soil under the roadbed, which greatly enhances the mechanical stability and smoothness of the roadbed 26, thereby achieving the goal of long-term stability of frozen soil roadbed and effective elimination of various engineering defects.

[0066] Example 4: To verify the regulation efficiency of the widely distributed cold-storage frozen soil subgrade provided by this invention, numerical simulation calculations were conducted under the action of engineering measures, taking into account the geological conditions of the Qinghai-Tibet Highway test project in the permafrost region of the Qinghai-Tibet Plateau. For ease of comparison, the boundary conditions of subgrade 26 and the subgrade of the highway ventilation pipe under the participation of internal mechanics and thermophysics were basically the same as those of the Qinghai-Tibet Railway.

[0067] The key parameters for the specific settings are as follows: the slope ratio of roadbed 26 is 1:1.5, the height of roadbed 26 is 3m, and the top surface width is 13m. An air-cooling control unit is installed within roadbed 26 at a height of 0.5m above the original natural ground surface. The width of the air-cooling control unit is slightly smaller than the height of roadbed 26 (approximately 20m), and the thickness of the control layer is 0.3m. Road surface, slope, and natural ground surface temperature data monitored at the Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Northwest Foothills River Test Site on the Qinghai-Tibet Plateau are used as the model boundary conditions. Based on field-measured air temperature data, a simulation of the cooling mode under strong forced convection is conducted.

[0068] The simulation results of the roadbed temperature field during the cold season (April 1st) after the installation of the air-cooled control unit are as follows: Figure 11 As shown in the figure. First, in terms of effectiveness, judging from the size and distribution of the contour lines, the lowest temperature value is -9°C, concentrated in the subgrade 26 base area (X=-10 to 10). The contour lines in this part are very dense, indicating that the soil temperature below the pavement changes rapidly, and the cooling effect is significant. In contrast, in the natural field area (X close to ±20m), the contour lines are relatively sparse, and the temperature is relatively higher, about -0.5°C. Second, in terms of morphology and symmetry, the contour lines in the figure are roughly symmetrically distributed along the center of subgrade 26, especially the 0°C isotherm, which is relatively flat, effectively eliminating the eccentric slope effect of permafrost subgrades.

[0069] The simulation results of the roadbed temperature field on October 1st, one year after the deployment of the air-cooled control unit, are as follows: Figure 12 As shown in the figure, after the warm season's heat absorption process, the lowest ground temperature at the moment of maximum melting depth in roadbed 26 reached -4°C, concentrated in the base area of ​​roadbed 26 (X approximately between -10 and 10, Y approximately between 0 and -5). The isotropic lines are dense in this part, indicating that the temperature changes rapidly in this area and the cooling effect is significant. The 0°C isotherm shifts upward by 3m, and the temperature inside roadbed 26 drops to -2 to -4°C, without the asymmetrical distribution of the temperature field in the lower part of roadbed 26.

[0070] Example 5: To further analyze the advanced performance of the widely distributed cold storage air-cooled roadbed, its cooling effect is compared with that of three published engineering measures: frozen soil ventilation pipe roadbed, self-controlled air door roadbed, and riprap foundation roadbed.

[0071] (1) Comparison with ventilation duct roadbed The measured ground temperature results on October 1st, the fourth year after the construction of the test roadbed for the ventilation duct of the Qinghai-Tibet Expressway are as follows: Figure 13 As shown in the figure (Zhang, et al. Cold Regions Science and Technology, 2020), the average soil temperature beneath the ventilation duct subgrade is approximately -1℃. The ground temperature field is asymmetrical along the center of the subgrade, with the low-temperature zone mainly concentrated near the shady slope, reaching a minimum temperature of -1.8℃. The upper limit of the frozen soil is approximately 0.5m higher than the natural ground surface. Comparative results show that the cooling effect of the widely distributed cold storage and air-cooled subgrade is significantly better than that of the ventilation duct subgrade. The lowest temperature of the widely distributed cold storage and air-cooled subgrade is approximately 7℃ lower than that of the ventilation duct subgrade, and the upper limit of the frozen soil is 1.5m higher.

[0072] (2) Compared with the subgrade engineering measures of the self-controlled ventilation door The measured ground temperature results of the test roadbed for the automatic ventilation duct of the Qinghai-Tibet Expressway on October 1st are as follows: Figure 14 As shown in the figure (Zhang, et al. Cold Regions Science and Technology, 2020), the average soil temperature beneath the self-controlled ventilation duct subgrade is approximately -1.5℃. The ground temperature field is asymmetrical along the center of the subgrade, with the low-temperature zone mainly concentrated near the shady slope, reaching a minimum temperature of -2℃. The upper limit of the frozen soil is approximately 1m higher than the natural ground surface. In comparison, the lowest temperature of the widely distributed cold storage and air-cooled subgrade is about 7℃ lower than that of the self-controlled ventilation duct subgrade, and the upper limit of the frozen soil is 1m higher. This further verifies the significant cooling effect of the widely distributed cold storage and air-cooled subgrade.

[0073] (3) Compared with the rubble-base subgrade The ground temperature and depth curve at the center of the roadbed after the implementation of the riprap roadbed in the Beiluhe test section of the Qinghai-Tibet Railway is as follows: Figure 15 As shown in the figure (Sun Zhizhong, Chinese Journal of Geotechnical Engineering, 2008), the implementation of the riprap foundation has a relatively limited cooling effect on the subgrade soil. The average ground temperature at a depth of 0 to -6m is approximately -0.8℃, and the average temperature at a depth of -6 to -16m is approximately -1.5℃. The minimum temperature of the widely distributed cold-storage air-cooled roadbed is about 7.5℃ lower than that of the riprap foundation roadbed, and the average temperature is about 3℃ lower, indicating that the former's cooling effect is far superior to that of the riprap foundation roadbed.

[0074] Through the implementation of this case, the ground temperature in the central area of ​​the roadbed and the main bearing layer was maintained at a sub-zero temperature, and a cold core with a temperature below -4℃ was formed in the bearing layer of the roadbed. At the same time, through air cooling regulation and cold storage, a large amount of cold energy was accumulated in the roadbed, which on the one hand provided a cold source to resist the warming in the warm season, and on the other hand improved the deformation resistance of the roadbed due to the sub-zero temperature.

[0075] In summary, the widely distributed cold storage and air-cooled roadbed demonstrates a significant advantage in cooling effect compared to ventilation pipe roadbed, self-controlled damper roadbed, and riprap roadbed, and provides a good guarantee for the stability and durability of the roadbed.

Claims

1. A widely distributed cold-storage frozen soil roadbed, characterized in that, It includes an air-cooling control unit, an aerodynamic unit, a refrigeration unit, a power supply unit, a temperature sensing unit, and a control unit; The power supply unit includes solar photovoltaic panels located above the roadbed slope; the power supply unit is connected to the control unit; The air-cooled control unit includes a phase change heat storage body, an air-cooled housing, an air exhaust channel, and an air circulation channel. Multiple phase change heat storage bodies are evenly distributed inside the air-cooled housing. Multiple parallel and spaced air circulation channels extend to the outside of the air-cooled housing between the multiple phase change heat storage bodies. Adjacent air circulation channels inside the air-cooled housing are staggered. Each air circulation channel inside the air-cooled housing has multiple air holes that connect the inside and outside on one side wall. Multiple air exhaust channels that communicate with the external environment are provided on the outer side wall of the air-cooled housing. The air circulation channel is located at one end of the outer side of the air-cooled box and is connected to the aerodynamic unit, which is connected to the refrigeration unit; temperature sensing units are provided on both the inner and outer sides of the air-cooled box; the control unit is connected to the temperature sensing unit, the aerodynamic unit, and the refrigeration unit respectively; The aerodynamic unit includes an air circulation power device, a first three-way valve, and a second three-way valve. The output end of the air filter is fixedly connected to the air circulation power device and a first delivery pipe via the first three-way valve. The output end of the air circulation power device is fixedly connected to a second delivery pipe that is fixedly connected to an air circulation channel. A third delivery pipe is fixedly connected to the second delivery pipe. The third delivery pipe is fixedly connected to the first delivery pipe and the corresponding air circulation channel via the second three-way valve. The air circulation power device, the first three-way valve, and the second three-way valve are all connected to the control unit. The refrigeration unit includes a refrigeration heat exchanger and a refrigeration machine. The refrigeration heat exchanger is installed on the second delivery pipeline. The refrigeration heat exchanger is connected to the refrigeration machine, and the refrigeration machine is connected to the control unit. The control unit includes a control module and a signal transmission module, and the control module is connected to the signal transmission module; The air exhaust channel is located at one end of the outer side of the air-cooled box, with an angle of 0~45° between the inclined section of the pipe opening and the vertical direction. A damper is installed at the pipe opening on the inclined surface, with the damper having a hinge fixedly connected to the corresponding position of the pipe opening at the upper end. A counterweight is installed at the lower end of the damper.

2. The widely distributed cold storage frozen soil subgrade according to claim 1, characterized in that, The power supply unit also includes a battery, a solar photovoltaic panel, and a connection between the battery and the control unit.

3. The widely distributed cold-storage frozen soil roadbed according to claim 1, characterized in that, It also includes waterproof geotextile and thermal insulation material. Thermal insulation material is installed above the air-cooled control unit, and waterproof geotextile is installed above the thermal insulation material.

4. The widely distributed cold storage frozen soil roadbed according to claim 1, characterized in that, The air-cooled enclosure is a hollow structure consisting of a top plate, a bottom plate, and an outer partition. Support columns are spaced apart inside the air-cooled enclosure.

5. A refrigeration method for a widely distributed cold storage gas-frozen soil roadbed as described in any one of claims 1-4, characterized in that, This includes external circulation cooling and internal circulation cooling, and the specific steps are as follows: Determine whether the temperature signal detected by the temperature sensing unit inside the air-cooled box is greater than the ambient temperature signal detected by the temperature sensing unit outside the air-cooled box. In response, only the aerodynamic unit is activated, while the refrigeration unit remains dormant. External air flows through the aerodynamic unit, enters through the air circulation channel, enters the inside of the air-cooled box through the air vents of the air circulation channel, and is then discharged through the air exhaust channel, thus achieving external circulation refrigeration. If no response is received, it is determined whether the temperature sensed by the temperature sensing unit inside the air-cooled box is greater than the temperature threshold set by the control unit. In response, the aerodynamic unit and the refrigeration unit are activated simultaneously. Air inside the air-cooling control unit flows out from one air circulation channel, passes through the refrigeration unit, cools the airflow, and then enters through another air circulation channel. The airflow enters the inside of the air-cooled chamber through the vents on the air circulation channel. The air inside the air-cooled chamber flows into the air circulation channel through the vents on the other air circulation channel. The above process is repeated to achieve internal circulation refrigeration.

Images